Author Topic: vintage lathe restoration - 3 phase supply.  (Read 24870 times)

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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!  :-+
 

Online 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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Online 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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Online 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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Online 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


 

Online 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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Online 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.
 

Online 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
 

Online 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)
 

Offline 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.
 

Online 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.
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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.
 

Online 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
 

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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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