Method for checking brake torque

Abstract

In an AC inverter drive connected to an AC induction motor on a material handling machine, the motor (which has a load holding brake and a pulse-emitting shaft encoder) moves a load in hoisting or lowering directions. A method for checking brake load-holding torque including the steps of decelerating the motor toward zero speed, setting the brake, applying "float" load-holding electrical power to the motor, changing the current flowing to the motor and checking for motor rotation by pulse-counting. Motor power is blocked if the number of counted pulses is less than a predetermined number or is increased if the number of counted pulses is greater than a predetermined number, the latter indicating that the brake is incapable of holding the load.

Dependencies are inferred from the claim text.