Author Topic: vintage lathe restoration - 3 phase supply.  (Read 24579 times)

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Offline capnahab

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vintage lathe restoration - 3 phase supply.
« on: August 30, 2016, 05:45:20 pm »
Dear Guys,
I am a surgeon in the UK so you may have to bear with me on technical matters (on both counts.) I was directed here after seeing Robrenz's fantastic videos on youtube.
I am restoring a 1957 lathe. It has a 2 speed 3 phase motor, - 3.75HP and 7.5HP. I have a 15HP rotary converter to power it , - professionally installed to the garage with a 10mm 60amp supply. The electrician however didn't know much about connecting it to the lathe. It works great at low speed.  When I try to start the motor in fast speed it seems to overload the converter. Phoned the converter manufacturer. I tested the voltage drop on start up - drops from the UK 240 supply to about 230 for a second, then back up to 240, - so pretty negligible.
I think the three wires of the converter output could be worked into the switch in the wrong order but I don't know how to explore the circuitry to determine how to fix the problem. I have a  multimeter and know the basics of how to use it. I enclose some photos of the switch, electrical panel and front control.
Any tips would be great.
ps proper 3 phase will cost me about $20,000, so I have discounted that...
 

Offline capnahab

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Re: vintage lathe restoration - 3 phase supply.
« Reply #1 on: August 30, 2016, 05:48:01 pm »
Sorry , and heres the lathe.
 

Offline eKretz

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Re: vintage lathe restoration - 3 phase supply.
« Reply #2 on: August 30, 2016, 06:07:16 pm »
Changing the order of the wires will do nothing but reverse the motor direction. Wondering why you didn't go with a variable frequency drive, was it too expensive? They can easily convert single phase to 3 phase, and also give you infinitely variable speed within their range of frequency.

BTW, beautiful old Dean Smith & Grace.
« Last Edit: August 30, 2016, 06:10:08 pm by eKretz »
 

Offline douardda

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Re: vintage lathe restoration - 3 phase supply.
« Reply #3 on: August 30, 2016, 06:25:44 pm »
By all means, please, install a VFD. This wonderful lathe deserves it.

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Offline capnahab

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Re: vintage lathe restoration - 3 phase supply.
« Reply #4 on: August 30, 2016, 06:31:12 pm »
Thanks eKretz,
The most powerful VFD available in the UK is about 2.5-3 Kilowatt. Not sure exactly why.
 

Offline HighVoltage

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Re: vintage lathe restoration - 3 phase supply.
« Reply #5 on: August 30, 2016, 06:41:02 pm »
I have a lathe that came with a single phase motor and speed was controlled through gear and belt changes.
Well that sucked big time.

Then I installed a 3 phase motor and frequency controlled drive system, based on a LENZE 3 phase 400V, 7.5 KW VFD
You can get them sometimes cheap on ebay.

After this mod, the lathe is a hundred times more useful and I never have to change gears again.

There are 3 kinds of people in this world, those who can count and those who can not.
 

Offline IanB

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Re: vintage lathe restoration - 3 phase supply.
« Reply #6 on: August 30, 2016, 06:41:59 pm »
I'm absolutely not an expert on rotary converters, but I wonder if the rotary converter does not have enough system (mechanical) inertia to cope with the startup load of the lathe motor. Does the converter "bog down" when you try to start the motor? If so, I wonder if fitting some kind of flywheel to the converter might help? (If it is at all possible to do so.)
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Offline Ian.M

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Re: vintage lathe restoration - 3 phase supply.
« Reply #7 on: August 30, 2016, 07:11:04 pm »
The other possibility would be if the control system contactor coils are being powered from the generated phase.  Control systems should always be powered from the original supply.  Its complicated by the tendency for control system manufacturers to attempt to balance single phase loads evenly over all three phases so some control box rewiring may be required
 

Offline IanB

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Re: vintage lathe restoration - 3 phase supply.
« Reply #8 on: August 30, 2016, 07:23:40 pm »
The other possibility would be if the control system contactor coils are being powered from the generated phase.  Control systems should always be powered from the original supply.  Its complicated by the tendency for control system manufacturers to attempt to balance single phase loads evenly over all three phases so some control box rewiring may be required

Perhaps this could be tested by simply rotating the order of the three phases connected from the converter to the lathe? There are three possibilities (1-2-3, 3-1-2, 2-3-1) and maybe one of these works better than the others?
I'm not an EE--what am I doing here?
 

Offline capnahab

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Re: vintage lathe restoration - 3 phase supply.
« Reply #9 on: August 30, 2016, 07:53:19 pm »
That's essentially what they guy at the rotary phase converter ?RPC manufacturer said. The generated phase being the likely problem. Obviously they aren't going to be able to give specific advice about every machine.
It's very common to use RPCs for heavy machines - this guy illustrates. - https://youtu.be/IZny57ddM8k . No one describes much in the way of machine rewiring. I just wondered if there was any EE logic to help me.
 

Offline edpalmer42

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Re: vintage lathe restoration - 3 phase supply.
« Reply #10 on: August 30, 2016, 07:56:52 pm »
You mentioned that the input power is only dropping from 240 to 230, but what about the output voltages?  Do you have a clamp-on ammeter to measure the current in the output lines?  Maybe there's a fault in the motor.

Ed
 

Offline capnahab

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Re: vintage lathe restoration - 3 phase supply.
« Reply #11 on: August 30, 2016, 08:05:54 pm »
Ed - good point , I will do that before I start switching the wires into the lathe.
 

Offline Andy Watson

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Re: vintage lathe restoration - 3 phase supply.
« Reply #12 on: August 30, 2016, 08:45:58 pm »
Are you trying to take this motor from a standing start to full speed in one step?
 

Offline capnahab

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Re: vintage lathe restoration - 3 phase supply.
« Reply #13 on: August 30, 2016, 08:57:00 pm »
Well, that could be the problem. I have no instruction manual that describes normal use. One of the pictures shows the front panel , two buttons, one for slow one for fast. When I push fast with the motor already running in slow absolutely nothing happens. No noises or change in either lathe or converter.in normal use with a true 3 phase supply  I suspect mechanically to change speed you put it in neutral then hit fast with the motor already running. The machine gear settings are the same.  Then re- engage the clutch.
If I hit fast from stopped it overloads the converter. One possibly problem could be the control panel not sending the fast signal through ?. Though why should it be any different than true 3 phase
 

Offline IanB

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Re: vintage lathe restoration - 3 phase supply.
« Reply #14 on: August 30, 2016, 08:58:58 pm »
I think you have not told us exactly what you mean by "overload the converter"? What does it do, exactly?
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Offline capnahab

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Re: vintage lathe restoration - 3 phase supply.
« Reply #15 on: August 30, 2016, 09:13:11 pm »
This video shows startup in slow, then press fast. Then stop and try starting from stopped to fast. Essentially the boost light continually flashes and the converter chatters .
https://youtu.be/Aryl-0iWgiQ
 

Offline KJDS

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Re: vintage lathe restoration - 3 phase supply.
« Reply #16 on: August 30, 2016, 09:30:06 pm »
I suspect that there is an issue with either the brushes or the windings on the fast coils of the motor.

Offline capnahab

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Re: vintage lathe restoration - 3 phase supply.
« Reply #17 on: August 30, 2016, 09:40:22 pm »
I think it's unlikely to be the motor, despite being from 1957 the lathe has lived in a tech College until I bought it. It runs perfectly in the slower speed. Can I text the motor somehow ?.
 

Offline IanB

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Re: vintage lathe restoration - 3 phase supply.
« Reply #18 on: August 30, 2016, 09:49:36 pm »
Hmm. I wonder how the motor changes from slow to fast? I wonder if it could be something like changing from a star to delta connection on the windings or something like that? (Bearing in mind I don't know about three phase motors and we need someone in this thread who does.)

I short, I am wondering if there is a wiring/connection problem of some sort between the converter and the lathe...?
I'm not an EE--what am I doing here?
 
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Offline Andy Watson

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Re: vintage lathe restoration - 3 phase supply.
« Reply #19 on: August 30, 2016, 09:54:26 pm »
I'm not convinced that it is overloading the convertor. I think it sounds like there is a contactor in the DSG that is dropping out (for some reason?) and the convertor is reacting to this.
May be time to sketch-out the circuit and work-out what it should be doing.
 
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Offline tautech

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Re: vintage lathe restoration - 3 phase supply.
« Reply #20 on: August 30, 2016, 10:25:49 pm »
OP
On a lathe group I'm a member on there is often discussion about power problems when 3 phase lathes are used in other than industrial environments where the mains supply is generally strong. Sometimes the lathes are tripping VFD's especially when cold and a often discovered fix for this is to change the viscosity of the headstock lubricant. It's just not quite that simple, one must match the particular properties of the recommended lubricant with a lower viscosity one. As these old lathes were designed to run for long day shifts the headstock temperature rise had to be catered for when the lathe got hot with a higher viscosity lubricant but today lubricant technology is vastly better and the additives make it so that much lower viscosity oils can now be used.
Benefits are much lower power requirements when the lathe is cold and surprisingly headstocks will often run cooler with modern lubricants.
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Offline capnahab

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Re: vintage lathe restoration - 3 phase supply.
« Reply #21 on: August 30, 2016, 10:33:13 pm »
I think a circuit diagram would definitely help. I will phone DSG tomorrow. Not holding out a lot of hope, -they have been through many changes of owner.
 

Offline edpalmer42

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Re: vintage lathe restoration - 3 phase supply.
« Reply #22 on: August 30, 2016, 10:39:56 pm »
Start at slow - okay - push the fast button - nothing happens
Start at fast - converter freaks out

The difference in behaviour is because in the first case, the motor is already spinning.  Do these motors have a centrifugal switch?

Regarding the wiring diagram, any chance it's bolted on the lathe or the motor itself?

Ed

P.S.  Yes Ian, we desperately need someone who knows 3 phase motors.   :-DD
 
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Offline tautech

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Re: vintage lathe restoration - 3 phase supply.
« Reply #23 on: August 30, 2016, 11:00:45 pm »
1440 and 720 RPM translates to 4 and 8 pole motor. The poles (windings) will be switched into another configuration to enable the high RPM mode.
Get a sparky or your local motor rewinder to check this motor is behaving properly, if it is suspect the switch over HW as not doing its job.
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Offline rch

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Re: vintage lathe restoration - 3 phase supply.
« Reply #24 on: August 30, 2016, 11:15:30 pm »
My only experience of using a three phase motor is using one with a variable frequency inverter drive, and I strongly recommend getting a suitably rated one on Ebay or somewhere. 

But my only other observation is that the incoming neutral wire does not go anywhere, and it is just possible it may be needed for the higher speed.   Of course, there would have to be somewhere to connect it!
 

Offline Andy Watson

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Re: vintage lathe restoration - 3 phase supply.
« Reply #25 on: August 30, 2016, 11:26:31 pm »
1440 and 720 RPM translates to 4 and 8 pole motor.
Yes. One particular configuration that I have encountered (on a much smaller lathe) was a Dahlander Connection. It switches from a delta connection of series coils to a parallel connection in star - as it does so the relative phase between pairs of windings reverses, doubling/halving the number of poles.
 

Offline Delta

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Re: vintage lathe restoration - 3 phase supply.
« Reply #26 on: August 30, 2016, 11:28:34 pm »
1440 and 720 RPM translates to 4 and 8 pole motor. The poles (windings) will be switched into another configuration to enable the high RPM mode.
Get a sparky or your local motor rewinder to check this motor is behaving properly, if it is suspect the switch over HW as not doing its job.

Beat me to it!

The ONLY way to change the speed of an induction motor driven with a fixed frequency is to change the number of poles.

At 50Hz, 2 pole pairs per phase = 1500 RPM (minus slip), 4 pole pairs per phase = 750 RPM, so for a 3 phase motor 12 poles = 1500 rpm, 24 poles(!) = 750. 

The motor must be a 24 pole(!) unit, and the control circuit switches half of the out for high speed.

I must admit, I have never came across (ooh err!) such a setup, but my guess would be that the motor / controller is wired incorrectly, causing poles to fight against each other, causing the extra load.

A circuit diagram is essential!

PS.  Where in the UK are you?  I'd love to come round to help!  :-+
 

Offline tautech

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Re: vintage lathe restoration - 3 phase supply.
« Reply #27 on: August 31, 2016, 12:13:14 am »
AFAIK for 3 phase 415440VAC 50 Hz 2 pole is ~2880 RPM, 4 pole ~1440 RPM, 6 pole ~960 RPM and 8 pole ~720 RPM.
All these configurations I have experienced and owned and torque of each type diminishes with increased RPM.

The Harrison L6 Mk3 I have has 2 speed 3 phase controls, the 2 speeds are selected by mechanical means and are lever activated, of which there are 4 positions, H & L for forward and reverse.

To do all this with relays/contactors would certainly require some nutting out but of course is entirely possible.

Edit
Voltage corrected as per Ian's post.
« Last Edit: August 31, 2016, 01:27:45 am by tautech »
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Offline IanB

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Re: vintage lathe restoration - 3 phase supply.
« Reply #28 on: August 31, 2016, 01:23:42 am »
AFAIK for 3 phase 440VAC 50 Hz 2 pole is ~2880 RPM, 4 pole ~1440 RPM, 6 pole ~960 RPM and 8 pole ~720 RPM.
All these configurations I have experienced and owned and torque of each type diminishes with increased RPM.

The Harrison L6 Mk3 I have has 2 speed 3 phase controls, the 2 speeds are selected by mechanical means and are lever activated, of which there are 4 positions, H & L for forward and reverse.

To do all this with relays/contactors would certainly require some nutting out but of course is entirely possible.

Just for reference, the UK in modern times has a consumer voltage of 240 V phase to neutral, 415 V phase to phase. Since this lathe says on the nameplate that the voltage is 400/440 V, I wonder if this means any voltage in that range is acceptable? Or does it mean there is a selection that can be made inside the lathe to choose one voltage or the other?

For a three phase motor at 50 Hz I read that the non-slip synchronous speed for a four pole motor would be 1500 RPM, for an eight pole motor 750 RPM. The nameplate values of 1440 RPM / 720 RPM would allow for the amount of slip at full load.

If the speed adjustment is done electrically, then something is being done by means of contactors to change the number of poles by rearranging the connections to the motor. Since the photos show the speed selection being done by push button, an electrical arrangement seems entirely possible to me.
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Offline tautech

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Re: vintage lathe restoration - 3 phase supply.
« Reply #29 on: August 31, 2016, 01:30:36 am »
AFAIK for 3 phase 440VAC 50 Hz 2 pole is ~2880 RPM, 4 pole ~1440 RPM, 6 pole ~960 RPM and 8 pole ~720 RPM.
All these configurations I have experienced and owned and torque of each type diminishes with increased RPM.

The Harrison L6 Mk3 I have has 2 speed 3 phase controls, the 2 speeds are selected by mechanical means and are lever activated, of which there are 4 positions, H & L for forward and reverse.

To do all this with relays/contactors would certainly require some nutting out but of course is entirely possible.

Just for reference, the UK in modern times has a consumer voltage of 240 V phase to neutral, 415 V phase to phase. Since this lathe says on the nameplate that the voltage is 400/440 V, I wonder if this means any voltage in that range is acceptable? Or does it mean there is a selection that can be made inside the lathe to choose one voltage or the other?

For a three phase motor at 50 Hz I read that the non-slip synchronous speed for a four pole motor would be 1500 RPM, for an eight pole motor 750 RPM. The nameplate values of 1440 RPM / 720 RPM would allow for the amount of slip at full load.

If the speed adjustment is done electrically, then something is being done by means of contactors to change the number of poles by rearranging the connections to the motor. Since the photos show the speed selection being done by push button, an electrical arrangement seems entirely possible to me.
Correct, edited post.

IMO the label voltage signifies the nominal voltage range.
Usually on the inside of the motor wiring connection cover any dual voltage configuration connection will be listed.
It's not apparent from this image:


So if we examine this pic from the Op we see a good bunch of 4 pole contactors presumably doing the 2 speed and reverse operations.

« Last Edit: August 31, 2016, 01:40:12 am by tautech »
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Offline edpalmer42

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Re: vintage lathe restoration - 3 phase supply.
« Reply #30 on: August 31, 2016, 04:21:37 am »
Start at slow speed - okay - change speed - nothing happens
Start at high speed - converter freaks out

The difference between these two is that in the first case, the motor was already spinning.  Do these motors have a centrifugal switch?  Is it driving one of the contactors?  Maybe the switch or one of the contactors is dirty or fried.

Ed


 

Offline tautech

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Re: vintage lathe restoration - 3 phase supply.
« Reply #31 on: August 31, 2016, 04:47:17 am »
Start at slow speed - okay - change speed - nothing happens
Start at high speed - converter freaks out

The difference between these two is that in the first case, the motor was already spinning.  Do these motors have a centrifugal switch?  Is it driving one of the contactors?  Maybe the switch or one of the contactors is dirty or fried.

Ed
Ed
3 phase motors do not have start and run windings like most single phase motors and therefore no centrifugal change over switch either.
Until we have a wiring diagram we cannot be entirely sure how the setup is configured and if it is/was even working properly on 3 phase before the OP got the lathe.
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Offline tautech

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Re: vintage lathe restoration - 3 phase supply.
« Reply #32 on: August 31, 2016, 04:58:10 am »
When we look carefully at this image again



We see a 6 way terminal block with presumably the incoming 3 phase supply to the motor.
There's 7 conductors, 1 set of 3 black and 1 set of 3 red and the earth.
One might deduce that the black wires are for 1 speed and the red for the other speed.

BUT one black wire is unconnected and terminated into a joining block. WHY?

If it's for the high speed and the convertor is trying to supply the motor with only 2 phases.....well that might explain the mayhem.  :-//
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Offline capnahab

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Re: vintage lathe restoration - 3 phase supply.
« Reply #33 on: August 31, 2016, 05:07:12 am »
Delta, I am near Ilkley in Yorkshire, you are welcome to come round.
The lathe top speed - mechanically is 720 rpm. It's 6 am in the Uk now - will try the circuit diagram today.
Thanks for all your interest and help.
 

Offline eKretz

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Re: vintage lathe restoration - 3 phase supply.
« Reply #34 on: August 31, 2016, 06:48:55 am »
When we look carefully at this image again



We see a 6 way terminal block with presumably the incoming 3 phase supply to the motor.
There's 7 conductors, 1 set of 3 black and 1 set of 3 red and the earth.
One might deduce that the black wires are for 1 speed and the red for the other speed.

BUT one black wire is unconnected and terminated into a joining block. WHY?

If it's for the high speed and the convertor is trying to supply the motor with only 2 phases.....well that might explain the mayhem.  :-//

I noticed this also, seemed very odd to me as well. I am pretty sure that larger than 2.5 - 3 kW VFDs are available in the UK - industry there certainly uses them. Personally I'd never use a phase converter setup when VFDs are available.
 

Offline edpalmer42

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Re: vintage lathe restoration - 3 phase supply.
« Reply #35 on: August 31, 2016, 06:58:51 am »
When we look carefully at this image again



We see a 6 way terminal block with presumably the incoming 3 phase supply to the motor.
There's 7 conductors, 1 set of 3 black and 1 set of 3 red and the earth.
One might deduce that the black wires are for 1 speed and the red for the other speed.

BUT one black wire is unconnected and terminated into a joining block. WHY?

If it's for the high speed and the convertor is trying to supply the motor with only 2 phases.....well that might explain the mayhem.  :-//

I don't think so.  Follow the yellow wire and see where it goes behind the black wire.  Right there you can see that there are actually two black wires.  So it looks like the cable with the grey sheath consists of four black wires and the yellow (maybe yellow-green) wire for ground.  The fourth black lead was just terminated in the joining block to insulate it.

One set of wires (black or red) appears to be the supply while the other set is the load.  The red wires are connected to terminals 1, 3, and 5 while the black wires are connected to terminals 2(?), 4, and 6.  The big 'fingers' below the connector block are U-shaped switch contacts that connect terminals 1-2, 3-4, and 5-6.  Terminal 2 gives the best view of the switch 'socket' on the left side of that terminal.  Kind of like a 6-way knife switch.

Ed
 

Offline tautech

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Re: vintage lathe restoration - 3 phase supply.
« Reply #36 on: August 31, 2016, 08:05:44 am »
When we look carefully at this image again



We see a 6 way terminal block with presumably the incoming 3 phase supply to the motor.
There's 7 conductors, 1 set of 3 black and 1 set of 3 red and the earth.
One might deduce that the black wires are for 1 speed and the red for the other speed.

BUT one black wire is unconnected and terminated into a joining block. WHY?

If it's for the high speed and the convertor is trying to supply the motor with only 2 phases.....well that might explain the mayhem.  :-//

I don't think so.  Follow the yellow wire and see where it goes behind the black wire.  Right there you can see that there are actually two black wires.  So it looks like the cable with the grey sheath consists of four black wires and the yellow (maybe yellow-green) wire for ground.  The fourth black lead was just terminated in the joining block to insulate it.

One set of wires (black or red) appears to be the supply while the other set is the load.  The red wires are connected to terminals 1, 3, and 5 while the black wires are connected to terminals 2(?), 4, and 6.  The big 'fingers' below the connector block are U-shaped switch contacts that connect terminals 1-2, 3-4, and 5-6.  Terminal 2 gives the best view of the switch 'socket' on the left side of that terminal.  Kind of like a 6-way knife switch.

Ed
You are right Ed.  :phew:
But what is this switch for?
Master main?
We need the OP to explain where this switch fits in.  :-//
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Offline HackedFridgeMagnet

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Re: vintage lathe restoration - 3 phase supply.
« Reply #37 on: August 31, 2016, 08:34:34 am »
AFAIK for 3 phase 440VAC 50 Hz 2 pole is ~2880 RPM, 4 pole ~1440 RPM, 6 pole ~960 RPM and 8 pole ~720 RPM.
All these configurations I have experienced and owned and torque of each type diminishes with increased RPM.

The Harrison L6 Mk3 I have has 2 speed 3 phase controls, the 2 speeds are selected by mechanical means and are lever activated, of which there are 4 positions, H & L for forward and reverse.

To do all this with relays/contactors would certainly require some nutting out but of course is entirely possible.

Just for reference, the UK in modern times has a consumer voltage of 240 V phase to neutral, 415 V phase to phase. Since this lathe says on the nameplate that the voltage is 400/440 V, I wonder if this means any voltage in that range is acceptable? Or does it mean there is a selection that can be made inside the lathe to choose one voltage or the other?

For a three phase motor at 50 Hz I read that the non-slip synchronous speed for a four pole motor would be 1500 RPM, for an eight pole motor 750 RPM. The nameplate values of 1440 RPM / 720 RPM would allow for the amount of slip at full load.

If the speed adjustment is done electrically, then something is being done by means of contactors to change the number of poles by rearranging the connections to the motor. Since the photos show the speed selection being done by push button, an electrical arrangement seems entirely possible to me.

Isn't the specified voltage for mains supply in  UK 230V?  single phase +10% - 6%, ie same as Australia and probably Europe? Not directly important to thread but I think its important to state the correct voltages.
 

Offline capnahab

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Re: vintage lathe restoration - 3 phase supply.
« Reply #38 on: August 31, 2016, 09:01:46 am »
This switch is the main electrical isolator for the machine. The image shows the supply cable coming into the top, with 4 black wires , 3 of which go to the switch. Not sure what is happening with the 4 th as mentioned above. I could test to see if it was live if someone advised me how. The three red wires go to the motor.
The red wires go to a box on the motor with straight through connector to the motor.
 

Offline rch

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Re: vintage lathe restoration - 3 phase supply.
« Reply #39 on: August 31, 2016, 09:12:22 am »
I thought this might be the neutral wire.  Of uncertain importance to steady three phase power, but could it be important to the convertor to have unbalanced currents going this way rather than via other phases?
 

Offline Delta

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Re: vintage lathe restoration - 3 phase supply.
« Reply #40 on: August 31, 2016, 10:26:38 am »


Isn't the specified voltage for mains supply in  UK 230V?  single phase +10% - 6%, ie same as Australia and probably Europe? Not directly important to thread but I think its important to state the correct voltages.

All mains voltages were "harmonised" accross the EU to 230v.  Except they weren't.  Nothing was changed anywhere, not a single transformer tap or voltage regulator.  Asymmetric tolerances were convenienly introduced however....

We "changed" from 240 +/-6% to 230 +10% -6%
Southern and eastern Europe went from 220 +/-6% to 230 +6% -10%
Do the maths on minimums and maximums before and after the "change"!

Just typical EU posturing.

So unless you asked a politician, it is entirely correct to say that the UK uses 240/415v.  (Just measured 247 here, but I am close to the substation)
 

Online Jeroen3

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Re: vintage lathe restoration - 3 phase supply.
« Reply #41 on: August 31, 2016, 11:07:30 am »
I thought this might be the neutral wire.  Of uncertain importance to steady three phase power, but could it be important to the convertor to have unbalanced currents going this way rather than via other phases?
Neutral is often used for control electronics, such as contactors. Not required for three phase electronic axle though.

You can't "just whack on a vfd", the motor needs reinforced insulation for that to work otherwise you will need to de-rate significantly. Get in touch with a vfd manufacturor first before buying one from ebay.

Swapping phases could work. The operation manual of your converter states:
Quote
Care should be taken with the connection of the machine to the output socket. If the
machine has a contactor starter the 400/415v-control coil must be fed from the phases
marked L1 and L2. If the control circuit is fed incorrectly (i.e. connected to the phase
marked L3) the contactor could chatter when operating. ....[more]....
in big bold text.
Which looks like what is happening. (watched video without sound)

Other method would be soft-start, which is more common on big stuff. But only if the converter is indeed not able to start it (wrong kVa:kVa ratio). But your lathe can't do that, I think.
 

Offline PaulAm

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Re: vintage lathe restoration - 3 phase supply.
« Reply #42 on: August 31, 2016, 03:14:35 pm »
A good installation with a VFD would entail rewiring the lathe.  They're not real happy when you use the machine controls to stop or reverse.  I use a VFD on a shear with good results, but when I use it on a drill press it always faults when using the drillpress on/off controls.

I use a rotary converter on a similar sized lathe and it works fine except for the highest speeds.   It's a 7.5hp converter with a 30A 220 breaker and it will always trip at the top end.  Current draw can get excessive when trying to spin up that much iron.

I'd put a clamp on ammeter and see what the draw is and if that looks reasonable I'd suspect a contactor  or internal wiring problem.
 

Offline woodchips

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Re: vintage lathe restoration - 3 phase supply.
« Reply #43 on: August 31, 2016, 03:25:13 pm »
Start from the beginning again.

It came from a lab, so presumably worked ok connected to a 400V 3ph supply. Therefore it should also work ok when connected to a simulated 3ph supply from a rotary converter.

The tricky questions. The rotary converter outputs 400V 3ph?. What size is the motor in the rotary converter? If you are trying to start 7hp then it really needs to be pretty close to 7hp.

Ah, those awful contactors! Just scrapped an A&S with those in, updating them to modern contactors is a really good idea, BUT, make sure you have an ACCURATE circuit diagram first.

Testing a rotary, or static, converter is simple, al you need is three analogue voltmeters that will read to 500V AC. Connect the VM across the three phases, start lathe whilst watching the voltmeters. One phase will stay pretty close to 400V, one phase will dip, one phase will rise. It is the amount of dip and rise that is important. Using the 400V meter as a base, the dip and rise from that reading should be similar, within 20V or so. Now try the high speed and observe the meters. My guess is that the 400 will be similar but the dip and rise will be very much larger, 100V or more. This means that the capacitor phase splitter in the converter isn't large enough.

If you want three Avo8 meters they are here for the taking, just off to the scrappy. I have three of the equivalent GEC Selectest meters, no real difference other than they don't explode if you drop them.

Last comment, don't even think about fitting a VFD. The static/rotary converter will quite happily run this sort of machine.

 

Offline capnahab

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Re: vintage lathe restoration - 3 phase supply.
« Reply #44 on: August 31, 2016, 04:41:52 pm »
Woodchips - cheers, the phase converter is 11 kilowatt - 15 HP. Should be man enough ?. I have two multimeters, could get another. When you say measure voltage across the three phases how do that for each multimeter - ? Between switch position 2+4,2+6 and 4+6.
 

Offline IanB

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Re: vintage lathe restoration - 3 phase supply.
« Reply #45 on: August 31, 2016, 05:34:11 pm »
Woodchips - cheers, the phase converter is 11 kilowatt - 15 HP. Should be man enough ?. I have two multimeters, could get another. When you say measure voltage across the three phases how do that for each multimeter - ? Between switch position 2+4,2+6 and 4+6.

A three phase supply typically has four power conductors: L1, L2, L3  and N. The neutral may be absent in some configurations. L1 - L3 are the "live" wires. With a 415 V supply, you will measure 415 V AC between any pair of live wires, e.g between L1 - L2, between L2 - L3 and between L3 - L1. These are the three voltages woodchips is asking you to measure, as they come out of the rotary converter.
I'm not an EE--what am I doing here?
 

Offline woodchips

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Re: vintage lathe restoration - 3 phase supply.
« Reply #46 on: August 31, 2016, 05:41:52 pm »
Yes, between the three live wires. Really two voltmeters are all that is required but the third is really really useful! Once the reference phase is identified then can use a DVM there, really just making sure that the voltage doesn't drop too much. Note that the voltmeters will all be floating at 230V ac doing these measurements, don't touch, put them on an insulating surface.

11kW, umm, are you sure this is a rotary converter? That it has a 11kW induction motor inside the cabinet? If it has then with the 11kW transformer it must weigh 150+ kg. Might be worth a look inside to see exactly what is there, with the mains off!

There won't be a neutral from the converter, it can't easily create one. Any neautral will be from the 230V supply and is essentially useless for anything.
 

Offline capnahab

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Re: vintage lathe restoration - 3 phase supply.
« Reply #47 on: August 31, 2016, 06:28:57 pm »
Yes it is very heavy. Theres a box with the capacitors and a bit of circuitry, and a big motor off the back. See pics.the second one is measuring the input voltages with the front door open.
 

Offline edpalmer42

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Re: vintage lathe restoration - 3 phase supply.
« Reply #48 on: August 31, 2016, 07:54:37 pm »
Actually, if I'm interpreting the specs correctly, it looks like the converter is running at full capacity.  Although it's rated for 11 KW, that's when more than one motor is involved.  It's only rated to start a 7.5 KW (10.0 HP) motor, which is what you've got.  So it should be able to do the job, but not much more.

Ed
 

Offline tautech

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Re: vintage lathe restoration - 3 phase supply.
« Reply #49 on: August 31, 2016, 08:07:34 pm »
Actually, if I'm interpreting the specs correctly, it looks like the converter is running at full capacity.  Although it's rated for 11 KW, that's when more than one motor is involved.  It's only rated to start a 7.5 KW (10.0 HP) motor, which is what you've got.  So it should be able to do the job, but not much more.

Ed
Look again, it's only 7.5 HP
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Offline tautech

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Re: vintage lathe restoration - 3 phase supply.
« Reply #50 on: August 31, 2016, 08:10:48 pm »
If you want three Avo8 meters they are here for the taking, just off to the scrappy. I have three of the equivalent GEC Selectest meters, no real difference other than they don't explode if you drop them.

Last comment, don't even think about fitting a VFD. The static/rotary converter will quite happily run this sort of machine.
Yep moving coil meters will be better to "see" what is happening than DMM's.
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Offline edpalmer42

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Re: vintage lathe restoration - 3 phase supply.
« Reply #51 on: August 31, 2016, 08:29:07 pm »
Actually, if I'm interpreting the specs correctly, it looks like the converter is running at full capacity.  Although it's rated for 11 KW, that's when more than one motor is involved.  It's only rated to start a 7.5 KW (10.0 HP) motor, which is what you've got.  So it should be able to do the job, but not much more.

Ed
Look again, it's only 7.5 HP

Doh!  Got confused between KW and HP.  Sorry!  :-[

Ed

P. S.  Double Doh!  Sorry for double posting earlier.  I looked in the thread and didn't my message so I thought I'd hit the wrong button. 
« Last Edit: August 31, 2016, 08:31:47 pm by edpalmer42 »
 
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Offline woodchips

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Re: vintage lathe restoration - 3 phase supply.
« Reply #52 on: August 31, 2016, 08:38:41 pm »
Does the box have a large auto transformer in it? Need to step the 230V up to 400V and at 11kW will be about 8 or 9" cube sort of size.

Caps look a bit anaemic too.
 

Offline capnahab

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Re: vintage lathe restoration - 3 phase supply.
« Reply #53 on: August 31, 2016, 09:04:08 pm »
Ok gentlemen (and ladies). I have at last found time from my chauffeuring duties.
Voltages across the three wires. measured singly , haven't got enough clip on test leads at the mo.

Lathe at rest
A-B 438 volts
A-C 450 volts
C-B 437 volts

Motor on low speed, no chuck turning,
A-B 433
A-C 430
C-B 414

Motor on low speed, chuck turning at fastest possible in low speed, 380 rpm (max mechanical load)
A-B 428
A-C 415
C-B 413

Motor attempted start in high speed, but motor never starts.
A-B drop to 370
A-C drop to 320
C-B drop to 360

Looks to my uneducated eye that  ? wire B is the weakling (? generated circuit) and perhaps I should swap B and C ?. ( see Jeroen's post above.).
 

Offline capnahab

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Re: vintage lathe restoration - 3 phase supply.
« Reply #54 on: August 31, 2016, 09:13:28 pm »
Sorry scratch that last sentence, don't know what I am talking about.
 

Offline tautech

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Re: vintage lathe restoration - 3 phase supply.
« Reply #55 on: August 31, 2016, 09:14:46 pm »
Ok gentlemen (and ladies). I have at last found time from my chauffeuring duties.
Voltages across the three wires. measured singly , haven't got enough clip on test leads at the mo.

Lathe at rest
A-B 438 volts
A-C 450 volts
C-B 437 volts

Motor on low speed, no chuck turning,
A-B 433
A-C 430
C-B 414

Motor on low speed, chuck turning at fastest possible in low speed, 380 rpm (max mechanical load)
A-B 428
A-C 415
C-B 413

Motor attempted start in high speed, but motor never starts.
A-B drop to 370
A-C drop to 320
C-B drop to 360

Looks to my uneducated eye that  ? wire B is the weakling (? generated circuit) and perhaps I should swap B and C ?. ( see Jeroen's post above.).
Of course it's worth a try but the motor rotation will change should it run.
Is your lathes rotation reversed using the motor control or a gearset in the headstock?
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Offline Ian.M

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Re: vintage lathe restoration - 3 phase supply.
« Reply #56 on: August 31, 2016, 09:16:13 pm »
If you swap any two wires, it will reverse the motor.   To keep it running the same way you have to rotate the wire sequence. 
e.g. Labeling the wires in lower case and the terminals in upper case, either a=>B
b=>C
c=>A

or
a=>C
b=>A
c=>B
 
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Offline capnahab

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Re: vintage lathe restoration - 3 phase supply.
« Reply #57 on: August 31, 2016, 09:27:35 pm »
The lathe chuck rotation is reversed mechanically by gears in the headstock. Thanks for the tip about reversing the motor and not just swapping.
 

Offline edpalmer42

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Re: vintage lathe restoration - 3 phase supply.
« Reply #58 on: August 31, 2016, 09:29:47 pm »
When I look at the picture of the switchgear, I see 4?, 6? relays/contactors.  When you push the slow button, I'd expect one or more of the relays to operate.  What about when you push the fast button?  Any change in the relays?

Any one of the relay or switch contacts could be dirty or have a broken or loose wire.

Ed
 

Offline tautech

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Re: vintage lathe restoration - 3 phase supply.
« Reply #59 on: August 31, 2016, 09:31:20 pm »
The lathe chuck rotation is reversed mechanically by gears in the headstock. Thanks for the tip about reversing the motor and not just swapping.
Swap a phase by all means and if it runs you can use the headstock gear set in reverse to run the lathe as normal.
Might be an ugly fix but a fix nonetheless.
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Offline capnahab

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Re: vintage lathe restoration - 3 phase supply.
« Reply #60 on: August 31, 2016, 09:50:20 pm »
Tautech, - I wasn't suggesting Imwas going to swap a pair of phases, it would only give me a limited range of forward speeds, and yes an ugly fix, - just saying thanks as I had forgotten that swapping a pair of wires would reverse the chuck.
Ed- there is no audible action in any switchgear when I hit fast. I have phoned the lathe manufacturer ( Dean Smith and Grace) for the circuit diagram.
 

Offline woodchips

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Re: vintage lathe restoration - 3 phase supply.
« Reply #61 on: August 31, 2016, 09:53:39 pm »
The direction of rotation is an irrelevance at the moment, particularly as it doesn't seem to rotate at all.

Which phase is the one straight from the output of the autotransformer? Looks like AB or BC, but the voltage shouldn't drop that much considering you have the other motor running all the time, it does run all the time?
 

Offline stj

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Re: vintage lathe restoration - 3 phase supply.
« Reply #62 on: September 01, 2016, 01:51:49 am »
thoughts.

why does the motor plate say "BRUSH", does it use brushes?

and this worked at some point, so a wiring fault is unlikely - probably a burned contact or open coil on one of the contactors.
 

Offline tautech

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Re: vintage lathe restoration - 3 phase supply.
« Reply #63 on: September 01, 2016, 02:03:47 am »
why does the motor plate say "BRUSH", does it use brushes?
It's a generic motor plate used for most Crompton Houston motors, notice there are NO specs for any brush listed. Some single phase high torque motors used brushes for starting torque the switched to plain induction for run mode.
« Last Edit: September 01, 2016, 02:05:58 am by tautech »
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Offline edpalmer42

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Re: vintage lathe restoration - 3 phase supply.
« Reply #64 on: September 01, 2016, 03:01:47 am »
In case you haven't found it, here's a 41 page message thread on DS&G lathes: http://www.practicalmachinist.com/vb/general/dean-smith-grace-lathe-owners-164418/

Ed
 

Offline edpalmer42

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Re: vintage lathe restoration - 3 phase supply.
« Reply #65 on: September 01, 2016, 03:07:18 am »
Ed- there is no audible action in any switchgear when I hit fast. I have phoned the lathe manufacturer ( Dean Smith and Grace) for the circuit diagram.

But when the unit isn't running and you hit the fast button there's a *very* audible action.  I'm really suspicious of that switchgear.

Ed
 

Offline capnahab

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Re: vintage lathe restoration - 3 phase supply.
« Reply #66 on: September 01, 2016, 06:10:44 am »
All that very audible action is from the chattering of the rotary converter.
 

Offline eKretz

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Re: vintage lathe restoration - 3 phase supply.
« Reply #67 on: September 01, 2016, 07:22:02 am »
A good installation with a VFD would entail rewiring the lathe.  They're not real happy when you use the machine controls to stop or reverse.  I use a VFD on a shear with good results, but when I use it on a drill press it always faults when using the drillpress on/off controls.

I use a rotary converter on a similar sized lathe and it works fine except for the highest speeds.   It's a 7.5hp converter with a 30A 220 breaker and it will always trip at the top end.  Current draw can get excessive when trying to spin up that much iron.

I'd put a clamp on ammeter and see what the draw is and if that looks reasonable I'd suspect a contactor  or internal wiring problem.

Yes, a machine's original switch gear should never be used to switch the motor when a VFD is installed - all switching should be managed by the VFD. If desiring to use the original switch gear it can be used to control the VFD remotely using low voltage signals. To avoid faults when accelerating or decelerating heavy inertial loads, set the accel/decel ramps so that accel/decel takes a little longer, this gives a soft start/stop effect and removes some of the spike in current. If you need rapid braking you'll have to install a DC load resistor to take the brunt of the load off of the VFD.

In this case, a VFD would be fine. Using one to convert single to 3 phase but not utilizing the frequency adjustment is pretty safe as far as "old motors with poor insulation" go - most of the older motors were built a hell of a lot better than their modern counterparts - especially those from suppliers of reputable companies like DSG. I've seen VFDs installed on hundreds of old machine tools with their original motors (using the frequency adjustment) and nary a problem if the motors are in good shape to begin with.
« Last Edit: September 01, 2016, 04:15:25 pm by eKretz »
 

Offline capnahab

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Re: vintage lathe restoration - 3 phase supply.
« Reply #68 on: September 01, 2016, 02:19:24 pm »
Dean Smith and Grace true to their reputation have come up with the goods. It helps that I live next door  ;) I have attached the circuit diag that is likely the one.
The service manager is in the field but says
- dual wound motor
- Burdon resistors on the high range that could be at fault (don't know how to test the motor or resistors...)
He suggests checking the resistance of each winding and the resistors in the panel.
he also mentioned checking the contacts on the 2R contactor (whats that ?)
Cheers
Nick
 

Offline Andy Watson

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Re: vintage lathe restoration - 3 phase supply.
« Reply #69 on: September 01, 2016, 03:41:47 pm »
Wow! I am amazed that DSG are still alive.

The diagrams shows that all the auxiliary electrics (contactors and lighting etc.) are fed from L1 and L3 - as has already been mentioned, these need to correspond to the phases given in the convertor instructions (L1 and L2 - I think).

What's that pneumatic/hydraulic looking contraption in the bottom right of the control box - is it a mechanical damper operating on the contactor?


he also mentioned checking the contacts on the 2R contactor (whats that ?)
Contactors are multi-way arrangments of contacts that are closed (or opened) simultaneously. In this case the contactors are operated electriccally by a solenoid. There are four lablled LS, HS, m2 and 2R - Low speed, High speed, Motor 2 (coolant motor) and one that removes the resistors from circuit. I am guessing that the last is time delayed such that the motor starts in high speed with the resistors in circuit. Then after a short delay the resistors are shorted-out.
 

Offline capnahab

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Re: vintage lathe restoration - 3 phase supply.
« Reply #70 on: September 01, 2016, 03:59:34 pm »
between the switch and the motor there is another box (see below) that I could possibly measure the resistance of each phase in ?.

 

Offline edpalmer42

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Re: vintage lathe restoration - 3 phase supply.
« Reply #71 on: September 01, 2016, 04:12:17 pm »
I just noticed what could be a disconnected wire in the switchgear.  See attached detail from the top left corner of the switchgear photo.
 

Offline Andy Watson

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Re: vintage lathe restoration - 3 phase supply.
« Reply #72 on: September 01, 2016, 04:17:21 pm »
I just noticed what could be a disconnected wire in the switchgear.  See attached detail from the top left corner of the switchgear photo.
I think that is a connection to the bottom of the contactor solenoid - all the other contactors have a similar connection.
 

Offline capnahab

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Re: vintage lathe restoration - 3 phase supply.
« Reply #73 on: September 01, 2016, 05:00:33 pm »
I have rotated the phases
A>B, B>C, C>A and here's the video. Early days but looks successful, the RPC hardly noticed and takes about 10 seconds to get up to 700rpm which isn't bad for a 14 inch chuck weighing about 80 pounds. Its nice to have the circuit diagram. I may need to replace the whole panel eventually. Having said that everything on the lathe is built to last a very long time.

Thanks very much guys for all your interest and help. Really appreciate it as it gave me the confidence to fiddle with the wiring.

https://youtu.be/are3efuZQZk
 

Offline Andy Watson

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Re: vintage lathe restoration - 3 phase supply.
« Reply #74 on: September 01, 2016, 05:08:56 pm »
Great news.

Having said that everything on the lathe is built to last a very long time.

Yes. I am extremely jealous ;)
 

Offline xygor

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Re: vintage lathe restoration - 3 phase supply.
« Reply #75 on: September 01, 2016, 05:19:46 pm »
You can't go from Fast to Slow and vice versa because they lock each other out.  Nothing should happen if you press Fast while it is already running in Slow, which is what you said happens.
There does appear to be a centrifugal switch called HS which activates 2R.
 

Offline xygor

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Re: vintage lathe restoration - 3 phase supply.
« Reply #76 on: September 01, 2016, 05:33:26 pm »
I think Jeroen3 nailed it.
"Similarly, a control transformer and/or lighting transformer with a primary winding of 415v must be fed from the L1 and L2 phases."
The control and lighting is on L1 and L3 on the lathe, so these must connect to L1 and L2 (or L2 and L1) on the converter.
 

Offline edpalmer42

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Re: vintage lathe restoration - 3 phase supply.
« Reply #77 on: September 01, 2016, 05:39:55 pm »
Congratulations!  So now that you've got it working, what do you plan on doing with it?

Ed
 
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Offline capnahab

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Re: vintage lathe restoration - 3 phase supply.
« Reply #78 on: September 01, 2016, 06:10:37 pm »
Yes I think Jeroen was on the right track , and RTFM of course. The answer was in the manual for the converter.
It still needs a lot of cleaning and restoration. The recommended oil at the time was Castor oil and its congealed everywhere. There are quite a few bits to make. My neighbour is into car rallies , - the ones where you can't have a car thats cost more than £100. So they require a bit of repair , so I have made parts for him.
BTW
the switch had a protective cover over it which is one of the few parts that is damaged (see pic ) - what is this material ?, or , what can i use to replace it ?.
 

Offline Andy Watson

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Re: vintage lathe restoration - 3 phase supply.
« Reply #79 on: September 01, 2016, 06:17:16 pm »
Looks like SRBP/Paxolin. Try ebay for small quantities.
 

Offline eKretz

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Re: vintage lathe restoration - 3 phase supply.
« Reply #80 on: September 01, 2016, 06:20:54 pm »
You could also use micarta or G10.
 

Offline IanB

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Re: vintage lathe restoration - 3 phase supply.
« Reply #81 on: September 01, 2016, 06:23:21 pm »
the switch had a protective cover over it which is one of the few parts that is damaged (see pic ) - what is this material ?, or , what can i use to replace it ?

It looks like some kind of resin bonded laminate. I think you could make a replacement out of PCB material, without any copper cladding.
I'm not an EE--what am I doing here?
 

Offline woodchips

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Re: vintage lathe restoration - 3 phase supply.
« Reply #82 on: September 01, 2016, 06:29:08 pm »
It seems that the circuit is for a two speed, two motor lathe, has yours actually got two physical motors rather than a multiwinding single motor where the windings are switched.

At least it works, start hacking metal now. Should be good to put a 1" drill straight in, no pilot!

What fixing doeas the lathe chuck have onto the spindle? Can't really see but is it an L2? Looking for an L2 spindle, so if you scrap the lathe........
 

Offline xygor

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Re: vintage lathe restoration - 3 phase supply.
« Reply #83 on: September 01, 2016, 06:38:46 pm »
It seems that the circuit is for a two speed, two motor lathe, has yours actually got two physical motors rather than a multiwinding single motor where the windings are switched. ...
The two motors are spindle (main) and coolant pump.
 

Offline tautech

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Re: vintage lathe restoration - 3 phase supply.
« Reply #84 on: September 01, 2016, 08:03:25 pm »
Yes I think Jeroen was on the right track , and RTFM of course. The answer was in the manual for the converter.
It still needs a lot of cleaning and restoration.
Good old White Spirits and elbow grease worked great when I cleaned all the grud from my lathe.


Quote
The switch had a protective cover over it which is one of the few parts that is damaged (see pic ) - what is this material ?, or , what can i use to replace it ?.
As suggested it's Paxolin, an industrial Formica type material.
Any stiff plastic will suffice but it won't be as flame resistant.
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Offline Delta

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Re: vintage lathe restoration - 3 phase supply.
« Reply #85 on: September 01, 2016, 08:04:37 pm »
Glad you got it working mate!   :-+

I'd I've learned something new!  https://en.wikipedia.org/wiki/Dahlander_pole_changing_motor
 

Offline eKretz

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Re: vintage lathe restoration - 3 phase supply.
« Reply #86 on: September 02, 2016, 01:59:33 pm »
It seems that the circuit is for a two speed, two motor lathe, has yours actually got two physical motors rather than a multiwinding single motor where the windings are switched.

At least it works, start hacking metal now. Should be good to put a 1" drill straight in, no pilot!

What fixing doeas the lathe chuck have onto the spindle? Can't really see but is it an L2? Looking for an L2 spindle, so if you scrap the lathe........

Haha! At least I HOPE you're kidding! That's a prime specimen of fine old British iron. I bet he'd scrap his wife before he scrapped that machine! And it ought to be able to drive way larger than a measly 1" drill straight in. Probably more like 3" - 4"! The spindle is likely a D1-6 anyway.
 

Offline capnahab

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Re: vintage lathe restoration - 3 phase supply.
« Reply #87 on: September 02, 2016, 02:26:15 pm »
Not sure the wife knows I have it..
The biggest drill I have is 60mm I think. Wil post some video.
Meanwhile I need some led bulbs , 2.5 v, 0.3 amp MES10  for the front panel and will try and source / make new coloured plastic domes. Perhaps I should start another thread.
 

Offline IanB

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Re: vintage lathe restoration - 3 phase supply.
« Reply #88 on: September 02, 2016, 05:28:03 pm »
Haha! At least I HOPE you're kidding! That's a prime specimen of fine old British iron. I bet he'd scrap his wife before he scrapped that machine! And it ought to be able to drive way larger than a measly 1" drill straight in. Probably more like 3" - 4"! The spindle is likely a D1-6 anyway.

Even if the lathe has the power to do that, good practice would surely be to start small and increase the hole size in steps.
I'm not an EE--what am I doing here?
 

Offline tautech

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Re: vintage lathe restoration - 3 phase supply.
« Reply #89 on: September 02, 2016, 08:16:59 pm »
Haha! At least I HOPE you're kidding! That's a prime specimen of fine old British iron. I bet he'd scrap his wife before he scrapped that machine! And it ought to be able to drive way larger than a measly 1" drill straight in. Probably more like 3" - 4"! The spindle is likely a D1-6 anyway.

Even if the lathe has the power to do that, good practice would surely be to start small and increase the hole size in steps.
Exactly.

Want to test it's capabilities, try a large free turning bar and if the slides are still tight it should peel a 3mm sorry 1/8" cut no problems. That"s 1/4" reduction in diameter each pass. With a lathe like this you can really knock some material off fast, just watch for them curly hot snakes trying to wrap you up when big cuts are taken.
Carbide tools are not so bad, the chip breaker design of the inserts sees to that.
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Offline eKretz

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Re: vintage lathe restoration - 3 phase supply.
« Reply #90 on: September 02, 2016, 11:37:16 pm »
No, best practice is to drill the hole size you need from the solid - unless you only need a drilled hole. Then it depends on run-out and diameter tolerance requirements. If the hole will be bored for finish, drill once slightly under finish size and bore. If reamed finish, drill slightly under finish size, true with boring bar or core drill and finish ream.

The whole point of a machine like this is to be able to eliminate all the unnecessary steps that need to be taken with a hobby grade machine. These machines were built to get work done FAST.

With 7.5 HP that machine would be good for between 1/8" to 1/4" depth of cut per side with carbide tooling. If the chips are peeling off it's running too slow. This will damage carbide as surely as running too fast. Good roughing speed for mild steel is 300 - 400 SFPM - for harder steel or tool steel alloys 250 SFPM. Finishing can be as high as 500 - 1100 SFPM with modern carbide tooling.
 

Offline tautech

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Re: vintage lathe restoration - 3 phase supply.
« Reply #91 on: September 03, 2016, 12:00:40 am »
No, best practice is to drill the hole size you need from the solid - unless you only need a drilled hole. Then it depends on run-out and diameter tolerance requirements. If the hole will be bored for finish, drill once slightly under finish size and bore. If reamed finish, drill slightly under finish size, true with boring bar or core drill and finish ream.

The whole point of a machine like this is to be able to eliminate all the unnecessary steps that need to be taken with a hobby grade machine. These machines were built to get work done FAST.

With 7.5 HP that machine would be good for between 1/8" to 1/4" depth of cut per side with carbide tooling. If the chips are peeling off it's running too slow. This will damage carbide as surely as running too fast. Good roughing speed for mild steel is 300 - 400 SFPM - for harder steel or tool steel alloys 250 SFPM. Finishing can be as high as 500 - 1100 SFPM with modern carbide tooling.
Sure, all that applies if you're pumping suds. Many hobbyists don't as most suds these days are water soluble and unless the lathe is in daily use the risk of the beds and slides rusting is too great.
So lighter cuts and smaller steps for hole drilling until the target diameter is reached, quite easy without suds if you are patient. For much work tool steels are OK and cheaper to equip with from the outset, but firmly limits what is possible if hard steels are encountered.
One can of course apply cutting oils neat and even some of the Rocol metal working pastes work fine for bigger cuts and hard steels.
Boring is the only way to finish holes with reasonable accuracy once an undersize hole has been roughed out.

At the end of the day one must work with the accessories on hand and much like test equipment the cost of the base unit is only the start.
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Offline capnahab

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Re: vintage lathe restoration - 3 phase supply.
« Reply #92 on: September 03, 2016, 07:12:03 am »
Great machining discussion, I think we will be kicked off here soon for OT but have a look at this guys videos - https://youtu.be/0cOhA2y8y6A
About 18.5 minutes in. Fantastic metal mowing. He really knows his stuff. I won't be using flood coolant as Tautech suggests.
eKretz - exactly.
There is a bit of a move towards spray mist coolant.

My biggest problem now is lifting the chuck and work on and off. Will need some sort of engine lift / hoist.
 

Offline tautech

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Re: vintage lathe restoration - 3 phase supply.
« Reply #93 on: September 03, 2016, 07:52:13 am »
Great machining discussion, I think we will be kicked off here soon for OT but have a look at this guys videos .....
I don't see why, this is your thread.

Quote
My biggest problem now is lifting the chuck and work on and off. Will need some sort of engine lift / hoist.
Will you really be doing such large/heavy work ?

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Offline Gyro

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Re: vintage lathe restoration - 3 phase supply.
« Reply #94 on: September 03, 2016, 09:28:29 am »

My biggest problem now is lifting the chuck and work on and off. Will need some sort of engine lift / hoist.

I'm not sure I'd want to be you first patient on a Monday morning - not after a weekend of lugging heavy chucks around and playing with your cutting depth!  ;D
Chris

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Offline woodchips

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Re: vintage lathe restoration - 3 phase supply.
« Reply #95 on: September 03, 2016, 11:48:43 am »
I agree with eKretz. Pilot holes are only for underpowered and, more important, flimsy machines. Must say that a pilot the size of the central web on the drill is easier than relieving the web to cut better. Just the same on a drill press, but only if the work is bolted down.

Had a visit from Harrison lathes when at school, back in the 60's, and their idea of a pro[per lathe was for it to ruduce a bar the size of the headstock spindle bore in one cut. For years I had just such a piece of swarf, and it wasn't 2 thou feed rate either. Their vist impresse me so much that when I bought a decent lathe I got a Harrison L5A. Must say that my brothers Colchester Student is evem better, look at the width of the bed.
 

Offline capnahab

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Re: vintage lathe restoration - 3 phase supply.
« Reply #96 on: September 03, 2016, 04:43:51 pm »
Nothing too heavy and not a great chip but heres some 3 inch titanium as a starter. Titanium seems to have a bad reputation for machining but I like it more than steel. If you get it too hot you can have an exciting fire as it burns like magnesium wire..

https://youtu.be/ZmKt9hXkB20
 

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Re: vintage lathe restoration - 3 phase supply.
« Reply #97 on: September 03, 2016, 04:45:50 pm »
 

Offline SeanB

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Re: vintage lathe restoration - 3 phase supply.
« Reply #98 on: September 03, 2016, 08:00:02 pm »
Tip for those relays is simply to clean the contacts, using a contact file ( or the smallest flat file in a set of regular needle files) to get the surfaces mostly flat. Nothing too rough, just take the bumps off once every few years and the contacts will survive. The broken insulator is Bakelite, available from most industrial material suppliers of plastics, so just get a small offcut of the right dimensions and cut with metalworking saws, avoiding the dust.

LED lights for the lathe are available, but the original lights are still available from the larger industrial suppliers, or they have LED retrofit kits. LED lighting for the work area is good, buy a good quality waterproof one ( and 2 spare ones, they will be broken sometime or the other) with a separate 12V transformer, and a decent mount. A smaller one on a magnetic clamp will also be invaluable.
 

Offline tautech

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Re: vintage lathe restoration - 3 phase supply.
« Reply #99 on: September 03, 2016, 11:34:07 pm »
It will be interesting to see how hard you can push this 3 phase lathe from a single phase supply.
Do you have access to a current clamp, preferably one with peak hold?
Bigger cuts at high speeds will be a good test.

If your supply is via a breaker at good trick is to the highest class "motor" rated breaker that allow significant periods and percentages of overload before they trip.
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Offline eKretz

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Re: vintage lathe restoration - 3 phase supply.
« Reply #100 on: September 04, 2016, 05:32:07 am »
Spray mist coolant would be a very good move. Machining without some form of coolant is a pretty big handicap - both to working speed and to tooling life. The largest cut I ever took on a lathe with carbide was about ¾" per side at .077" feed rate. That was a 52" swing lathe, an old German made machine called Schiess. I served my apprenticeship in a very large shop that did a lot of repair and new work for the big steel mills - US Steel, Inland, I/N Tek, Arcelor Mittal, etc. The largest lathe was a Niles with 72" swing, it had something like a 200 HP DC drive. That was a cool place to work.

Water soluble coolants won't cause rusting of the lathe unless they're mixed too thinly. Mixed in the correct ratio, they leave behind an oily residue - at least the good quality ones do.
« Last Edit: September 04, 2016, 05:36:55 am by eKretz »
 

Offline capnahab

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Re: vintage lathe restoration - 3 phase supply.
« Reply #101 on: September 04, 2016, 09:10:27 pm »
The largest cut I ever took on a lathe with carbide was about ¾" per side at .077" feed rate.
- blimey. making my lathe look small.

tautech, - yes me too, will try and get hold of a current clamp. When I turn fast motor on and go up to 720 rpm the motor on the converter speeds up a bit  but it docent struggle to keep the lathe going. As you say I will be interested in how much current it draws.

Meanwhile I have nearly got a replacement for the switch contact cover.
G10 I think.
 

Offline tautech

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Re: vintage lathe restoration - 3 phase supply.
« Reply #102 on: September 04, 2016, 09:40:40 pm »
Spray mist coolant would be a very good move.
How is that normally done?
Is a higher pressure pump required?
Are "off the shelf" submersible spray mist pumps available?
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Offline Cyberdragon

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Re: vintage lathe restoration - 3 phase supply.
« Reply #103 on: September 04, 2016, 10:38:08 pm »
You can get kits to add spray lubricators to metal working machines that don't have them.
Take your pick
http://koolmist.com
http://www.sterlinggundrills.com/spraymist-kits.php
http://littlemachineshop.com/products/product_focus.php?Focus=Coolant
Exc.
*BZZZZZZAAAAAP*
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Offline eKretz

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Re: vintage lathe restoration - 3 phase supply.
« Reply #104 on: September 05, 2016, 07:34:59 am »
Normally the spray mist coolant is distributed with compressed air. The liquid coolant is pulled into a mid pressure air stream via siphon - the air is passed over the top of a liquid pick-up tube. So no liquid pump is necessary, only compressed air. The better systems are actually quite impressive, almost able to cool as well as flood coolant. They can be adjusted to provide from hardly any liquid to quite a lot. For most modern carbide machining (high speed, high feed, low D.O.C. - mostly CNC machines with recirculating ball guide ways) they are more than adequate. Flood coolant still rules the roost for heavier duty box way machine tools and drilling though.

BTW, just found a couple old photos you might find interesting. One is of the old 52" Schiess lathe on which I was O.D. grinding a tapered journal, the other is an ~24" swing American engine lathe on which I made a replacement crankshaft for a large air compressor.





Capn, the switch cover looks good, nice job.
« Last Edit: September 05, 2016, 08:00:33 am by eKretz »
 
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Offline Len

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Re: vintage lathe restoration - 3 phase supply.
« Reply #105 on: September 05, 2016, 03:47:15 pm »
You can get kits to add spray lubricators to metal working machines that don't have them.
Take your pick
http://koolmist.com
http://www.sterlinggundrills.com/spraymist-kits.php
http://littlemachineshop.com/products/product_focus.php?Focus=Coolant
Exc.

Or you can make your own using a soda bottle:
[Edit: Skip to 9:30. Stupid forum software screwed up the youtube link.]

https://youtu.be/G3wUoPdK_ms
 

Offline capnahab

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Re: vintage lathe restoration - 3 phase supply.
« Reply #106 on: September 05, 2016, 04:17:32 pm »
Lovely to see the old lathes and methods at work. The crankshaft must have needed a lot of careful setup, - makes neurosurgery seem a bit crude, tho at times it can be very elegant.
 

Offline eKretz

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Re: vintage lathe restoration - 3 phase supply.
« Reply #107 on: September 05, 2016, 06:18:14 pm »
Yes large crankshafts do need a lot of careful setup. Order of operations is also critical - if things are done in the wrong order it can result in scrap due to distortion/movement of the steel. Drilling the oil holes from one journal to the other on large crankshafts (sometimes the holes can be 2 or 3 feet deep!) can also be an interesting proposition.
 

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Re: vintage lathe restoration - 3 phase supply.
« Reply #108 on: September 06, 2016, 08:02:42 pm »
Thanks eKretz,
The most powerful VFD available in the UK is about 2.5-3 Kilowatt. Not sure exactly why.

Most VFDs that have a single phase input I have come across are indeed low power. Higher power VFDs typically have a 3-phase power input (not a problem in industry). If you only have single phase power available in your home, a VFD is therefore not an option for a high power machine...

It is maybe also possible to find high power VFDs with a DC bus input (typically 600Vdc), but then you need to find/built a very capable DC power supply  8)
 

Offline capnahab

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Re: vintage lathe restoration - 3 phase supply.
« Reply #109 on: September 06, 2016, 09:08:57 pm »
Yes this is exactly why VFD won't work for this sort of motor. I can get a 6kW VFD in the UK but it is only 230 volts.
 

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Re: vintage lathe restoration - 3 phase supply.
« Reply #110 on: September 07, 2016, 01:10:05 am »
Thanks eKretz,
The most powerful VFD available in the UK is about 2.5-3 Kilowatt. Not sure exactly why.

Most VFDs that have a single phase input I have come across are indeed low power. Higher power VFDs typically have a 3-phase power input (not a problem in industry). If you only have single phase power available in your home, a VFD is therefore not an option for a high power machine...

It is maybe also possible to find high power VFDs with a DC bus input (typically 600Vdc), but then you need to find/built a very capable DC power supply  8)
All you need is a rectifier made from a large cap or two and some large diodes.
« Last Edit: September 07, 2016, 01:12:15 am by NiHaoMike »
Cryptocurrency has taught me to love math and at the same time be baffled by it.

Cryptocurrency lesson 0: Altcoins and Bitcoin are not the same thing.
 

Online Jeroen3

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Re: vintage lathe restoration - 3 phase supply.
« Reply #111 on: September 07, 2016, 05:29:52 am »
Yes this is exactly why VFD won't work for this sort of motor. I can get a 6kW VFD in the UK but it is only 230 volts.
Get a three phase one, and connect three times one phase. Just like your stove. Which is often >3kW as well. There you just use more wires and a higher amp MCB.
*Not all VFD support this.
 

Offline woodchips

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Re: vintage lathe restoration - 3 phase supply.
« Reply #112 on: September 07, 2016, 04:37:12 pm »
Some comments.

Be cautious using coolant with carbide tooling, if the tool isn't completely flloded all of the time then the thermal shock can break them.

Don't just wire the inputs on a three phase inverter together across a single phase supply. The inverter is assuming the much smoother rectified DC from the three phase. At the very least you will need to up the current rating of the rectifiers and increase the smoothing capacitance.

If running from a DC source then the easiest is to use something like the Farnell/Advance etc DC PSUs stacked in series. These are rated to be connected in series to 250V, so connect to make +200V and -200V having first checked there are no earth connection problems.
 

Offline _Wim_

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Re: vintage lathe restoration - 3 phase supply.
« Reply #113 on: September 07, 2016, 06:28:09 pm »
Thanks eKretz,
The most powerful VFD available in the UK is about 2.5-3 Kilowatt. Not sure exactly why.

Most VFDs that have a single phase input I have come across are indeed low power. Higher power VFDs typically have a 3-phase power input (not a problem in industry). If you only have single phase power available in your home, a VFD is therefore not an option for a high power machine...

It is maybe also possible to find high power VFDs with a DC bus input (typically 600Vdc), but then you need to find/built a very capable DC power supply  8)
All you need is a rectifier made from a large cap or two and some large diodes.


Good tip! I did not think about doing it that way. That is indeed an easy and affordable solution...
 

Offline _Wim_

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Re: vintage lathe restoration - 3 phase supply.
« Reply #114 on: September 07, 2016, 06:32:22 pm »
*Not all VFD support this.

Thats the problem, how to know if your VFD supports this? You wont find such a thing in the manual, as nobody in industry would typically do this. For consumer equipment this is indeed sometimes done (for example my induction cooking plate), but it is also documented in the manual.
 

Offline _Wim_

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Re: vintage lathe restoration - 3 phase supply.
« Reply #115 on: September 07, 2016, 06:34:55 pm »
If running from a DC source then the easiest is to use something like the Farnell/Advance etc DC PSUs stacked in series. These are rated to be connected in series to 250V, so connect to make +200V and -200V having first checked there are no earth connection problems.

I am unsure of what kind of PSUs you are talking about. I would suspect this to be quite an expensive solution for higher powers unless I am missing something
 

Offline PaulAm

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Re: vintage lathe restoration - 3 phase supply.
« Reply #116 on: September 09, 2016, 12:50:35 pm »
You can run most 3 ph VFDs from a single phase supply, you just have to derate them.   I' d had no problems running a 3hp motor on a 5hp VFD fed with single phase, for example.  That's a fixed frequency situation; I'm not sure how well it would work if you're going to use the VFD for speed control.

Of course there's http://www.phaseperfect.com/p/t/overview if you have the money.
 

Offline woodchips

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Re: vintage lathe restoration - 3 phase supply.
« Reply #117 on: September 09, 2016, 08:47:58 pm »
The Farnell etc PSUs are just a standard single voltage brick, many people make them. Something like 24V 10A are common, used in industrial electronics and so few other places they are thrown away, I have just done that so nothing to photograph. Floating switch mode supplies to 250V does not seem a rare atribute.

Make sure you have reverse polarity diodes across the outputs though!
 

Offline cncjerry

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Re: vintage lathe restoration - 3 phase supply.
« Reply #118 on: September 09, 2016, 10:28:59 pm »
without reading back thru this thread, there was a problem between the high and lo speed of the motor.  Was this with/without a chuck?  Meaning did the problem go away without the chuck mounted?
 

Offline tautech

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Re: vintage lathe restoration - 3 phase supply.
« Reply #119 on: September 10, 2016, 07:43:57 pm »
For those following this thread, the OP has started another:
https://www.eevblog.com/forum/repair/restore-lathe-electrial-panel-lights-mainly/
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