Understanding Three Phase Transformer Construction — Lesson 7

This lesson covers the construction and working of a three-phase transformer as a single unit. It begins with the concept of joining three single-phase transformers, with the secondary binding placed on the outer limbs. The lesson explains that the instantaneous value of the flux in the central limb will be zero due to the 120° phase difference between Phi A, Phi B, and Phi C. This allows for the central material to be avoided. The lesson also introduces a simplified way of constructing a transformer using plane laminations with two windows.

Video Highlights

01:20 - Discussion on the constructional features of a three phase transformer
05:52 - Discussion on the magnetizing current required in the phases of the transformer
17:05 - Discussion on the calculation of the line currents of the transformer
20:43 - Explanation of the turns ratio of the HV and LV windings of the transformer
37:42 -Discussion on the zigzag connection of the transformer

Key Takeaways

• A three-phase transformer can be visualized as three single-phase transformers joined together.
• The secondary binding is placed on the outer limbs of the transformers.
• Due to the 120° phase difference between Phi A, Phi B, and Phi C, the instantaneous value of the flux in the central limb is zero.
• A simplified construction method involves using plane laminations with two windows.