Understanding Three-Phase Transformers — Lesson 1

This lesson covers the concept of three-phase transformers, focusing on their types, connections, and applications. It begins with an explanation of the Sumpner test, which is used to determine the equivalent circuit parameters of transformers. The lesson then delves into the two types of three-phase transformers: a bank of three single-phase transformers and a three-phase transformer as a single unit. The lesson explains how these transformers are used to change the voltage level in a three-phase power system. The lesson also covers the marking of transformer terminals, the connection of primary coils in a star, and the calculation of line-to-line voltage. The lesson concludes with a discussion on the total KVA of a three-phase transformer.

Video Highlights

02:24 - Introduction to three-phase transformers and their types
09:16 - Explanation of how to mark the terminals of the transformer
13:15 - Demonstration of how to connect the primary coils in star
28:38 - Explanation of how to connect a balanced three-phase load to the transformer
31:27 - Calculation of the total KVA for a three-phase transformer

Key Takeaways

• Three-phase transformers can be a bank of three single-phase transformers or a three-phase transformer as a single unit.
• The Sumpner test is used to determine the equivalent circuit parameters of transformers.
• In a star connection, the line-to-line voltage is root 3 times less than the supply voltage.
• The total KVA of a three-phase transformer can be calculated using the formula root 3 times line-to-line voltage times line current.