Motor Spinning Backwards or forwards when the VFD is off
/Hi- Part of the VFD startup process is verifying the motor rotation is correct when the motor is running on the VFD AND in bypass. If you need help with this pls see the manual or call us.
Sometimes a customer calls about a motor that is “freewheeling” backwards or forwards when the drive is off. This happens if a fan is connected to a common plenum and is air is being sucked past it, causing the motor to rotate.
This doesn’t hurt the drive but can cause other problems-
The VFD can trip on overcurrent as it tries to “catch” a motor spinning backwards at high speed during startup.
Equipment that is still moving but commanded off can cause other problems or safety issues for the operators.
There are a couple of points to check here:
Set parameter 1-73 Flying Start to [1] “Enabled”. The VFD will test for a rotating motor prior to starting. If needed it will slow it down and start spinning the correct direction, avoiding motor overcurrent. This function adds about 10 seconds to the startup process.
Set parameter 1-80 Function at Stop to [1] DC Hold/Motor Preheat. Then set 2-00 current percent to the lowest value that will hold the motor. Start low and work your way up, excess current adds heat to the motor and wastes electricity.
