Q9Electrical Machines and Drives
Question
2 marks
Q.9. What is the necessity of controlled rectifier for DC drives? [2]
Answer
A controlled rectifier converts the fixed AC supply voltage into a variable, adjustable DC output voltage by varying the firing (delay) angle of its thyristors, which is essential for DC drives because a DC motor's speed is directly proportional to its armature voltage (for constant field flux); a controlled rectifier therefore allows smooth, stepless speed control of the DC motor directly from the AC mains without needing a separate variable DC source or resistive controllers, while also enabling regenerative braking capability in fully-controlled bridge configurations.