Patent ID: 8831787

Claim:
A method for operating a motorized hoist, the hoist comprising a motor and operable to raise a maintenance platform, said motor having an input for receiving voltage and current representative of motor operation, the method comprising: receiving, by a power controller, said voltage and current representative of motor operation and determining an estimated power based on the voltage and current; determining, by the power controller, a capacity of said motor to meet motor operating conditions based on a pattern of said current; determining, by the power controller, a degree of overload of said motor based on said estimated power; and inhibiting, by the power controller, further operation of the hoist as a function of said capacity and said degree, wherein said degree is based on an estimate of power required to elevate the platform, the estimate of power based on a peak of successive half cycles of waveforms of the current and voltage to derive an RMS value of said estimated power as: P= 0.5 *V peak-ave *I peak-ave .