Also talk about solar lamps and lanterns of power factor

Recently on the Internet, see an article of PFC function of lamps and lanterns, general reading and feeling explanation of PFC is not very clear, I just have so a little knowledge on PFC, also might as well take out a 'axe'.

lamps and lanterns is a very important parameter in - — Power factor ( PFC） People tend to be ignored, so what is the power factor, power factor what is the point? 1, the power factor of power factor characterization of the lamps and lanterns is the ability of the active power output. Power is the rate of energy measurement, it is in the dc voltage V and current product of A and b. In communication system is more complicated: that is part of the alternating current power transmission in the load cycle is not, it is called the reactive current or harmonic current, it makes the apparent power ( Voltage in the Volt by current Amps) Is greater than the actual power. Apparent power and real power ranging from raising power factor, power factor is equal to the ratio of actual power and apparent power. So the communication system in the actual power is equal to the apparent power multiplied by the power factor. I. e. , the power factor = actual power/apparent power. Only linear load power factor, such as electric heater and the bulb is 1, many equipment's actual power and apparent power difference is small, and can be neglected, and like capacitive equipment such as lamps and lanterns of the difference is very big, very important. A recent study of the American journal of PC Magazine lamps and lanterns is typical of the power factor is 0. 65, namely the apparent power ( VA) Than the actual power ( Watts) Big 50%! 2, apparent power, apparent power, namely the product of the ac voltage and ac current. Expressed in formula is: S = UI. Type, S is the rated power output, the unit is VA ( Volt ampere) ； U is rated output voltage, the unit is V, such as 220 V, 380 V, etc. ; I was rated output current, the unit is A. Apparent power includes two parts: active power ( P) And reactive power ( Ｑ） 。 Active power refers to the direct part of the work. For example makes lights shine, the motor rotation, the electronic circuit work, etc. Because the power to do work into heat and can be felt by people directly, so some people will produce an illusion, namely the active power as the apparent power, what does not know active power is only part of the apparent power, expressed in type: P = UIcos theta = = Scos theta UI, F. Type, is the active power P, the unit is W ( Watts) ； F = cosine theta is called power factor, and theta is in different voltage and current phase in phase with nonlinear loads. Reactive power is stored in the circuit but not directly to work that part of the power, expressed in type: Q = Ssin theta = UIsin theta. Type, Q for reactive power, the unit is var ( Spent) 。 For lamps and lanterns and other all work with dc voltage of electronic circuit, cannot leave the reactive power works. Users are generally recognized as such devices only need to lamps and lanterns active power, without the need for reactive power. Since reactive power does not work, want to use it! So of course they will think the lamps and lanterns of power factor to 1 is best. Because it can give maximum output power. However, it's actually not the case. If there is a lamp, when the ac mains input rectifier, get pulsating dc voltage, if not to make any processing, pulsating voltage is directly provided to the lamps and lanterns, there is no doubt that the circuit can not work normally. Although at this time the power factor is close to 1 of lamps and lanterns, can be this good. Circuit can work properly in order to let the lamps and lanterns, must to provide a smooth dc voltage. The 'smooth' must be followed in the lamps and lanterns of rectifier the filter capacitor C. This filter is like a reservoir, the capacitor must be stored in a sufficient number of charge, when the gap between rectifier half-wave, make the working voltage of circuit still uninterrupted, to maintain a normal level. In other words, even if no input power between two pulse half wave, the voltage level of Uc has no significant change, this function is accomplished by within the capacitor energy storage, this part of the stored in the capacitor energy is the reactive power. So, lamps and lanterns is to rely on reactive power support, to ensure correct use of active power circuit implementation of normal use. Therefore, not only need active power of lamps and lanterns, also need reactive power, both be short of one cannot.