LED lighting and power factor

AC current through the load, the increase in the load on the AC voltage and AC current through the load generation phase, people from the power factor leads to the concept. People to produce, electricity from the grid, the grid provides a frequency of 50Hz or 60Hz AC. AC load as a resistance, inductance, capacitance of three types:
1, when the AC through pure resistance load, the increase in the resistance of the AC voltage and AC current through the resistor is the same phase, the phase angle between them that ф = 0 °, while the consumption of active resistive load power grid to reveal the energy.

2, when the alternating current through a pure inductive load, the AC voltage on the phase advance phase AC current 90 °, the angle between them ф = 90 °, resulting in the inductive load reactive power, power supply, power in the inductor into short-term storage in the magnetic field into electrical energy and then back to the grid, so periodic cycle, the results did not reveal the power grid, so that the "reactive power", but have a "reactive power" and "reactive current" or actually exist.

3, when the alternating current through a pure capacitive load, also similar to this, but its phase AC voltage on the AC current phase lag 90 °, the angle between them ф = - 90 °.

Here, the definition of the phase angle advance is positive, the phase lag angle is negative. Actual load is the resistance, inductance inductance, capacitance of the capacitance of three types of complex objects, the composite collectively, the "impedance", which is written in mathematical formulas: impedance Z = R + j (XL - XC,. Where R is resistance, XL is inductive reactance, XC as capacitance if (XL-XC,> 0, called the "inductive load"; the other hand, if (XL - XC, <0 is called "capacitive load."

Alternating current through the inductive load, the AC voltage phase AC current phase advance (0 ° <ф <90 °); alternating current through the capacitive load, the AC voltage AC current phase of the phase lag (-90 ° <ф <0 °); electrical engineering to define the angle ф is the power factor angle, power factor, the cosine of the angle ф Cosф called the power factor. For the resistive load, the voltage and current phase difference of 0 °, therefore, the circuit is a maximum power factor (Cos 0 ° = 1,; and pure inductive circuit, voltage and current phase difference of 90 °, and is voltage leading current; in pure capacitive circuit, voltage and current phase difference was - 90 °, the current leads the voltage in the last two circuits, the power factor is zero (Cos 90 ° = 0,. for the general the load circuit, power factor between 0 and 1 by mathematical impedance Z = R + j (XL - XC), if XL = XC, then Z = R, that is, the impedance Z becomes a pure resistance, power factor will be equal to 1.

This means that the inductive load and capacitive load can compensate each other, a circuit inductance of the inductive component is exactly equal to the value of the capacitance value of capacitive element can be fully compensated, the approach to power factor compensation from this. Alternating current through the load impedance, the resulting total power S called "apparent power" apparent power S, including active power P and reactive power Q two components. One active power P = S * Cosф, reactive power Q = S * Sinф. Only when the power factor equal to the maximum value of 1 Cosф that ф = 0 °, the reactive component of Q was equal to zero, the active power P is equal to the value of apparent power S. However, the actual working load capacity only with the active power related.

Power factor and LED lighting

This paper describes the power factor, power factor, the concept of compensation, the capacitive loading characteristics of LED lamps, LED lighting in the argument is no need to increase the power factor compensation circuit conclusions.

The harmful effects of low power factor

(1) power supply device with a load capacity is compromised, that reduces the load capacity. If a device can give out the 100KVA apparent power, if power factor is 0.7, you can only reveal the active power of 70KW; if the power factor of 0.9, is able to give out 90KW of active, visible improve the power factor of great significance.

(2) reactive current transmission lines because there is an increase of transmission line losses. For example, the power factor of 0.7, to reveal the active power 70KW, you need to confess 100KVA apparent power, power transmission line current increases, the line loss will inevitably increase.

Power factor compensation

Energy for the electricity sector is based on "apparent power" to calculate, but the tariff collection is based on "active" to calculate the user's "meter" and to "active form", both of between a "power factor" discount, so the power factor is very concerned about the electricity sector data. If the user does not achieve the desired power factor, power consumption is relatively sector resources. At present the domestic provisions in terms of power factor must be between 0.9 inductive to 1.

May take the following approach to power factor correction:

(1) semi-centralized, concentrated Compensation Act, requires all electricity distribution companies room to install power factor controlled device, the size of the power factor real-time detection, automatic investment or the removal of compensation for the number of power capacitors for motor run compensation (due to Enterprise is the main electricity load motor, so that the local electricity network power factor compliance and this way from the late seventies, early eighties already enforced, has less than twenty years. there are the The installation of power factor power supply is also controlled device to its power under the jurisdiction of the region to further compensation.

(2) dispersion compensation method, requires each electrical appliance uses advanced technology will be designed to meet the power factor standard, so no matter when and where electricity power factor can ensure compliance. But this will increase costs, increase the electrical size, and some electrical appliances on the volume size limit is very strict, increase the design difficulty.

Electric light sources lighting and power factor compensation review by the incandescent electric light is the beginning of an incandescent bulb is a purely resistive load, no power factor compensation. After the 1950s, the rapid spread into the main fluorescent lighting, ballasts using a silicon inductors, high reliability, long life, there are still a small amount used, most no power factor compensation measures may be by cost factors, or people do not understand the power factor correction, energy-saving consciousness is not strong. Have adequate capacity plus access for power factor compensation capacitors, is used in 30W, 40W on the high-wattage fluorescent lamp, 20W the following rarely used. After the 1990s, people's environmental, energy conscious, developed a three-color phosphor energy-saving lamps, the optical power efficiency. Electronic ballasts also come out later, accompanied by three-color phosphor lamp, energy-saving effect is more significant. IC manufacturers are offering home and abroad with a light source with power factor correction chip for electronic ballasts, excellent performance, but increased the cost and volume of electronic ballasts, the people can not accept its price, only about in high-end lighting products. A large number of electronic ballasts include the popularization of energy-saving lamps are not used to add any power factor compensation measures, which popular in the market of energy-saving lamps, fluorescent lamps everywhere. That is basically what the previous lamp power factor compensation measures, but we are using.

LED power consumption is a more efficient, light power smaller than the energy-saving lamps. LED lighting will certainly be more progress, environmental protection, energy saving is more appropriate. LED lamps are power factor compensation increases, the author's view is:

(1) According to expert analysis, LED capacitive load. Many grid inductive load, such as motors, transformers and so on. Often need access to compensate for capacitive load, power factor controlled device is for this purpose. LED capacitive load, precisely compensates for inductive load more power led to the problem of low power factor, it is well spent. From this understanding, I believe that in principle, LED lighting eliminates the need for power factor compensation measures.

(2) interior lighting with a single lamp LED lamps are low-power, power does not exceed 30W. Lighting power small impact on the grid is small, I believe that these lamps can remove the power factor compensation measures, but added bad, but will lose LED lamps are able to compensate for capacitive load inductive load power due to low power factor leading to more the function. These lamps are mostly low-power compact small size, interior space is very limited, such as MR16, PAR30, PAR38 lamp cup, power increases and then fit the PCB, is a good thought plus power factor compensation measures can not be put into. Also increase the power factor compensation will bring down the efficiency of side effects, or the cloud more harm than good. Furthermore costs affect sales. Moreover, the electricity sector has taken measures to cope compensate for power factor, lamp manufacturers need not go superfluous.

(3) more than 100W of power plus power factor can be considered compensatory measures, a large load on the power grid is also a large impact, such as 100 watts to hundreds of watts of LED lights. Street are public welfare, the cost of a slight increase that is OK, the power increase is also a PCB board position can be placed. Increase the power factor compensation measures can help alleviate some of the electricity sector adjustment burden is too large to prevent excessive capacitive load compensation.(more information please visit www.greendyled.com)