Network chokes

A line choke attenuates voltage surges in the network when large loads are turned on or off. Using a choke significantly affects the shape of the consumed current, bringing it much closer to a sinusoidal waveform. Using a choke in the range from 10 kHz to 300 kHz reduces load interference by up to 30 dB and extends the service life of intermediate circuit capacitors. Using a choke limits the rate of current rise if the converter fails for any reason. This allows the input power circuit breaker to trip, minimizing damage and, consequently, reducing repair costs. The coefficient characterizing the non-sinusoidal waveform is 66% without a choke, and 89% with a choke. Converter reliability increases by 5-7 times.

A line choke reduces harmonics in the line voltage and protects frequency converters from harmful effects from the power supply network. Most types of variable frequency drives distort the line voltage, generating high harmonics. A line choke effectively reduces harmonic components generated by the frequency converter.

A line choke is also used to protect the input circuits of frequency converters from peak overvoltages that can be generated by lightning strikes, as well as other equipment connected to the line, such as powerful electric motors started directly from the grid. Low-power frequency converters are most susceptible to negative influences from the grid, such as welding equipment, powerful thyristor regulators, DC drives, etc.

Thus, a line choke acts as a two-way buffer between the drive and the grid, reducing the harmful effects of one on the other.