Allen Bradley Powerflex4 invertor questions

I am considering replacing some old invertors with brand new Powerflex 4s. They will have a single phase 230v input and they will have to supply 230v 3 phase to existing motors wired in delta so they are rated at 230v.

The existing invertors are controlled directly from 24v digital outputs from a PLC and I want to configure the new invertors to accept these signals to run/not run and to change the speed from low to high.

This will mean that the PLC 0 volts would have to be connected to all the pin 4s, the digital common terminal. Will this cause a problem, tying all the terminal 4s together?

Can anyone explain what exactly is meant by 2 and 3 wire control as needs to be selected in parameter PO36.

I'll use digital input 1 as the high preset speed, to change from low to high speed.

Can anyone see any flaws in the project?

This explains 2 & 3 wire http://www.patchn.com/twowire.htm

Have not read the PowerFlex manual but if its has its own control ckt power then you may need to use interposing relays or relay outputs.

I'll have to give myself a refresh by reading the power flex 4 manual but I'll try to send you in a direction.

3 wire is like a start stop circuit using two inputs of the drive from two switches a start and a stop. Two wire is what your looking for a single signal from a PLC that would start the drive and stop it when power is removed.

You also have to program two preset speeds of the drive so that you can use a another PLC output connected to a drive input that would switch the drive speed between the two presets.

Make sure your ladder sends the speed signal to the drive before it sends the start signal (this should be part of your plan already).

I think the Powerflex has an internal control power supply that can be used, or not. In your case you DO NOT want to use any Powerflex internal control power, but instead want to use the 24 VDC that powers your PLC inputs and outputs.

If you do not use the Powerflex internal control power, then you can tie all of your Powerflex Pin 4's together. Otherwise, not.

Thanks for the response. That explains that the two wire option is the one that I want to use. I want the motor to run when the PLC output is on and stop when it goes off.

I have looked at a few invertors and all the others requires volt free contacts for the inputs. The Powerflex4 has the facility to accept digital inputs. Thats why I have chosen that type.

The speed input needs to run the motor at about 30Hz when no input is present and increase to about 75Hz when it is high. I intend setting the minimum frequency at 30 and configure the dig inputs to preset frequency, setting input 1 at 75Hz.

I'll ask my boss to buy one to try. Thanks again.