Running brushless servomotor with frequency inverter

My job is to try to control brushless servo motor with frequency inverter. I just connected such motor to a frequency inverter and I tried running it.
I set frequency inverter to 5Hz and motor is not running smoothly, it's actually jumping on the table, which I think means it's producing abnormal torque.

I never controlled brushless servo motor with frequency inverter, what I need to check out?

One of the phases was broken, now it runs smoothly. Now I need to check if I can connect motor's encoder to encoder card of frequency inverter, and see if I can have closed loop control. Stay tuned.

I'm having issues with finding catalogue/manual for this brushless servo motor.
It's Lafert B5602Z-01051. I specifically need encoder wiring diagram, since there are 12 wires and I don't know why would you need so many for an encoder.

Any help?

doomsword said:

I specifically need encoder wiring diagram, since there are 12 wires and I don't know why would you need so many for an encoder.

Any help?

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I can't help with this specific motor encoder diagram, but a servo motor encoder contains a lot of information. The encoder signals, A, NotA, B, NotB, Z, NotZ, Supply Voltage and Common, Voltage Sensing (detecting voltage drop on cable to compensate), Temperature sensor for the motor. Just to name a few off the top of my head.

Tharon said:

I can't help with this specific motor encoder diagram, but a servo motor encoder contains a lot of information. The encoder signals, A, NotA, B, NotB, Z, NotZ, Supply Voltage and Common, Voltage Sensing (detecting voltage drop on cable to compensate), Temperature sensor for the motor. Just to name a few off the top of my head.

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Thank you for your input, I still am unsure how to find out what is wired where.

Another issue I'm now having is with tuning this brushless servo motor. I set it's SPM (Surface Permanent Magnet) motor, and I calculated it's power using P=M*w.

How would I know if it's SPM or IPM, and how is power calculated for such motors?

It may be an interesting project but rather inefficient use of both the VFD and Servo. The VFD will likely not be robust enough to get the most out of the servo. I suggest you get a VFD capable 3 phase motor and add an encoder.

RussB said:

It may be an interesting project but rather inefficient use of both the VFD and Servo. The VFD will likely not be robust enough to get the most out of the servo. I suggest you get a VFD capable 3 phase motor and add an encoder.

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VFD is Mitsubishi A800 that can run PM motors, and it has encoder card. Idea is to see if it can run it good enough. If it can then they'd use it instead of servo driver.
I don't know if this motor is good enough to be run by VFD, I think it was run by servo driver.

All the servo motors I have delt with are capable of better performance than any 'cheap' drive I have known. So if this is just an attempt to save a ljttle monney,IMHO it' a waste of time.
So unless this is just a learning exersize get a drive and motor that are designed to work together.

Bump

We've managed to run it in open-loop speed control, now we need to close the loop.
It seems this motor has differential encoder, with A+, A-, B+, B-, Z+ and Z- for phases, 5+ and GND for voltage supply, and HU, HV, HW pins which I believe it's Hall sensor.

I've never dealt with Hall sensor, should these pins wired or I need just to connect A,B and Z signal to encoder card which will know speed of this motor?

I believe it's incremental encoder. Also, beginner's question, if it were absolute encoder then I wouldn't be able to get position by counting pulses? Absolute encoders need communication to send their position to driver, they can't pulse it somehow?

If this motor is a permanent magnet synchronous servo motor, there is no point in connecting the encoder for speed loop accuracy since this motor is synchronous to the incoming power frequency. That means that there is no motor slip and therefore no speed error. The encoder on this type of motor would be intended for position control, in my opinion.

There would be negligible speed error in the drive itself but with modern drives this is in Parts per Million and therefore probably not significant.

I'm not a servo guy so I might be missing something here but I don't know what it might be.

Thanks for your answer.

Actually, inverter can't control PM motor using incremental encoder, so we couldn't close the loop. More, inverter can control PM motor only in sensorless speed control mode (no torque or position control), and loop can only be closed with resolver (again, just vector control in speed mode).
And you're right, this was more likely for position control. But it seems positioning is not so precise here (we're on milimeter range), so we will try to put it on a machine and try to control it using only sensors and built-in PLC.