Servo Drive Issues - Not many Caps

[bdoss@calysta.com]

Having trouble with an API Controls brushless servo drive; drive does not properly control motor, rather, motor just stutters and hums rather than rotating smoothly. Have positively tested the motors against working drives. There look to be only a few caps and some other diodey type things. The tall cylindrical caps are not bulging but might be a little less than perpendicular to the plane of the PCB. No juices or sauce exploding from any of the caps either. Anything look funky to you professionals out there? Many thanks in advance.

[R_J]

Re: Servo Drive Issues - Not many Caps

My first guess would be the block (igbt ipm) attached to the heat sync, I can't see the number but it is most likely a bunch of fets and drivers that control the output to the motor. I have not worked on any that small but the ones I repair us a 7mbp150ra-060 which are for larger motors. look up that parts pdf and you should be able to check if the output fets are shorted

[floppydisk]

Re: Servo Drive Issues - Not many Caps

Hi,

How would you check if the Fets/transistors are shorted or bad? Below is the schematic and also a link to the datasheet.



Here's the datasheet:


Even if we do find that it is shorted, it looks like finding that part is not easy. Any suggestions on that? I found one on Ebay in germany (I think).

Thanks,
Mark

[keeney123]

Re: Servo Drive Issues - Not many Caps

So this is a 3 phase motor. Have you made sure the diode are not blown on one of the phases?

[bdoss@calysta.com]

Re: Servo Drive Issues - Not many Caps

I have not checked diode integrity. I am a newb. Can you advise on that procedure?

[floppydisk]

Re: Servo Drive Issues - Not many Caps

@keeny123. Just to be clear, we want to make sure the diodes are all working between:
K --> R, S, & T
R, S & T --> A
U, V, & W --> E or N
P1 --> EU, EV, and EW

I would take a continuity test on a multi-meter and check to see if I have continuity?

Thanks - Mark

[Per Hansson]

Re: Servo Drive Issues - Not many Caps

There are some decent videos on Youtube on how to test an IGBT.
Try to search Google for example: IGBT testing with multimeter

[bdoss@calysta.com]

Re: Servo Drive Issues - Not many Caps

@keeny123. Just to be clear, we want to make sure the diodes are all working between:
K --> R, S, & T
R, S & T --> A
U, V, & W --> E or N
P1 --> EU, EV, and EW

I would take a continuity test on a multi-meter and check to see if I have continuity?

Thanks - Mark

I tested the leads mentioned in both diode-test mode and resistance/continuity with my DMM. The component is still on the PCB, PCB is not powered, shorted gates to emitters prior to testing. Here's what I got:

Diode Mode:
K --> R (0.552V/"OL"), S (0.552V/"OL"), & T (0.552V/"OL")
R (0.552V/"OL"), S (0.552V/"OL") & T (0.552V/"OL") --> A
U (0.429V/"OL"), V (0.428V/"OL"), & W (0.429V/"OL") --> E or N (E=N)
P1 --> EU (0.429V/"OL"), EV (0.429V/"OL"), and EW (0.429V/"OL")

Resistance Mode:
K --> R, S, & T (3.042 Ohm, all same)
R, S & T --> A (decaying signal, 35 Ohm and dropping)
U, V, & W --> E or N (1.812 Ohm, E=N)
P1 --> EU, EV, and EW (1.812 Ohm)

Is this component still working?

[R_J]

Re: Servo Drive Issues - Not many Caps

Going by the diode tests it seems to be o.k. Usually a transistor or diode will short and when checked would show a dead short.

Do you get any faults showing on the status display?

[bdoss@calysta.com]

Re: Servo Drive Issues - Not many Caps

The drive display shows "d" when powered up with setpoint of zero, and "E" with any non-zero setpoint. It's a single character display.
According to the manual, "d" is "bus voltage not present." "E" is "Enabled, bus voltage present."