[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

[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]

Thanks for all, motor was OK, report from remanufacturer had one more zero, in delta is 0,09 ohms, not 0,009 ohms. The problem was a intermitent failure in one of the current meters, isolated amplifiers in servo driver.

So, for this kind of motor these resistance values are ok, 0,23 in star, and 0,09 in delta

[landslide1]

Thanks for all, motor was OK, report from remanufacturer had one more zero, in delta is 0,09 ohms, not 0,009 ohms. The problem was a intermitent failure in one of the current meters, isolated amplifiers in servo driver.

So, for this kind of motor these resistance values are ok, 0,23 in star, and 0,09 in delta

could you give me some more info on how you fixed the servo driver?
I have a 6055 drive that has good wave forms on the drive board but is still giving AL-12 and the motor is ok like yours.

[harrimansat]

Thanks Robowi, I can measure inductance too, but I need a good motor to compare, now my motor has 0.9mH and 0.003 ohms phase to phase.

[metalcutting]

Make motor off line and put +05 -05 v in phase to phase and see the voltage dropping phase to phase and compare to earth

[harrimansat]

Thanks Robowi, do you know how I can calculate the current in a motor with no load, motor has 0.9mH 0.09ohms at 200V 50 Hz 4 poles

[joeavaerage]

Hi,
a calculation like that is not so simple, The data you have might adequately describe the electrical properties of the stator but what you don't know is
the back EMF generated by the rotor once it starts to spin.

If there were no rotor and therefore no back EMF then the current calculation goes something like this:

I(amps) = V_in / ( R_stator + jx2x50xPIx L_stator )
I =200 / (0.09 + j x 0.282)

Thus the current is primarily inductive;
I (approx.)=200/2.82
I =707 A (inductive)

Its not uncommon for a simple calculation like this to produce astonishing results. This situation would occur if you directly connected 230V AC to the motor and flipped
the switch. It would almost certainly take out the fuses and/or circuit breakers. That would be the inrush current. Once the motor starts spinning the back EMF will
reduce the current substantially.

Lets do the calculation but instead of 50Hz input voltage lets assume 400Hz as would be supplied by a VFD at maximum speed.
I= 200/(0.09 +j x 2.26)
I=88A (inductive)

Even at 400 Hz the inrush current is still very high, but prehaps not faulty either.

I understand you are looking for some clear test to determine whether the motor is faulty or not. Doing a calculation of peak inrush current
is not especially informative.

Until recently I worked for a company that had a big three phase Variac. Had you presented the motor to me for testing I would have followed the path
you have taken but arrived at the conclusion that to attempt to connect direct to three phase power was going to end in disaster.
I would however have been able to use the Variac and so present as little as 5V-10V AC three phase to it. That is I could test it in such a manner
that even if it were faulty there would still be no sparks or smoke!

In absence of a three phase Variac you will have to use a VFD but ensure that the V,f gradient is such that the current remains low until you can establish
whether its good or not.

Craig