Elevator Main Contactor: Safety Trip De-Energisation, EN 81-20 Dual-Channel Monitoring, Forced-Guided Contact and Main Switch

The main contactor (also called the line contactor or input contactor) is the primary power-switching device in the elevator control cabinet. In relay-logic controlled elevators: (1) The main contactor energises when a call is registered and all safety conditions are met; (2) It de-energises when the car stops at a landing, cutting main power to the drive/motor after the brake has applied; (3) On any safety circuit trip (safety relay de-energises), the main contactor immediately drops out, removing power from the drive. In VVVF-controlled elevators: the main contactor may be replaced by or supplemented with a drive input contactor; however, EN 81-20 requires that the final isolation between the drive and motor is achieved by the direction contactors (up/down contactors), not the drive's internal switching — because the drive IGBTs could fail in the on-state. EN 81-20 Annex A lists the requirements for contactors in safety circuits: (a) dual-channel monitoring to detect welded contacts; (b) mechanical interlocking between up and down contactors to prevent simultaneous energisation; (c) forced-guided contact design (IEC 60947-5-1 Annex L) to ensure that the monitoring circuit accurately reflects the power contact state. Main switch (isolator): a separate main switch (isolator) is required in the machine room to provide full isolation of the elevator electrical supply for maintenance; this is distinct from the main contactor.

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