PowerFlex 523 Speed Reference

Hello,

I am looking to upgrade some controls and logic on one of our pieces of equipment in our manufacturing plant. I need to be able to force an Allen Bradley VFD into a low frequency run condition with a single output from a SLC 500 rack.

The VFD we are using is an AB PowerFlex 523, 3 Phase 480 Volts, 3 HP. Currently the control for frequency is from a pot switch on the operator panel and the wires from that pot run directly to the VFD to control the motor speed.

The jumpers are set as follows:

Analog IN = 0-10V
Analog OUT = 0-10V
Digital IN = SRC
DigInTermBlk05Sel = Digital Input


So to reiterate, the outcome I need is to be able to bypass the control from the pot with an output from my SLC 500 rack (120V) to force the VFD to run at a predetermined frequency.

Thank you for your help in advance.

You can program one of your digital inputs as a predetermined speed reference. When this input is on you bypass pot reference and use this new reference.

Likely want an interposing relay as well since your output is 120V.

Edit: to add a little more detail.

From you output you will want to wire to a 120v coil on a relay to switch 24VDC from a N.O contact to digital input 5 or 6 on the Powerflex whichever you decide to set parameters for preset frequency, when this input is high it should override the pot input by the chart in the manual.

pg39, 49, 89 should be helpful as well as the entire manual.

https://literature.rockwellautomation.com/idc/groups/literature/documents/um/520-um001_-en-e.pdf

Thank you for the clarification. I wired in a N.O. coil to send 24v to the Dig In 05 terminal. I changed the parameter t065 = 2 which is for Speed Ref 3. P051 is for Speed Ref 3 control set it = 2 which is the keypad. I then set the keypad = 10.00 hz.

I modified my equipment's logic to activate the 120v output when the conditions are met, it pulls in the coil, sends the 24v to the terminal 05, the drive front LCD starts to run up the frequency from 0, but then falls back down and I get a F064 Overload fault. The motor and VFD in question runs fine with the pot and normal logic, only when I try to use that terminal to force the preset speed to 10.00 hz does it fault out.

*I've already checked my min freq value (P043) and it is 10.00. Machine will run when the pot runs the VFD at 10.00 hz as well.

What could I be missing?

Hmm not sure, maybe try increasing your accel time.

It could be that the Accel rate for when you use the pot is based on the fact that you can only turn a pot so fast, so even though the rate is high, it doesn't cause an OL. But when you use the Preset speed, that rate, based on the overall time to get to the MAX speed, ends up too steep for getting to 10Hz.


Less complicated way to get what you want AND have a separate Accel rate:

Program your JOG frequency to be 10Hz, and set your Digital Input 5 as a Jog input (t065 = 8). If the VFD is NOT running, it will run at the Jog speed (A431), using the Jog accel / decel rate (A432, a separate parameter from normal accel/decel). then of you give it any other command to run while in Jog mode, the new command overrides the Jog command. But it will not return to Jog mode until it gets a Stop command, then the Jog is re-initialized.

But the drive will NOT go into Jog mode if it is ALREADY running from some other source. For Jog to work, the drive must be stopped first. If that's something you want to initiate at the same time, you would need to program your PLC logic to command a stop right before giving the Jog command.

Thank you for the help. I found an output for a brake solenoid that I wasn't deactivating with my new logic, so now it will run with how I previously wired it.

I did not explain fully what I want to happen so I will now.

Machine needs to be in time mechanically, it has an encoder running off drive shaft to tell machine to do certain things during that 360 degree rotation. I want to have a homing function that will stop machine when the encoder reads 0.

Currently the machine has a run mode that uses the operator pot. Then already has a jog function that just bypasses the pot to run at the lowest frequency. (10.00 hz)

I want to be able to run my home function at a frequency less than 10.00 hz as it has trouble stopping at 0 while running 10.00 hz, and I would like to leave the jog an run mode range alone. I can't seem to nail it down in the manual, but is there a way to bypass the "global" min freq setting from P043?

*My decel is 0.70 sec

I think the only way to adjust the min frequency on the fly is through the analog input t091 which you are already using for speed reference 1, I can't think of how this would work but maybe possible. Someone else might know or have other ideas.

Have you already tried playing around with stop modes as a potential solution for the homing issue?