Type 4011 AC Dynamic Lowering hoist controller provides
braking action by applying a single-phase connection to the primary of a
three-phase wound rotor motor. It is recommended where slow lowering
speeds are not required for overhauling loads of 50% or more and for hoists
that do not use mechanical or electric load brakes.
Five speed points are provided for hoisting.
Lowering is controlled by three master switch points. In the
first-point lowering, single-phase power is applied to the motor primary
with a dynamic braking connection. An overhauling load will lower at
a speed depending on the load, but a non-overhauling load will not lower.
On second-point lower, weak down torque drives down non-overhauling loads
and permits accurate inching of light loads.
If the motor accelerator closes and drives the load down
in regeneration. This prevents motor overspeeding with an overhauling
load on the hook. The third-point lowering accelerates the motor to
full speed similar to full-speed hoisting.