OBJECTIVE: POWER FACTOR IMPROVEMENT APPARATUS: © Power Source 1Resistor Capacitor Inductor Wattmeter Voltmeter Ammeter ‘Connecting Wires CIRCUIT DIAGRAM: THEORY: ‘The power factor of an AC electric power system is defined asthe ratio ofthe real power flowing to the load to the apparent power, and is a number between 0 and I (frequently expressed as 2 percentage, e.g. 0.5 pf = $0% pf). Real power is the capacity of the cireuit for performing work in a particular time. Apparent power is the product of the current and voltage ofthe circuit. Due to energy stored in the load and retumed to the source, or due to @ non-linear load that distorts the ‘wave shape of the current drawn from the source, the apparent power can be greater than the real power. In an electric power system, « load with low power factor draws more current than a load with a high power factor for the same amount of usefil power transferred. The hi the energy lost inthe distribution system, and requie larger wires and other equipment. Because of the costs of larger equipment and wasted energy, electrical utilities will usually charge a higher cost to industrial or commercial customers where there isa low power factor. Linear loads with low power factor (such as induction motors) can be corrected with a passive network of capacitors oF inductors. The devices for correction of power factor may be at a central substation, or spread out over a distribution system, or built into power-consuming equipment. Circuits containing purely resistive heating elements (filament lamps, strip heaters, cooking stoves, etc.) have a power factor of 1.0. Circuits containing inductive or capacitive elements (electric motors, solenoid valves, lamp ballasts, and others) often have a power factor below 1.0.AC power flow has the three components: real power (P), measured in watts (W); apparent power (S), measured in volt-amperes (VA); and reactive power (Q), measured in reactive volt- amperes (var). “The power factor is defined as: In the case ofa perfectly sinusoidal waveform, P, Q and S can be expressed as vectors that form Vector triangle such that: S=PG Ig is the phase angle between the current and voltage, then the power factor is equal tolC0S @|, and P= Sleosd| Since the units are consistent, the power factor is by definition a dimensionless number between O.and 1. When power factor is equal to 0, the energy flow is entirely reactive, and stored energy in the load returns to the source on each cycle. When the power factor is 1, all the energy supplied by the source is consumed by the load. Power factors are usually stated as "leading" or "lagging" to show the sign ofthe phase angle. Power factor correction: It is often desirable to adjust the power factor ofa system fo near 1.0. This power factor correction (PFC) is achieved by switching in of out banks of inductors of capacitors. For example the inductive effect of motor loads may be offset by locally connected capacitors. When reactive elements supply or absorb reactive power near the load, the apparent power is reduced Power factor correction may be applied by an electrical power transmission utility to improve the stability and efficiency of the transmission network. Correction equipment may be installed by individual electrical customers to reduce the costs charged to them by their electricity supplier. A high power factor is generally desirable in @ transmission system to reduce transmission losses and improve voltage regulation at the load. Power factor correction brings the power factor of an AC power circuit closer to I by supplying reactive power of opposite sign, adding capacitors or inductors which act to cancel the inductive or capacitive effects of the load, respectively. For example, the inductive effect of motor loadsmay be offset by locally connected capacitors. If a load had a capacitive value, inductors (also known as reactors) are connected to correct the power factor. In the electricity industry, inductors are said to consume reactive power and capacitors are said to supply it, even though the reactive power is actually just moving back and forth on each AC cycle. PROCEDURE: Connect the circuit as shown in circuit diagram. Close switch 1 and open switch 2. Note the readings in the table. Now close switch 2 and vary the capacitance. Note corresponding readings and observe the effect of capacitor on power factor. k increases with capacitance and as a result power factor is improved. OBSERVATIONS AND CALCULATIONS: