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Influence of voltage nonsinusoidality

Nonsinusoidal voltage - distortion of the sinusoidal shape of the voltage curve.


  Electric receivers with a non-linear current-voltage characteristic consume a current whose shape of the curve differs from the sinusoidal one. And the flow of such a current through the elements of the electrical network creates a voltage drop on them, different from the sinusoidal, this is the cause of the distortion of the sinusoidal shape of the voltage curve.

For example, semiconductor converters consume a current of a trapezoidal shape, figuratively speaking - snatch from a sinusoid a piece of a rectangular shape.

35% of electricity is converted and consumed
At a constant voltage.

Sources of non-sinusoidal voltage are: static converters, arc steelmaking and induction furnaces, transformers, synchronous motors, welding installations, gas-discharge lighting and household appliances and so on.

Strictly speaking, all consumers, except for incandescent lamps, have a non-linear current-voltage characteristic.

Increase in underrecipitation of electric power, due to the braking effect on the induction counters of harmonics of the reverse sequence.

The function describing the non-sinusoidal voltage curve can be decomposed into a Fourier series of sinusoidal (harmonic) components, with a frequency of n times the frequency of the power supply network-the frequency of the first harmonic (f n = 1 = 50 Hz, f n = 2 = 100 Hz, f N = 3 = 150 Hz ...).

In connection with various features of generation, propagation through networks and influence on the operation of equipment, the even and odd harmonic components are distinguished, as well as the direct sequence components (1, 4, 7, etc.), the reverse sequence (2, 5, 8 and Etc.) and zero sequence (harmonics multiple of three).

With increasing frequency (harmonic component numbers), the harmonic amplitude decreases.