Alfa Laval BRPX-413 Separator

[mgodby]

Heres what Ive got
An Alfa Laval Centrifuge, 40 HP motor and a Powerflex 400 Powering the whole affair with 2 wire control and internal frequency, 300 second accel.
The unit starts, but throughout the accel time and at commanded frequency
Im observing wild current fluctuations and its erratic and unstable.
The Alfa Laval Tech told me to auto tune the damn thing but as far as I can tell that's not an option or requires special software ( executive drive )
Rockwell is moving on this at the speed of a snail and I would like to clear this off my plate and move on.
The Rockwell knowledge base suggests several options but nothing concrete.

 

[harryting]

That brings back memories. I had the pleasure to clean these things many many years ago and I don't miss it.

It's very hard to trying to troubleshoot this with the info provided. Have you tried to put the VFD in manual and does it still do wild swings? Is there a speed feedback or just simple frequency setpoint?

 

[widelto]

I got two of them down here not the same model, but I use powerflex 755 instead, but my accel time is 12 minutes. No problem at all. My units are very old, in the past they were using delta-star starting method.

 

[mgodby]

reply

its a simple frequency setpoint.
The Tech at Alfa Laval said this was a common problem they had with powerflex inverters and to try an autotune.
I don't believe autotune is an option.
I will do a manual start, but I presume the results will be the same.

 

[widelto]

Did you hear any abnormal noise or see any abnormal movement like shaking for instance.
Have you tried to do it with no mechanical connection on the motor, i.e. just the motor. ?
Auto tune is not a bad option.

 

[RJP71]

A Powerflex 400 VFD will not work in that application. You need to use a Powerflex 753 or 755. I'm not a VFD expert, but I believe it has something to do with one of them being capable of constant torque.

We have several similar machines running at our company.

Rick

 

[mgodby]

Reply

Thanks for the great advice everyone

 

[Elcan]

I dealt with several of those centrifuges in the past. Just to make sure, is the VFD in vector mode? It won't work in scalar mode.

 

[mgodby]

reply

I was trying to use a Powerflex 400 for this application.
I have been informed, that it wont work for a centrifuge.
Its a high inertia load and I believe it requires constant torque.
I don't believe you can do a vector mode on the 400 either.
Nor can I do an auto tune like a PF 70 does.

 

[mgodby]

I think after some discussions with Alfa Laval, that I should have went with a
Powerflex 755.
The PF 400 wont work and I don't think it does vector

 

[widelto]

My people here also tell me that we used a Yaskawa A1000 drive in the past with no problem at all, yaskawa is cheaper that AB at least here.