Overview of the arc mechanism and extinguishing in the circuit breaker of a more-electric aircraft

Abstract

A more-electric aircraft refers to an aircraft whose secondary power is unified from the traditional multi-energy, such as mechanical energy, hydraulic energy, and pneumatic energy, to the electrical energy, which has the advantages of a simple system structure, high reliability, high maintainability, and high energy efficiency. The most advanced architecture of its power system is the 360–800 Hz variable frequency AC power supply and the 270 V high-voltage DC power supply, which have been applied in the Airbus A380, Boeing B787, F-22, and other more-electric aircraft. As power consumption increases, the power distribution, power network, and cable layout in a more-electric aircraft become more complex, and the probability of electrical faults such as short circuits increases. The arc generated by fault current not only severely affects the life, reliability, and safety of cable and electrical equipment but also limits the capacity expansion of an aviation power system and the improvement of flight performance. The circuit breaker in a more-electric aircraft is a key device for arc extinguishing. Analyzing the complex mechanism of the arc-discharging process in a circuit breaker helps improve the arc-extinguishing performance. To further promote research on the arc mechanism and extinguishing technology of circuit breakers in more-electric aircraft power systems, in this paper, the structure of civilian and military more-electric aircraft power systems and the difficulties in the electrical fault and protection are first analyzed. Then, the research status of the arc-extinguishing technology of the aviation variable frequency AC circuit breaker and the 270 V high-voltage DC circuit breaker are summarized. For an intermediate-frequency vacuum arc, the instantaneous input power inside the gap and at the anode increases with the current frequency, which indicates that the half-wave input power increases with the frequency and proves that the transition state arc is an important source of anode ablation during intermediate-frequency arcing. Under the same current condition, the frequency increases. On the one hand, when the value of di/dt increases, the arc-extinguishing ability decreases with increasing frequency. On the other hand, intensifying the skin effect leads to an increase in the arc center pressure, arc contraction, and magnetic field hysteresis, which is not conducive to arc extinguishing. In addition, the metal vapor density vaporized by droplets reduces the recovery strength of the dielectric after the current zero, which is not conducive to arc extinguishing. For the 270 V DC arc, air, nitrogen, helium, hydrogen, and other gas are presently used in aviation power systems, among which hydrogen is the research hotspot. Finally, future research trends of arc extinguishing technology for aviation circuit breakers are predicted.

Keywords

• more-electric aircraft
• aviation 270 v dc power system
• variable frequency power system
• aviation circuit breaker
• arc