CSLB C-10 Electrical ContractorElectrical Theory and CalculationsMedium
A 240V single-phase motor draws 30 amps with a power factor of 0.8. What is the approximate real power consumed by the motor?
- A7.2 kW
- B6.24 kW
- C5.76 kW
- D9.0 kW
Show answer & explanationAnswer & explanation
Correct answer: C. 5.76 kW
For a single-phase circuit, real power (P) = V × I × PF. Substituting the values: P = 240V × 30A × 0.8 = 5760 W, which is 5.76 kW.
Why the other options are wrong
- A. This would be the apparent power (V*I), not accounting for PF.
- B. This might result from using the square root of 3, which is for three-phase power.
- D. This could be a miscalculation or an incorrect application of the formula.
Single-Phase Real Power
The actual power consumed by a single-phase AC load, calculated as Voltage × Current × Power Factor.
- P = V × I × PF
- Power factor (PF) represents the efficiency of power usage.
- Measured in watts (W) or kilowatts (kW).
Memory trick: Single phase, V-I-PF, just multiply.