Unidrive SP, closed loop vector mode Overcurrent issues.

Hi, has anyone had any experience setting these drives up in closed loop Vector mode?

The issue I have is with a Unidrive SP, and encoder card (as I need to repeat the signal to a plc, with the z pulse)

I've got issues, with a drive that previously ran fine open loop, and now trips out on overcurrent. The relevant alarm mentions feedback as a potential cause more than once, and is certainly what has been introduced.

The drive runs slow, and is hunting, and after a minute times out on a current alarm. (as mentioned before, it ran fine open loop)

It.Ac (Output current overload timed out (I2t) - accumulator value can be seen in Pr 4.19)

* The encoder cable / connections appear fine.
* The encoder is generating signal, we switched it the the HSC on our PLC and they inputs showed an alternate pattern.
* Encoder cable is shielded

I'm can't stop thinking that I have missed something obvious, thoughts anyone?

Thanks.

Encoder feedback is the wrong sense.

Hi, thanks for your response, can you please elaborate a little.

Sounds like u might have some noise on the feedback signal coming back to your drive. Are u using a shielded cable?

Thanks Gravedigger.

Yes the feedback cable is shielded. We considered the noise scenario, would our issues be as pronounced as the ones we are experiencing through noise?

I should have also mentioned earlier, that we are using a full quadrature setup.

Any other thoughts?

I'll give our Local CT tech guy a ring shortly.

Thanks.

I believe that you supplied the key clue. The drive is hunting. Your P, I, and possibly D gains are too high and are constantly yanking the motor around trying unsuccessfully to settle to the setpoint. The loop needs retuning.

We did find an issue with the encoder cabling, which has been sorted, but it now shudders in both directions.

The static Autotune is providing fairly ordinary results.

I've tried playing with the P&I gains a little with no real improvement. It is still going out on it.ac

We have also had a scope meter on the A, A/, B, and B/ which all appear to be ok.

I've reset the drive to default, performed a closed loop static tune, (manually entering the powerfactor afterwards), and this hasn't helped either.

Manually spin the motor in the positive direction and check what the speed feedback from the encoder indicates positive.

Hi, problem was sorted some time ago, but I'd better throw the rest of the story in as it may help someone else someday?

As suggested above, there was an issue with the encoder direction. It was the other side of a gearbox from the motor mechanically. Which required the A,A/ and B,B/ to be swapped (pin pairs 1,2 and 3,4)

Once this was done we got it to run, but the performance at low speed was too jerky, which was due to the reduced pulses per revolution, once again as a result of the encoders location.

The encoder was now moved on to the back of the motor, which is obviously a better place for closed vector anyhow. So the encoder wires were put back, and the desired results were achieved.

As a side issue, we experienced an issue with the drive seemingly dropping out of open loop mode. It would boot saying it was in closed loop, but you could unplug the encoder and it made no difference! It wasn't in RFC mode, we checked that, it did this to us numerous times before we actually unplugged the encoder and figured out what was happening. We tried resetting the drive to factory parameters, and ended up in the same predicament. We ended up getting the local rep around and he did a reset using the software & cable that we couldn't justify, he did a reset, which strangely reset additional parameters that the procedure in the manual had not. After this was done, the drive did not drop out of closed loop again. .... strange? Sadly, had we have bough the Cable it may have paid for itself....

encoder feedback issue or motor overload

vk_bt1 said:

Hi, has anyone had any experience setting these drives up in closed loop Vector mode?

The issue I have is with a Unidrive SP, and encoder card (as I need to repeat the signal to a plc, with the z pulse)

I've got issues, with a drive that previously ran fine open loop, and now trips out on overcurrent. The relevant alarm mentions feedback as a potential cause more than once, and is certainly what has been introduced.

The drive runs slow, and is hunting, and after a minute times out on a current alarm. (as mentioned before, it ran fine open loop)

It.Ac (Output current overload timed out (I2t) - accumulator value can be seen in Pr 4.19)


* The encoder cable / connections appear fine.
* The encoder is generating signal, we switched it the the HSC on our PLC and they inputs showed an alternate pattern.
* Encoder cable is shielded

I'm can't stop thinking that I have missed something obvious, thoughts anyone?

Thanks.

Click to expand...

check encoder connection both side ( drive or motor) if found ok then replace the encoder. May be encoder faulty. check motor actual current with pr 0.12 if there is variation in amp then replace the encoder.

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