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SICROWBAR AC overvoltage protection is used to protect power semiconductors (thyristors and diodes) in converters against overvoltages between the phases of a three-phase line supply. The range of applications is not restricted to protecting DC drive converters, but can also be used for infeed/regenerative feedback units of AC drive systems that are equipped with thyristors. Overvoltages that occur on the AC side of converters are mainly caused by switching operations when disconnecting from the line supply at the transformer primary. This applies both to operational switching operations (shutdown under no-load conditions) as well as in the case of a fault (shutdown under load).
Overvoltage protection is normally used in the following configuration:
