Why it is essential to use Line contactor with ATS48?
Actually, Line contactor is used for:
- Safe disconnection of ATS48, moreover, it is used for switching, the line contactor acts as switching device that switches the supply power to the starter due to contactor’s high mechanical durability compared with circuit breaker which is used for protection purpose not switching
Note that Relay R1 can control the line contactor on the basis of the RUN and STOP commands and to indicate faults. Relay R1 is activated by a RUN command (or a preheating command). It is deactivated at the end of braking or deceleration or when the motor switches to freewheel mode after a STOP command. It is also deactivated when a fault occurs. The motor switches to freewheel mode at this point.
- if ATS48 thyristor (or more thyristors) are faulty without presense of short-circuit and motor is thus supplied unexpectedly with voltage, fuses does not bring you possibility to automatically disconnect ATS from line voltage although ATS signalizes fault by fault relay. You can see that some disconnection (controlled electrically via ATS48 R1 relay) is useful for motor protection.
- To comply with our Coordination tables in accordance with standards IEC 60947-4-1 and IEC 60947-4-2, Line contactors are specified
- When the starter is in stop state, and if a thyristor is in short circuit (damaged), a current can circulate through a motor winding which the starter can not detect because it is in stopstate. For safety reason, to avoid this risk, you have to use a line contactor witch opens the starter supply circuit. This contactor is controlled by ATS48 through R1 assigned to "isolation relay (r1l)". If there is a thyristor in short circuit at RUN command the starter will trip in PHF (synchronisation unbalanced) and the line contactor will be opened.