What is a transformer connection?
A transformer connection is how a series isolation transformer is wired into an airfield lighting circuit. Its primary leads join the circuit cable in series, and its secondary leads feed a short cable to one light fitting.
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A transformer connection is how a series isolation transformer is joined into an airfield lighting circuit. All the lights on a circuit share one loop of primary cable that carries a constant current from the constant current regulator (CCR). The transformer’s primary leads are joined into that loop, so current comes in on one lead, passes through the primary winding and leaves on the other to carry on to the next light.
The secondary side is separate. A short cable from the secondary leads feeds only the one fitting, and the transformer passes energy to it magnetically, with no direct electrical path from the primary. That keeps the fitting isolated from the primary circuit, and it lets the primary loop stay closed when a lamp fails or a secondary cable is disconnected. The joints are made with purpose-made, sealed plug-and-receptacle or moulded connectors, so the transformer can be disconnected, tested or replaced without re-jointing the main cable. Unplugging a primary connector opens the series loop, so isolate and make the circuit safe under site procedures first, and treat the secondary as live as well.
Frequently Asked Questions
Q1What is a transformer connection in AGL?
The way a series isolation transformer is wired into an airfield lighting circuit. Its primary leads connect in series with the circuit’s primary cable, and its secondary leads connect through a short cable to the light fitting.
Q2Is the transformer primary connected in series or in parallel?
In series. The primary winding is one link in the circuit’s loop, so the same constant current from the constant current regulator (CCR) passes through the primary of every transformer on that circuit. Each secondary then feeds only its own fitting.
Q3Why do the other lights stay on when one lamp fails?
When a lamp fails or its secondary cable is disconnected, the secondary stops carrying current, but the primary winding is still part of the loop. Series isolation transformers are designed to allow this, so the primary current keeps flowing and the other lights stay lit. An open secondary can develop a raised voltage and heat the transformer, so it is still treated as live and corrected promptly. A break on the primary side is different: it opens the whole series loop.
Q4What can go wrong at a transformer connection?
Water in a connector, a loose or badly made joint, or damaged insulation can cause a high-resistance joint, heating or an earth fault, and a fault on the primary side can affect the whole circuit. This is why connections are sealed, supported and checked with continuity and insulation-resistance tests during installation and maintenance.
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