EU Rail Tackles EMI: EN 50592 Ensures Axle Counter Safety

EN 50592 is crucial for railway safety. It standardizes testing rolling stock’s electromagnetic compatibility with axle counters, preventing interference and ensuring reliable train detection.

December 15, 2024 2:02 am

Understanding EN 50592: Electromagnetic Compatibility Testing for Axle Counters

EN 50592 is a European standard titled “Railway applications – Testing of rolling stock for electromagnetic compatibility with axle counters.” Its primary purpose is to define a standardized measurement method to verify that a unit of rolling stock is electromagnetically compatible with various types of axle counters used in railway signaling.

This standard is critical for ensuring the safety and reliability of modern railway networks. As trains incorporate more powerful and complex power electronics (such as traction inverters, auxiliary converters, and regenerative braking systems), the risk of electromagnetic interference (EMI) with sensitive trackside equipment like axle counters increases significantly. Failure of an axle counter due to EMI could lead to dangerous signaling malfunctions.

The Core Principles of EN 50592

The standard operates on the fundamental principles of Electromagnetic Compatibility (EMC), focusing specifically on the relationship between the rolling stock (the source of emissions) and the axle counter (the potential victim of interference).

Axle Counters: These are vital components of modern signaling systems. They are track-mounted devices that detect the passage of a train’s wheels. By counting the axles entering and leaving a defined track section, the system can safely verify if the section is clear or occupied.
Electromagnetic Interference (EMI): The powerful electrical systems on a train generate magnetic fields across a wide range of frequencies. If the strength of these fields at the specific operating frequencies of an axle counter is too high, it can disrupt the sensor’s ability to detect wheels correctly, leading to a “false clear” or “false occupied” state.
Emission Limits: EN 50592 sets out the maximum permissible levels of magnetic field emissions from the rolling stock in the frequency bands relevant to axle counters. The goal is to ensure that the train’s “electromagnetic noise” is kept below the immunity threshold of the trackside equipment.

The Testing Methodology in Detail

EN 50592 provides a precise and repeatable methodology for conducting tests. This ensures that results are consistent regardless of where or by whom the test is performed. The process involves measuring the magnetic field generated by the rolling stock under various operational conditions.

Test Setup and Conditions

The test requires positioning a specific measurement coil (antenna) near the track at the same position where an axle counter sensor would be installed. The rolling stock is then operated in several distinct modes to simulate its entire operational lifecycle and capture worst-case emission scenarios.

Standstill: Testing is performed with the train stationary but with auxiliary systems running (e.g., HVAC, compressors, lighting). This identifies interference from non-traction systems.
Constant Speed: The train moves at various specified speeds over the measurement point to assess emissions from the traction system under a steady load.
Acceleration: The train accelerates at maximum power through the test zone. This phase typically generates significant low-frequency magnetic fields from the traction motors and inverters.
Braking: Both rheostatic and regenerative braking modes are tested. Regenerative braking, in particular, can be a major source of high-frequency EMI as power is fed back into the overhead line or a third rail.

Measurement Parameters and Acceptance Criteria

The key parameter measured is the magnetic field strength (H-field), expressed in Amperes per meter (A/m). Measurements are taken across a defined frequency spectrum that covers the operating frequencies of common axle counter types.

To pass the test, the measured magnetic field emissions from the rolling stock, under all specified operating conditions, must remain below the limits defined in the standard. These limits are carefully derived from the known immunity levels of axle counter equipment, ensuring a sufficient safety margin for reliable operation.

Comparison of Rolling Stock Operating Modes for Testing

Different operational modes of a train produce unique electromagnetic emission profiles. The table below outlines the objectives for testing each mode as specified by EN 50592.

Operating Mode	Objective of the Test	Key Potential Interference Sources
Standstill (Auxiliaries On)	To measure emissions from non-traction systems and ensure they do not interfere with axle counters when a train is stopped at a station or signal.	Auxiliary Power Converters, HVAC systems, Battery Chargers, Compressors.
Constant Speed	To assess the steady-state emissions from the traction system during normal running conditions at various speeds.	Traction Inverters (PWM frequency harmonics), Traction Motors, Line Filters.
Maximum Acceleration	To measure the worst-case low-frequency magnetic field emissions generated when the traction system is under maximum power draw.	High currents in traction motors and power cables, inverter switching transients under heavy load.
Regenerative Braking	To measure high-frequency emissions generated when kinetic energy is converted back into electrical energy and fed to the line. This is often a worst-case scenario.	Traction Inverters operating in regeneration mode, harmonics injected into the overhead line, brake choppers.

Scope and Importance in the Railway Industry

Compliance with EN 50592 is mandatory for any new or modified rolling stock intended for operation on European railway networks that use axle counters. The standard is essential for:

Rolling Stock Manufacturers: They must design and build vehicles that meet these emission limits.
Railway Operators: They rely on the standard to ensure that new fleet acquisitions will not disrupt their existing signaling infrastructure.
Testing and Certification Bodies: They use the standard as the definitive procedure for vehicle type approval and certification.
Signaling System Suppliers: They use the emission limits as a benchmark for the required immunity levels of their axle counter products.

Ultimately, EN 50592 serves as a critical link in the chain of functional safety for railways. By controlling the electromagnetic environment, it ensures that one of the most fundamental pieces of signaling technology—the system for detecting a train’s presence—can operate with the highest degree of reliability and safety.

Frequently Asked Questions (FAQ) about EN 50592

What is the primary purpose of EN 50592?
The primary purpose of EN 50592 is to provide a standardized test procedure to ensure that the electromagnetic emissions from railway rolling stock do not interfere with the safe and correct operation of trackside axle counters.

Why is testing for EMC with axle counters so important?
It is critically important for safety. If electromagnetic interference from a train causes an axle counter to fail—for example, by missing the count of an axle—the signaling system could wrongly report a track section as clear when it is still occupied, creating a severe risk of collision.

What kind of equipment on a train can cause interference with axle counters?
The main sources of interference are power electronic systems, including traction inverters that control the motors, auxiliary converters that power onboard systems like HVAC and lighting, and regenerative braking systems that feed power back to the grid.

Does EN 50592 apply to all types of rolling stock?
Yes, the standard applies to all types of railway rolling stock, including electric multiple units (EMUs), diesel multiple units (DMUs), locomotives, and high-speed trains, that are intended to operate on lines equipped with axle counters.