Controlling a (VFD) Variable Frequency Drive


#1

I would like to install some VFD’s for my condenser fan motors. My Refrigeration tech is concerned about power failure and having to reset the VFD manually. Is there an interface that can control the VFD and allow a reset following a power failure remotely?

I have an exisiting Opto system that controls the entire refrigeration operation using the digital I/O boards.


#2

Yes, what you are describing is very possible. I use Opto22 equipment to control the VFD’s in my new machine builds and retrofits, including the remote reset function. The exact implementation will depend on the VFD.


#3

Yes sensij is right. As long as the vfd has the ability to do reset via a digital input then you should be fine. Alternatively if a power cycle is required make sure you have control over the contactor that supplies the vfd. If a fault occurs then drop power to reset the device and away you go.


#4

Hi Chuck,
One other thing to watch out for is the state of your digital “run” control line. Some drives are programmable so that if when they power up if this line is high they will start running. Otherwise, be sure to turn your run line off, reset any faults via a digital out from your controller to the vfd, then set the run line high again. i have had drives come up after a power failure and operators clear the fault via the drives keypad, but they forget that the control system will need to cycle the run command off and on again to get it to run.


#5

I’ve been using Allen-Bradley PowerFlex drives recently. We use a single digital output Run command, a digital input fault indicator, and a 0-10 volt output for speed control. I’ve noticed with these drives that the run command must cycle after clearing a fault. These drives also include programmable inputs so you could setup a digital signal to reset the fault.