What is Power factor , power factor improvement
Power factor is the ratio of real power and apparent power or it is the ratio or actual power and apparent power.
Power factor formoula
Power factor = actual power / apparent power
Or = KW/ KVA
It is also from cosine angle of phase angle between voltage and current.
Actual power = V I cosφ.
Reactive power = V I sinφ.
Apparent power = V I
The power factor is the cosine of the phase angle between voltage and current.
Disadvantage of low power factor
1. Higher current required large cables, switch gears, transformers, alternator etc. thus the capital cost of the equipment is increased.
2. Higher current give rise to higher copper losses in the system and therefore the efficiency of the system is reduced .the cost of energy loss is also increased.
3. Higher current produce large voltage drop in cables and apparatus and due to which voltage regulation is poor.
Causes of low power factor
- Induction motor is the most commonly used in industries. It is used for different purposes. At full load a three induction motor operates at a power factor of .8 lagging and the power factor of single phase induction motor is about .6 lagging
- Miscellaneous equipment like arc lamp, welding equipment etc. also contributes to low power factor in the system.
- • The transformer drop magnetizing current from the system. This current is at zero lagging power factor.
Effect of low power factor
• To meet the load requirement at low power factor, the capacity of power plant, transmission and distribution equipment has to be more.
• For the same active power, operation of an existing power system at a low power factor means overloading the equipment at time of full load.
• For the same active power, a low power factor means a greater current and hence higher energy loss.
• Low power factor causes the voltage regulation to be poor.
Advantage of power factor improvement
Installation of power factor improvement devices to raise the power factor, results in or more of the following advantages
• Reduction in circuit current
• Increase in voltage level at load
• Reduction in copper losses in the system due to reduction in current.
• Reduction in investment cost of the system facilities/KW of the loads supplied.
• Improvement in power factor of generator to increase of load carrying capacity
• Reduction in demand charges for large consumers
Methods of power factor improvement
Improving power factor means reducing the phase difference between voltage and current by use of capacitor. This help to improve power factor of the load
• Synchronous condenser:
They are 3 phase synchronous motor with no load attached to its shaft. The synchronous motor has the characteristics of operating under any power factor leading, lagging or unity depending upon the excitation. For inductive loads, synchronous condenser is connected towards load side and is overexcited.
• Phase advancer:
This is an ac exciter mainly used to improve pf of induction motor. They are mounted on shaft of the motor and is connected in the rotor circuit of the motor. It improves the power factor by providing the exciting ampere turns to produce required flux at slip frequency.