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TECH Talk: Airfield Lighting Circuits
From REILs to regulators, PAPIs to portables - TECH Talk explores the more technical aspects of airport lighting. This issue we explore airfield lighting circuits and the reason behind using current driven series circuits.
FLIGHT LOG: With 15 years experience with Flight Light, you've gained extensive knowledge about airfield lighting. Would you share some the basics of airfield lighting circuits?
MATT: Happy to. Let's begin with current vs. voltage. On an airfield, lights need to be evenly lit, so we use a current driven circuit to accomplish this. If we had a voltage driven circuit, say from a city's power source, we'd experience voltage drops along the circuit. The lights would become increasingly dim the further they are down the runway.
Stable output current is required for consistent lighting. So, on an airfield, you control incoming power to create your typical 6.6 Amp current (20 Amp for military). This is done with a regulator.
On a current driven airfield lighting circuit, the regulator allows for an even distribution of 6.6 Amps across the whole series circuit.
On a series circuit, power is run through the primary side of an isolation transformer for each light. The secondary side is hooked up to the lamps, causing them to light.
This way, if a lamps burns out, the continuous loop on the primary (linked transformers) keeps the flow of regulated electricity going.
The regulator will notice the drop in load and make an adjustment so the remaining lights stay evenly lit. We test each of our regulators to make sure they maintain the 6.6 Amp current - even if 30% of the lamps are out.
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