Measured data and analysis of 7 specifications of LED light source of 3 well-known brands in China

The actual measurement is carried out on 7 LED light sources of 3 well-known brands in the world. The data is listed below, and the data is analyzed to interpret the connotation of the data.

The power factor is the ratio of active power to apparent power. In the absence of harmonics, the power factor is expressed by cosφ; the power factor is the ratio of active power to apparent power. When there is harmonics, the power factor is expressed by PF.

PF=P/S

Cosφ=P/S1

To protect the manufacturer, replace the brand with A, B, C, please forgive me!

The data is analyzed below.

1. Deviation between measured power and nominal power

Table 2 LED lamp measured power and nominal power

It can be seen from Table 2 that 1) the measured active power of the LED lamp has different degrees of deviation from its nominal power, and the highest deviation is nearly 25%; 2) both positive and negative deviations indicate that the manufacturing standard is missing or poorly executed, resulting in This result.

Figure 1 Active power deviation of LED lights

2. Apparent power, active power, and reactive power are the rules of the right triangle.

Under normal circumstances, the apparent power S, the active power P, and the reactive power Q conform to the right triangle principle, S is a hypotenuse, and P and Q are two right angle sides. The rightmost column of Table 3 is SQRT (S2-P2-Q2). Under normal circumstances, the value should be 0, but it can be seen from the table that the value is not 0, but the value is larger. Therefore, there is a fourth power in the LED lamp.

Table 3 LED lamp power meter

3, power factor

There are two different concepts of power factor, PF and cosφ, which have different meanings. PF contains the influence of harmonics. The fourth power mentioned above is caused by harmonics. When the line load is pure, the two power factors are equal, that is, PF = cos φ. Table 4 lists the comparison and calculation methods for power factor.

Table 4 Power Factor Table

For visual representation, Figure 2 plots the curves for cosφ and PF and the difference between the two, where red is cosφ and blue is PF.

4, harmonic

There will be a certain amount of harmonics in the LED light that needs to be treated. But there is a price to pay for harmonics. Therefore, some products evade the responsibility that should be borne in order to save costs and cut corners.

Table 5 Harmonics of LED

As can be seen from Table 5, there are two LED lights with high harmonic content, THDI is over 130%, very bad!

As can be seen from Fig. 3, the lower the PF, the larger the THDI and the more severe the harmonics. vice versa.

5 Conclusion

For the test of this three brands and seven LED lights, the following conclusions can be drawn:

1) The deviation between the nominal power and the actual power is large, and the maximum deviation is nearly 1/4;

2) The LED lamp does not conform to the principle of apparent power, active power, and reactive power right angle triangle, that is, the Pythagorean string theorem, there is a fourth power;

3) The power factor PF and cosφ are two different concepts, and the PF contains the influence of harmonics;

4) The LED lamps tested in this test have different degrees of harmonics. The lower the PF, the larger the THDI and the more serious the harmonics.

Note: The conclusions of this article are only responsible for this test sample!

Test conditions

This test is to study the harmonics of civil building lighting. Therefore, it is necessary to conduct experimental research on energy-saving lamps, straight-tube fluorescent lamps and LED lighting sources commonly used in civil buildings, and study the harmonic characteristics when using this kind of light source in large quantities. The magnitude of the harmonic current. Therefore, from the practical engineering application, a test platform for simulating the actual engineering conditions is built in the laboratory, so that the test data can not only derive the harmonic characteristics after the large-scale use of the energy-saving lamps, but also enable the test results to be closely integrated with the actual engineering. stand up. The test equipment and equipment of the laboratory are shown in Table 1.

Table 1 Test equipment and equipment

Table 1 Test Equipment

The power supply in the test must meet the relevant requirements of GB 17625.1-2003:

(1) The test voltage shall be the rated voltage of the equipment under test, and the single-phase test voltage shall be 220V. The test voltage variation range shall be within ±2.0% of the rated voltage, and the frequency variation range shall be within ±0.5% of the rated frequency. The UPS in Table 1 can guarantee the purity of the power supply.

(2) When the equipment under test is connected in the normal operation mode, the test voltage harmonic content rate shall not exceed the index of Table 2.

Table 2 Test voltage harmonic content rate

(3) The peak value of the test voltage should be between 1.40 and 1.42 times its effective value, and should peak at 87°~93° after zero crossing.
The measuring instrument is the main instrument of this test, as shown in Tables 3, 4 and 5.

Table 3 Fluke 1760 Related Parameters

Table 3 Fluke 1760 Parameters

Table 4 Voltage transformer related parameters

Table 4 Voltage transformer parameters

Table 5 Current transformer related parameters

Table 5 Current transformer parameters

Therefore, our test is tested under the laboratory environment and the power supply voltage is relatively pure. The data is scientific, effective, high precision, and the conclusion should be more accurate.