Motor analysis for protection engineers

摘要

A motor analysis program called MotorLab, which allows a protection engineer to complete a motor analysis in a matter of minutes, is described. MotorLab uses the minimum essential motor rating, torque, and thermal data to produce plots of the starting current, terminal voltage, speed and torque for any desired condition of source voltage and impedance. The program plots the time-current plot of the motor thermal limit and starting current in log-log format and automatically coordinates the stator, locked rotor, and fault characteristic. It also checks the security of the application. The main purpose of the program is to determine the temperature rise in the motor, which is used to determine settings for a microprocessor-based relay that employs thermal models to determine temperature. The attributes of the program are illustrated by an analysis of a 4160 volt, 6000 HP, 720 RPM, high-inertia, induced-draft fan motor.