Understanding Electrical Braking in Motors — Lesson 7

This lesson covers the concept of electrical braking on DC shunt or separately excited motors. It explains the process of DC dynamic braking, where the armature is disconnected from the supply and connected across a resistance, resulting in a reversal of the armature current and the development of an opposing electromagnetic torque. The lesson also discusses the calculation of braking torque and the factors affecting it. It introduces the concept of regenerative braking, where the kinetic energy is not dissipated but fed back to the supply. The lesson concludes with a discussion on series motors, their construction, and the large starting torque they can produce.

Video Highlights

01:25 - Discussion on how to calculate the braking torque at T equal to zero
06:21 - Explanation of the process of regenerative braking in a downhill scenario
18:23 - Discussion on the construction and operation of a series motor
35:37 - Explanation of the importance of back EMF equation and torque equation in understanding the operation of shunt and series motors
37:00 - Discussion on the potential problems of starting a series motor without any mechanical opposing torque

Key Takeaways

• In DC dynamic braking, the armature is disconnected from the supply and connected across a resistance, resulting in a reversal of the armature current and the development of an opposing electromagnetic torque.
• The braking torque in DC dynamic braking is a function of time and gradually collapses to zero.
• In regenerative braking, the kinetic energy is not dissipated but fed back to the supply. This method of braking does not bring the machine to a stop but stabilizes it.
• Series motors can produce a very large starting torque, making them suitable for applications that require a high starting torque.