CCR Input/Output Contactor

A CCR Input/Output Contactor is an electrically operated switching device used to control the power flow to and from a Constant Current Regulator (CCR). It consists of two separate contactor assemblies within a single enclosure or as individual units: the input contactor that connects the CCR to the AC mains supply, and the output contactor that connects the CCR's output to the series lighting circuit.

The contactors are typically controlled by the ALCMS, a PLC, or a local control panel, enabling remote start/stop of the CCR and automatic isolation during fault conditions. The input contactor provides overcurrent and short‑circuit protection coordination (often with a circuit breaker upstream), while the output contactor isolates the high‑voltage series circuit during maintenance or when the CCR is not in use. These contactors are designed for frequent operation and must withstand the high inrush currents and transient voltages characteristic of AGL power systems.

The input/output contactor pair exists to let a CCR be started, stopped, and isolated remotely and automatically, rather than requiring a technician to physically operate a switch at the equipment shelter every time the regulator needs to be energised or taken offline. Separating the input and output functions serves a specific purpose: the input contactor manages the CCR's connection to the mains supply and coordinates with upstream overcurrent protection, while the output contactor independently isolates the high-voltage series circuit, so either side can be controlled or protected without necessarily affecting the other. Their rating for frequent operation and high inrush tolerance reflects the reality that ALCMS-driven remote control means these contactors may cycle far more often than a component in a simpler, manually operated system would ever need to, making that durability central to the component's purpose rather than incidental to it.

CCR Input/Output Contactors are installed in airfield electrical rooms, equipment shelters, and AGL power centres. They are used in every AGL installation that requires remote or automated control of CCRs, including:

• Runway Lighting Systems: Controlling CCRs that power runway edge, centreline, threshold, and touchdown zone lighting circuits.
• Taxiway Lighting Systems: Managing CCRs for taxiway edge, centreline, and stop bar circuits.
• Approach Lighting Systems: Controlling CCRs for approach lighting configurations (ALSF-1, ALSF-2, MALSR, etc.).
• Integration with ALCMS: Allowing remote start/stop and automatic fault isolation from the central control system.
• Redundant CCR Schemes: Enabling seamless transfer between primary and standby CCRs by controlling the output contactors to connect the appropriate regulator to the circuit.
• Maintenance Isolation: Providing a visible break and a safe means of isolating the CCR for servicing, without interrupting the entire lighting system.

The contactor pair is installed within or immediately adjacent to the CCR cabinet in the equipment shelter, with the input contactor wired between the mains supply (and its upstream circuit breaker) and the CCR, and the output contactor wired between the CCR's output and the series circuit it feeds. Mounting within the same enclosure as the CCR keeps the high-current wiring runs short, reducing both voltage drop and the length of exposed conductor carrying the CCR's input and output currents. Control wiring from the ALCMS, PLC, or local control panel is run to the contactor coils separately from the power wiring, kept clearly labelled given that a CCR bank in a larger equipment room may have several contactor pairs operating independently. Because these contactors are expected to cycle far more frequently under remote control than a manually switched device would, their mounting position allows the clearance and ventilation the manufacturer specifies for contactors rated for frequent operation, rather than the tighter spacing that might suit an infrequently switched device.

The CCR Input/Output Contactor assembly consists of two independently controlled electromagnetic contactors. Each contactor has a coil that, when energised, closes the main contacts to complete the circuit. De‑energising the coil opens the contacts, disconnecting the circuit.

Key functional aspects include:

• Input Contactor: Connected between the mains supply (typically 400V AC, 3‑phase) and the CCR's input terminals. It is controlled by the ALCMS or a start/stop signal. When closed, it supplies power to the CCR. When open, the CCR is completely de‑energised, allowing safe maintenance.
• Output Contactor: Connected between the CCR's output and the series lighting circuit (the primary cable). It isolates the high‑voltage series circuit (up to several kV) when the CCR is off. Because this is a constant-current loop, the output contactor is only ever opened once the CCR's electronic protection has already ramped output current to zero — on a fault (e.g., overcurrent, earth fault) the CCR's internal regulation reduces current first, and the contactor's opening confirms isolation rather than interrupting live current itself. It is never used to break the loop under load.
• Interlocking: Electrical and mechanical interlocks prevent the output contactor from closing if the input contactor is open (ensuring the CCR is powered before connecting the load). Additional interlocks may be provided for safety and to prevent connecting two CCRs to the same circuit simultaneously.
• Auxiliary Contacts: Each contactor provides auxiliary contacts (normally open and normally closed) for status feedback to the ALCMS or control system, indicating whether the contactor is closed or open.
• Arc Suppression: The input contactor is fitted with arc chutes to safely quench the arc that can form when it interrupts mains current during a fault trip. The output contactor, which only ever switches at zero current, does not perform this live-interruption role — arcing on the output side is what the zero-current interlock is specifically designed to avoid, since interrupting a live constant-current loop can produce a dangerous multi-kilovolt transient.

The input/output contactor pair is the physical enable point beneath every layer of control logic described elsewhere in the AGL system — nothing the ALCMS or a CCR's own regulation can do matters if this assembly isn't closed. Command authority for the input contactor sits with the ALCMS (or a local start/stop station), and it may interrupt real current on a fault trip, coordinated with the upstream breaker. The output contactor's opening is different in kind: it is gated by the CCR's own protection circuitry ramping output current to zero first, so an overcurrent or earth fault is cleared electronically before the output contactor ever opens — it confirms isolation on a dead loop rather than interrupting a live one, and this sequencing happens faster than a control-room decision loop could react. This is a deliberate division of authority — the ALCMS decides when the circuit should normally be live, while the contactor assembly's own interlock decides, independent of any external command, when it must not be. Auxiliary contact feedback closes the loop by reporting actual contactor position back to the ALCMS, so the control system's picture of "circuit energised" is always confirmed by hardware state rather than assumed from the last command sent.

Each contactor is built with silver-alloy or silver-tungsten contacts sized for its respective duty — the input contactor rated for the three-phase mains current feeding the CCR, the output contactor rated for the lower-current, higher-voltage series circuit on the CCR's secondary side — and both are engineered for the mechanical and electrical life needed to withstand frequent remote-controlled cycling rather than the occasional manual switching a simpler installation might see. The two contactors are typically mounted within the CCR's own cabinet on a common DIN rail or subpanel, positioned to keep the high-current conductors between contactor and CCR as short as practical, and spaced according to the manufacturer's clearance and ventilation requirements so heat from frequent switching doesn't shorten contact life. Indoor cabinet installations use an IP20 enclosure relying on the CCR shelter's environmental control, while contactors in unconditioned or outdoor enclosures step up to an IP54-rated weatherproof housing. Control coil wiring is terminated separately from the power connections at a dedicated low-voltage terminal block, and auxiliary contacts used for remote status feedback are wired through their own cable entry to keep control signals isolated from the switched power conductors.