eGigElectrical engineer interview questions and answers
Electrical interviews cover machines, protection, power factor, safety and practical site or plant work. Expect questions on panels, motors and transformers.
12 questions. Read each one, start the timer and answer out loud as if you were in the room, then open the tip. Nothing is recorded.
What is power factor, and how do you improve it?
What a good answer covers
The ratio of real power to apparent power. Improve a low (lagging) power factor with capacitor banks.
MCB, MCCB and RCCB: what is the difference?
What a good answer covers
An MCB protects small circuits from overload and short circuit, an MCCB does the same at higher currents, an RCCB trips on earth leakage to protect people.
Star or delta: what is the difference?
What a good answer covers
In star, line voltage is √3 times phase voltage. In delta, line current is √3 times phase current. Star-delta starters cut motor starting current.
Why is earthing needed?
What a good answer covers
To carry fault current safely to the ground, protect people from shock and let protection devices trip.
How does a transformer work, and why is it rated in kVA?
What a good answer covers
By mutual induction between windings. Its losses depend on voltage and current, not on the load’s power factor, so it is rated in kVA.
What is the difference between a fuse and a circuit breaker?
What a good answer covers
A fuse melts and must be replaced. A breaker trips and can be reset.
How do you test insulation resistance?
What a good answer covers
With a megger, between conductors and to earth, and compare readings with the minimum values.
What is a DOL starter, and when is it used?
What a good answer covers
A direct-on-line starter connects the motor straight to the supply. It is used for small motors.
What do you do before working on a panel?
What a good answer covers
Isolate, lock out and tag, test that it is dead, wear PPE and work under a permit.
What is the difference between AC and DC?
What a good answer covers
AC changes direction periodically, at 50 Hz in most of Asia, Europe and Africa (60 Hz in the Americas). DC flows in one direction, as from batteries and solar panels.
Have you worked with PLC or SCADA?
What a good answer covers
Name the system and what you did: wiring, programming, troubleshooting or monitoring.
How do you read a single-line diagram?
What a good answer covers
Follow power from the source through breakers, transformers and buses to loads, noting ratings and protection.
All 12 questions with answers
1. What is power factor, and how do you improve it?
The ratio of real power to apparent power. Improve a low (lagging) power factor with capacitor banks.
2. MCB, MCCB and RCCB: what is the difference?
An MCB protects small circuits from overload and short circuit, an MCCB does the same at higher currents, an RCCB trips on earth leakage to protect people.
3. Star or delta: what is the difference?
In star, line voltage is √3 times phase voltage. In delta, line current is √3 times phase current. Star-delta starters cut motor starting current.
4. Why is earthing needed?
To carry fault current safely to the ground, protect people from shock and let protection devices trip.
5. How does a transformer work, and why is it rated in kVA?
By mutual induction between windings. Its losses depend on voltage and current, not on the load’s power factor, so it is rated in kVA.
6. What is the difference between a fuse and a circuit breaker?
A fuse melts and must be replaced. A breaker trips and can be reset.
7. How do you test insulation resistance?
With a megger, between conductors and to earth, and compare readings with the minimum values.
8. What is a DOL starter, and when is it used?
A direct-on-line starter connects the motor straight to the supply. It is used for small motors.
9. What do you do before working on a panel?
Isolate, lock out and tag, test that it is dead, wear PPE and work under a permit.
10. What is the difference between AC and DC?
AC changes direction periodically, at 50 Hz in most of Asia, Europe and Africa (60 Hz in the Americas). DC flows in one direction, as from batteries and solar panels.
11. Have you worked with PLC or SCADA?
Name the system and what you did: wiring, programming, troubleshooting or monitoring.
12. How do you read a single-line diagram?
Follow power from the source through breakers, transformers and buses to loads, noting ratings and protection.
Before the interview
- Read the job description twice and match two of your examples to what it asks for.
- Keep printed copies of your resume, ID proof and certificates ready, even for online rounds.
- Know your current CTC, expected salary and notice period. Check typical pay in our salary guide, and compare offers with the in-hand salary calculator.
- Genuine employers never ask you to pay for an interview, training kit or joining. Report anyone who does.