Understanding Harmonics in Magnetic Flux — Lesson 9

This lesson covers the concept of third harmonic exciting current and third harmonic flux in magnetic materials. It explains that if the exciting or magnetizing current is purely sinusoidal at 50 Hertz, the flux created in the core will have a fundamental and a third harmonic component. Conversely, to create a pure sinusoidal flux at 50 Hertz, the exciting current must have a 50 Hertz component and a predominant third harmonic component. This is due to the double-valued function nature of the BH curve of the material. The lesson concludes with a qualitative discussion on the nature of the flux and exciting current required to create sinusoidal flux.

Video Highlights

00:38 - Explanation of the relationship between exciting current and flux in the core
05:16 - Discussion on the impact of the connection on the magnetizing current and flux in the core
21:00 - Discussion on the impact of connecting the supply neutral to the primary side neutral of the transformer
28:58 - Explanation of the implications of third harmonic flux and exciting current in a single-phase transformer
32:21 - Conclusion of the lecture and introduction to the next class

Key Takeaways

• If the exciting current is purely sinusoidal at 50 Hertz, the flux created in the core will have a fundamental and a third harmonic component.
• To create a pure sinusoidal flux at 50 Hertz, the exciting current must have a 50 Hertz component and a predominant third harmonic component.
• The nature of the BH curve of the material, which is a double-valued function, plays a significant role in the creation of the third harmonic component.
• Understanding the nature of the flux and exciting current required to create sinusoidal flux is crucial in dealing with magnetic materials.