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POWER  FACTOR

#CAUSES OF LOW POWER FACTOR 

Induction Motor is the most commonly used A.C. motor.it is used for a variety of variety of purposes at full load a 3-phase induction motor operates at a power factor of around 0.8 lagging. At part loads, the power factor is still poorer. the power factor is still poorer. the power factor of single-phase induction motors is about 0.6 lagging 

Causes of low Power Factor. The main cause of 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.

The transformer drow a magnetizing current from the system .this current is at a power factor of zero lagging. Miscellaneous equipment like are lamps, welding equipment etc. also contribute to low power factor in the system 

# EFFECT OF LOW POWER FACTOR

To meet the load requirement at a low power factor the capacity of a power plant, transmission and distribution equipment has to be more than that which be necessary if the load was demanded at unity power factor. For the same active power, an operation of an existing power system at a low power factor means overloading the equipment at times of full load.
For the same active power, a low power factor means a greater current and hence higher energy losses. Low power factor causes the voltage regulation to be poor 


# ADVANTAGES OF POWER FACTOR IMPROVEMENT 


 1 Reduction in circuit current 
2  Increase in voltage level at load 
3  Reduction in copper losses in the system due to a reduction in current 
4  Reduction in investment in the system facilities per kW of the load supplied
5  Improvement in the power factor of the generators 
6  Reduction in kVA loading of the generators and circuits. This reduction in kVA loading may 
    relieve an overloaded conduction or release capacity  for additional growth
7  Reduction in kVA  demand charges for large consumers 

For a DC circuit, the power is P=VI, and this relationship also holds for the instantaneous power in an AC circuit. However, the average power in an AC circuit expressed in terms of the RMS voltage and current is
where φ is the phase angle between the voltage and current. The additional term is called the power factor

From the phasor diagram for AC impedance, it can be seen that the power factor is R/Z. For a purely resistive AC circuit, R=Z and the power factor = 1.

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