Understanding Electrical Machines: Core Losses — Lesson 7

This lesson covers the concept of core losses in electrical machines, focusing on hysteresis and eddy current losses. It explains how these losses occur, the factors they depend on, and how they can be minimized. The lesson also introduces the empirical formula for calculating hysteresis loss and discusses the importance of the area enclosed by the BH curve. It further explains the role of the magnetizing branch in determining the maximum flux and how the core loss resistance should be connected in parallel with the magnetizing reactance. An example of a practical transformer is used to illustrate these concepts.

Video Highlights

01:49 - Discussion on the nature of alternating current and its impact on energy supply
05:10 - Explanation of how the energy absorbed by the coil represents hysteresis loss per unit volume
15:34 - Discussion on how to reduce hysteresis loss by choosing the right magnetic material
18:35 - Explanation of the factors on which hysteresis loss depends
30:14 - Discussion on how core loss is represented in the equivalent circuit of a practical transformer

Key Takeaways

• Core losses in electrical machines are primarily due to hysteresis and eddy current losses.
• These losses depend on factors such as the area enclosed by the BH curve, the maximum flux density (B Max), and the frequency of supply.
• The empirical formula for hysteresis loss suggests that it is proportional to B Max raised to the power of 1.6 and the frequency.
• The magnetizing branch plays a crucial role in determining the maximum flux, which remains practically the same from no load to full load condition.
• The core loss resistance, which represents the core loss, should be connected in parallel with the magnetizing reactance.