Top 10 Transformer Questions for Electrical Engineering Interviews

The transformer is an electrical device which steps up and steps down the ac voltages. Given below are top 10 transformer questions for electrical engineering interviews.

Question 1: Why short circuit test is performed on transformers?

Answer: The short circuit test is performed for calculating the copper losses.

Question 2: Why open circuit test is performed on transformers?

Answer: Open circuit test is performed for determining core losses.

Question 3: What happens when a 60 Hz transformer is connected to 50 Hz supply?

Answer: The peak flux and magnetization current of device increases. Learn it in detail

Question 4: What is Buchholz relay?

Answer: It is a gas actuated relay that is installed in oil immersed transformers for providing protection.

Similar Reading: 20 Different types of relays

Question 5: What is instrumentation transformer, also mention its types?

Answer: The transformers used with electrical instruments such as voltmeters, ammeters for protection and instrumentation purposes. They are of two types:

  1. Current transformer (CT) [Download free whitepaper on CTs]
  2. Potential transformer [Download free whitepaper on PTs]

Question 6: Why transformer core is laminated?

Answer: Transformer core is laminated for providing protection against eddy current losses.

Question 7: Name the transformer cooling methods?

Answer: 5 types of cooling methods are used for transformers:

  1. ONAN: Natural oil cooling (ON), Natural air cooling (AN)
  2. ONAF: Natural oil cooling (ON), Forced air cooling (AF)
  3. OFAF: Forced oil cooling (OF), Forced air cooling (AF)
  4. ODAF: Directed oil cooling (OD), Forced air cooling (AF)
  5. OFWF: Forced oil cooling (OF), Forced water cooling (WF)

Question 8: Explain the behavior of iron losses from no load to full load?

Answer: They essentially remain constant from no load to full load.

Also, learn top 10 MCQs on transformers

Question 9: Why OC test is performed on LV side?

Answer: Doing so allows you to deal with lower voltage levels.

Question 10: What should be the ideal voltage regulation, Why it is not achievable for real-world transformers?

Answer: The ideal VR should be 0. It is practically not possible since the output voltage varies from no load to the full load condition.

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