Hi everybody,

I have to control 6 Siemens H-Compact 690V Variable Speed Drive using AB PLC.

In the Automatic Mode, I just have a step input and the drives will start automatically and the speed will be controlled by parameters directly inputed to the drives.

In the Manual Mode, I have to use a switch (just like an accelerator) to provide ramp input to either accelerate or decelerate the drive.
The data will be send to the drives via DeviceNet.

Please can anybody help me how to write the Ladder program for a ramp input and its corresponding output?

Thank you in advance

DKD

Use a self re-setting timer and simple math.

When timer done bit is true;
IF output is < setpoint THEN
output:= output+5 (you will have to decide the value of the addition, and the value of the timer preset)
Else output:= setpoint
Endif;

The code for Automatic Mode should be simple. Create a Tag array called Drive_Auto_Speed of type Real[10]. Yes you only have 6 but I am allow for expansion. Let your HMI manipulate these tags and move them to the drive speed command when in auto.



In Manual Mode it will be a little trickier. The translation of what you want to American English is questionable. Does your accelerator give on / off signal or is it an analog from 0 to 10 V or 4 to 20 ma. If it is on/off then Ken's logic is fine, if it is analog then you'll need to read the input and I'd sugggest pushing it thru a PID to get your output. The 4-20 would be your Setpoint abd the Drive Speed would be your Process Variable. The Drive Command would be your Control Variable.



You'll need RSNetworx for DeviceNet and the EDS files for the Siemens Drives. If you ahve these and follow the manuals, the Drive Start/Stop and Speed commands should wind up as plain language tags in RS5K logic.

Be glad to elaborate more once we know more about your application.

Doesn't Function Block programming have a ramp block???