Three-Phase Power
Electrical Science · C&G 2365 Unit 302 · Free section
Domestic wiring is single-phase, but industry runs on three: three line conductors 120 degrees apart share the load and keep motors turning smoothly. Between any line and neutral you measure one voltage; between two lines, root three times more — in the UK, roughly 230 V and 400 V.
Star and delta connections, line versus phase quantities, and balanced-load power calculations are where Level 3 science exams concentrate, and where sign-up-and-cram revision usually falls apart. Interactive diagrams beat memorised formulas here.
Our lessons build the picture first, then drill the calculations with fresh numbers each time.
Common questions
- Is there a free Three-Phase Power quiz?
- Yes. Three-Phase Power is taught in the Electrical Science section of TradeTraining, which is free — you can practise in your browser without paying anything.
- Where does Three-Phase Power sit in the City & Guilds scheme?
- Three-Phase Power maps to C&G 2365 Unit 302. On TradeTraining it lives in the Electrical Science section as bite-size lessons with practice questions.
- Why is three-phase 400 V and single-phase 230 V?
- Both live on the same supply: 230 V is measured from one line to neutral, while 400 V is measured between two lines. The two figures differ by the square root of three, which falls out of the 120-degree spacing between phases — not from a separate, higher-voltage source.