Need a little more information on what you are trying to accomplish.
First off just to be clear, you will not be running more than one motor at a time?
OR WILL YOU??
If you are going to run more than 1 motor at a time, I dont think you can program your way out of that. How will you get more than 1 frequency out of the VFD at a time? (If they were all going to run the same speed then no problem just need large drive and seperate overload, but 4 different speeds at the same time, I dont think so)
If you only want to run 1 motor at a time then this is doable.
You say they have different low and high Hz requirements, so I take this to mean each motor will need to vary in speed when in use, and you will not have just 4 separate fixed frequencys, one for each motor?
If they need to vary in speed (and you will only be running one motor at a time) then you could use something like a 4 position switch (or 4 selections from HMI) to tell plc which motor should run. The input from this switch will move logic in the plc to a seperate/individual routine for that specified motor.
This way each routine can be unique, and have its own Scaling set up for each motor within the routine.
If you only need fixed frequencys 1 for each drive ( and they will run at different times) then you can do this through the plc or just use 4 digital inputs into drive with fixed frequency setpoint configured for each in the drive itself.
Either way you will need to have 4 contactors installed also. 1 for each motor on the load side of the VFD. Each routine in your program will pull in the appropriate contactor for motor chosen when start is initiated.
(Interlock your start signal to the drive through a Aux contact on each contactor, or use feedback from contactors and interlock drive start in your program. This way the appropriate contactor will be pulled in and lined up with the correct motor at Drive startup.)
If all 4 motors are of the same size and spec then thats good as motor parameters can be set the same and used for every motor.
If not then you will need to provide individual overload protection on the load side for each motor also, or have your drive switch parameter sets internally for each motor.
(I know you can do this with Siemens drives, so I am sure other brands are the same, but I think Siemens is limited to 3 Parameter Sub Sets (Different set ups within the drive)
Give a little more info as to exactly what you are trying to do and how you will be controling the speed (freq) of the drive, and someone will be able to better point you in the right direction.
BCS
