Power Factor Correction — MCQs – EE

1. Power factor (PF) is defined as:
(A) Ratio of active power to apparent power
(B) Ratio of reactive power to apparent power
(C) Ratio of apparent power to active power
(D) Ratio of voltage to current

2. The power factor of a purely resistive load is:
(A) 1 (unity)
(B) 0
(C) 0.5 lagging
(D) 0.5 leading

3. Lagging power factor occurs when:
(A) Current lags the voltage (inductive load)
(B) Voltage lags the current
(C) Load is purely resistive
(D) Load is capacitive

4. Leading power factor occurs when:
(A) Current leads the voltage (capacitive load)
(B) Current lags the voltage
(C) Load is resistive
(D) Load is inductive

5. Poor power factor causes:
(A) Higher line currents for the same active power
(B) Reduced current
(C) Reduced losses
(D) Increased efficiency

6. Benefits of power factor correction include:
(A) Reduced line losses, improved voltage regulation, and lower demand charges
(B) Increased reactive power only
(C) Reduced active power delivered
(D) Higher frequency

7. Capacitors are commonly used for:
(A) Power factor correction in inductive loads
(B) Reducing active power
(C) Increasing line current
(D) Frequency correction

8. Synchronous condensers are used for:
(A) Power factor correction and reactive power compensation
(B) Voltage sags mitigation only
(C) Frequency control only
(D) Harmonic filtering only

9. Static VAR compensators (SVCs) are:
(A) Fast-acting devices for dynamic power factor correction
(B) Slow-acting mechanical devices
(C) Only used for frequency control
(D) Capacitor banks without control

10. The reactive power (Q) of a load is given by:
(A) Q = P × tanφ
(B) Q = P × cosφ
(C) Q = P × sinφ
(D) Q = P / cosφ

11. The apparent power (S) in a system is:
(A) S = √(P² + Q²)
(B) S = P – Q
(C) S = P × Q
(D) S = P / Q

12. Leading reactive power can be provided by:
(A) Capacitors
(B) Inductors
(C) Resistive loads
(D) Transformers

13. Lagging reactive power can be supplied by:
(A) Inductors or synchronous machines
(B) Capacitors
(C) Resistive heaters
(D) Static resistors

14. Over-correction in power factor can cause:
(A) Leading power factor, which may cause overvoltages
(B) Lagging power factor
(C) Reduced voltage
(D) Reduced harmonic levels only

15. In industrial plants, power factor correction is often achieved using:
(A) Capacitor banks connected in parallel with loads
(B) Series reactors
(C) Step-down transformers
(D) Static resistors

16. Power factor correction improves:
(A) Voltage regulation along the distribution lines
(B) Transformer efficiency only
(C) Motor speed only
(D) Cable insulation rating

17. For a load with P = 100 kW and power factor of 0.8 lag, the required reactive power (Qc) to achieve unity PF is:
(A) 60 kVAR
(B) 50 kVAR
(C) 80 kVAR
(D) 100 kVAR

18. Step capacitors can be switched in stages to:
(A) Gradually correct power factor
(B) Reduce frequency
(C) Reduce voltage sag
(D) Increase harmonics

19. Power factor correction at the load is more effective than at the supply side because:
(A) It reduces line currents immediately
(B) It increases reactive power losses
(C) It increases voltage drop
(D) It has no effect

20. The maximum power factor improvement is limited by:
(A) System voltage and permissible overvoltage
(B) Transformer rating only
(C) Load current only
(D) Cable size only

21. Harmonic currents can affect power factor correction by:
(A) Causing capacitor overheating
(B) Reducing active power
(C) Reducing voltage
(D) Improving PF automatically

22. Automatic power factor controllers (APFC) are used to:
(A) Switch capacitor banks based on real-time load requirements
(B) Control motor speed
(C) Reduce transformer losses
(D) Increase frequency

23. Power factor correction in long cable feeders is important to:
(A) Reduce line losses and voltage drop
(B) Increase load current
(C) Increase harmonic distortion
(D) Reduce transformer rating only

24. Synchronous motors used for PF correction can operate at:
(A) Leading, lagging, or unity power factor
(B) Unity only
(C) Lagging only
(D) Leading only

25. Excessive PF correction can cause:
(A) Ferranti effect and overvoltages in lightly loaded lines
(B) Increased losses
(C) Voltage sag
(D) Reduced load current

26. Industrial PF targets are usually:
(A) 0.95 to 0.99
(B) 0.8 to 0.85
(C) 0.6 to 0.7
(D) 1.0 only

27. PF correction in three-phase systems is usually done:
(A) Phase-to-neutral or phase-to-phase using delta or star connected capacitors
(B) Only series connection
(C) Only in single-phase loads
(D) Using resistors only

28. Capacitor banks must be sized to:
(A) Correct the reactive power without causing leading PF
(B) Only supply active power
(C) Reduce line voltage
(D) Increase harmonic distortion

29. Power factor improvement reduces:
(A) Line current and I²R losses in conductors
(B) Transformer rating only
(C) Motor losses only
(D) Frequency fluctuations

30. The main goal of power factor correction is to:
(A) Improve efficiency, reduce losses, and optimize utilization of electrical equipment
(B) Increase voltage only
(C) Reduce frequency fluctuations
(D) Improve insulation rating only