Power factor has never been a problem. In the past, there were regulations in the country that power factor requirements were required for power exceeding 75 watts (until now, there is no power factor requirement for laptops below 75 W). So there has never been any power factor requirement for the luminaire. Just like fluorescent lamps, the power factor is very poor, no one has ever put forward any opinions, and the state has not made any demands. Later, with the energy-saving lamps, although the country put forward a request, it is very loose, and it has requirements for more than 15 watts, while most of the energy-saving lamps are less than 15 watts. So it is equal to no request. Only after the appearance of LED lamps, they are strictly required. Only those below 5 watts are not required. Above 5W, the power factor must be >0.7. In addition to the small MR16 spotlights, which are 3 watts, most of the LED luminaires are more than 5 watts. So this rule just caught the neck of the LED. So let's take a closer look at the power factor problem!
What is the power factor?
We know that all generators are rotating machines and the resulting voltage is a sine wave. This is what we call AC. One of the advantages of AC power is that it can be changed by a transformer to change its voltage, and it can be raised to hundreds of thousands of volts for long-distance transmission to reduce the loss in transmission. After the destination, it will be reduced to become our common city. Electricity. Our current utility is 220V, 50Hz AC. In electrical engineering, alternating current can be represented by vectors. The vector can represent voltage as well as current. For a purely resistive load, the voltage and current are in phase, while for a pure capacitive load or a purely inductive load, the current and voltage are out of phase, but have a phase angle of 90 degrees, or phase difference. In a purely inductive load, the voltage on it is 90 degrees ahead of the current, while the voltage on the pure capacitive load is 90 degrees behind the current.
If we use a waveform, the voltage is usually expressed as a cosine wave. If the current lags behind the voltage, it is an inductive load. The leading voltage is a capacitive load.
Figure 1. Relationship between AC voltage and AC current for inductive loads
Because virtually no pure and pure capacitors exist, the actual load can only be called an inductive load or a capacitive load. At this time, there is an angle φ between the AC voltage and the AC current. For the inductive load, we call this angle φL, and for the capacitive load, the angle is called φC. (See Figure 2)
Figure 2. Vector representation of inductive and capacitive load voltages and currents
Street Light,Street Lamp,Outdoor Light,Outdoor Lamp
Jilin Province Wanhe light Co.,Ltd , https://www.wanhelight.com