交换电流过负载时，加在该负载上的交换电压与经过该负载的交换电流发生相位差，人们便从中引出功率因数这一观点。人们消费、生存用电来自电网，电网提供频率为50Hz或60Hz的交换电。作为交换电的负载有电阻、电感、电容三品种型：

1、当交换电经过纯电阻负载时，加在该电阻上的交换电压与经过该电阻的交换电流是同相位的，即它们之间的相位夹角ф= 0°，同时在电阻负载上斲丧有功功率，电网要供出能量。

2、当交换电经过纯电感负载时，其上的交换电压的相位超前交换电流相位90°，它们之间的夹角ф= 90°，在电感负载上发生无功功率，电网供应的电能在电感中变为磁场能长久贮存后又回馈到电网变为电能，云云周期性循环，后果电网并不供出能量，故谓“无功功率”，但发生“无功功率”的“无功电流”照旧实践存在的。

3、当交换电经过纯电容负载时，亦相似于此，只不外其上的交换电压的相位滞后交换电流相位90°，它们之间的夹角ф= - 90°。

这里，界说相位角度超前为正，相位角度滞后为负。实践负载是电阻、电感的感抗、电容的容抗三品种型的复物，复合后统称“阻抗”，写成数学式便是：阻抗Z= R+j （ XL – XC、。此中R为电阻，XL为感抗，XC为容抗。假如（ XL– XC、> 0， 称为“理性负载”；反之，假如（ XL – XC、< 0称为“容性负载”。

交换电经过理性负载时，交换电压的相位超前交换电流相位（0°<ф<90°）；交换电经过容性负载时，交换电压的相位滞后交换电流相位（-90°<ф< 0°）；电工学界说该角度ф为功率因数角，功率因数角ф的余弦值即Cosф叫做功率因数。关于电阻性负载，其电压与电流的位相差为0°，因而，电路的功率因数为1最大（Cos 0°=1、；而纯电感电路，电压与电流的位相差为90°，而且是电压超前电流；在纯电容电路中，电压与电流的位相差则为- 90°，即电流超前电压。在后两种电路中，功率因数都为零（Cos 90°= 0、。关于一样平常性负载的电路，功率因数就介于0与1之间。由数学式阻抗Z= R+ j （ XL – XC），假如XL = XC，则Z= R，即阻抗Z酿成了一个纯电阻，功率因数便即是1。

这便是说，理性负载和容性负载可以相互赔偿，一个电路里的理性元件的感抗值恰好即是容性元件的容抗值则可以完全赔偿，功率因数赔偿的措施就源于此。交换电经过阻抗负载时，发生的总功率S称“视在功率”，视在功率S包罗有功功率P和无功功率Q两个重量。此中有功功率P = S*Cosф，无功功率Q = S*Sinф。只要当功率因数Cosф值即是最大值1即ф= 0°时，无功重量Q才即是零，有功功率P即是视在功率 S的值。但负载的实践事情才能只与有功功率相干。

** 功率因数与****LED照明**

本文次要叙说了功率因数、功率因数赔偿的观点，由LED灯具容性负载特点，论证在LED照明灯具内无需增长功率因数赔偿电路的结论。

** 功率因数偏低的坏处**

（1） 供电设置装备摆设的带负载才能被打了扣头，即低落了带负载才能。如某设置装备摆设能供出100KVA的视在功率，若功率因数为0.7，则只能供出70KW的有功功率了；若功率因数为0.9，则能供出90KW的有功功率，可见进步功率因数很故意义。

（2） 输电线路由于无功电流存在，增长了输电线路消耗。比方功率因数为0.7，要供出70KW的有功功率，则必要供出100KVA的视在功率，输电线路的电流增大，线路消耗一定增大。

** 功率因数赔偿办法**

供电部分供的电能因此“视在功率”来盘算的，但收电费倒是以“有功功率”来盘算的，用户的“电度表”实为“有功功率表”，两者之间有一个“功率因数”扣头，以是功率因数是供电部分十分在意的一个数据。用户假如没有到达抱负的功率因数，绝对地便是在斲丧供电部分的资源。现在就国际而言功率因数划定是必需介于电理性的0.9～1之间。

**可接纳以下方法举行功率因数赔偿：**

（1） 半会合、会合赔偿法，要求用电企业的各个配电房必需安置功率因数自控安装，及时检测功率因数巨细，主动投入或切除赔偿电力电容器的个数，用于电念头运转赔偿（因企业次要用电负荷是电念头、，做到部分用电网络功率因数达标。这个措施从上世纪七十年月末、八十年月初便已强迫实行，至今少说已有二十多年。另有各个供电所也安置功率因数自控安装，对其下辖供电地区进一步赔偿。

（2） 疏散赔偿法，要求每个用电用具设计时便接纳先辈技能，满意功率因数达标，如许不管何时何地用电均能包管功率因数达标。但如许做会增长本钱、增长电器体积，而有的电器对体积巨细限定很严厉，加大了设计难度。

电光源照明灯具与功率因数赔偿的回忆电光源是由白炽灯胆开端的，白炽灯胆是纯电阻负载，没有功率因数赔偿的题目。上世纪50年月后，日光灯敏捷遍及成了次要的照明灯具，镇流器用的是硅钢片电感，牢靠性高，寿命长，至今仍有大批接纳的，大少数没有什么功率因数赔偿步伐，大概是遭到本钱要素的影响，抑某人们对功率因数赔偿不甚理解，节能认识不强。也有加接得当容量的电容器作功率因数赔偿的，多用在30W、40W大瓦数日光灯上，20W以下很罕用。上世纪90年月后，人们的环保、节能认识加强，开辟出三基色萤光粉节能灯，其光成效更高。电子镇流器也随后问世，配上三基色萤光粉灯管，节能结果愈加明显。国际外一些集成电路厂商推出了带有源功率因数赔偿的灯用芯片，用于电子镇流器，功能良好，但增长了本钱和电子镇流器体积，老黎民还不克不及承受它的代价，约莫只用在高端灯具产品上。少量的遍及型电子镇流器包罗用于节能灯的都没有加什么功率因数赔偿步伐，这在市道市情盛行的节能灯、日光灯上到处可见。也便是说以往的灯具根本上没有什么功率因数赔偿步伐，但各人都在用。

LED耗电更省，灯具功率比起节能灯还要小。LED照明固然更为前进，对情况掩护、节能减排更为相宜。LED灯具能否加功率因数赔偿，笔者的见解是：

（1） 据专家剖析，LED为容性负载。电网的理性负载甚多，比方电念头、变压器等等。每每必要接入容性负载举行赔偿，功率因数自控安装便是作此用处的。LED为容性负载，恰好赔偿了电网因理性负载多招致功率因数低的题目，正是用得其所。源于这种了解，笔者以为LED照明灯具准绳上无需加功率因数赔偿步伐。

（2） 室内照明用的单盏LED灯具均是小功率的，功率不会凌驾30W。灯具功率小对电网的影响也小，笔者以为这类灯具完全可以免除功率因数赔偿步伐，加了反而欠好，反而会得到LED灯具是容性负载可以赔偿电网因理性负载多招致功率因数低的功效。这些小功率灯具多是小体积紧凑型的，外部空间非常有限，比方MR16、PAR30、PAR38灯杯，电源PCB板增大后放不下，便是好意想加功率因数赔偿步伐也加不进。另有加了功率因数赔偿后会带来服从降落的反作用[fǎn zuò yòng]，或云得失相当[dé shī xiàng dāng]。再则本钱增长影响贩卖。况且供电部分已接纳了应对步伐对电网功率因数举行赔偿，灯具厂家大可不用再去多此一举[duō cǐ yī jǔ]。

（3） 功率100W以上的可以思索加功率因数赔偿步伐，功率大的负载对电网的影响也大，比方一百瓦到数百瓦的LED路灯。路灯属于公益奇迹，本钱略增长一点无大碍，电源PCB板增大一点也有地位可放。加功率因数赔偿步伐可以协助供电部分加重一些调治包袱，避免容性负载过大发生过分赔偿。

The concept of power factor is derived from the phase difference between the ac voltage applied to the load and the ac current applied to the load as it flows through the load. People produce and live electricity from the power grid, which provides alternating current with a frequency of 50Hz or 60Hz. There are three types of load as alternating current: resistance, inductance and capacitance:

1, when an alternating current by purely resistive load, and the resistance of the ac voltage, and through the resistance of the alternating current is in phase, the phase Angle between them ф = 0 °, active power consumption on the resistance load at the same time, the grid for the energy.

2, when an alternating current by pure inductance load of the ac voltage phase advance of alternating current phase 90 °, the Angle between them ф = 90 °, the reactive power in the inductance load, the power supply of electricity in inductance into a magnetic field can short storage and then back to the grid into electricity, so cycle, the power grid is not for the energy, the so called "reactive power", but "reactive power" of "reactive current" still exist.

3, when an alternating current by pure capacitance load, also like this, but its the ac voltage on the phase lag phase alternating current to 90 °, the ф = - 90 ° Angle between them.

Here, the phase Angle lead is defined as positive, and the phase Angle lag is defined as negative. The actual load is a complex of three types: resistance, inductive reactance of inductance and capacitive reactance of capacitance, which are collectively referred to as "impedance" after compound. Written in mathematical formula, it is: impedance Z= R+j (XL -- XC). Where R is resistance, XL is inductive reactance and XC is capacitive reactance. If (XL - XC, > 0, called "perceptual load"; Conversely, if (XL - XC, < 0 is called "capacitive load".

Alternating current (ac) by inductive load, the voltage phase advance of alternating current phase (0 ° < ф < 90 °); Alternating current (ac) by capacitive load, the ac voltage phase lag of the alternating current phase (- 90 ° ф < 0 °); Electrotechnics defines this Angle as the power factor Angle, and the cosine of the power factor Angle is called the power factor. For resistive load, the voltage and current of the phase difference of 0 °, therefore, the power factor of the circuit is 1 the largest (Cos 0 ° = 1, And pure inductance circuit, voltage and current of the phase difference of 90 °, leading current and voltage; In pure capacitance, voltage and current of the phase difference is - 90 °, the current voltage in advance. In the two circuits, the power factor is zero (90 ° = 0, Cos. For circuits of general load, the power factor is between 0 and 1. From the mathematical expression impedance Z= R+ j (XL -- XC), if XL = XC, Z= R, that is, impedance Z becomes a pure resistance, the power factor is equal to 1.

That is to say, the inductive load and the capacitive load can compensate each other, and the inductive element in a circuit whose inductive reactance value is exactly equal to the capacitive element's reactance value can be fully compensated. This is the source of power factor compensation. When the alternating current passes through the impedance load, the total power S generated is called "apparent power", and the apparent power S includes active power P and reactive power Q. Where, active power P = S*Cos, reactive power Q = S*Sin. Only when the power factor Cos ф value is equal to the maximum 1 ф = 0 °, namely reactive component Q is equal to zero, the value of the active power P is equal to the apparent power S. However, the actual working capacity of the load is only related to the active power.

Power factor with LED lighting

This paper mainly describes the concepts of power factor and power factor compensation. Based on the capacitive load characteristics of LED lamps, it is proved that there is no need to add power factor compensation circuit in LED lamps.

The harm of low power factor

(1) the load capacity of the power supply equipment is reduced, that is, the load capacity is reduced. If a device can provide 100KVA of apparent power, if the power factor is 0.7, it can only provide 70KW of active power; If the power factor is 0.9, the active power of 90KW can be provided, so it is significant to improve the power factor.

(2) transmission line loss is increased due to the existence of reactive current. For example, if the power factor is 0.7, the apparent power of 100KVA should be provided if the active power of 70KW is to be provided. As the current of the transmission line increases, the line loss will inevitably increase.

Power factor compensation method

The electric energy provided by the power supply department is calculated as "apparent power", but the electricity charge is calculated as "active power". The "watt-hour meter" of the user is actually "active power meter", and there is a "power factor" discount between the two, so the power factor is a data that the power supply department CARES about very much. If the user does not reach the ideal power factor, it will consume the resources of the power supply department. At present, the power factor must be between 0.9 ~ 1 of the inductance.

Power factor compensation can be carried out in the following ways:

(1) a focused, concentrated compensation method, requests each transformer room electricity companies to install power factor control devices, real-time detection of power factor size, automatic or removal of the number of power capacitor compensation, used in motor running compensation (for enterprise, is the main power load motor, do local power network power factor. It has been enforced since the late 1970s and early 1980s and has been in place for at least two decades now. There are also power factor automatic control devices installed in each power supply station to further compensate the power supply area under its jurisdiction.

(2) decentralized compensation method, requires that each electrical appliance design will use advanced technology, to meet the power factor standard, so that no matter when and where electricity can ensure that the power factor standard. But this will increase the cost, increase the volume of electrical appliances, and some electrical appliances on the size of the volume restrictions are very strict, increasing the difficulty of design.

Review of electric light source lighting fixture and power factor compensation electric light source started from incandescent bulb. After the 1950 s, fluorescent lamp 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, may be affected by the cost factor, or people not understanding of power factor compensation, energy saving awareness is not strong. Also add add add the capacitor of appropriate capacity to make power factor compensation, multi-purpose on fluorescent lamp of 30W, 40W big wattage, 20W the following is used rarely. Since the 1990s, people's awareness of environmental protection and energy saving has been enhanced, and tri-color fluorescent powder energy saving lamp has been developed, with higher light efficiency. Electronic ballast also came out later, with three - color fluorescent powder lamp, more significant energy - saving effect. Some integrated circuit manufacturers at home and abroad launched a lamp with source power factor compensation chip, for electronic ballast, excellent performance, but increased the cost and volume of electronic ballast, people can not accept its price, about only in high-end lamps and lanterns products. A large number of popular electronic ballasts, including those used for energy-saving lamps, have not been added with any power factor compensation measures, which can be seen everywhere in the popular energy-saving lamps and fluorescent lamps on the market. That is to say former lamps and lanterns basically does not have what power factor compensation measure, but everybody is using.

Leds consume less power and are less powerful than energy-saving lamps. Of course, LED lighting is more progressive and more suitable for environmental protection, energy conservation and emission reduction. Whether power factor compensation is added to LED lamps or not, the author's opinion is as follows:

(1) according to expert analysis, LED is capacitive load. The inductive load of power network is very much, for example motor, transformer and so on. Often need to be connected to the capacitive load compensation, power factor automatic control device is for this purpose. LED is a capacitive load, which exactly compensates for the low power factor caused by multiple inductive loads in the power grid. From this understanding, the author believes that LED lighting without power factor compensation measures in principle.

(2) all single LED lamps for indoor lighting are low-power, and the power will not exceed 30W. Small power of lamps has a small impact on the power grid. The author believes that such lamps can be completely exempted from power factor compensation measures. It is not good to add LED lamps, but they will lose the function that capacitive load can compensate the power factor of the power grid due to multiple inductive loads. These small power lamps and lanterns are mostly compact in small size, and the internal space is very limited, such as MR16, PAR30, PAR38 lamp cup, power PCB board increased after not put, is a good idea to add power factor compensation measures are not added. There will be a power factor compensation after the efficiency decline side effects, or cloud outweighs the benefits. Moreover, the increase in costs affects sales. Besides, the power supply department has taken measures to compensate the power factor of the power grid.

(3) if the power is more than 100W, additional power factor compensation measures can be considered. High-power load has a great impact on the power grid, such as 100W to 100W LED street lamps. Street lamps belong to public welfare undertakings, so a slight increase in cost is not harmful. If the power PCB board is increased a little, there will be a place to put it. The additional power factor compensation measures can help the power supply department to reduce some of the regulatory burden and prevent the capacitive load from excessive compensation.