W31X2M1G7.5 – TE Connectivity 7.5 Amp Thermal Circuit Breaker
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The W31X2M1G7.5 is a high-reliability, single-pole, "push-to-reset" thermal circuit breaker from TE Connectivity's Potter & Brumfield line. This component is a flight-critical safety device, engineered to provide precise, repeatable overcurrent protection for aircraft electrical circuits. Its fundamental purpose is to automatically interrupt the flow of current in the event of an overload or short circuit, thereby protecting the circuit's wiring from overheating and preventing a potential in-flight fire.
This is a thermal-type circuit breaker, which operates on a proven and robust bimetallic element. It is designed to be "trip-free," meaning the internal contacts cannot be held closed against an overcurrent condition. When the breaker trips, the push-button extends, often revealing a white band that provides a clear visual indication of the tripped state. As a trusted component used for decades by major airframe manufacturers, the W31 series is a benchmark for quality and reliability in aircraft circuit protection.
Key Features
TE Connectivity / Potter & Brumfield OEM: A globally recognized leader in high-performance electrical components, ensuring the highest standards of quality and reliability.
Push-to-Reset Single Pole Design: A simple, robust, and industry-standard interface for manual reset after an overcurrent event has been cleared.
7.5 Amp Current Rating: Precisely calibrated to protect wiring and systems with a nominal current draw at or below 7.5 amperes.
Thermal Bimetallic Strip Actuation: A time-proven, reliable mechanism that responds to overcurrent conditions based on heat generation, providing an inverse time-current trip curve.
Trip-Free Mechanism: A critical safety feature that prevents the breaker's contacts from being manually held closed during an active fault condition.
Visual Tripped Indication: The push-button extends and typically displays a white collar when tripped, providing an immediate visual cue to the pilot.
Technical Specifications
Part Number: W31X2M1G7.5
Component Type: Thermal Circuit Breaker
OEM Manufacturer: TE Connectivity / Potter & Brumfield
Current Rating: 7.5 Amperes
Voltage Rating: Up to 250 VAC / 32 VDC
Actuation Mechanism: Bimetallic Thermal Element
Reset Type: Push-to-Reset
Mounting Style: Panel Mount with Knurled Nut
Terminal Type: #8-32 Screw Terminals
Governing Specifications: UL Recognized, CSA Certified, and manufactured to meet or exceed rigorous aviation standards.
Aircraft Compatibility
The W31X2M1G7.5 is a standard electrical system component used in a vast range of general aviation, corporate, and transport category aircraft from numerous manufacturers, including Textron (Cessna, Beechcraft), Piper, Mooney, Cirrus, and others. It is not specific to any one airframe but is selected based on the electrical load requirements of the circuit it protects.
Crucial Note: The correct amperage rating for a specific circuit must be verified against the aircraft's Wiring Diagram Manual and Illustrated Parts Catalog (IPC).
Applications
The W31X2M1G7.5 is used for the primary circuit protection of numerous aircraft systems, including but not limited to:
Avionics and Navigation Equipment
Interior and Exterior Lighting
Instrumentation and Engine Monitoring
Autopilot and Flight Director Systems
Flap, Trim, and Landing Gear Actuator Motors
Why Choose W31X2M1G7.5?
Choosing a genuine, high-quality TE Connectivity W31 series circuit breaker is a critical decision for electrical system safety. The entire purpose of a circuit breaker is to fail safely to protect the aircraft. A failure of a breaker can manifest in two dangerous ways: it can fail to trip during a genuine overcurrent, leading to an electrical fire, or it can "nuisance trip," causing a loss of power to an essential system like navigation or flight controls. The W31 series is a proven, OEM-trusted design that guarantees reliable, repeatable performance. Using a cheap, non-certified, or automotive-grade breaker introduces an unacceptable risk to the aircraft's electrical system and the safety of flight.
The operation of the W31X2M1G7.5 is governed by the thermo-mechanical properties of its bimetallic strip. This strip, which acts as both the primary conductor and the actuator, is a composite element formed by bonding two dissimilar metals with significantly different coefficients of thermal expansion. Current from the circuit flows directly through this strip. Under normal operating loads, the resistive heat generated (P=I2R) is minimal and is safely dissipated. During an overcurrent condition, however, the heat generated increases exponentially. This causes the two metals in the strip to expand, but the metal with the higher coefficient of thermal expansion expands more, forcing the strip to bend. This breaker exhibits an inverse time-current (I-T) characteristic: a minor overload (e.g., 125%) generates heat slowly and may take minutes to cause the strip to bend enough to release its mechanical latch, allowing for temporary, harmless inrush currents from motors or lamps. A major short circuit (e.g., 1000%), by contrast, generates intense heat almost instantly, causing the strip to snap open in milliseconds. This I-T curve is carefully engineered to be just below the thermal damage curve of the copper wire it is designed to protect, ensuring that the breaker will always open the circuit before the wire's insulation can melt.
Note: This is a flight-critical electrical system safety component. A circuit breaker is a protective device, not a switch for routine use. If a breaker trips in flight, it indicates a fault in the circuit. After allowing a brief cooling period (1-2 minutes), a single reset may be attempted. If the breaker trips again, a persistent fault exists, and it MUST NOT be reset again. All electrical system work must be performed by a certified A&P or avionics technician in accordance with the aircraft's maintenance and wiring diagram manuals.
Documentation
The definitive technical data for this component is available on the TE Connectivity W31 series datasheet. Applicability for a specific aircraft circuit must be confirmed via the aircraft's official Wiring Diagram Manual.