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:
- Current transformer (CT) [Download free whitepaper on CTs]
- 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:
- ONAN: Natural oil cooling (ON), Natural air cooling (AN)
- ONAF: Natural oil cooling (ON), Forced air cooling (AF)
- OFAF: Forced oil cooling (OF), Forced air cooling (AF)
- ODAF: Directed oil cooling (OD), Forced air cooling (AF)
- 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.