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Power Factor

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Power Factor: Power factor is defined as the cosine of the angle between voltage and current. Power factor is the measure of how effectively the incoming power is used from total/apparent power in an electrical system. A high power factor indicates that the power supplied to the electrical system is effectively used.  A system with low power factor doesn’t effectively consume the incoming electric supply and results in losses. There is no power factor involved in DC circuits due to zero frequency. But, in AC circuits, the value of power factor always lies between 0 and 1. Cause of Low Power Factor: Some causes of low power factor are  a) The presence of harmonic current in the system reduces power factor.  b) Improper wiring leads to three-phase imbalance causing low power factor.  c) When the system is loaded lightly, the voltage increases, increasing the magnetization current demand of the machine. This causes a poor power factor in the system.  d) The current drawn by inductive load
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Energy Audit and Energy Management

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Energy Audit:   As per Indian Energy Conservation Act 2001, Energy Audit is defined as: “The verification, monitoring and analysis of use of energy including submission of technical report containing recommendations for improving energy efficiency with cost benefit analysis and an action plan to reduce energy consumption.” The main purpose energy audit is to increase energy efficiency and reduce energy related costs. Energy audit is not an exact science. It involves collection of detailed data andits analysis.Energy audit is a fundamental part of an energy management program in controlling energy costs. Need of Energy Audit: * The three top operating expenses are energy (both electrical and thermal), labour and materials. * Energy would emerge as a top ranker for cost reduction. * primary objective of Energy Audit is to determine ways to reduce energy consumption per unit of product output or to lower operating costs. * Energy Audit provides a “ bench-mark” (Reference point) for managi
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Surge impedance Loading

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Surge Impedance Loading: A transmission line may considered as generating capacitive reactive volt-amperes in shunt capacitance and consuming (absorbing) inductive reactive volt-amperes in its series inductance. The load at which inductive and capacitive reactive volt amperes are equal and opposite is called the surge impedance Loading or (nature load of the line). "The power delivered by the line to purely resistive load equal to its surge impedance the load at which the inductive and capacitive reactive volt-amperes are equal and opposite, is called surge impedance Loading of the line." Capacitive volt-amp. generated in the line = V *I = V / Xc = V² / ωL Inductive volt-amp.  absorbed in the line = V * I = I *XL = I² *ωL Under natural load conditions, Capacitive volt-amp. = Inductive volt-amp.             V² * wc   =    I² * ωL    or,  V / I   = √(L/C) =  Zo = Surge impedance At this load V and I are in same phase. At this Zo is purely resistive. There is not present imagina
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Skin Effect

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Skin Effect: If DC is passed in a conductor, the current density is uniform over the cross section of the conductor but when alternating current flows through a conductor, the distribution tends to become non uniform. There is a tendency of the current to crowd near the surface of the conductor. This is called skin Effect. The current density is maximum at the surface of the conductor and minimum at the center of the conductor. The effect is equivalent to a reduction of the cross-section area of the conductor and, therefore the effective resistance of the conductor is increased. Skin effect is caused by opposing eddy currents induced by the changing magnetic field resulting from the alternating current. Fig. Skin Effect Skin Effect increases with increase in  i.) frequency ii.) Diameter of Conductor iii.) Permeability Method to Reduce Skin Effect: I.) Always use high conducting material such as copper, almunium etc. II.) We should use stranded wire instead of solid wire. III.) Frequenc
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Proximity Effect

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 Proximity Effect occurs in high A.C. Voltage transmission lines. It occurs two or more overhead conductor due to flux linkages. When two or more conductor are in proximity, their electromagnetic field interact with each other, with the result that the current in each of them is redistributed such that the greater current density is concentrated in that part of the strand most remote from the interfering conductor. In each case, a reduced current rating results from the apparent increases of Resistance. Apart from the skin effect the non uniformity of the current distribution is also caused by proximity Effect.Proximity effect is more in case of power cables.  Let's take a case, Two conductors; current flows in same direction: Fig. Current flow same direction We know that, Φ = LI  It's mean flux is directly proportional to inductor.  Inductive reactance (XL) = 2πfL     We can write, L =  XL / 2πf Now, we can says that, inductor is inversely proportional to frequency. Conditions
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