Type 4012 is an effective hoist controller for
applications where speeds can very with the load and frequent lowering is
not required. Timing devices or frequency responsive relays for
accelerating contactors provide smooth acceleration control.
The first hoist position of the master switch provides
low torque for taking up slack cable and hoisting light loads.
Subsequent master switch points allow additional contactors to close until
the desired hoisting speed is attained. Movement of the master switch
in the lowering direction produces similar results. The load is
driven downward against the retarding action of the mechanical load brake
and timed or frequency responsive accelerating relays provide smooth
Type 4012 reversing control panels are suitable for use
with a ac wound rotor motors on crane hoist drives.
Type 4012 controllers are for use on hoists that are
equipped with a mechanical load brake or a means of providing control of
overhauling loads. These controllers provide good speed control
hoisting and lowering, within the capability of the mechanical load brake.