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Eddy nồng độ hiện tại cao hơn ở các đầu của các cuộn dây do hiệu ứng số đông của lĩnh vực rò rỉ từ các chi cuộn dây. Xoáy quanh co hiện thiệt hại gia tăng là quảng trường của hiện tại hài hòa và bình phương của tần số | 6 Power Factor 6.1 INTRODUCTION Power factor is included in the discussion of power quality for several reasons. Power factor is a power quality issue in that low power factor can sometimes cause equipment to fail. In many instances the cost of low power factor can be high utilities penalize facilities that have low power factor because they find it difficult to meet the resulting demands for electrical energy. The study of power quality is about optimizing the performance of the power system at the lowest possible operating cost. Power factor is definitely an issue that qualifies on both counts. 6.2 ACTIVE AND REACTIVE POWER Several different definitions and expressions can be applied to the term power factor most of which are probably correct. Apparent power 5 in an electrical system can be defined as being equal to voltage times current 5 V X I 10 5 73 X V XI 30 where V phase-to-phase voltage V and I line current VA . Power factor PF may be viewed as the percentage of the total apparent power that is converted to real or useful power. Thus active power P can be defined by P V X IX PF - 10 P 73 X V XIX PF-3 0 In an electrical system if the power factor is 0.80 80 of the apparent power is converted into useful work. Apparent power is what the transformer that serves a home or business has to carry in order for that home or business to function. Active power is the portion of the apparent power that performs useful work and supplies losses in the electrical equipment that are associated with doing the work. Higher power factor leads to more optimum use of electrical current in a facility. Can a power factor reach 100 In theory it can but in practice it cannot without some form of power factor correction device. The reason why it can approach 100 power factor but not quite reach it is because all electrical circuits have inductance and capacitance which introduce reactive power requirements. The reactive power is that 2002 by CRC Press LLC P ACTIVE POWER Q REACTIVE
