The main contactor or the circuit breaker in front of the three-phase armature circuit infeed of the converter is used to switch on the power section in a correct manner when the electronics and the voltage for the thyristor modules is enabled if the unit is still not operational. This is the reason that the contactor or the circuit breaker must always be energized via terminals XR1-109-110. When a circuit breaker is used, a motor-operated mechanism must be used to close the circuit breaker and an undervoltage release to open the circuit breaker.

Selection criteria

The internal control sequence guarantees that the switching operations are always made in a no-current condition. When selecting the main contactor, the utilization category AC-1 or for a circuit breaker, the maximum rated current I_n max should be used as basis. If the current and voltage quantities permit it, then generally, the more cost-effective solution using a contactor is preferred over a circuit breaker.