Electrically-operated crane control unit 4012

An effective hoist controller for applicationswhere speeds can vary with the load andfrequent lowering is not required. Timingdevices or frequency responsive relays foraccelerating contactors provide smoothacceleration control.The first hoist position of the master switchprovides low torque for taking up slack cableand hoisting light loads. Subsequent masterswitch points allow additional contactors toclose until the desired hoisting speed isattained. Movement of the master switch in thelowering direction produces similar results. Theload is driven downward against the retardingaction of the mechanical load brake and timedor frequency responsive accelerating relaysprovide smooth acceleration.Type 4012 reversing control panels are suitablefor use with ac wound rotor motors on cranehoist drives.Type 4012 controllers are for use on hoists thatare equipped with a mechanical load brake or ameans of providing control of overhaulingloads. These controllers provide good speedcontrol hoisting and lowering, within thecapability of the mechanical load brake.Panels are arranged for use with a power limitswitch and separate ac or rectifier operated dcbrakes.