Speed Control of Three-Phase Induction Motor — Lesson 5

This lesson covers the concept of speed control in three-phase induction motors. It explains the traditional methods of speed control, such as varying the rotor resistance or supply voltage, and the limitations of these methods. The lesson then introduces modern methods of speed control, which involve changing the frequency of the supply, thereby altering the synchronous speed. It also discusses the importance of maintaining a constant voltage-to-frequency ratio to prevent motor saturation. The lesson further explains how to control the speed of the motor both below and above its rated speed by adjusting the supply frequency and voltage.

Video Highlights

00:28 - Traditional methods of speed control
03:51 - Modern methods of speed control
10:22 - Importance of maintaining a constant voltage-to-frequency ratio
11:14 - Controlling speed below the rated speed
22:16 - Controlling speed above the rated speed

Key Takeaways

- Traditional methods of speed control, such as varying the rotor resistance or supply voltage, have limitations and are not as effective as modern methods.
- Modern methods of speed control involve changing the frequency of the supply, which alters the synchronous speed of the motor.
- It's crucial to maintain a constant voltage-to-frequency ratio when changing the frequency to prevent motor saturation.
- The speed of the motor can be controlled both below and above its rated speed by adjusting the supply frequency and voltage.