Johnson Controls ITI Electrician Interview Questions and Answers

The current in a 3 phase system depends on the voltage and power of the system.

• The current in a 3 phase system can be calculated using the formula: I = P / (sqrt(3) * V)

• Where I is the current, P is the power, and V is the voltage

• For example, if the power is 1000W and the voltage is 240V, the current would be approximately 4.33A

MCB stands for Miniature Circuit Breaker, a device designed to protect electrical circuits from overloads and short circuits.

• MCB is a type of circuit breaker that automatically switches off electrical circuits during abnormal conditions like overload or short circuit.

• It is commonly used in residential and commercial electrical installations to protect wiring and electrical equipment.

• MCBs are available in different curr...read more

To check AC DC current, use a multimeter set to the appropriate setting and connect the probes to the circuit being tested.

• Set the multimeter to the AC or DC current setting depending on what you are testing.

• Ensure the multimeter probes are connected correctly to the circuit being tested.

• Read the current measurement displayed on the multimeter.

• For AC current, make sure the multimeter is set to the appropriate range (e....read more

To check cable continuity, use a multimeter to measure resistance between two points on the cable.

• Use a multimeter set to the resistance or continuity mode.

• Connect one probe to one end of the cable and the other probe to the other end.

• A low resistance reading indicates good continuity, while a high resistance or infinite reading indicates a break in the cable.

• Check for continuity in each conductor of the cable separate...read more

PVC stands for Polyvinyl Chloride, a type of plastic commonly used in construction and electrical applications.

• PVC is a versatile material known for its durability and resistance to chemicals.

• It is commonly used in electrical wiring, plumbing pipes, and vinyl flooring.

• PVC is lightweight, easy to install, and cost-effective compared to other materials.

• Examples of PVC products include PVC pipes, PVC electrical conduits,

The motor work in AC is based on electromagnetic induction, while in DC it is based on the Lorentz force principle.

• AC motors work on the principle of electromagnetic induction, where a changing magnetic field induces a current in the rotor coils.

• DC motors operate based on the Lorentz force principle, where a current-carrying conductor in a magnetic field experiences a force.

• Examples of AC motors include induction motor...read more

Rewinding a 72 slot 50 hp motor involves disassembling the motor, removing the old windings, and replacing them with new windings.

• Disassemble the motor carefully to access the windings

• Remove the old windings without damaging the core

• Calculate the number of turns and wire gauge needed for the new windings

• Wind the new coils carefully and evenly in the slots

• Connect the windings properly and test the motor for functionalit

NO NC stands for Normally Open and Normally Closed. They refer to the state of a switch or relay when it is not activated.

• NO (Normally Open) - the switch is open (off) when not activated

• NC (Normally Closed) - the switch is closed (on) when not activated

• Used in electrical circuits to control the flow of current

• Commonly used in control panels, automation systems, and safety circuits

Earthing points are checked by using a multimeter to measure the resistance between the earthing point and the earth electrode.

• Use a multimeter set to the resistance mode

• Connect one probe to the earthing point and the other probe to the earth electrode

• Check the resistance reading on the multimeter

• A low resistance reading indicates a good earthing connection

• Repeat the process for all earthing points in the system

Fan rewinding is the process of replacing the copper wire coils in the stator of a fan motor to restore its functionality.

• Disconnect the fan from the power source before starting the rewinding process.

• Remove the fan blades and outer casing to access the stator.

• Carefully unwind the old copper wire coils from the stator and measure their length and gauge.

• Select the appropriate gauge and length of copper wire for rewindin...read more

A contactor relay is an electrical device used to control a high-power circuit with a low-power signal.

• Contactor relay consists of a coil, contacts, and an enclosure.

• When the coil is energized, it creates a magnetic field that pulls the contacts together to close the circuit.

• Contactor relays are commonly used in motor control circuits to start and stop motors.

• They can also be used in lighting control, heating systems,