100W Isolating Transformer

The 100W Isolating Transformer is a heavy‑duty single‑phase transformer designed for power‑hungry AGL applications. With a secondary rating of 100W, it sits above the standard 45W/65W tiers, capable of driving high‑intensity approach lighting fixtures, large obstruction beacons, or even multiple low‑power fixtures connected in parallel on the secondary side — though the standard range extends further still, up to 150W, 200W, 300W, and 500W ratings for the most specialised loads.

The 100W transformer features a substantially larger core, heavier gauge windings, and enhanced thermal management to handle the increased power dissipation. It provides the same galvanic isolation and constant‑current transfer as lower‑power variants, but is built to withstand the thermal and electrical stresses associated with high‑power operation. While less common than the 45W and 65W variants, it is essential for specialised applications where maximum light output is required.

The 100W isolating transformer exists to power fixtures at the upper end of typical AGL demand — high-intensity approach lights, large obstruction beacons, or even several lower-power fixtures wired together on the secondary side — without exceeding what a single standard transformer can safely deliver. Its purpose is the same isolation and fault-tolerance role every unit in the family provides, sized for a fixture or fixture group that draws meaningfully more power than the common 45W or 65W ratings.

The larger core, heavier windings, and improved thermal handling exist because a transformer carrying more secondary power dissipates more heat, and that heat has to be managed properly or the unit's working life — and the reliability of the circuit it protects — would suffer.

The 100W isolating transformer is deployed in the most demanding AGL applications, including:

• High‑Intensity Approach Lighting Systems (ALS): ALSF‑1 and ALSF‑2 configurations with high‑power barrettes and crossbars requiring maximum luminous output.
• High‑Intensity Obstruction Lights: High‑intensity white flashing obstruction lights on tall structures (e.g., >150m) requiring up to 200,000 cd peak intensity.
• Large Airport Beacons: Rotating beacons and heliport beacons with high‑power lamps (100W halogen or equivalent LED).
• Sequenced Flashing Lights: High‑intensity flashing approach lights requiring high instantaneous power.
• Multiple Fixtures on a Single Transformer: Some configurations use a 100W transformer to power two 45W fixtures or a combination of low‑power fixtures in parallel.
• Critical Runway Lighting: Some CAT III runways use 100W transformers for edge lights where maximum intensity is mandated.

The transformer is typically installed in handholes or pits with enhanced ventilation, given the higher heat dissipation. It uses standard L‑823 primary connectors and heavy‑gauge secondary cabling to handle the increased current.

The 100W transformer is installed in a handhole or pit with enhanced ventilation to manage its greater heat dissipation, sited adjacent to the high-intensity fixture, beacon, or obstruction light it serves. The primary connects into the series loop via a standard L-823 connector, while heavy-gauge secondary cabling carries the higher current to the fixture. Where a single 100W unit is used to power two lower-wattage fixtures in parallel, the enclosure is sized to route both secondary cables cleanly, and the pit location is chosen to keep both cable runs within the manufacturer's maximum secondary length.

The 100W transformer operates on the same electromagnetic induction principle as other isolating transformers, but with design optimisations for high‑power operation. The primary winding is connected in series with the 6.6A constant‑current loop. The primary current induces a secondary voltage—typically 15.15V (for a 100W lamp at 6.6A, V = P/I = 100W/6.6A ≈ 15.15V) or 24V/48V for specialised configurations.

Specific design features for the 100W variant include:

• Large Core Cross‑Section: The core is significantly larger to handle the higher flux density and minimise saturation at high currents.
• Heavy‑Gauge Windings: Primary and secondary windings use thicker copper wire to reduce I²R losses and prevent overheating at full load.
• Enhanced Thermal Dissipation: The encapsulation compound is formulated for high thermal conductivity, and the form factor often includes cooling fins or a larger surface area for heat rejection to the surrounding soil or concrete.
• Optimised Turns Ratio: Typically designed for a secondary voltage around 15V at 6.6A, providing the required power while maintaining efficient primary‑secondary coupling.
• Regulation Performance: Maintains secondary voltage within ±5% across the full dimming range (2.8A to 6.6A), ensuring consistent light output.
• Robust Short‑Circuit Protection: The leakage impedance limits secondary fault currents, protecting the loop, though the higher power means short‑circuit conditions must be addressed promptly.

The 100W transformer occupies the same position in the control chain as any other isolating transformer: an Airfield Lighting Control and Monitoring System (ALCMS) selects the required brightness step based on prevailing RVR, ATC instruction, or pilot-controlled lighting input, and the CCR regulates the whole loop to the corresponding fixed current (2.8A–6.6A, 5-step). The transformer has no addressable identity of its own — it converts whatever current the loop is carrying at that moment into roughly 15.15V on the secondary side, and cannot be commanded independently of the rest of the loop. At this wattage the transformer sits at the boundary between single-fixture and multi-fixture applications, so a loop fault detected upstream by the CCR's voltage monitoring may affect either a single high-output fixture or a small parallel group depending on how the secondary is wired — which is why the load-aggregation behaviour covered next matters as much as the fault-detection principle itself.

At 100W the transformer sits at the boundary between single-fixture and multi-fixture duty, and its construction reflects the larger winding this implies: a laminated core wound for a 100W secondary is enclosed in a moulded shell and fully encapsulated — vacuum-impregnated and back-filled with epoxy or polyurethane resin — giving the completed unit, typically 6.0–9.0 kg, its IP68 rating without any separate gasketed enclosure. Insulation is specified to Class H for the higher continuous operating temperature this size runs at. Leads terminate in sealed L-823 splice connectors rated for burial and continuous immersion, and because the secondary may feed more than one fixture in parallel, the base can housing it in is sized to accommodate the additional splice connections a multi-fixture group requires.