The power factor correction

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1.1 What is power factor?

Power factor is defined as the ratio of true power (kW) to apparent power (KVA) of an AC electric power system. True power is the capacity of the circuit in particular time that is needed to perform work and apparent power is the product of the voltage and current of the circuit. Essentially, it is a measure of how efficiently the electrical power is consumed and in the real world, the ideal power factor is near to unity or 1 which is in demand from lots of big companies. The higher the power factor used, the more efficiently electrical power is being used.

1.2 Cause of poor power factor

Unfortunately, almost all the electrical equipment currently has lower power factor that was 0.7 or less by highly inductive loads such as induction motors, power transformers, fluorescent lighting and other inductive loads as it require some current to make magnetic field in order to perform their desired work. This situation is called as reactive power that stated as wattles because the waste of power consumption is happened. Reactive power also connected with the stored-energy component such as capacitor and inductor, and discharged back during each of AC cycle. In fact, the decrease of power factor is caused by the increased of the angle between the real power and reactive power.

1.3 Why do we need to improve power factor

There are some of benefits can be achieved by improving the power factor such as:-

a) Environmental friendly - the greenhouse effect and fossil fuel depletion can be reduced.

b) Substantial financial saving

c) Long-life electrical components - reduced burden on electrical components.

d) Reduction of voltage drops at the point of use - under-limit voltage drop can make the component broken down which will increase the current as reduced in efficiency.

e) Heat loss of transformer and other distribution equipment can be reduced.

f) The system capacity increased.

g) Distribution component's life can be extended.

1.4 Power factor correction

Nowadays, all bigger companies are struggling in order to improve the power factor of their products as it is economically viable.

This can be achieved by installing the suitable capacitor in series to electrical network to lessen the magnitude of reactive power as it used to neutralize the magnetising current in the circuit. In addition, this capacitor can draw current that leads the voltage, thus leading the power factor. Situation 1 and 2 are attached to prove the increase of the power factor when another capacitor is added.

Situation 1: Before correcting power factor

Firstly, we assumed that the real power in this circuit is 4.2W, capacitor used is 0.22µF and frequency is 60 Hz.

Also note that the supply voltage is 240 VAC.

Find the value of X

X =1jωC

= 12π*60*0.22μ

= 12.06 KW Real power (4.2 W)

V=IR Apparent power = real2 + reactive2

I capacitor = 24012.06K = (4.2)2(4.775)2

= 19.9mA = 6.36 VA

P capacitor = I2R so, power factor is

= (19.9m)2(12.06K) = real powerapparent power

= 4.775 VAR = 4.26.36

Pf = 0.66

Situation 2: After correcting power factor (adding another capacitor in series)

Find value of total capacitance;

Capacitance total = 220n(220n)220n+220n


Find the value of X; Real power (4.2 W)

X =1jωC

= 12π*60*0.11μ

= 24.11 KW = 4.83 VA


I capacitor = 24024.11K

= 9.95mA

P capacitor = I2R

= (9.95m)2(24.11K)

= 2.387 VAR

In terms of reducing power consumption of the circuit, the idea of correcting power factor would be the most possible recommendation due to the marketing currently will mostly invite any product that low use of power consumption. The key point of this idea is by installing capacitor in series with the existed capacitor in the circuit as shown in figure 3(b). When the 240 VAC is supplied to the circuit, the current will drawn by the capacitor thus leading the voltage and automatically, the power factor will increase. Besides, no hard wiring is needed to install the component, thus make it friendlier to the users. Be mindful that the cost also considerably very cheap and economical would be easier to get at any electronics shop. Then, by applying this idea, lots of advantages can be achieved such as no greenhouse effects that we are very concern about currently, and the life span of the components used can be extended due to the reduce of the heat loss of individual component.


Lots of ideas have been showered by each member of the group, and had gone through the evaluation stage to discard similar or unnecessary ideas. The remaining ideas that had been chosen can be promising to solve the problem of the maintained and non-maintained circuit of 8 Watt Bulkhead Emergency Light Fitting. Further investigation into the possibility of improving the power consumption of the emergency light had been carried out successfully. Through the research, several ideas had been chosen for recommendation.

The first recommended idea is all about how to improve the efficiency of the problem circuit by taking care of the power factor circuit on the maintained emergency light. Engineers are really needed by a large number of companies to work out on the efficiency of a product that will lead to the use of low power consumption. In this situation, the use of power factor will be really promising as the power factor that is closer to 1 is very welcoming in the current market. In our problem circuit, the power factor can be corrected by adding capacitor in series with existed capacitor to neutralize the magnetising current drawn by inductance loads such as the transformers and fluorescent lighting.

The second recommended idea is optimizing the fluorescent lamp of the control circuit as typical inductive ballast can be used. This ballast then introduce two Start Circuit for lamp which is in parallel and series condition that will work under low-temperature and low-pressure. For a better energy saving, the start circuit in parallel control can be used to increase the power factor of the circuit thus reduce the power consumption. Yet, the start circuit in series control is actually used for a better performance when the temperature is less than 10 degrees below zero or the voltage is smaller than 170V. A few step can be taken easily by adding a few compatible components such as diode and capacitor to both of the circuit, thus leading to a reduction of the power consumption of the circuit. The cost is relatively very cheap although it is wise to note that it is better to use both of the start circuit into the control circuit of lamp for this matter.

Next, photo luminescent (PL) material that makes use of "glow in the dark" concept would be very inviting to the market currently. This recommendation is just an alternative to replace the emergency light because it is very eco-friendly and greener. PL material can be used as paints and sticky strips thus the installation process is much easier without any hard wiring is needed. Other than that, the lifetime of this material is longer compared to the fluorescent tube life span. The maintenance of this material is virtually zero because no batteries or electricity had been used. Meanwhile, the improved PL materials have been available in the market that can glow longer and up to 20 times brighter than fluorescent tube. Eventually, this idea would be promising to be used in the future.

The overcharging of the Nickel Cadmium battery also has to be taken into account because it can cause adverse effects to the battery itself such as it improves the power consumption, raises safety risk and shortens its lifetime. In order to overcome this problem, a timer can be used for a certain time by switching off the power directly when the battery is fully charged where there is no need human care for it to operate normally.

To conclude, the power factor, lamp of fluorescent tube, material, and overcharges of battery are promising aspects to ponder to reduce the power consumption of the emergency light fitting. In the future, more detailed and extensive research should be conducted by BLE Ltd based on these ideas which could benefit the society in energy consumption that has eluded us for a long time.