Operational control system for lift and elevator machinery

Claim 1

Operational control system for electrodynamic braking of lift and elevator machinery, said machinery comprising a one-speed A.C. asynchronous motor of the short-circuit type equipped with a mechanical brake, characterized by means for sensing the speed of the lift, a D.C. source for feeding the field windings of the A.C. asynchronous motor to produce a rectified magnetic braking flow through the rotor of the said asynchronous motor to produce electrodynamic braking, and integrating means for integrating the output signal from the member sensing the number of rotations to generate a reference signal for the retardation distance, and converting means having a root-extracting function to linearize the reference signal for the retardation distance, first comparator means for comparing the output signal indicating the number of revolutions with the linearized signal for the retardation distance to produce a fault signal for controlling an electric control signal for said D.C. direct current source, second comparator means for comparing the fault signal with a reference level corresponding to the available maximum electrodynamic braking to produce a signal for activating existing mechanical brake in said machinery.