AB ML1100 Analog output

Can someone please help? I want to control the speed of a AB PowerFlex 4 AC drive with a AB ML1100, using a 4 - 20mA output signal. My problem is that I need to invert the output signal from the PLC, so that when the signal is 4mA the drive speed must run at a 100% of the rated speed and 20mA the drive must slow down. Apparently the drive's input signal can't be inverted. Thanks

Not sure if I understand you corretly. What I think you are saying is that you want to Run a Motor faster via a analog output signal. The speed is based on the level of a analog input signal. The low the input the faster the motor is supposed to run.

Is this what you are trying to do?

Johan Jacobs said:

Can someone please help? I want to control the speed of a AB PowerFlex 4 AC drive with a AB ML1100, using a 4 - 20mA output signal. My problem is that I need to invert the output signal from the PLC, so that when the signal is 4mA the drive speed must run at a 100% of the rated speed and 20mA the drive must slow down. Apparently the drive's input signal can't be inverted. Thanks

Click to expand...

What you have to do is to use an SCP instruction like this:
input: min=o max=100 ( may be you have different values)
output: max 4 mA, min 20 mA ( may be different valuees, PID etc), then move this data to your 4-20 mA output card.

Refer to parameters A112 and A113 in the Powerflex 4 (frn 6) for inversion

I do have 2 motors. I am monitoring the current on motor A, convert it into a 4 -20mA analog input signal into the PLC. Motor B is controlled via the PLC analog output signal into the VSD. As soon as motor A's current is high, the output analog signal to the VSD must drop to ex. 4mA to slow motor B down. If I use the normal PID, SCL, SCP functions the analog input signal to motor B VSD will also go up linear. I have never used the PID function, so I am not sure which function will work the best.

Thanks, will do. I have asked the local supplier and they said one cannot do it with the drives parameters, but I'll check it out.

I listed the firmware number (6) because some of the more advanced settings may not exist on earlier firmware revisions.

Maybe you could use the SUB(tract) instruction to invert. If you subtract the actual analog value from the Maximum analog value expected it will invert the values.
Source A = integer value for Max output, Source B = Direct integer value derived from other logic, Output = Inverted integer value.

Example:
SOR SUB N7:0 N7:1 N7:2 EOR