ATV930 Speed Loop Optimization

[Boris11]

Hello everyone!

I kindly ask you to help me with Speed Loop Optimization for ATV930:

The PFC is working correctly, but I have a problem with motor speed fluctuation

around reference speed in FVC control mode (closed loop).

It is about 3-4 rpm @ 1500 rpm, but it leads to mechanical stress for gearbox

in my case. How to remove or decrease the motor speed fluctuation?

Best regards,

Boris Churkin

[BJacqz · Accepted solution]

Speed loop gain settings are available in your product. I advise you to use SoMove software, you will then easily be able to see all the speed loop optimization settings.

SSL, SPG & SIT are the first settings I would propose to set, and you have much more, a test of moving one setting at a time will help you to find the good compromise...

Hope it helps

[Denys]

I have same issue with ALT930 for hoist application in a close loop operation. With 50Hz speed setpoint, the RPM is fluctuate around 5 RPM. When I reduce speed to 45Hz, it became stable. 
I'll try with the proposed solution by BJacqz 

[Denys]

And it's working. I solve the problem with fluctuation.

It didn't appear on the smaller size motor like 160kW, also hoist. So default settings were enough. But for 250kW motor hoist, it was a problem with fluctuation. 
Now after reducing proportional SPG (from 40 to 10%) and increasing SIT (from 150ms to 2000ms) it working well. During the load test will check again. 

[Slayer90]

Hy guys, I have same problem with hoist application, motor power 132kw. With fix speed after ramp up the current star abnormaly fluctuation like a sine signal. If i set a mode svc V Instead Fvc all works fine. I checked all for motor encoder and switch to another drive but still works bad.. Any idea for the problem? I tried to change values for speed loop but Nothing change.

Thanks for help

[Denys]

Hello @Slayer90 ,
I am not professional drive commissioning engineer and also require a lot of support, but I had similar problem before, when in FVC (with encoder) there was a speed fluctuation and in SVC mode (without encoder) wasn't.
We also replace the inverter and the encoder and even put a temporary encoder cable (which by the way improve, but not solve the issue).
Solution in my case, was the encoder cable proper earthing, to prevent the cable magnetization. The trick was in earthing the encoder cable shield to the inverter body (Encoder cable shielding, ATV930 Installation manual) and to connect this shield to the encoder's earth terminal. Encoder (we use AB type) has 7 terminals, as power, neutral, A+/B+, A-/B- and one more for the earthing connection, where we connect the cable shield, which was earthed on the drive side only. 

After the proper connections the fluctuations helps.

And right now it come back after mechanical disassemble and assemble the hoist  gearbox. And in any mode FVC or SVC I have fluctuations in speed. This one is really strange and I'm looking for solution. Sure will ask mechanical to disassemble it again. 

[Slayer90]

ok thanks for the information. However, I have current fluctuations, not speed. in my case I solved the problem by inserting a value increased by approximately 10% of the rated motor current instead of the motor current write on motor nameplate. Most likely the engine has some problem or the nameplate on it has some incorrect value. I had also tried with a temporary cable for the encoder but nothing had changed.