[landslide1]

my drive board has blown and I would like to see if the motor is ok without sending it way for full testing.

I have meged the cable and motor individually between u,v,w and ground. all are over 350Mohm at 1000V

there are no shorts to ground between U,V,W and ground.

U,V,W are connected as a continuity test.

resistance on windings are even (crappy multimeter with 0.2ohm lead resistance)
U-V 0.5ohm (0.3ohm subtracting test leads)
U-W 0.5 ohm
V-W 0.5 ohm
I'm testing this through the motor cable so now I'm thinking I should do it without the cable?

I read in another thread that a test for magnetism is shorting the cables. I shorted the windings and turn the motor by hand and I feel no resistance (demagnetised). can any confirm that this is valid for magnetism?

[Al_The_Man]

The shorting test only applies to a P.M. motor. Not with a induction motor.
Al.

[landslide1]

Thanks Al

can you offer any further advice on how I may verify the motors function? my servo amplifyer blew the igtb with an alarm 12 and I'm tying to get it running again but unsure why it blew in the first place.
I have read it is usually a earth leak or short in the windings. the insulation checks ok from what I have been reading. am i checking the windings correctly? (apart from not using a milli ohm meter).

[guhl]

For detecting inter-turn short-circuit you may use inductance meter. Inductance values have to be similar.
Find blown power transistor in the drive and replace it.

[landslide1]

I ended up taking the motor to an electrical repairer. they megged it and ran it and they say it is ok.

So I’m left wondering what caused the over current alarm and caused the drive to blow?

the only thing not tested on the motor was the pulse generator. the sensor doesn’t seem to have any magnetism.

the input voltages are also differing W110V V124V U146V measured to ground. They are all balanced between phases 212V W-V, W-U, V-U.

the transistor module has been replaced and it boots without error but I’m worried about running it without diagnosing the original cause.

[cincyice58]

I ended up taking the motor to an electrical repairer. they megged it and ran it and they say it is ok. So I’m left wondering what caused the over current alarm and caused the drive to blow?the only thing not tested on the motor was the pulse generator. the sensor doesn’t seem to have any magnetism.the input voltages are also differing W110V V124V U146V measured to ground. They are all balanced between phases 212V W-V, W-U, V-U.the transistor module has been replaced and it boots without error but I’m worried about running it without diagnosing the original cause.

the megohm reading you got of 300megs, was that at the motor or at the drive with u v w disconnected at the bottom of the drive so you checked cables and motor windings together? measuring leg to ground 0-10 megs bad, 10-100 megs going bad, over 1000 ok, so at 300 you may have a motor cable wire breaking down in coolant or oil? But if you had an al 12 on the drive, it is already damaged, send the drive to fanuc for repair.

[oscilloman]

Is there air running over the drive board? Allot of dust? All fans working? Filters are clean? Spindle moves freely when you turn it by hand?

[landslide1]

the spindle and cable have been meged and tested as ok by motor winding/electrical shop.

the spindle board may be damaged but after replacing the transistor module, Im getting AL-02 spindle sensor.

I spoke to a local CNC repairer who was very generous and open with advice and he indicated since the spindle sensor has no magnetism it is likely to be a problem.
he said he uses the magnesium to help set the gap and if you can't feel it then something is wrong with the sensor. He said he would replace the sensor first then check the drive.