In
this article, we are going to discuss the Power
Factor Correction Methods. Here we will cover all the concepts related to Power
factor correction such as

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**What is power factor correction? Why Power factor correction?**All methods of power factor correction and its advantages and disadvantages, Power factor correction formula in detail. But before that, we have to clearly understand the concepts of power factor and causes and disadvantages of low power factor. I have already written an article on this topic. So please follow these articles through the given link.**Must Read:**

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**What is Power Factor
Correction?**

Power factor correction is a technique of improving the power
factor of Electrical system near to unity (1) by
using extra electrical equipment which can absorb or supply reactive
power to the circuit. Actually, the concept behind the power factor correction is
Reactive power compensation technique, which can be done by using a capacitor bank
and synchronous condenser in parallel of the circuit.

Power factor correction will not affect the amount of true or
real power of the circuit, whereas it will reduce the apparent power and reactive
power in the circuit. It also reduces the total line current drawn by load and
hence the burden of an electrical system.

The main source of low power factor is Inductive
loads in the circuit, which normally operates at very low power factor (0.2 - 0.3) at light loading conditions and
rises to approx 0.8 at full load. Since low power factor has
negative effects in the power system. So the techniques used to improve the
power factor of the overall electrical circuit are known as Power factor
correction.

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**Why
Power Factor correction?**

To understand the concepts let us consider an example of a single phase induction motor. It draws a total line current of 10 Amps at a power factor
of 0.75. Then the useful current will
be 10x0.75 =
7.5 A. Also the
useful power to the motor is 230 ×
7.5 =
1.725kW. But the total input power of the motor that has to be supplied is 230 × 10 = 2.3 kVA.

Without power factor correction, to achieve the required output of 1.725 kW (7.5 A) we have to supply a power of 2.3 kVA (10 A) to the motor. Also current of 10 A is flowing in the circuit but only 7.5 A of that current is producing useful output. Hence burden on system and also utility bill increases due to poor power factor.

Without power factor correction, to achieve the required output of 1.725 kW (7.5 A) we have to supply a power of 2.3 kVA (10 A) to the motor. Also current of 10 A is flowing in the circuit but only 7.5 A of that current is producing useful output. Hence burden on system and also utility bill increases due to poor power factor.

There are so many benefits of power factor correction such as:

- Reduction in Electricity bill
- Reduction in copper losses of transformers and distribution equipment which increases the efficiency of the system.
- Reduction in voltage drop which increases voltage regulation.
- It reduces the line current which decreases the burden on cables and also increases the life of the equipment.

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**Power
Factor Correction Formula**

As we discussed in my previous
Article, A low power factor is mainly due to lagging current drown by the
inductive loads. So before moving to the methods of power factor correction,
please note the following points.

- For pure inductor, current lags behind the voltage by 90 degrees.
- For a pure capacitor, current leads the voltage by 90 degrees.
- So it is simply that if we use a capacitor in parallel to draw the leading current we can cancel the effect of lagging inductive current. Hence we can improve the power factor of the circuit.

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**Power Factor Correction
methods**

The various methods of Power-factor improvement are as follows:

- By using a capacitor bank
- By using synchronous condenser
- By using phase advancer

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**1. Power factor correction by
using a capacitor bank**

In this
method, A bank of capacitors is connected in parallel across the load. Since
the capacitor takes leading reactive power, Overall reactive power taken from
the source decreases. Hence the system power factor improves. A control system
usually provided to monitor the power factor of the system and switches the
capacitor ON and OFF as per requirement.

Here Star and
Delta connected capacitor bank is shown in the figure.

Both the
connections improve the system power factor. But generally, delta connected
capacitor bank is preferred for power factor improvement. Because in delta
connected system the capacitor value required per phase becomes one-third times
(small in delta) of star connected system.

Advantages and Disadvantages of this method are as mentioned below.

Advantages and Disadvantages of this method are as mentioned below.

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**Advantages**

- Low losses.
- Low maintenance.
- Lightweight.
- No foundation required. Hence Easy to install.

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**Disadvantages**

- Capacitors get easily damaged due to overvoltage
- Short life (8-10 years)
- Once damaged, the repair is costly and uneconomical.
- Due to constant switching, switching surges and harmonics may be produced.

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**2. Power factor correction by
Synchronous condensers**

When a 3-phase synchronous motor runs in overexcited mode, it
draws leading current and behaves as a capacitor. Hence synchronous condenser
is nothing but an overexcited synchronous motor running without mechanical load
(at No load).

The most attractive feature of the synchronous condenser is that
it gives dynamic power factor correction over a wide range of its excitation. When
under excited, it operates at a lagging power factor and therefore absorbs
reactive power from the bus. When overexcited it works at leading power factor
and generates reactive power therefore, behaves as a capacitor.

A static capacitor bank provides PF control in discrete steps
whereas a synchronous condenser furnish continuous control of power factor
correction.

Advantages and Disadvantages of this method are as mentioned below.

Advantages and Disadvantages of this method are as mentioned below.

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**Advantages:**

- Reliable and long life span (almost 25 years)
- Flexible and continuous control of power factor.
- Not affected by harmonics.
- No switching required hence free from switching surges.

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**Disadvantages:**

- It has more losses as compared to a capacitor bank
- High maintenance cost
- It produces Noise pollution
- It has slow response due to the large time constant of its field circuit whereas capacitor bank offers fast response.
- A synchronous condenser can be installed only at one place whereas capacitor bank can be distributed at many places hence due to this the capacitor bank is more effective in controlling reactive power flow and voltage profile.
- Uneconomical for below 500kVA.

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3. **Power factor correction by Phase Advancer**

- It can be used only for Induction Motors.
- Since we know that stator winding of induction machine draws lagging current from the main supply.
- Hence, to improve the power factor of Induction
motor, we have to supply this lagging current from an alternative source. Therefore
this alternative source is the
**phase advancer**. - A phase advancer is basically an AC exciter, which is mounted on the same shaft of the main motor and connected in the rotor circuit. It supplies exciting ampere turns to the rotor circuit of induction motor at a slip frequency. So this way we can improves the power factor of the induction machine.
- Another attractive feature of phase advancer is that if we supply more amp-turns than needed, the motor will operate in an overexcited state (at leading PF).

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