Scott-T Transformer : Archit Electricals

A Scott-T transformer (also called a Scott connection) is a special transformer arrangement used to convert between three-phase and two-phase electrical systems.

What it does

Converts 3-phase power → 2-phase power, or the reverse
Useful when older 2-phase equipment needs to run from a modern 3-phase supply

How it’s built

It uses two single-phase transformers:

1. Main transformer
Connected across two phases of the 3-phase supply

2. Teaser transformer
Connected between the third phase and a midpoint (tap) on the main transformer

This setup creates two output voltages that are:

Equal in magnitude
90° out of phase (true two-phase system)

Key features of SCOTT-T Transformer

Balanced load on the 3-phase side (if designed correctly)
Efficient phase conversion
No rotating parts (unlike motor-generator sets)

Where it’s used

Supplying two-phase motors (older industrial systems)
Electric furnaces
Railway traction systems (historically)
Interfacing between different power systems

Simple intuition

Think of it as a clever way to “split” a 3-phase system into two perfectly timed waves that behave like a 2-phase system—without wasting energy or causing imbalance.
If you want, I can show a diagram or walk through the voltage relationships step by step.