Crane Hoist with Ward-Leonard Control

A good way to find out is to discuss the symptoms with the crane manufacturer directly.

Check your grounds to be sure they are secure and bonded. I had similar issue on a crane few years ago. Different controller but we were getting interference from magnetic fields as gen-set spun up. Other wise consult your manufacture as suggested earlier.

Is it possible the hoist is driving to the neutral position against whatever pre-applied load is present, even bare rigging. De-load the hoist, free the brake and try again to see if it still travels. Record your findings and present them to the certified crane repair professional I'm sure you've already called.

What you are seeing may be normal. Before you release a hoist brake, the motor must be engaged and putting out enough torque to be capable of holding the load, otherwise if the load starts to drop, the motor torque may not be enough to stop and reverse it.

What you're seeing on starting the MG set is the hoist motor taking the slack in the coupling. There should be very little slack but there's always a bit.

With it being a Ward-Leonard control sometimes its difficult to get the drive to stop completely under no load, there's always a bit of residual magnetism in the control exciter. With you saying it can be either way it looks to me as if it's due to residual left over from the last hoist or lower. To get rid of the residual Ward-Leonard use a suicide shunt* that at the moment a stop is called for reverses the polarity of the exciter for a split second. It could be that the timing is a bit out, a bit too much giving reversed residual, or not enough and not killing it. Unless it's giving you real problems leave it alone, they are an absolute swine to set up.

*Lovely name for it.

Just remove the brake and use the reverse control to stop the crane motion.a lot of problems can be solved. Hit

Funy

We clamped the rope and slackened the brake and wound some slack off. On starting the MG set the motor turned at about 2RPM. I'm not going to worry about that. It's not going to cause problems with the brake.