Powerflex 525 motor disconnect stop

[Electromatic]

I'm working on a tank mixer with a pre-fabricated control panel that's using an AB Powerflex 525 VFD for the mixer motor. I'm installing a local motor disconnect after the drive and before the motor and have included early-break aux contacts to signal the drive before motor power is shut off. Can I use these contacts to simply open the RUN input command, or do I need to signal a STOP command? There is what appears to be a factory jumper installed directly on the drive terminal blocks between +24V and STOP.

 

[ptonsparky]

Open the run command is all I've done in the past but mine always needed and additional Start command afterwards. Yours looks like it could immediately restart on closing the disconnect if the control is in Hand. Not sure if that is what you want it to do.

 

[don_resqcapt19]

If it is not set up for coast to stop when you open the run command, the output will still be driving the motor and there is a risk of damage to the VFD. The aux contact must be set up in a way that tells the drive to stop providing any power to the motor and to do that, you need to initiate a coast to stop function.

 

[petersonra]

Open the run command is all I've done in the past but mine always needed and additional Start command afterwards. Yours looks like it could immediately restart on closing the disconnect if the control is in Hand. Not sure if that is what you want it to do.

 

[Jraef]

What Bob showed is exactly how to do it, that is what those terminals are for. Regardless of how the drive is programmed, opening that circuit removes power from the transistor gates so they do not fire. That’s what you want.

 

[Electromatic]

Thanks for the feedback and instruction!
Since this will be altering the assembled control panel, I'm going to leave it up to the GC and/or the provider as to whether they want me to do this. Neither the GC or the mixer/panel & drive provider had ever heard of using disconnect aux contacts between a drive and motor.

 

[Jraef]

It’s not 100% necessary, but there is a risk of damaging the transistors if you don’t. Some people are unaware of that risk, others are willing to accept it to avoid the added cost. Both often end up regretting it later and adding it AFTER they lose a VFD (and the associated downtime costs).

 

[milmat1]

I sometimes use the disconnect feedback to signal an "External Fault" input to the drive. Then program the drive for what action you wish to take during an "External Fault"..