A. Induction motors.B. Resistive loads.C. Synchronous Motors.D. All of the above.Answer: A. Induction motors.
Explanation: Power factor:- The ratio of the actual electrical power dissipated by an AC circuit to the product of the r.m.s. values of current and voltage. The difference between the two is caused by reactance in the circuit and represents the power that does no useful work.
- The main cause of the low Power factor is Inductive Load. As in pure inductive circuit, Current lags 90° from Voltage,
- This large difference of phase angle between current and voltage causes zero power factor. Basically, all those circuit having Capacitance and inductance (except resonance circuit (or Tune Circuit) where inductive reactance = capacitive reactance (XL = Xc), so the circuit becomes a resistive circuit),
- Power factor would exist over there because Capacitance and inductance cause in difference of phase angle (θ) between current and voltage.
- there are a lot of disadvantages of low Pf and we must improve Pf.
Improving Power Factor with Capacitors:- The reactive component (KVAR) of any electrical distribution system can easily be reduced in order to improve power factor by using capacitors.
- Capacitors are basically reactive loads. They tend to generate reactive power hence they find good use in power factor correction application.
- So instead of having the utility company supply the reactive power that you will end up paying for, get a capacitor bank and have them supply the reactive energy to the system.
Variation in the Power System Loading- The load demand in the modern power system is not constant throughout the day.
-
The demand is high during the morning and evening hours and the light during the rest of the day.
- When the system is loaded lightly, the voltage increases, increasing the magnetization current demand of the machine. This causes a poor power factor in the system.
Harmonic Current: - The presence of harmonic current reduces the power factor in the system.
- Due to high voltage also reduce power factor of the systems.
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 which 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 low load period, the supply voltage is increased which increases the magnetization current, this results in the decreased power factor.
Key Points:- Incandescent lamp is a coiled tungsten filament lamp.
- Incandescent lamps produce light as a result of the heating effect of an electrical current flowing through a filament wire
- As it is a highly resistive circuit, the power factor of an incandescent lamp is very high and ideally, it is unity.
A. Induction motors.
B. Resistive loads.
C. Synchronous Motors.
D. All of the above.
Answer: A. Induction motors.
Explanation:
Power factor:
- The ratio of the actual electrical power dissipated by an AC circuit to the product of the r.m.s. values of current and voltage. The difference between the two is caused by reactance in the circuit and represents the power that does no useful work.
- The main cause of the low Power factor is Inductive Load. As in pure inductive circuit, Current lags 90° from Voltage,
- This large difference of phase angle between current and voltage causes zero power factor. Basically, all those circuit having Capacitance and inductance (except resonance circuit (or Tune Circuit) where inductive reactance = capacitive reactance (XL = Xc), so the circuit becomes a resistive circuit),
- Power factor would exist over there because Capacitance and inductance cause in difference of phase angle (θ) between current and voltage.
- there are a lot of disadvantages of low Pf and we must improve Pf.
Improving Power Factor with Capacitors:
- The reactive component (KVAR) of any electrical distribution system can easily be reduced in order to improve power factor by using capacitors.
- Capacitors are basically reactive loads. They tend to generate reactive power hence they find good use in power factor correction application.
- So instead of having the utility company supply the reactive power that you will end up paying for, get a capacitor bank and have them supply the reactive energy to the system.
Variation in the Power System Loading
- The load demand in the modern power system is not constant throughout the day.
- The demand is high during the morning and evening hours and the light during the rest of the day.
- When the system is loaded lightly, the voltage increases, increasing the magnetization current demand of the machine. This causes a poor power factor in the system.
Harmonic Current:
- The presence of harmonic current reduces the power factor in the system.
- Due to high voltage also reduce power factor of the systems.
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 which 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 low load period, the supply voltage is increased which increases the magnetization current, this results in the decreased power factor.
Key Points:
- Incandescent lamp is a coiled tungsten filament lamp.
- Incandescent lamps produce light as a result of the heating effect of an electrical current flowing through a filament wire
- As it is a highly resistive circuit, the power factor of an incandescent lamp is very high and ideally, it is unity.
