Exam Question
Q3
(a) Explain how the efficiency and regulation of a transformer can be assessed by open circuit and short circuit tests?
(12)
(b) What is meant by equivalent resistance?
(4)
ETO
ETO Exam papers
📅 Feb 2026
Reference Answer
### (a) Transformer Efficiency and Regulation by OC & SC Tests
The efficiency and voltage regulation of a transformer can be determined without directly loading it, which is particularly advantageous for large-capacity transformers. This is achieved by performing two simple tests: the Open Circuit (OC) Test and the Short Circuit (SC) Test, which determine the transformer's losses and circuit parameters.
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#### 1. Open Circuit (OC) Test
The efficiency and voltage regulation of a transformer can be determined without directly loading it, which is particularly advantageous for large-capacity transformers. This is achieved by performing two simple tests: the Open Circuit (OC) Test and the Short Circuit (SC) Test, which determine the transformer's losses and circuit parameters.
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#### 1. Open Circuit (OC) Test
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