EN 3841-303:2004

Overview

EN 3841-303:2004 is the CEN/AECMA aerospace test method that specifies how to verify the dielectric strength of circuit breakers used in aerospace electrical equipment and systems. Intended to be used together with EN 3841-100 (General), this part defines the dielectric test procedure, measuring points and pass/fail criteria for leakage and breakdown. Key terms: EN 3841-303, dielectric strength, circuit breakers, aerospace test methods.

Key topics and technical requirements

• Test environment: Tests are carried out after stabilization at the environmental conditions defined in EN 3841-100 (temperature, pressure, humidity relevant to ground and altitude conditions).
• Test voltage and waveform: An a.c. test voltage (50 Hz) is applied progressively with a maximum rate of increase of 250 V/s.
• Dwell time: When the specified test voltages are reached, they are maintained for 1 minute while monitoring.
• Monitoring and limits:
  • Monitor for leakage current, electrical breakdown, or other defects during the 1-minute hold.
  • There must be no leakage current ≥ 1 mA, no breakdown and no defects reported.
  • Recorded dielectric values must meet the requirements specified in the applicable product standard for all admissible temperatures at ground and maximum altitude.
• Measuring points:
  • With circuit breaker closed (ON): between each pole terminal and all other connections (including signal contacts); between all connections and earth/mounting.
  • With circuit breaker open (OFF): between each connection and all other connections (including signal contacts); between all connections and earth/mounting.

Applications and who uses this standard

• Aerospace circuit breaker manufacturers - to qualify products for dielectric performance and ensure compliance with aerospace electrical safety requirements.
• Test houses and certification bodies - to perform standardized dielectric verification during type approval and acceptance testing.
• Quality, R&D and maintenance engineers - for incoming inspection, periodic verification, and failure investigations of aircraft circuit breakers.
• Systems integrators and OEMs - to validate component compatibility with aircraft power systems and environmental conditions.

Related standards

• EN 3841-100 - Aerospace series – Circuit breakers – Test methods – Part 100: General (normative reference; defines environmental stabilization and general test conditions).
• Product-specific circuit breaker standards - define the actual voltages and pass criteria to be used with EN 3841-303.

This concise guide helps engineers and test personnel apply EN 3841-303 for reliable dielectric testing of aerospace circuit breakers, ensuring safe operation under specified environmental and altitude conditions.