The Type 4014 controller relatively simple yet provides
great precision in load handling. It is particularly useful for
handling variable loads at preselected subsynchronous speeds, and also
provides slower and more stable lowering speeds than other ac stepped wound
rotor hoist motion controllers. Typical applications are in assembly
or manufacturing operations where the crane is used frequently.
In this system the eddy current brake and the wound
rotor motor are coupled directly to a common shaft. The brake serves
as an artificial load for the motor and develops braking torque by
frictionless means; thus, lowering control is stable even at very slow
The controller acts as a plain reversing controller with
five master switch points for hoisting and five for lowering. In
hoisting, the eddy current brake is energized in the first and second point
hoist and de-energized in the last three points hoist. When energized
during hoisting, the brake artificially loads the motor thus causing light
hook loads to be hoisted slowly. For lowering, the brake is energized
on the first four points lowering and de-energized on the fifth. When
the brake is energized during lowering, its torque opposes the motor torque
and permits loads to be lowered slowly.
Type 4014 reversing control panels are suitable for use
with ac wound rotor motors on crane hoist drives with eddy current brakes.