Understanding Speed Control for DC Motors-3 — Lesson 5

This lesson covers the methods of speed control for DC motors, focusing on two primary methods: varying the armature voltage while keeping the field current constant, and field control. The lesson explains how these methods work, their applications, and their limitations. For instance, varying the armature voltage is suitable for constant load torque drive, while field control is adopted for speeds above the rated speed. The lesson also provides a detailed explanation of how to calculate the new speed of the motor when the field current is changed or when the motor is required to run at a higher speed.

Video Highlights

00:56 - Explanation of how varying armature voltage is suitable for constant load torque drive
05:28 - Explanation of how field control is adopted above rated speed
13:53 - Explanation of how to calculate the new speed and armature current when field current is reduced
28:24 - Discussion on the importance of quick estimation in engineering
32:02 - Conclusion of the lecture and what to expect in the next class

Key Takeaways

• There are two primary methods of speed control for DC motors: varying the armature voltage while keeping the field current constant, and field control.
• Varying the armature voltage is suitable for constant load torque drive, while field control is adopted for speeds above the rated speed.
• Calculations for the new speed of the motor when the field current is changed or when the motor is required to run at a higher speed can be done using the equations provided in the lesson.
• Quick estimation of the new speed can be done by neglecting the armature resistance drop.