I have an Atlas Copco rotary vane pump which is wired into a temperature on/off switch (Johnson Controls) so the pump and start and stop based on my outside air temperature settings. It is powered with a Lenze VFD. This pump station is remote and it's not practical to visit each time I want to start or stop the pump according to sap flow.

The issue I run into is upon a cold startup, the pump will begin to turn and ramp up to operating speed for a few minutes but then shut off due to an over current fault from the VFD. The VFD does not automatically reset and requires a power cycle to reset and start again (again, not practical). However, the same thing happens after a restart unless I close the inlet valve to the pump so the oil heats up faster. The pump oil is cool so viscosity is high, so it takes more current to run the pump at rated speed. The pump rated power is 3HP and rated current is 9A. I have been slowly increasing the overcurrent trip setting on the VFD to 12-13 amps to try to allow the pump to warm up before it trips, but have not been successful yet. I don't want to allow too much current into the motor for too long.

Has anyone else set up one of these vane pumps this way? I'm curious how other people avoid this problem. Two possible ways to solve the problem might be to enable a VFD automatic reset function if it exists or derive the right short term electrical current limit so the pump motor continues to run and warm up the oil.

Thanks for any advice out there!

James