⚡ MCQ Practice — Category 11
Power Factor & Energy
kW, kVA, kVAR, PF correction, capacitor bank — energy management ke technical sawaal. 5 parts mein divide.
50 Questions
5 Parts
Easy → Hard
Part 01
PF Basics
Q 1–10
Easy
Start
Part 02
kW/kVA/kVAR
Q 11–20
Easy–Med
Start
Part 03
Capacitor Bank
Q 21–30
Medium
Start
Part 04
Penalty/Billing
Q 31–40
Med–Hard
Start
Part 05
Gulf Site
Q 41–50
Hard
Start
📖 Theory + Gulf Rules — Power Factor & Energy Management
Power Factor – Kya Hai Aur Kyon Important Hai?
Power Factor (PF) Gulf interviews mein ek key topic hai – kW, kVA, kVAR, capacitor bank sizing, aur utility penalties – ye sab concepts samajhna zaroori hai.
Power factor = Real Power (kW) / Apparent Power (kVA) = cos(φ). Low PF (lagging) ka matlab hai system se zyada reactive current draw ho raha hai jo actual work nahi kar raha.
Gulf Rule: Most utilities (DEWA, ADDC, Kahramaa) minimum PF threshold (typically 0.85–0.90) set karte hain – isse kam PF pe bill mein penalty/surcharge lagta hai.
Power Triangle – KW, kVAR, kVA
Real Power (kW)
- Actual useful work
- Unit: kiloWatt (kW)
- Resistive loads (heaters, lighting)
Reactive Power (kVAR)
- Magnetic field create/maintain
- Unit: kiloVolt-Ampere Reactive
- Inductive loads (motors, transformers)
Apparent Power (kVA)
- Vector sum of kW + kVAR
- Unit: kiloVolt-Ampere
- Total power supplied by utility
Formula
- kVA² = kW² + kVAR²
- PF = kW / kVA
- kVA = kW / PF
Capacitor Bank – PF Correction
Working
- Capacitor leading reactive power provide karta hai
- Inductive lagging reactive power cancel/offset karta hai
- Net reactive power demand from utility reduce
Types
- Fixed – constant load, manual
- Automatic (APFC) – varying load, controller based
- Detuned – with reactors for harmonic protection
Over-correction caution: Excessive leading PF (overcorrection) se voltage rise, equipment stress, aur some utilities leading PF penalty bhi charge karte hain – target PF typically 0.95-0.98 range maintain karein.
Utility Billing & Penalties
- kVA Demand Charge – maximum demand ke hisaab se charge, infrastructure capacity cost.
- PF Penalty – actual PF threshold se kam hone par additional surcharge.
- Savings – PF improvement se penalty avoid, demand charge reduce, aur losses kam.
Power Factor Improvement Benefits
| Benefit | Explanation |
|---|---|
| Reduced kVA demand | Same kW ke liye lower kVA – lower demand charges |
| Reduced I²R losses | Lower current = less cable/transformer loss |
| Penalty avoidance | No surcharge if PF above threshold |
| Increased system capacity | Existing infrastructure mein more kW load add kar sakte hain |
| Better voltage regulation | Voltage dip kam hota hai |
Capacitor sizing formula: kVAR = kW × (tan φ1 – tan φ2) where φ1 = existing PF angle, φ2 = target PF angle. Use multiplication factors from standard tables for quick estimation.
Gulf Interview – Power Factor Ke Sawaal
- PF improvement kyun karte hain? – To reduce kVA demand, avoid penalty, and save energy.
- KVAR calculation kaise karte hain? – Given kW, current PF, target PF – use formula or table.
- Capacitor bank connection? – Star or delta, with discharge resistor, fuse/MCB protection.
- APFC controller ka kaam? – Continuously monitor PF and switch capacitor steps automatically.
- Harmonics issue? – Use detuned reactors to avoid resonance and protect capacitors.
Power Factor Calculator
kVAR required, capacitor sizing, savings calculator – all-in-one tool for Gulf electricians.