Harjai Computers Interview Questions and Answers

Preventive maintenance on a motor involves inspecting, cleaning, lubricating, and testing the motor to ensure optimal performance and prevent breakdowns.

• Inspect the motor for any signs of wear or damage

• Clean the motor and its components to remove dirt and debris

• Lubricate moving parts to reduce friction and wear

• Test the motor's performance using appropriate tools and equipment

• Replace any worn out parts or components as needed

An overload relay works by monitoring the current flowing through a motor and tripping when the current exceeds a set limit.

• Monitors the current flowing through a motor

• Trips and interrupts power when current exceeds a set limit

• Protects the motor from damage due to overloading

• Can be reset manually after tripping

A star-delta starter is used to reduce the starting current of a motor by initially connecting the motor windings in a star configuration and then switching to a delta configuration.

• The motor windings are initially connected in a star configuration during starting to reduce the starting current.

• After a certain period, the windings are switched to a delta configuration to achieve full speed and torque.

• This transition from star to delta configuration is controlled by a timer or...read more

A thermal relay is used to protect electrical circuits from overloads by monitoring the temperature of the circuit and tripping when it exceeds a certain threshold.

• Monitors the temperature of the electrical circuit

• Trips and disconnects the circuit when temperature exceeds a set limit

• Protects against overloads and overheating

• Commonly used in motor protection applications

Insulation resistance is measured using a megohmmeter to apply a high voltage and measure the resistance of the insulation material.

• Use a megohmmeter to apply a high voltage to the insulation material

• Measure the resistance of the insulation material to determine its insulation resistance

• Insulation resistance is typically measured in megaohms (MΩ)

• Regular insulation resistance testing helps prevent electrical failures and ensures safety

Undervoltage faults occur when the voltage in a system drops below the normal operating level, leading to potential equipment damage or malfunction.

• Undervoltage faults can be caused by issues such as power supply fluctuations, equipment failures, or overloaded circuits.

• These faults can lead to equipment damage, reduced efficiency, or complete shutdown of systems.

• Examples include a power surge causing a drop in voltage, or a faulty transformer leading to undervoltage condition...read more

Overvoltage faults are electrical faults that occur when the voltage in a circuit exceeds the normal operating range.

• Overvoltage faults can damage electrical components and equipment.

• They can be caused by lightning strikes, power surges, or faulty equipment.

• Protective devices like surge protectors and voltage regulators can help prevent overvoltage faults.

• Examples include a power surge from a lightning strike damaging a computer or a faulty transformer causing a voltage spike...read more

An RDOL starter is a type of reduced voltage starter used in electrical systems to reduce the starting current and torque of a motor.

• RDOL stands for Reduced Direct Online starter.

• It is used to start induction motors in a controlled manner.

• RDOL starters reduce the voltage supplied to the motor during starting to limit the inrush current.

• This helps in reducing mechanical stress on the motor and connected equipment.

• Commonly used in applications where a soft start is required to ...read more