METHOD OF DETECTING OVERLOAD OF MOTOR

摘要

PURPOSE:To detect constant overload at all times without depending upon the magnitude of applied voltage in the detection of the overload of a motor. CONSTITUTION:A period tn is measured from pulses continuously generated with the revolution of a motor (ST1), and the next period tn+1 is measured when the next pulses are generated. A cycle is continued while the period tn+1 is used as a new one tn when the period tn+1 is smaller than a discrimination value consisting of the sum of the period tn and a value obtained by multiplying the square of the period tn by a constant B, and load is discriminated as overload and the motor is stopped when the period tn+1 is larger than the discrimination value (ST2-ST5). The constant B is acquired by multiplying each constant determined by the used motor by a coefficient correcting a delay by a mechanical time constant. Accordingly, overload can be discriminated by formula using the period without being converted into the number of revolution, thus simplifying processing, then allowing discrimination without being subject to the effect of voltage fluctuation.