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Auxiliary Power Unit

An Auxiliary Power Unit (APU) is an independent system that provides power for critical functions to operate without the main engine running. When reliability and overcurrent protection for sensitive components are paramount, high-reliability fuses are a vital component in ensuring the safety and longevity of Auxiliary Power Units. To this end, AEM's selection of hi-rel fuses are absolutely critical for APUs in demanding mililtary and aerospace applications.

Block Diagram

Block Diagram for Auxiliary Power Unit Circuit Protection


AEM Hi-Rel is a worldwide leading provider of high-reliability fuses and ferrite chip beads for a wide range of mission-critical applications, including aircraft power management systems. 


High-reliability fuses are indispensable components within auxiliary power units (APUs), providing critical overcurrent protection to safeguard the entire system. Their robust design ensures that they can withstand the harsh environmental conditions often encountered by APUs, including extreme temperatures, vibration, and shock.

By isolating fault conditions, AEM's high-reliability fuses prevent cascading failures and ensure the continuous, safe operation of the APU. This is critical for starting main aircraft engines, providing ground power, and delivering emergency backup power.

Features of AEM Hi-Reliability Solid Body Fuses:

  • Thick film fusible element construction with glass arc suppressing system 
  • Designed and screened for high reliability applications where failure is not an option 
  • QPL approved to MIL-PRF-23419/12 
  • Manufactured and screened in AEM's San Diego Facility 
  • Material and process traceability maintained for all fuse products (Group A & B screening and data standard) 
  • Supplied with gold plated or Sn/Pb terminal finishes