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Having issues with 3 phase industrial motor... looking for ideas
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Andy Watson:

--- Quote from: dom0 on October 15, 2019, 02:35:57 pm ---Then it would only turn the wrong way

--- End quote ---
It might turn the wrong way - very inefficiently.
duak:
I think the motor is most likely not wired correctly and the previous VFD was programmed to make it work that way.  If it was configured delta, the V/Hz could have been turned down but to get full power, the current limit could have been turned up perhaps leading to its demise.  A lathe can be a hard load to drive because of the inertia of the spindle & chuck when in the highest or fastest speed.

Just to make sure we're on the same length of wave:

1.) is the motor NEMA or IEC and what voltage is it wired for?  Full specs would be handy but a shot of the data plate is good enough.

2.) is the line input single or three phase?  I expect three because of the power ratings.

3.) how are you measuring the line voltage - leg to leg or leg to neutral?  380 V is not common in the US (or Canada).

Most four pole motors can usually tolerate a 50% speed increase as manufacturers use a similar rotor design in their two pole motors.  On the other hand, the lathe gearing and bearings may not be up to an increase.  Lathe chucks are often cast and have a definite RPM limit; they do indeed come apart.  If they don't disintegrate, they can release the workpiece being held due to being expanded by the radial forces on the jaws and body.
jmelson:

--- Quote from: Corporate666 on October 15, 2019, 03:28:05 am --- The machine is running on 380V 3-phase (measured right at 400V at the input).

The problem is that when the VFD is started, the motor turns at a few RPM and is incredibly jerky.  Then after several seconds, the VFD gives an overheat alarm and errors out. 


-I bypassed the VFD entirely and the 10hp motor in the lathe starts immediately and runs smoothly.  BUT.. when I checked with a clamp on amp meter, I was seeing 30 amps on each phase!  This is essentially with no load (in high-gear, a 1:1 connection thru to the motor). 

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Well, this is not far out of line.  A 10 HP 240 V motor would draw about 30 A per line at idle, then the phase angle changes from nearly 90 degrees to close to zero as the load increases to full load.  This is the typical characteristic of an induction motor, they draw near full-load current but at 90 degrees lagging at idle.

Are you sure the motor is a 380 V motor?  Is it a dual-voltage motor that is now wired for the wrong voltage?

If it is a 240 V motor, then the VFD should be able to be programmed for a different V/F curve, so it gets 240 V at 60 Hz.

What is the current limit setting in the VFD?  It might be set to a much lower default value, causing it to trip on what may be a normal load for a 10 Hp motor.

Jon
Kalin:
Important information needed. Is it a 3 lead motor connection in the peckerhead or possibly 9 lead or 12 lead? I have seen the behaviour in improperly connected 9/12 lead 3 phase motors. I could help you troubleshoot this but more info is needed.
Corporate666:
Thanks for the replies.  I didn't get much of a chance to look more at this today, however I am pretty confident that the issue is the motor is indeed wired for 240V instead of 380V.  It would explain everything that I have observed.  I initially thought the motor may have been wired in delta instead of wye, but didn't pursue this avenue too much, since I had checked the VFD and it was a 380Vin/380Vout vector drive unit, and because the motor is buried in the machine with the wiring on the back side (of course) and the motor plate wedged against the casting, so almost impossible to check either without removing the motor.

The previous drive was most likely set up to operate in V/F mode, whereas the new unit I was operating in sensorless vector mode.   I'll have to dig into the settings a bit to see how to limit the V/F settings, if I can't just re-wire the motor to operate on 380 (which I would prefer).  The new drive does not have a simple Vmax setting I can see, rather it allows adjustment of the V/F curve through numerous parameters... but either way I think I'll try to rewire the motor if feasible instead.

I'll keep you all posted, thanks again!
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