EN 3661-006:2006

EN 3661-006:2006 Overview

EN 3661-006:2006 is a European standard developed by CEN specifying the requirements for aerospace series single-pole circuit breakers. These circuit breakers are temperature compensated and have rated currents ranging from 20 A to 50 A. Designed specifically for use in aircraft on-board electrical systems, they operate reliably within a wide temperature range of −55 °C to 125 °C and up to an altitude of 15,000 meters. This part of the standard (Part 006) focuses on circuit breakers equipped with a polarized signal contact and a bus bar connection version. The circuit breakers feature a push-pull single push-button actuator with delayed action "trip-free" tripping, enhancing operational safety and reliability in aerospace environments.

Key Topics Covered

• Circuit Breaker Design and Operation
  Defines single-pole circuit breakers with temperature compensation and rated currents from 20 A to 50 A. These units incorporate a polarized signal contact which opens when the main contacts are closed and vice versa.

• Environmental and Mechanical Conditions
  Certified to function in extreme aerospace conditions, it supports operation at ambient temperatures ranging from −55 °C to 125 °C and altitudes up to 15,000 m. Mechanical endurance, vibration resistance, shock tolerance, and corrosion resistance meet rigorous aerospace requirements per related standards.

• Electrical Characteristics

  • Rated voltages of 28 V DC and 115 V AC (360 Hz to 800 Hz)
  • Trip thresholds for overload protection with delayed action tripping
  • Capability to sustain high short-circuit currents (up to 4,000 A DC)
  • Low voltage drop performance to ensure minimal electrical losses
  • Auxiliary polarized signal contact with diode rated for a maximum of 0.5 A at 125 °C

• Installation and Connection
  Connections are made via bus bars ensuring stable integration into aircraft electrical circuits. Installation hardware meets EN 6113 standards, and recommended tightening torques are specified to assure secure attachment.

• Marking and Identification
  Clear marking guidelines cover manufacturer details, rated current codes, electrical diagrams, and part numbers to maintain traceability and facilitate maintenance in aerospace settings.

Practical Applications

• Aircraft Electrical Systems
  Ideal for protecting circuits on-board commercial and military aircraft, these circuit breakers prevent overloads and short circuits, ensuring continuous safe operation of electrical equipment at high altitudes and temperature extremes.

• Aerospace Equipment Manufacturing
  Manufacturers of aerospace electrical components can leverage this standard to produce compliant circuit breakers that ensure system reliability and meet stringent safety regulations.

• Maintenance and Repair Operations
  The clear technical and marking specifications aid maintenance teams in identifying, testing, and replacing circuit breakers for effective lifecycle management of aircraft electrical systems.

• System Integration
  The bus bar version simplifies system design and installation, reducing wiring complexity and improving system robustness in aerospace applications.

Related Standards

• EN 3661-001: Provides the comprehensive technical specifications for single-pole temperature compensated circuit breakers rated 20 A to 50 A.
• EN 3841-305: Defines test methods for short-circuit performance of circuit breakers.
• EN 6113: Specifies connecting and attachment hardware for aerospace circuit breakers.
• EN 3155-016: Covers electrical contacts used in aerospace connectors, relevant to the accessory contacts of the circuit breakers.
• TR 6083: Details cut-out dimensions for installing electrical components on aerospace panels.
• MIL-S-19500: Dictates quality standards for semiconductor devices such as diodes used in signal contact circuits.

Why EN 3661-006 Matters

EN 3661-006:2006 ensures that circuit breakers used in aerospace are robust, reliable, and compatible with harsh operational environments. By standardizing performance, dimensions, installation, and marking, it supports interoperability and safety essential for aviation electrical systems. Adoption of this standard helps aerospace manufacturers comply with international safety regulations and supports maintenance best practices, maximizing aircraft operational readiness and safety.

Keywords: aerospace circuit breakers, single-pole circuit breaker, temperature compensated, polarized signal contact, bus bar connection, aircraft electrical systems, EN 3661-006, aerospace electrical standard, circuit breaker rated current, aviation electrical safety.