Variable speed drive of DC motor using phase control rectifier

Abstract

The main purpose of this project is to control the DC motor speed by varying the input voltage at the DC motor terminal. The DC motor speed is depended on how much voltage that supplied to the DC motor terminal. The input voltage at the DC motor terminal is varied by using voltage phase controlled rectifier. Thyristor type SCR (Silicon Controlled Rectifier) is suitable to use for voltage phase controlled rectifier. A 180V, 1800RPM DC motor is used and the input AC voltage to rectify is 240V, 50Hz which is the standard supply from Tenaga Nasional Berhad (TNB). Before the DC motor is applied, resistor is used as the load. It is to make sure that the output voltage is direct current and can be varied freely. At the end of this project, it can be conclude that the alpha angle that suitable to vary the motor speed is only range from 110°(1862 RPM,183.3V) to 180°(0 RPM,0V). The DC motor is in its maximum speed during 110° alpha angle. The DC motor suffered over voltages when the alpha angle applied is smaller from 110°.