I am writing PLC code for 6 VFD's at 6 equal intervals on a 2 km conveyor belt and I would like any programming suggestions for
calculations of the output of each VFD.
Right off the top I would use one drive as the master and have the others follow. Apps trying to control each drive individually have proven to be a mess.
But can the physical app handle that?
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Well, it may depend on the belt configuration. If the belt is segmented, so each motor drives a separate belt (the output of one feeds the
input of another), then just have one controller set the rate of the others. If you've photeyes or other proximity sensors, you can coordinate the stop/start of each based on the presence/passage of material.
Alternatively, if all motors drive the same belt, you may want to coordinate the drives more carefully. It may not be sufficient to have
one master rate dictate the speeds of the others. Perhaps you can use a load trim controller to trim the master setpoint to each motor to achieve a uniform load on each motor. So, there'd be a master speed setpoint which is trimmed by a load controller (one for each motor) to minimize the deviation from the average load of all 6 motors. See "www.loadcontrols.com":http://www.loadcontrols.com for info on a load sensor.
good luck
Since you have a PLC as a Master to Control each drive I would recommend you to use an encoder for each VFD as a Feedback to the PLC it is important to have a precise Feed back from your 6 VFD for this you could derive a good reference of
calculation values to set each drive speed because you have the capability to monitor each drive in a very precise way.
I have done it before using an Allen Bradley 1336 Impact Drives communicating to a PLC thru Controlnet Protocol and the result is quite very
impressive..................
[email protected]
Eduardo Manuel C. Cipriano
Sr. Systems Engr.
Systems Engineering Department
Yokogawa Phils. Inc.
