Power factor of Brief Introduction of LED lamps

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1, the power factor

The power factor characterizes the ability of the lamp output active power. Power is a measure of the energy transfer rate in the DC circuit voltage V and current A and the product. In th e exchange system is far more complex: that part of the cycle of AC current in the load where transmit power, it is called reactance current or harmonic current, it makes the power (voltage multiplied by current Volt Amps) is greater than the actual power. Leads to the power factor, apparent power and actual power ranging from power factor equal to the actual ratio of the power and apparent power. Exchange systems, the actual power is equal to the apparent power times the power factor : Power factor = real power / apparent power. led high bay lighting load power factor of electric heaters and light bulbs for one, many devices real power and apparent power difference is very small, negligible, like capacitive equipment such as the lighting of this difference is very important. Recent study showed that U.S. PCMagazine magazine lamp typical power factor of 0.65, apparent power (VA) Power (Watts) 50%!

2, the apparent power

As the product of power: AC voltage and AC current. Formula is expressed as: S = UI where S is the rated output power in VA (voltammetry); U is the rated output voltage, the unit is V, 220V, 380V, etc.; I is the rated output current, the unit is A. Apparent power includes two parts: the active power (P) and reactive power (Q). The active power is directly acting the part. Such as to cause the lamp lights up, the motor rotates, so that the electronic circuit work. After doing work of this power into heat, people feel that some people have an illusion, as the active power to apparent power, everyone knows the active power is only apparent part of the power, expressed by equation : p = Scosθ = UIcosθ = the UI? F. where, P is active power, the unit is W (watts); F = cos θ is called the power factor, and θ is the non-linear load voltage and current phase phase. Reactive power is stored in the circuit, but is not directly acting the part of power, expressed as: Q = Ssinθ = UIsinθ. Where, Q is the reactive power, the unit is var (lack of).

(3) reactive power

Lamps and all other electronic circuits rely on DC voltage, leave the reactive power does not work. General users that the lamps and the like devices will require the active power, without the need for reactive power. Since the reactive power is not acting, you want it and where to use! So of course they think that the power factor is one of the lamp. Because it gives the maximum output power. However, the reality is not the case.

A lamp when the AC mains input rectifier, pulsating DC voltage, if the ripple voltage of any processing, it is provided directly to the lamp, no doubt, the circuit did not work. At this time the lamp power factor close to 1, but what use is it. In order for the lighting circuit to work properly, must provide a smooth DC voltage. "Smoothing" must be performed by the filter capacitor connected to the lamp rectifier behind to complete. This filter is like a reservoir capacitor which must be stored a sufficient number of charge, when the gap between the half-wave rectifier circuit voltage remains uninterrupted, able to maintain a normal level. In other words, even if the input electrical energy between two half-wave pulse Uc voltage levels without a significant change, this function is achieved by the energy storage capacitor to this part of the energy stored in the capacitor is reactive power. Therefore, the lighting is to rely on the support of reactive power, in order to outdoor post lights that the circuit is correct use of active power to achieve normal use. Therefore we can say that the lamps not only need active power, reactive power, both are indispensable.