无功和有功功率（Reactive and active power）.doc

无功和有功功率（Reactive and active power） Active power and reactive power are preliminary Active power: In an alternating current circuit, the power consumed by the resistor is called active power and is represented by the letter P. The unit is expressed in watts (W): Single-phase active power: P=UIcos Phi Type: P - power, for active power (W); U - phase voltage (V); I - phase current (an); Cos Phi - power factor. Three-phase active power: P=UIcoscos Phi Type: P - power, for active power (W); U - line voltage (V); I - line current (an); Cos Phi - power factor. The size and nature of the load power factor, such as the incandescent light bulb, the nature of resistance furnace resistance load, the power factor of 1; general nature with inductive load, the power factor is less than 1; the load capacitance, power factor greater than 1; the ratio of reactive power factor of power for work in the total power. Two, reactive power: In a circuit with inductor or capacitor, in each half cycle, the power energy into the magnetic field (or electric field) energy stored and then released, and the storage of magnetic (or electric) energy returned to power again, just this energy exchange, and no real energy consumption, we have this switching power value, called reactive power. The so-called reactive power is not useless electrical power, but its power is not converted to mechanical energy, heat only. The formula is as follows: Reactive power =UIsin. The unit is deficient (Var) or kilovar (kVar). Before answering this question, explain several terms: active power, reactive power, apparent power. ??? active power: in the circuit, which is dissipated in the resistor element, the power of irreversible transitions (such as transformed into heat, light, or mechanical energy), called active power;??? Reactive power: in the circuit, inductance element magnetic field, establishment of power capacitor element the electric consumption is said to have no power, this power is with the AC cycle, with