ABB Maintenance Engineer Interview Questions and Answers

Current is the flow of electric charge in a circuit.

• Current is measured in Amperes (A)

• It is the rate of flow of electric charge through a conductor

• Current can be either direct current (DC) or alternating current (AC)

• In a series circuit, the current remains the same throughout

• Ohm's Law relates current, voltage, and resistance: I = V/R

Voltage is the difference in electric potential between two points in a circuit, measured in volts.

• Voltage is the force that pushes electric current through a circuit

• It is measured in volts (V)

• Voltage is the potential difference between two points in a circuit

• Higher voltage means more potential energy available to move electrons

• Voltage can be DC (direct current) or AC (alternating current)

VCB full form is Vacuum Circuit Breaker.

• VCB stands for Vacuum Circuit Breaker.

• It is a type of circuit breaker that uses a vacuum to extinguish the arc when the contacts open.

• VCBs are commonly used in medium voltage applications.

• They are more reliable and require less maintenance compared to other types of circuit breakers.

MCB full form is Miniature Circuit Breaker.

• MCB stands for Miniature Circuit Breaker.

• It is an electromechanical device that protects an electrical circuit from overcurrent.

• MCBs automatically switch off electrical circuits during abnormal conditions.

• They are commonly used in residential and commercial buildings for electrical safety.

• Examples of MCB brands include Schneider Electric, Siemens, and Legrand.

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

• Transformers consist of two coils of wire, known as the primary and secondary coils.

• The primary coil is connected to a power source, creating a magnetic field when current flows through it.

• This magnetic field induces a voltage in the secondary coil, allowing for the transfer of electrical energy.

• Tra...read more

Star delta controlling is a method used to reduce the starting current of induction motors.

• Star delta controlling involves initially connecting the motor windings in a star configuration for starting, then switching to a delta configuration for running.

• It is commonly used for large induction motors to reduce the starting current and torque.

• The transition from star to delta configuration is typically controlled by a mot...read more

In star delta connection, typically two contactors are used.

• In star delta connection, one contactor is used for star connection and another contactor is used for delta connection.

• The star contactor is typically rated for the current of one winding, while the delta contactor is rated for the full motor current.

• Using two contactors helps in reducing the starting current and torque in the motor.

• For example, a 3-phase moto...read more

Single line diagram for DOL is a simple representation of Direct-On-Line motor starter circuit.

• DOL starter consists of a contactor, overload relay, and start/stop push buttons.

• The single line diagram shows the connections between these components.

• The power supply is connected to the contactor, which is then connected to the motor.

• The overload relay is connected in series with the motor to protect it from overloading.

• St...read more

There are various types of conveyors, gears and gearboxes, and bearings used in mechanical maintenance. Pulling bearings requires proper technique.

• Types of conveyors include belt, roller, chain, and screw conveyors

• Types of gears include spur, helical, bevel, worm, and planetary gears

• Types of bearings include ball, roller, and sleeve bearings

• To pull a bearing, use a bearing puller tool and apply force evenly to avoid da