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Homemade Skip Band?

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toygasm4u

Electrical
May 17, 2006
37
Greetings all,
I have a VFD application that uses a 0-10VDC signal for reference, and the VFD doesn't have a skip band option. Problem is, I need one, and would prefer to do this without replacing several, SEVERAL, drives.

If my skip band requirement is only in the 5-10Hz range, is there a work around?
 
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If setting the minimum frequency to slightly above 10 Hz, as said by Laplacian doesn't work - you may need to run at low frequencies - then a simple opamp circuit can do the job. It may need some thinking - but definitely possible.

Gunnar Englund
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
 
I'd consider using something like a micro PLC so that you can easily set the dead band. Just feed the signal in and do some math and feed it back out.

 
Use a set point relay on the 0-10V signal, and set up the output contacts in series with your run command. Then set up the setpoint relay to turn off the run command if the 0-10V signal is above or below the setpoints.

If you want the motor to run at 5 Hz when the command is +5 and -10Hz, then you will need the VFD to have a jog feature that has it run at a pre-programmed speed when an input is closed. If this is the case, then just have the setpoint relay put the VFD in Jog mode during the dead band range instead of turning it off.

Here is an example of a setpoint relay you could use.
Action Instruments setpoint relay link

JRaef.com
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