help with spindle motor winding resistance 10hp

[harrimansat]

Hi

Someone knows de resistance value phase to phase for a AC spindle motor 10hp, A06B-1008-B200.

I read 0,008 ohms, is a 200V 35amp motor, I have over current in dc link, but with a 2.2kw motor it Works

Thanks

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[generaldisarray]

phase to phase is a short.
any phase to ground should be greater than 100Megohm

[harrimansat]

yes, but I need to know resistance value pahse to pase for this kind of motor to determine if is good or not, I think that is about 0.040 ohms, but I have 0.008.

[Jim Dawson]

Are all of the phase to phase readings the same? 0.008 does seem a bit low.

[harrimansat]

Yes all three with the same value, I have a driver error over current in dc link, but with a little 2.2kw motor driver works. Fanuc doesn´t have resistance winding data for this type of motor

[Jim Dawson]

I just checked my A06B-0754-B200 7.5KW, 31 amp. I get about 0.1 ohm phase to phase, measured at the drive

I used my Fluke 87-V meter.

[harrimansat]

I just checked my A06B-0754-B200 7.5KW, 31 amp. I get about 0.1 ohm phase to phase, measured at the drive

I used my Fluke 87-V meter.

Thanks, do you have any way to draw the motor with 1 amp DC for example and measure the voltage in mv, or a megger. FKUKE V87 resolution is 0.1 ohms only

[Jim Dawson]

Not easily.

[Eldon_Joh]

Just use a D cell battery, connect a 10 gauge wire, 1 foot or 10 feet long. compare the voltage across the wire with the voltage across the coils in the motor. 1 foot of 10 awg is very close to .0010 ohms. you'll need to check both voltage a few times because the current is going to start dropping pretty quickly. or use two volt meters at the same time.

[Robowi]

For spindle windings you can use an LCR meter. They are much cheaper than a milli ohm meter and give a much clearer answer if your windings are good or bad by measuring inductance. I use this one: https://www.peakelec.co.uk/acatalog/lcr40-atlas-lcr-meter.html

[Eldon_Joh]

For spindle windings you can use an LCR meter. They are much cheaper than a milli ohm meter and give a much clearer answer if your windings are good or bad by measuring inductance. I use this one: https://www.peakelec.co.uk/acatalog/...lcr-meter.html

unfortunately both of the strangers in this thread would have to have the same lcr meter to get any meaningful information.

[Jim Dawson]

unfortunately both of the strangers in this thread would have to have the same lcr meter to get any meaningful information.

Very true, I think it would get close, but that is not really the best way to test a motor. I have a LCR meter but I'm not sure the results would be meaningful. I'm running a job in the lathe so tearing into it to get some readings is not going to happen. If I had the motor on the bench, then I would spend the time to set up a proper test.

I would take the motor to a motor shop and have it checked out. That motor is a standard 3 phase induction motor, not a servo. Running it on a 3 phase line and getting amp readings would be the best test.

[Eldon_Joh]

Very true, I think it would get close, but that is not really the best way to test a motor. I have a LCR meter but I'm not sure the results would be meaningful. I'm running a job in the lathe so tearing into it to get some readings is not going to happen. If I had the motor on the bench, then I would spend the time to set up a proper test.

I would take the motor to a motor shop and have it checked out. That motor is a standard 3 phase induction motor, not a servo. Running it on a 3 phase line and getting amp readings would be the best test.

unfortunately 8milliohms sounds like a direct short across more than just one coil of wire, more like a coil group or between several coils. you'll know really quickly if you have a shorted turn. maybe with a thermal camera you could fix it before a complete rewind is required.

[joeavaerage]

Hi,
I have a milliohm meter, not an expensive one , but still about $800USD. Does a good job down to 1mOhm at about 1%
but will read down to 10uOhm at about 10%. Has proven to be very useful in detecting faults in transformers and high current
paths in welders.

At 8 mOhm is pretty low, what confidence do you have in the accuracy and repeatability of that measurement?

I think you would be better off trying to measure the inductance of the coils, Any shorted turns would show up very dramatically
in an inductance measurement.

Craig

[harrimansat]

Hi, inductance is 0.9mH, I´have used a WAYNE KERR 6425 RLC METER

[joeavaerage]

Hi,
what about the other two phases? Inductance imbalance is quite pronounced in faulty three phase machines.

Craig

[harrimansat]

I have to check it, all that I have is the report from a repair center. When I test the motor with my oscilloscope and a current probe, motor draws 180 amp on start up. Repair center saids that in star configuration motor has 0,23 ohms, and in delta 0,003 ohms!!!!

[john-100]

some thing does not add up

if the 0.23 ohms is the resistance of 2 coils in series

the resistance across 2 wires from the Delta connected motor
will be one coil in parallel with the other 2 coils connected in in series

the resistance will be
the product divided by sum of the parallel resistances

0.115 x 0.23 divided by 0.115 +0.23

= 0.02645/0.345
= 0.0766 ohms which is a lot more than the Repair center said


0,003 ohms looks more like a short circuit

John

[harrimansat]

Thanks John-100, is what I´ve seen.
Now I only need to measure a good motor to compare, or a FANUC motor specs to claim at repair center.
I´m wating for FANUC EU answer

some thing does not add up

if the 0.23 ohms is the resistance of 2 coils in series

the resistance across 2 wires from the Delta connected motor
will be one coil in parallel with the other 2 coils connected in in series

the resistance will be
the product divided by sum of the parallel resistances

0.115 x 0.23 divided by 0.115 +0.23

= 0.02645/0.345
= 0.0766 ohms which is a lot more than the Repair center said


0,003 ohms looks more like a short circuit

John

[harrimansat]

Anyone else has a FANUC spindle motor and a low resistance meter?