TN-115-7.5

Power supply function of the TN-115-7.5 transformer

The TN-115-7.5 converts 115 V AC from the aircraft electrical system into 7.5 V AC for low-voltage lighting consumers. The input side is connected to the aircraft 115 V, 400 Hz AC lighting bus, while the output side feeds contour light circuits. This allows external or contour lighting elements to operate from a stable low-voltage source instead of being connected directly to the main aircraft AC network. Correct transformer operation is important for reliable brightness and safe operation of the connected lamps.

TN-115-7.5 in contour and navigation light circuits

The transformer is used in the power supply chain of contour lights, sometimes described together with aircraft navigation or outline marking lights. Depending on helicopter design, the secondary winding may supply lamps installed on rotor blade tips, fuselage contour positions or other lighting points specified by the aircraft documentation. The exact consumer circuit should always be checked by the aircraft wiring diagram, because the same transformer designation may be used in different lighting layouts.

Hermetic construction of the TN-115-7.5

The TN-115-7.5 is a sealed low-voltage power transformer built in a stamped metal housing. The internal transformer assembly is filled with compound, which protects the windings from moisture, vibration and environmental exposure. This construction is practical for helicopter service, where electrical equipment may be exposed to vibration, temperature changes and long operating periods. During inspection, attention should be paid to the housing, connector, mounting flanges, grounding point and any signs of overheating or mechanical damage.

Installation of the TN-115-7.5 on helicopters

The transformer is mounted on aircraft structural elements, in electrical equipment areas, behind interior panels, in radio / equipment compartments or near lighting circuits depending on helicopter layout. The housing includes mounting flanges with holes for rigid attachment. Grounding is normally provided through the metal mounting points and / or a dedicated grounding terminal on the housing. Proper grounding matters because the transformer body is part of the aircraft electrical installation and must be securely bonded to the airframe.

Electrical connection of the TN-115-7.5

The TN-115-7.5 is connected through a fixed aircraft plug connector mounted on the housing. The internal electrical scheme is simple: one primary winding and one secondary winding. The primary winding receives 115 V AC at 400 Hz from the aircraft lighting power circuit, typically controlled through the relevant cockpit circuit breaker or lighting switch. The secondary winding supplies 7.5 V AC to the contour light lamps or related low-voltage lighting circuits. Connector pin assignment must be checked by the aircraft wiring documentation.

Supply and maintenance of TN-115-7.5

For procurement or replacement, the transformer should be specified by the full designation TN-115-7.5 / TN-115-7,5. The required condition should be confirmed before shipment: new production, from storage, repaired, overhauled or tested serviceable. Since it is an aviation electrical component, passport, acceptance stamp, quality document or repair documentation may be required. Before installation, insulation resistance, winding continuity, output voltage, connector condition, housing integrity, mounting flanges and grounding should be checked.