OT ABB DCS 400 tuning (hello DickDV)

[allscott]

I recently inherited a 250HP ABB DCS400 drive. We hooked it up to a machine that was transfered from a sister plant and started it up last week connected to a 150HP straight shunt DC motor.

I wasn't involved in the initial set up but our senior electrician (who I have confidence in) started it up without tuning it. The machine doesn't require precise speed or torque control at all so I didn't question it.

The electrician who set it up is off work and I was called down to look at it last week because it was overshooting badly (200 RPM, while ramping up to 1750RPM). I decided to run through the autotunes in hopes getting better control.

I diconected the load and did a field tune, and armature tune, and a speed loop tune. I reconnected the load to the machine and it went completely stupid. Trying to ramp up to full speed almost instantly, running backwards even though the command reference is always positive. I ended up settting it back to factory defualts and setting it up again without auto tuning.

The machine is running again over the weekend with highly exagerated ramps and EMF feedback because I thought maybe there was an issue with the tach.

Any ideas what went wrong?

 

[DickDV]

It's been 3-4 years since I've worked on one of these but I've still got the Instruction Manuals.

My first question is whether you are taking the motor over base speed? Or, to ask the same question another way, Are you doing field weakening or is the field current held to a constant value?

 

[JRW]

Dick
These are tuned without the load?

 

[allscott]

It's been 3-4 years since I've worked on one of these but I've still got the Instruction Manuals.

My first question is whether you are taking the motor over base speed? Or, to ask the same question another way, Are you doing field weakening or is the field current held to a constant value?

No field weakening, field current is constant. Just trying to run the motor up to base speed. I tuned it disconnected from the load. The manual isn't real clear whether it should be tuned with the load coupled or not.

This is a very high inertia machine. It takes almost 2 minutes to get it up to speed without going into current limit.

 

[JRW]

I know Dicks the ABB expert but how can the drive
Calculate gains without the load?

 

[DickDV]

Generally, I don't like to use the startup wizards on drives but the DCS400 wizard is actually quite good and I'll usually use it, especially if there is no field weakening.

I would recommend going thru the wizard as outlined on pages 6-9 thru 6-16 in the manual. Be sure to get the field current set right. The armature tuning is to be done with the motor uncoupled.

When you get to setting up the speed feedback loop, reconnect the load before doing the tuning.

I'd also caution you on picking the correct terminals for the tach connection. Calculate the maximum output voltage of the tach. That would be at maximum speed, of course. Then connect the tach wires to the terminals with the proper voltage range. The little trim pot next to these terminals is where you adjust the speed error out.

See what happens with this and get back. I'll try to stick with you on this until we get it right. Unfortunately, the manual doesn't read very well, in my opinion, so getting a handle on what it means is sometimes tricky.

 

[allscott]

I finally got back to this today, the machine has been down working on mechanical issues for awhile.

I tried the speed loop tuning again with the load connected and it failed on a #10 alarm. I don't have the book in front of me at the moment so I don't know the description of the alarm in front of me. I do know that what the book said was kind of greek to me. I will post the description of the failure tomorrow.

While running the machine everyone else other than me is happy with the way it runs. I would like to get the over/under shoot under better control.

Under factory defaults Kp = .200, and KI= 5000ms. If I can't get it to autotune I am considering bumping up KP and lowereing KI under trial and error until I get it to respond satisfactorily. Am I on the right track?

Lethargic is how I would describe the motor right now.