How to Determine the Right Circuit Breaker for an Aircraft
With the safety of countless onboard systems being dependent on continuous and stable electrical power, protective components like circuit breakers must be integrated into aircraft to promptly sense and interrupt electrical faults or overcurrent conditions. With a variety of circuit breaker types and other factors to consider, choosing the appropriate option requires a decent understanding of aviation-specific standards, how certain breaker variants function, and system-level differences. This blog will serve as an informative guide to determine the right circuit breaker for aircraft applications, touching on some of the most common types to help guide your selection.
Standards for Aviation Circuit Breakers
Circuit breakers are common across general industrial and residential settings, but you cannot use just any option for aircraft. Aviation platforms regularly experience exposure to high altitudes, fluctuating temperatures, extreme vibrations, and electromagnetic interference. As such, the standards for circuit breakers used in aviation are enforced by internationally recognized authorities, including:
FAA (Federal Aviation Administration) Regulations: FAA regulations under 14 CFR Part 25.1357 outline general requirements for electrical protective devices in transport category aircraft.
RTCA DO-160: This standard specifies environmental testing requirements, including thermal, vibration, and EMI resilience, which are particularly critical for avionics circuit protection.
MIL-PRF-83383 and MIL-C-5809: These U.S. military performance specifications are applied for qualifying thermal and magnetic circuit breakers.
Any selection process needs to begin with ensuring compliance with the relevant standards above, but to validate compatibility with the specific aircraft and intended system, also consider factors like:
Current Rating: The selected circuit breaker must be rated to handle the system’s normal operating current without nuisance tripping while still being effective against overloads.
Voltage Rating: The breaker's voltage rating has to meet or exceed the system voltage, which is typically 14V or 28V DC in general aviation aircraft or 115V AC in larger commercial or military aircraft platforms.
Power Source Type: Determine whether the electrical system operates on DC, AC, or a combination of both, and also be sure to validate if the breaker is designed for compatibility with the specific power source configuration.
Temperature Range: The circuit breaker should function without interruption in the temperatures associated with the area it will be placed in.
Integration Needs: Evaluate whether the system requires panel-mounted or remotely mounted circuit breakers, and decide if manual reset or auto-reset functionality is more suitable for the given application and its accessibility.
Popular Types of Aircraft Circuit Breakers
Thermal Circuit Breakers
Thermal circuit breakers operate using a bimetallic strip that responds to excess current by heating up and bending, mechanically tripping the breaker and interrupting current flow. This process is inherently time-delayed, as the tripping speed depends on the magnitude and duration of the overload.
Compact, mechanically simple, and available in both auto-reset and manual-reset formats, these breakers are cost-efficient options in environments with predictable electrical loads. However, in addition to their slower response, they are also susceptible to nuisance trips under high ambient temperatures.
Best Applications
Thermal circuit breakers are frequently employed in general aviation aircraft, particularly systems like lighting, cabin electronics, or basic communication circuits where rapid overcurrent spikes are not frequent and simplicity takes precedence over fast reaction times.
Magnetic Circuit Breakers
Magnetic circuit breakers rely on an electromagnetic solenoid that reacts almost instantaneously to overcurrent events. When the current exceeds the calibrated threshold, the generated magnetic field activates a mechanical latch that quickly opens the circuit.
These breakers deliver very responsive protection, especially against short circuits, and their performance remains stable regardless of changes in ambient temperature. The drawbacks they come with are mostly tied to their installation, having a greater initial expense and heftier size than some other variants.
Best Applications
Magnetic circuit breakers are preferred in avionics, navigation equipment, and instrumentation systems, where there is a very low tolerance for power interruptions and environmental variability must be managed.
Thermal-Magnetic Circuit Breakers
Thermal-magnetic circuit breakers incorporate both a bimetallic element and an electromagnetic coil. The thermal component offers time-delay protection against sustained overloads, while the coil presents an immediate response to sudden, high-current events. This hybrid design supports a balanced protection profile for a broad range of electrical conditions, although their larger footprint may necessitate reinforced or custom mounting locations.
Best Applications
Thermal-magnetic circuit breakers are perfect in scenarios where multi-tiered protection is necessary, such as in main power distribution panels, auxiliary power units, or other setups that combine large current loads with sensitive electronics.
Electronic Circuit Breakers
Electronic circuit breakers, also known as solid-state breakers, use microprocessor-controlled sensors to detect anomalies, electronically disconnecting the circuit by commanding a semiconductor switch to open. While they require more complex integration with electronic systems and have a somewhat high initial cost, they are compact, highly accurate, and come with the potential to incorporate digital features–like current monitoring, trip history logging, and remote reset capability.
Best Applications
Next-generation aircraft, UAVs, or other advanced avionics architectures benefit from the high-performance, data-capable circuit protection that electronic circuit breakers offer.
Procure Circuit Breakers through Speedy Industrials
All in all, different aircraft models or onboard systems will call for specific circuit breakers to ensure safe and efficient operation. Aside from accounting for the different variants and implementation considerations, implementing circuit breakers into an aviation system requires working with a dependable supplier to guarantee their integrity. Speedy Industrials, owned and operated by ASAP Semiconductor, is a trusted source for aviation-grade circuit breakers and other electrical protection devices.
This website offers access to a wide array of components for various needs, all of which are sourced from leading manufacturers and vetted suppliers. With thousands of quality options on one centralized database and a dedication to providing competitive fulfillment options, we streamline sourcing efforts for professionals around the world. Kick off procurement at your convenience to see why so many customers choose Speedy Industrials as their go-to purchasing platform.