Understanding Magnetizing Current from B-H Curve — Lesson 2

This lesson covers the fundamental concepts of electrical machines, focusing on transformers and DC machines. It explains the structure of a transformer, which consists of at least two coupled coils wound on a common magnetic circuit. The lesson also discusses the concept of a magnetic circuit, which comprises a magnetic core made of ferromagnetic material. It delves into the calculation of flux in a DC magnetic circuit and the impact of alternating current on the magnetic circuit. The lesson further explains the relationship between the applied voltage and the induced voltage in a coil excited by an AC voltage source. It also discusses the effect of changing the core material on the current drawn by the coil.

Video Highlights

01:50 - Explanation of how the amount of flux can be calculated in a DC magnetic circuit
03:45 - Discussion on how a coil excited by AC will have an induced voltage
08:50 - Explanation of how the induced voltage will oppose the supply voltage
16:12 - Discussion on how the peak value of the flux is fixed by the supply voltage and frequency
28:44 - Discussion on how the current drawn can be reduced by using better magnetic material
31:25 - Conclusion of the lecture and announcement of continuation in the next lecture

Key Takeaways

• A transformer consists of at least two coupled coils wound on a common magnetic circuit.
• The magnetic circuit comprises a magnetic core made of ferromagnetic material.
• In a coil excited by an AC voltage source, the applied voltage and the induced voltage are in phase.
• Changing the core material of a coil can affect the current drawn by the coil.