IEC61000-3 harmonic testing system

Harmonics generated by electrical systems can be divided into the following two categories:

1. Transient harmonics (wave harmonics). The generation of transient harmonics is caused by the operation of electrical switches used in the electrical system. 

2. Steady-state harmonics, which are generated by nonlinear loads in the power system.These nonlinear loads include: a. current source harmonics: high-power ac devices, such as large electrolytic power supply, large electrochemical power supply, electric locomotive, steel rolling machinery and equipment, medium-high frequency heating furnace, arc furnace, frequency converter, general frequency converter, etc.The common feature of these load devices is the use of high-power power semiconductor devices;B. Voltage source harmonics: large-capacity transformer, motor, welding machine, core reactor, voltage transformer with iron core, etc.;C. Other devices such as TV sets, battery chargers and fluorescent lamps also generate harmonics. Although the power consumption of a single device is small, the harmonic components injected into the power supply system by them cannot be ignored due to their wide range of use and large quantity.These nonlinear electrical equipment (or called nonlinear load) significant characteristics is that they access non sinusoidal current from the power grid, that is to say, even when the power supply to the load is a sine wave voltage, but because they are not only its current with voltage synchronous change of voltage and current characteristics of nonlinear, makes the flow through the grid current is a sine wave, the current waveform is composed of fundamental wave and fundamental frequency into integer times harmonic components, namely the harmonic, serious distortion of grid voltage, grid also have to produce this kind of load harmonic provide extra electricity.Among them, the current source harmonics has the largest impact on the power grid, while the voltage source harmonics has the smallest impact on the power grid.The frequency conversion speed regulation control system has been applied more and more widely this year.

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