Understanding Hopkinson Test and Machine Connections — Lesson 1

This lesson covers the concept of the Hopkinson test and the connection of machines in a detailed manner. It explains how two machines are connected as a shunt machine and how their armatures and fields are arranged. The lesson further elaborates on the concept of separately excited field windings and the conditions for paralleling the armatures of the two machines. It also discusses the concept of adjusting field currents, the polarity of voltage, and the back EMF of the motor. The lesson concludes with a detailed explanation of power drawn from the supply, total rotational loss, and the calculation of the efficiency of the machine.

Video Highlights

00:52 - Discussion on the field winding of the machines and the supply
08:18 - Explanation of the efficiency of the generator
21:24 - Explanation of the operation of the machines when connected to a DC bus
26:54 - Discussion on the scenario when the prime mover is detached

Key Takeaways

• The Hopkinson test involves the connection of two machines as a shunt machine with separately excited field windings.
• The armatures of the two machines are paralleled under certain conditions and are mechanically coupled to run at the same speed.
• The field currents of the machine are adjusted to ensure the polarity of the voltage and the back EMF of the motor.
• The power drawn from the supply accounts for all the losses in the machine, including field copper loss, armature copper loss, and total rotational loss.
• The efficiency of the machine can be calculated by subtracting the losses from the input power.