Smart starting of induction motor by changing core magnetic flux value

Single-phase squirrel cage and three-phase induction electromotors are the most popular electromotors used in industry from long ago. When an induction motor starts with direct connection method, it takes a lot of current from the power supply (several times the nominal current); so, several methods have been devised to start such electromotors. These methods either reduce the voltage of the stator or increase the value of rotor resistance. In this paper a new method is presented that reduces the value of the magnetic flux in stator core resulting in reduction of induction voltage in the rotor bars culminating in reduction of rotor and stator currents. This system reduces the electromotor loss and smartly protects itself against damages due to overload. Process functions are analyzed, the uses of the system are discussed and the operation of the electromotor is simulated in Matlab version 7.11.0.584 (R2010b) and Maxwell 16.0.

I. Introduction

Induction motors are most used in the Industry and its operation is based on induce the voltage in the bars or windings of the rotor and then make a magnetic field in rotor and consequently, make a mechanical torque in motor. Induction motors consist of the rotor and stator. Stator have a three-phase windings in the core. Rotor of the motor have a two types, first one is many bars that Short circuited with two rings and second type is many windings that that short circuited all of them in the end of the windings [1].