Parker 590 speed error

RE: Parker 590 speed error

Daniel Cliffe — Mon, 26 Apr 2021 16:14:53 GMT

Sorry, I assumed that "repaired" meant "rewound" in this case since you mentioned a resistance change. If you want to run an armature current loop autotune, you can leave the system coupled. The motor does not (and should not) move during an autotune. This is specific to DC drives like the 590+ (Parker AC drives need to be uncoupled during autotune).

Please keep my original response to your question in mind: you might be asking more of this system than it can deliver. A speed setpoint of 0.4% is unusual for brushed DC drives. Many motors do not handle this speed well and some motors risk overheating at these low speeds. If your speed demands are always very low, I suggest getting a gearbox.

RE: Parker 590 speed error

meladyousef89@gmail.com — Mon, 26 Apr 2021 07:23:26 GMT

thanks for your help,

but motor hasn't been rewound , but if I need to armature current loop autotune , does I need to disconnect Mechanical coupling or No need , as ABB drive must be uncoupled but no information at Parker drives

RE: Parker 590 speed error

Daniel Cliffe — Tue, 20 Apr 2021 15:34:25 GMT

Ah, yes. Anytime you get a motor rewound, you need to do an armature current loop autotune. You can find the procedure here.

Also please note that you should not run a field autotune as it is unnecessary.

RE: Parker 590 speed error

meladyousef89@gmail.com — Tue, 20 Apr 2021 08:41:36 GMT

Dear Cliffe ,

thanks for this valuable information

but I assume something , this motor was repaired recently ,

if armature resistance or field was changed slightly , will cause this problem !!!!

so at this time I need to make auto tune again

***During normal working speed demand was 4 % and every thing is OK

when decrease the speed "controlled by operator via canopen" reach to 0.4 % speed error increase reach to 0.1 to 0.2 % and motor sound not OK

RE: Parker 590 speed error

Daniel Cliffe — Mon, 19 Apr 2021 14:28:14 GMT

Good morning. This is actually not that uncommon. At low speed, it is more difficult to control speed accurately. There are two reasons for this:

Your rate of speed measured in encoder counts per second is very low. The data from the encoder is therefore very coarse at low speed and the control suffers as a result.
Many machines require less torque at low speed. If the torque requirement is low enough, the drive may slip into the "discontinuous region", where the portions of the waveform cut up by the SCRs no longer overlap. Current fluctuations in the discontinuous region are naturally higher and there is not much that can be done about it.

So, what options do you have? I think the simplest one is to get a higher resolution encoder. If you are currently using a 1,000 line encoder, try using a 5,000 line encoder. You will need to alter the encoder resolution parameter, but the change is quite simple.

Overall, your performance requirements are pushing the boundaries of what a brushed DC motor and drive can be expected to do. If you never need to go above 10% speed setpoint, consider getting a 10:1 gearbox so that you can run the motor faster.

If you need to run at high speed and low speed and maintain accurate speed at both ranges, maybe a flywheel will help. This is not something on which I can provide lots of advice, but perhaps a local machine builder could.

The only other option I can conceive to handle very high and very low speeds while keeping very close to the speed setpoint is to use a servo motor with a high resolution encoder. Parker makes servo motors up to about 21 kW.