I'm trying to use a VFD to control an older lathe I purchased, be re-using the only motor control contactors are the fwd/reverse inputs to the VFD. The control circuit uses one contactor (A Taian Electric C-11G) for logic related to the foot brake, and when that contactor is closed, operator of the forward or reverse switches open and close the main motor contractors as appropriate.
The problem I'm having is that the forward/reverse control circuits will randomly fail to operate, even though all of the switches are in the correct location. The brake contactor will be closed (as it should be) and when I operate the forward control lever, the contactor will snap open (even though it shouldnt). Other times I'll repeat this exact same process at the brake contactor will remain closed and the main motor control contactor will close as well.
Is it possible for a contactor to fail in a way that makes it intermittent like this? I had assumed it would either weld itself closed or fail to operate at all. I also noticed that the brake contactor seems to have a very loud electrical hum when it's operating, more so than anything else in the control box.
The problem I'm having is that the forward/reverse control circuits will randomly fail to operate, even though all of the switches are in the correct location. The brake contactor will be closed (as it should be) and when I operate the forward control lever, the contactor will snap open (even though it shouldnt). Other times I'll repeat this exact same process at the brake contactor will remain closed and the main motor control contactor will close as well.
Is it possible for a contactor to fail in a way that makes it intermittent like this? I had assumed it would either weld itself closed or fail to operate at all. I also noticed that the brake contactor seems to have a very loud electrical hum when it's operating, more so than anything else in the control box.