CCR & Power Distribution

Constant Current Regulators (CCRs) are the specialised power supplies that feed AGL series circuits. They take mains AC voltage (typically 415V or 230V) and convert it to a regulated, high-voltage, constant-current output — most commonly 6.6A for standard AGL circuits, or 20A for high-current loops. The CCR maintains this current regardless of load variations, fixture count or cable length, which is the fundamental requirement of a series circuit.

Power distribution encompasses the switchgear, distribution panels, changeover systems and monitoring equipment that sit between the utility supply and the CCRs — ensuring that power is available, selectable, protected and monitored across the entire AGL system.

CCRs exist because the series-circuit architecture underlying most AGL loops depends on a specific electrical behaviour that ordinary mains supply can't provide on its own: a constant current that stays fixed regardless of how many fixtures are on the loop, how long the cable run is, or how the load shifts as fixtures fail or are added. Without that regulation, every fixture on a loop would receive an inconsistent, load-dependent brightness rather than the precise, repeatable intensity steps pilots and controllers rely on for visual guidance in every visibility condition.

Power distribution around the CCR exists to make sure that regulated current is never at the mercy of a single point of failure in the incoming supply. Changeover systems and monitored switchgear let the airfield fall back to standby power automatically if the primary utility feed is lost, since a lighting outage during an approach or departure is not a delay that can be tolerated the way an outage in an ordinary building might be. Together, the CCR and its supporting distribution infrastructure are what turn an unpredictable utility feed into the dependable, precisely controlled current every fixture on the airfield depends on.

CCRs and distribution equipment are typically housed in a dedicated AGL equipment room or shelter, often at the airfield's electrical centre:

• CCR Units: Individual regulators for each series circuit — one per runway edge circuit, approach circuit, taxiway circuit, stop-bar circuit, etc.
• Distribution Panels: Main and sub-distribution boards that feed the CCRs from the utility supply, with circuit breakers and protection devices.
• Changeover Systems: Automatic or manual changeover switches that allow a CCR to feed alternate circuits in case of failure, or to swap between primary and standby power sources.
• Monitoring & Control: Remote terminal units (RTUs), supervisory control and data acquisition (SCADA) interfaces, and local control panels that allow operators to select intensity steps, switch circuits, and monitor circuit health.
• Standby Power: Diesel generators or UPS systems that maintain AGL operation during mains power failure, connected through the distribution switchgear.

CCRs and their associated distribution panels are installed in a dedicated, weatherproof equipment room or shelter positioned close to the circuits they feed — often at or near the airfield's electrical centre — to keep the high-voltage series cable runs to each circuit as short as practical. Each CCR is mounted on its own base or rack within the room with adequate clearance for ventilation and maintenance access, wired on the input side to the distribution panel's protected circuit breakers and on the output side to the series circuit cable leaving the building through a sealed cable entry. Changeover switchgear and standby power connections (generator or UPS) are installed so that a loss of the primary utility feed transfers the CCRs to backup power automatically, with the transfer wiring tested at commissioning to confirm the changeover completes within the time the airfield's operating category allows. Monitoring and control wiring back to the ALCMS or local RTU is run separately from the high-current power cabling to avoid interference, and the room itself is fitted with earthing and surge protection appropriate to a facility that sits at the point where utility power is converted into the high-voltage current feeding every fixture on the airfield.

A CCR is essentially a variable transformer (or a solid-state equivalent) with closed-loop current regulation. It senses the actual output current and adjusts the voltage automatically to maintain the setpoint — typically 6.6A RMS, with selectable steps corresponding to different intensity levels (e.g. 2.8A for low intensity, 6.6A for high intensity).

Key functional aspects include:

• Constant-Current Regulation: The CCR compensates for load impedance changes — whether a fixture fails or a connector develops a high-resistance joint — by adjusting voltage to keep current constant.
• Selectable Intensity Steps: The air traffic controller or AGL operator selects an intensity step (typically 5 or more steps) which the CCR translates into a corresponding output current level. All fixtures on that circuit brighten or dim together.
• Fault Protection: The CCR monitors for open-circuit, short-circuit, earth leakage and other fault conditions, tripping and alarming if it detects a hazardous condition.
• Voltage Compliance: The CCR is designed to deliver up to several thousand volts (typically up to 5kV or more) across the series circuit to overcome cable impedance and maintain current, particularly on long circuits with many fixtures.
• Remote Control: Modern CCRs are monitored and controlled via a remote control system, allowing the operator to change intensity steps, switch circuits on/off, and read fault status from the control tower or maintenance office.

The CCR's own architecture is a closed-loop feedback controller sitting between the utility supply and the series circuit. Incoming AC power is conditioned and fed through a regulation stage — a variable-ratio transformer or a solid-state converter — that sets the output current; a current sensor on the output continuously measures the actual series-loop current and feeds that reading back to the regulation stage, which adjusts its output voltage to hold the current at the commanded setpoint regardless of how the load impedance changes downstream. The commanded setpoint itself, along with on/off and step selection, is normally driven remotely by the ALCMS rather than set locally, and the CCR reports its own current, voltage and fault status back to that same remote system, making it the executing node in the airfield's wider control hierarchy rather than a self-contained one.

A CCR is built around a power transformer or solid-state inverter core, mounted within a floor-standing or wall-mounted steel cabinet sized to the unit's power rating, with the high-voltage output winding and its associated insulation kept physically separated from the input and control sections to maintain the isolation the series circuit design depends on. Cooling is provided either by natural convection through louvred vents in the cabinet, or by forced-air fans for higher-power units, with the cabinet's internal layout arranged so heat-generating components have clear airflow paths. The control and protection electronics, including current regulation circuitry, fault detection, and any remote communication interface, are mounted on a separate panel or sub-enclosure within the cabinet, wired to the power section through protected cable runs and circuit breakers. The cabinet itself is constructed from corrosion-resistant sheet steel, powder-coated or galvanised, with a lockable door for restricted access and gasket seals around door edges and cable entries to achieve the enclosure's rated ingress protection, since CCRs are typically installed in equipment rooms or outdoor cabinets exposed to airfield weather conditions.