In ac circuits, the phase difference between voltage and current (Φ) cosine is called power factor, with symbol cos Φ said on numerical value, the power factor is the ratio of active power and apparent power, namely the cosine Φ = P/S.

The size of the power factor is associated with the load characters of circuit, such as incandescent bulbs, such as resistance furnace resistance load power factor is 1, general circuit with inductive load power factor is less than 1. The power factor is an important technical data of the power system. Power factor is a measure of the efficiency of electric equipment of a coefficient. Low power factor, conversion circuit used in alternating magnetic field is illustrated reactive power is large, which reduces the equipment utilization rate, increase the line power loss. So, the power supply departments of the power factor of power unit has the certain standard.

Incandescent bulb is purely resistive load, there is no problem of power factor compensation. Fluorescent lamp in the 1960 s rapidly became the main lighting lamps and lanterns, is silicon steel sheet inductance ballasts, high reliability, long life, there are still a few USES, most has no power factor compensation measures, also have take appropriate amount of capacitor for power factor compensation, multi-purpose on the large wattage fluorescent lamp, rarely use below 20 w, the result is a low power factor, reactive power, energy saving effect at a discount. After the 1990 s, people's energy saving consciousness enhancement, to develop energy-saving lamps trichromatic fluorescent powder, the higher light efficiency, electronic ballast and then, with tricolor phosphors on the tube, the energy saving effect is more significant. Some integrated circuit manufacturers at home and abroad launched a source of power factor compensation lamp with chips, used for electronic ballast, excellent performance, but increases the cost and electronic ballast volume, ordinary people also can't accept the price, only products of lamps and lanterns for the government. A lot of affordable electronic ballast including the highest penetration of energy-saving lamps, did not add any power factor compensation measures, that is to say, the lamps and lanterns of past basically do not have any power factor compensation measures.

LED lamp power consumption more provinces, lamps and lanterns light than energy-saving lamps have good efficiency, LED is a kind of more advanced environmental protection and energy saving lighting products, conform to the requirements of the national policy of energy conservation and emissions reduction. LED lamps and lanterns is whether to add the power factor compensation, chengdu Liu Gong think the month:

(1) with LED for capacitive load, the perceptual load and power grid, such as electric motors, transformers, etc., often need access to compensate the capacitive load, LED lights to compensate the power grid of the low power factor caused by inductive load more problems, combined with the single LED indoor lighting lamps and lanterns are of low power, small influence to power grid power of lamps and lanterns is small, so the LED lighting lamps and lanterns, in principle, do not need to add the power factor compensation measures, added it will lose the LED lamp can compensate power grid caused by inductive load more than the advantages of low power factor.

(2) the LED lamps and lanterns can revoke the power factor compensation measures, these small power lamps and lanterns is more small compact size, internal space is very limited, the power supply PCB increase after not put, and add the power factor compensation brings efficiency drops, the side effects of moreover cost increase impact sales.

(3) more than 100 w power leds can consider to add the power factor compensation measures, power load impact on power grid is also big, such as one hundred watts to several hundred watts of the LED street light. Street lamp belongs to public welfare undertakings, obstruction for just add a little cost, increase power supply PCB board is for the position can be put. Because of street lighting is dedicated power supply, power factor compensation measures can prevent line power supply capacitive load is too large to produce excessive compensation.