Mohan Energy Corporation Interview Questions and Answers

Different types of tests to be performed in power transformer

• Insulation resistance test

• Ratio test

• Polarity test

• Vector group test

• No-load test

• Load test

• Temperature rise test

CB is a switch that can interrupt the circuit during fault conditions, while an isolator is a switch that can only isolate the circuit.

• CB is used for protection against overcurrent, short circuit, and earth fault

• Isolator is used for isolation of a circuit for maintenance or repair work

• CB can be operated manually or automatically, while isolator is operated manually only

• CB has contacts that can break the circuit, while isolator has no such contacts

The rating of equipment in a substation is crucial for its efficient functioning.

• The rating of transformers should be based on the maximum load they are expected to carry.

• Circuit breakers should be rated for the maximum fault current they may encounter.

• Busbars should be rated for the maximum current they may carry.

• Lightning arresters should be rated for the maximum voltage they may encounter.

• The rating of capacitors should be based on the reactive power requirement of the sys...read more

A power transformer is an electrical device that transfers electrical energy between two or more circuits through electromagnetic induction.

• It is used to step up or step down the voltage of an alternating current (AC) power supply.

• It consists of two or more coils of insulated wire wound around a magnetic core.

• The primary coil is connected to the input voltage source and the secondary coil is connected to the output load.

• Examples include distribution transformers, power transf...read more

Relays are used to control high voltage or current circuits with low voltage signals.

• Electromagnetic relays use an electromagnet to open or close a circuit.

• Solid-state relays use semiconductors to switch the circuit.

• Thermal relays protect motors from overheating by tripping the circuit when the temperature exceeds a set limit.

• Time delay relays are used to delay the opening or closing of a circuit for a specific time period.

• Reed relays use a magnetic field to control the switc...read more