Powerflex 525 Rotate Autotune

Hi all,

I have a powerflex 525 which I'll be using in VVC mode, and the manual says I should perform a rotate tune to use the drive in VVC mode. It also notes that the motor must be uncoupled from the load for this test, or the results may be invalid.

Just wanted to quickly sanity check - does that mean I have to uncouple the motor from the gearbox, or just uncouple the load from the motor-gearbox output shaft?

ASF said:

Hi all,

I have a powerflex 525 which I'll be using in VVC mode, and the manual says I should perform a rotate tune to use the drive in VVC mode. It also notes that the motor must be uncoupled from the load for this test, or the results may be invalid.

Just wanted to quickly sanity check - does that mean I have to uncouple the motor from the gearbox, or just uncouple the load from the motor-gearbox output shaft?

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I just read the manuals as I am interested in powerflex in general; but I have *no* direct experience.

It doesn't make any sense to me to tune the system up without the load.

Rotate tune is done decoupled from the load so the drive can measure the motor characteristics without the effects of the load. It is different from PID motion tuning. Powerflex 700 and 755 Drives Tuning manual states that the load must be disconnected unless it is a low friction load (I don't have that same reference for a 525). I have always disconnected the gearbox when performing a rotate tune.

drforsythe said:

Rotate tune is done decoupled from the load so the drive can measure the motor characteristics without the effects of the load. It is different from PID motion tuning. Powerflex 700 and 755 Drives Tuning manual states that the load must be disconnected unless it is a low friction load (I don't have that same reference for a 525). I have always disconnected the gearbox when performing a rotate tune.

Click to expand...

So is there a second part where the load is taken into account?

In our applications, which mostly utilize gearmotors, the motor cannot be uncoupled from the gearbox without setting it on the floor (not desired.)
To Rotate Tune, or check rotation, we remove the chain from the chain coupling on the output shaft of the reducer. This uncouples it from the load of the lifter or conveyor.

Peter Nachtwey said:

So is there a second part where the load is taken into account?

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On higher performance drives like the “7 series”, yes. The 520 series drives, like most small inexpensive “component class” drives, do not really have a torque regulator loop, they estimate torque, hence the Vector mode being specifically called “Vector Velocity Control” (VVC). So having a load that might be variable connected to the motor during the rotating auto tune will affect the algorithm accuracy in terms of speed regulation capability since it’s estimation of torque will be skewed by the load.

Sometimes it is not possible to disconnect a gearbox and I have done it with the gearbox attached. Yes, it represents a small amount of load, but as I see it, the gearbox represents a non-variable part of the mechanical system, so it actually becomes part of the equations anyway.

Thanks jraef, appreciate your input.

@Peter in this case the motor is just running a simple conveyor, there's probably little need for tuning the load as such. I just need to run the drive in VVC mode because I have a very wide speed range to achieve, 0.5-60Hz, and to get those low speeds I need encoder feedback and a drive in VVC mode. And the manual says I need to do a rotate autotune to run the drive in VVC mode.