Three-Phase Transformers is one of 9 topics in the Grade 12 Electrical Technology CAPS syllabus, covered across 3 lessons on Study Vault. Below are real practice questions from this topic with full worked answers.
Sample practice questions
Easy
1. A transformer transfers electrical energy from one circuit to another through which principle, without a direct electrical connection?
Electromagnetic induction
Direct current conduction only
Chemical reaction
Mechanical friction
Answer: Electromagnetic induction — A transformer transfers electrical energy through electromagnetic induction, without a direct electrical connection between the primary and secondary circuits.
Easy
2. Which transformer connection is commonly used at the final distribution transformer, supplying both three-phase and single-phase consumer loads?
Delta-star (delta primary, star secondary)
Star-star only
Delta-delta only
No connection can supply both three-phase and single-phase loads
Answer: Delta-star (delta primary, star secondary) — A delta-star connection is commonly used at the final distribution transformer, since the star secondary provides the neutral point needed for single-phase supply alongside three-phase supply.
Medium
3. Name the type of transformer loss that occurs in the winding resistance and increases with load current (an I-squared-R type loss).
Answer: copper losses — Copper losses are I-squared-R losses in the winding resistance, which increase with load current, distinct from iron losses which occur whenever the transformer is energised.
