EN 3841-304:2004

Overview

EN 3841-304:2004 (Aerospace series) is a CEN European standard that specifies a method for verifying the tripping points of circuit breakers used in aerospace electrical systems. It is intended to be used together with EN 3841-100 (general test conditions). The standard defines test conditions and procedures to confirm minimum and maximum tripping points, overload tripping, trip‑free behaviour and altitude/temperature effects on tripping performance.

Key topics and technical requirements

• Test setup and mounting

  • Circuit breakers are mounted per EN 3841-100 and the applicable product specification.
  • Tests use a constant current (d.c. or a.c. at the frequency indicated in the product standard) and a resistive load.
  • Tests are performed at normal airflow and with terminals stabilized to the specified temperature ±5 °C prior to testing.

• Minimum tripping point

  • Apply the current specified in the product standard; the breaker must not trip during the specified minimum tripping time.
  • Terminal temperature is measured during the test using thermocouples or low‑conductivity sensors placed on a terminal close to the housing.
  • Terminal temperature rise must not exceed 75 K.

• Maximum tripping point

  • When subjected to the current specified for the maximum tripping point, the breaker must trip within the time specified in the product standard.

• Overload tripping

  • Apply the overload currents specified in the product standard and measure tripping time.

• Trip‑free release

  • Verify that overload tripping occurs even when the actuator (button) is held in the closed position, in accordance with the technical specification.

• Minimum tripping points at altitude

  • Tests in a low pressure/temperature chamber: hold the test temperature for at least 1 hour, then bring the chamber to the pressure corresponding to the specified altitude and apply the specified current for a 1 hour test period.

• Conformance

  • Tripping points and trip times must meet the values and limits defined in the applicable product standard.

Applications and users

• Aerospace manufacturers and suppliers validating aerospace circuit breakers during design, production qualification and batch acceptance testing.
• Test laboratories performing compliance testing and environmental/altitude qualification.
• Quality assurance, certification bodies and system integrators verifying tripping time and safety performance of aircraft electrical protection devices.
• Designers ensuring circuit breaker performance under temperature and altitude conditions.

Related standards

• EN 3841-100 - Aerospace series – Circuit breakers – Test methods – Part 100: General (required reference).
• This part is published under CEN and was prepared by AECMA‑STAN; consult the CEN catalogue for other EN 3841 series documents relevant to environmental and electrical tests.

Keywords: EN 3841-304, circuit breaker tripping points, aerospace circuit breakers, test methods, tripping time, altitude testing, trip‑free release, EN 3841-100.