Elevator Auxiliary Relay: Function, Rating, and Role in Control Panels

Auxiliary relays in elevator control systems serve as signal amplifiers and galvanic isolators between the low-voltage control logic (typically 24 V DC) and the load circuits (230 V AC lighting, fan, indicator lamp supplies). They are also used to create latching (memory) functions, time-delay sequences, and interlocks in older relay-logic panels. In modern microprocessor-based controllers, many auxiliary relay functions are performed by PLC output modules or solid-state relays (SSRs), but electromechanical relays remain common for safety-critical outputs due to their physical contact separation and fail-safe characteristics. Key specifications include coil voltage, contact rating (typically 10–16 A), number of poles (SPDT or DPDT), and electrical endurance (minimum 300,000 operations under rated load). Regular inspection should verify contact resistance and coil continuity.

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