Abstract:
The electrical motors are very important machine in our live, and they are widely used in the different fields . The alternating current (a.c.) motors and the direct current (d.c.) motors are represent the two main type of the electrical motors. The motors speed is an important operation factor in the motor operation and his properties. The motors speed control is essential to ensure proper work for the motors operation.
There are so many semiconductor devices that can be used to control the speed of the a.c. motors, such as the thyristors, bipolar junction transistors, triacs, and the insulated gate transistors family. All these semiconductors have different properties and variation on the switching speed, which represent the main factor in the electrical motor speed control.
An electronic circuit is designed to control the speed of single phase induction motor using inverter techniques. The inverters are devices that convert a d.c. voltage into an a.c. voltage. The pulse width modulation technique convert the a.c. voltage into variable magnitude voltage and variable frequency while keeping constant ratio (volt/hertz) , which allows wide range variation in the motor speed control. The power transistors, metal oxide semiconductor field effect transistors (MOSFET) are used as control switch. The control and driving signals are generated by electronic circuit to switch the power transistors( MOSFET) ON and OFF.
The circuit which is designed for the induction motor speed control allows to control the speed with wide range and constant torque. The power MOSFETs , IRF640 which are used in this research permit control of speed for induction motor power up to 3200KVA.
