Power Factor

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Power Factor: Most Complicated Parameter but simplest & smallest energy efficiency measure

In an ideal case like in resistive load current in AC. power supply system should be in the same phase but in practice this never happen. Most of the equipments are either inductive loads with resistance or capacitive loads will resistance. In case of inductive load the current will lag the voltage by few degrees say an angle 01 and in case of capacitive loads the current will lead the voltage by an angle say 02. Cos 01 is called lagging power factor and cos02 is called leads power factor. In the early days correction of power factor was not given much importance as the power tariff were low. But in mid 60 transmission companies realised the importance of power factor.

If the power factor is low, for the same supply voltage & load current drawn will be higher with low power factor, higher current will result in higher Cu losses i.e. ( I2R) In cable & transmission wires and increasing the transmission losses . it used to be two part tariff . a fixed portion based on the contracted demand & variable charges based on the kwh consumed. It is a well-known fact that electricity users relying on alternating current - with the exception of heating elements - absorb from the network not only the active energy they convert into mechanical work, light, heat, etc. but also an inductive reactive energy whose main function is to activate the magnetic fields necessary for the functioning of electric machines. The power factor is thus the ratio between active power and apparent power (vectorial sum of active and reactive power), an indicator of the quality of a facility's electric system since the lower the power factor is, higher the inductive reactive component will be in relation to the active component.

It is possible to produce reactive energy, where necessary, by installing power capacitors or automatic power factor correction systems. Capacitors absorb a current that is 180% out of phase with the inductive reactive current; the two currents are algebraically summed together so that circulating upstream from the point of installation of the capacitor is a reactive current that is equal to the difference between the inductive and capacitive currents. Power factor is significantly affected by variations in load and ultimately your electricity bill will not decrease noticeably. Instead, installing a power factor corrector should allow you to achieve comprehensive efficiency improvements throughout your entire system and significantly lower your electric bill.

Power supply companies realised this issue and started insisting consumers to improve their power factor to 0.85 as in the industry most of load were inductive load like induction motors, induction furnace & welding transformers etc. Consumers started installing fixed type capacitors on their bus bars. Power supply companies further realised the benefit of power factor improvement and started giving 1 % rebate for every 0.01 increase beyond 0.90 & penalty on customers if power factor is below 0.9. With the advancement of technology now-a-days most of the consumers are able to maintain 0.95 to 0.999 power factor. With the help of automatic power factor control panels & real time power factor controllers. And the power supply companies have made their tariff based on the fixed charges on contract demand & variable charges on KVAH units.

Since each customer has different types of load the power factor control has to suit the load profile like welding loads, 3-Phase induction motors. Most appropriate power factor correction system thus consists in the installation of an automatic capacitor bank on the bus bars of the distribution panel and, if necessary, fixed capacitor banks for correcting the power factor of the transformer, asynchronous motors and any loads absorbing considerable quantities of reactive power. The automatic system of the capacitor bank has the task of switching in the necessary capacitance according to the load requirements at each given moment.