Thomson Press India Electrician Interview Questions and Answers

There are three types of protection in a transformer.

• The three types of protection are overload protection, overcurrent protection, and overvoltage protection.

• Overload protection protects the transformer from excessive heat caused by too much current.

• Overcurrent protection protects the transformer from damage caused by excessive current.

• Overvoltage protection protects the transformer from damage caused by excessive vol...read more

The 4 protection devices for an oil type transformer are Buchholz relay, pressure relief valve, oil level indicator, and winding temperature indicator.

• Buchholz relay detects gas accumulation and oil level changes

• Pressure relief valve releases excess pressure to prevent explosion

• Oil level indicator monitors oil level to prevent damage to transformer

• Winding temperature indicator measures temperature to prevent overheatin

MPCB stands for Motor Protection Circuit Breaker.

• MPCB is an electrical device used to protect motors from overloading, short circuits, and phase failures.

• It is a combination of a circuit breaker and a contactor.

• MPCBs are commonly used in industrial and commercial applications.

• They are available in different sizes and ratings depending on the motor's power and voltage requirements.

An induction motor works by inducing a magnetic field in the rotor through electromagnetic induction.

• The stator creates a rotating magnetic field

• This induces a current in the rotor, creating a magnetic field

• The interaction of the two fields causes the rotor to rotate

• Induction motors are commonly used in industrial and residential applications

DC motors use direct current to produce rotational motion while induction motors use alternating current and electromagnetic induction.

• DC motors have a commutator and brushes while induction motors do not.

• DC motors have a constant speed while induction motors have a variable speed.

• DC motors are more efficient at low speeds while induction motors are more efficient at high speeds.

• DC motors are commonly used in small app...read more

Relays are electrical switches that control the flow of electricity in a circuit.

• Electromechanical relays use an electromagnet to mechanically open or close the circuit.

• Solid-state relays use semiconductor devices to control the flow of current.

• Time-delay relays introduce a time delay before opening or closing the circuit.

• Thermal relays protect against overheating by sensing temperature changes.

• Reed relays use a reed s...read more

The speed of a 6 pole motor depends on the frequency of the power supply.

• The speed of a motor is determined by the number of poles and the frequency of the power supply.

• For a 6 pole motor, the speed can be calculated using the formula: Speed (RPM) = (120 * Frequency) / Number of Poles.

• The speed of a 6 pole motor will vary depending on the frequency of the power supply.

• For example, if the frequency is 60 Hz, the speed o...read more

The maximum oil temperature of a transformer depends on its design and insulation class.

• The maximum oil temperature is typically specified by the manufacturer.

• For most transformers, the maximum oil temperature is around 95-105 degrees Celsius.

• Exceeding the maximum oil temperature can lead to insulation breakdown and damage to the transformer.

• Regular monitoring and maintenance are essential to ensure the oil temperature