W58XC4C12A30 – TE Connectivity 30 Amp Thermal Circuit Breaker
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The W58XC4C12A30 is a high-reliability, single-pole, "push-to-reset" thermal circuit breaker from TE Connectivity's Potter & Brumfield line, engineered for demanding aerospace applications. This flight-critical safety device provides precise, repeatable overcurrent protection for 30-ampere aircraft electrical circuits. Its fundamental purpose is to automatically interrupt current flow during an overload or short circuit, protecting wiring from overheating and preventing potential electrical fires. It is designed to be "trip-free," meaning the internal contacts cannot be held closed against an overcurrent condition.
Operating on a proven bimetallic thermal element, the W58XC4C12A30 offers a robust and dependable means of circuit protection. When the breaker trips due to an overcurrent event, the push-button extends, typically revealing a white band that provides immediate visual indication of the tripped state. As a widely utilized component from a leading manufacturer, specified by numerous airframe OEMs, the W58 series represents a standard 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.
30 Amp Current Rating: Precisely calibrated to protect higher-load circuits with a nominal current draw at or below 30 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 suitable for various load types.
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 or maintenance personnel.
Robust Construction: Designed for panel mounting with a threaded bushing and features secure #10-32 screw terminals for reliable electrical connections.
Technical Specifications
Part Number: W58XC4C12A30
Component Type: Thermal Circuit Breaker
OEM Manufacturer: TE Connectivity / Potter & Brumfield
Current Rating: 30 Amperes
Voltage Rating: Up to 250 VAC / 50 VDC (Verify specific rating on component marking/datasheet).
Actuation Mechanism: Bimetallic Thermal Element.
Reset Type: Push-to-Reset.
Mounting Style: Panel Mount, Threaded Bushing.
Terminal Type: #10-32 Screw Terminals (per "C12" designator).
Governing Specifications: UL Recognized (File E69248), CSA Certified (File LR22191), and manufactured to meet rigorous aviation standards.
Aircraft Compatibility
The W58XC4C12A30 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, Bombardier, Embraer, 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 W58XC4C12A30 (30 Amp) is used for the primary circuit protection of numerous high-load aircraft systems, including but not limited to:
Landing Gear Motor Circuits
Electric Flap Motor Circuits (larger aircraft)
Main Avionics Bus Feeds
Environmental Control System Components (Heaters, Blowers)
Galley Power Circuits
Inverter or Converter Power Feeds
Why Choose W58XC4C12A30?
Choosing a genuine, high-quality TE Connectivity W58 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 wiring and prevent fires. A failure of a breaker can manifest in two dangerous ways: it can fail to trip during a genuine overcurrent, leading to wire overheating and potential fire, or it can "nuisance trip," causing an unexpected loss of power to an essential system. The W58 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 W58XC4C12A30 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 (e.g., brass and steel). Current from the circuit flows directly through this strip. Under normal operating loads, the resistive heat generated ($P=I^2R$) 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% of rated current) 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. A major short circuit (e.g., 1000% of rated current), 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 (per standards like MIL-W-22759 or similar), ensuring that the breaker will always open the circuit before the wire's insulation can melt or ignite.
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
TE Connectivity W58 Series Datasheet (Note: Direct linking may change; search "TE Connectivity W58 Series Datasheet" if broken).
Definitive applicability must be confirmed via the aircraft's official Wiring Diagram Manual and Illustrated Parts Catalog (IPC).