Voltamp Transformers Service Engineer Interview Questions, Process, and Tips

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

• Consists of two coils of wire, known as primary and secondary coils

• Primary coil is connected to a source of alternating current

• Alternating current in primary coil creates a changing magnetic field

• This changing magnetic field induces a voltage in the secondary coil

• Voltage in secondary coil can be hig...read more

Safety devices in transformers include pressure relief devices, Buchholz relay, and temperature sensors.

• Pressure relief devices are used to release excess pressure in the transformer to prevent explosions.

• Buchholz relay is a gas and oil operated relay that detects internal faults in the transformer.

• Temperature sensors are used to monitor the temperature of the transformer and prevent overheating.

Controlling devices in transformers are used to regulate voltage, protect against overloads, and ensure efficient operation.

• Controlling devices such as tap changers are used to adjust the voltage ratio of the transformer to maintain a constant output voltage.

• Protective devices like relays are used to detect and isolate faults such as overloads, short circuits, and overvoltage conditions.

• Monitoring devices like temperat...read more

Delta connection and star connection are two types of connections used in electrical circuits. Delta connection is used for three-phase systems, while star connection is used for single-phase systems.

• Delta connection is used in three-phase systems where the load is balanced and the power requirement is high.

• Star connection is used in single-phase systems where the load is unbalanced and the power requirement is low.

• Del...read more

Delta and star connections are two methods of connecting three-phase electrical systems, affecting voltage and current distribution.

• Delta connection (Δ) connects each phase to two others, forming a closed loop.

• Star connection (Y) connects each phase to a common neutral point.

• In delta, line voltage equals phase voltage; in star, line voltage is √3 times phase voltage.

• Delta is used for high power applications; star is us...read more

OSR detects overcurrent, while Buchholz relay protects transformers from faults by sensing gas and oil flow.

• OSR (Overcurrent Relay) is used to detect overcurrent conditions in electrical circuits.

• Buchholz relay is specifically designed for oil-filled transformers to detect gas accumulation and oil flow.

• OSR operates based on current levels, while Buchholz relay operates based on physical changes in the transformer oil.

• E...read more

Radiators in transformers dissipate heat, ensuring efficient operation and preventing overheating through oil circulation.

• Transformers generate heat during operation due to electrical losses.

• Radiators are external heat exchangers that cool the transformer oil.

• The oil circulates through the radiator, transferring heat to the air.

• Cooling fins increase the surface area for better heat dissipation.

• In larger transformers, f...read more

To calculate voltage and current from transformer power in KVA, use the formulas: Power (KVA) = Voltage (V) x Current (A).

• Power (KVA) = Voltage (V) x Current (A) / 1000

• For a 100 KVA transformer at 400V: Current = 100,000 VA / 400V = 250 A.

• For a 50 KVA transformer at 230V: Current = 50,000 VA / 230V ≈ 217.39 A.

• Voltage can also be calculated if current is known: Voltage = Power (KVA) x 1000 / Current (A).