The control methods for prevent to overload make use of motor power factor relay

摘要

PURPOSE: A method for controlling overload protecting operation using power-factor relay of motor is provided to prevent damage of motor and equipment connected to the motor by controlling overload in an accurate manner through a linear recognition for load. CONSTITUTION: An apparatus for controlling overload protecting operation comprises a microprocessor/operational amplifier(1); a sensor input unit(2); an overload power-factor input switch(3); a no-load power-factor input switch(4); a starting load permitting input switch(5); a shock load permitting time input switch(6); a restarting switch(7); a self-diagnosis switch(8); an overload control unit(9); a load display unit(10); an overload indicating lamp(11); a shock load indicating lamp(12); a fault indicating lamp(13); and current sensors(CT1,CT2,CT3) for sensing current of each of three-phase powers(R,S,T). The signal input through the sensor input unit which processes the current sensed by current sensors is computed through the microprocessor/operational amplifier, and processed in the overload control unit when overloaded in such a manner as to cut off power to the motor.