Correct Answer - Option 4 : Large kVA rating of equipment, large copper loss and poor voltage regulation
Power factor:
- The overall power factor is defined as the cosine of the angle between the phase voltage and phase current.
- In AC circuits, the power factor is also defined as the ratio of the real power flowing to the load to the apparent power in the circuit.
Hence power factor can be defined as watts to volt-amperes.
- It is also defined as the ratio of resistance to the impedance of the circuit.
- So that by increasing resistance, the power factor can be increased. But due to power losses practically it is not used.
- Typically capacitor is used for power factor improvement purposes.
Disadvantages of low power factor:
- Large kVA rating of the equipment
- Greater conductor size
- Large copper losses
- Poor voltage regulation
- The reduced handling capacity of the system
- The cost of station and distribution equipment is more for a given load
Causes of low power factor:
- Most of the AC motors are of induction type (1φ and 3φ induction motors) which have a low lagging power factor
- These motors work at a power factor that is extremely small on light load (0.2 to 0.3) and rises to 0.8 or 0.9 at full load
- Arc lamps, electric discharge lamps, and industrial heating furnaces operate at a low lagging power factor
- The load on the power system is varying; being high during morning and evening and low at other times
- During a low load period, the supply voltage is increased which increases the magnetization current, this results in the decreased power factor
Low power factor can be avoided by:
- Using synchronous motors instead of induction motors
- Using high-speed induction motors to low-speed machines
- Not operating induction motors at less than the rated output
- By using the following equipment
- Static capacitors
- Synchronous condenser
- Phase advancer
- Use of high power factor equipment
High inductive element in series with the load is not used for the power factor improvement.
