Anti-shock safety of industrial electric installations with built-in frequency converters

Frequency converters are commonly used in drives with controlled rotational speed of three-phase induction motors. The power inverter built in the system is a component with varying impedance, is switched into the circuit between the supply source and the load. The load is subject to the assessment of reliability of shock protection. The internal setup of the power inverter causes that the shorting circuit is different from circuits with linear components. The difference relies on the impossibility to determine the instant short-circuit impedance. In the paper on the example of an industrial installation with built-in power inverter, made in accordance with current requirements of in-rule standards and internal regulations at the considered plant, an analysis of reliability of used measures for anti-shock protection during a fault was carried out.