US What IEC 61373 covers
IEC 61373 is the international standard for shock and vibration testing of electrical and mechanical equipment fitted to railway rolling stock. In Europe it is published as EN 61373. It defines how equipment is mounted on a vibration table, what levels it is tested at and how long for, so that a computer, display or switch can be qualified for life on a train.
Vibration on a train varies hugely with location: equipment on the axle takes far harsher shocks than equipment in a cabinet inside the car body. IEC 61373 groups mounting positions into categories and defines random vibration, long-life and shock tests for each. The edition long in use dates from 2010, and IEC has since published a revised edition, so check which one a test report cites.
The mounting categories
The category is set by where the equipment will sit on the vehicle, not by what it is. The same computer can need a different test depending on where it is installed.
| Category | Mounting position | Test frequency range | Shock, approximately | Typical equipment |
|---|---|---|---|---|
| Category 1, Class A | Cubicles and assemblies mounted directly on or under the car body | 5 to 150 Hz | 30 to 50 m/s² (3 to 5 g), 30 ms | Equipment cabinets, roof and underframe boxes |
| Category 1, Class B | Anything mounted inside a cubicle that is itself body mounted | 5 to 150 Hz | 30 to 50 m/s² (3 to 5 g), 30 ms | Computers, switches and recorders in a rack |
| Category 2 | Mounted on the bogie | 5 to 250 Hz | Around 300 m/s² (30 g) | Bogie sensors and junction boxes |
| Category 3 | Mounted on the wheelset or axle | 10 to 500 Hz | Around 1,000 m/s² (100 g) | Axle speed sensors and odometry |
The test levels are root-mean-square accelerations shaped across the frequency range to match measured train vibration. Exact values depend on the axis and the edition, so the datasheet or test report is the place to confirm them.
The three tests
Each category is tested in all three axes: vertical, transverse and longitudinal.
-
//
Functional random vibration. Simulates normal running across the frequency range at service levels, with the equipment powered and working throughout.
-
//
Long-life testing. Accelerated vibration at raised levels, typically five hours per axis, representing years in service. The equipment is checked afterwards for damage and loosened parts.
-
//
Shock. Short, sharp half-sine pulses that represent coupling, buffing and track defects, applied in both directions on each axis.
-
//
By location. Test levels depend on where the equipment is mounted, so a report should state the category and class tested.
Why most computers are Category 1
Computers on trains are usually body mounted, so Category 1 is the common requirement. Class B is the usual case for a computer fitted inside a cabinet or rack, and Class A for equipment bolted straight to the vehicle structure, such as an enclosure under the floor or on the roof.
Passing the test is mostly about construction. Solid-state storage, soldered or locked memory, screw-down connectors such as M12, and boards held firmly at several points all help a computer through the long-life test. Fanless designs have an advantage here, because there are no fans or bearings to loosen.
Our digital train case study uses a rolling stock computer listed to IEC 61373, and our railway computers cover the wider range, with railway panel PCs for cab and passenger displays.
What to check on a test report
A line on a datasheet saying a product meets IEC 61373 is a starting point. Before relying on it for a project, check the details behind it.
-
//
Category and class. The report should state the category and class tested. Category 1 Class B does not cover a computer bolted directly to the car body.
-
//
Mounting during the test. Equipment is tested as it will be installed. If the test used a bracket, rack or isolation mounts, the installation should use the same.
-
//
Functional checks. Confirm the equipment was powered and monitored during the functional test, not only inspected afterwards.
-
//
Edition and laboratory. Note the edition of the standard and whether the test house is accredited, since railway assessors will ask for both.
How IEC 61373 fits with other standards
IEC 61373 rarely appears alone. EN 50155, the main standard for electronic equipment on rolling stock, refers to it for shock and vibration rather than defining its own tests, and refers to EN 50121-3-2 for EMC. A railway computer datasheet therefore usually lists all three. Our EN 50155 summary explains how they fit together.
Military and vehicle standards such as MIL-STD-810 also include vibration methods, but their profiles are built for different platforms. A result under one does not carry over to the other, so railway projects normally ask for IEC 61373 by name. Our comparison of MIL-STD-810G vs MIL-STD-810H covers the military side.
Quick answers on IEC 61373
IEC 61373: common questions
What is the difference between IEC 61373 and EN 61373?
None in practice. EN 61373 is the European adoption of IEC 61373, with the same tests and levels.
What does Category 1 Class B mean?
Equipment inside a body-mounted cabinet. It is the category for items such as computers in a rack or enclosure that is itself fixed to the car body, and the most common requirement for computers.
Is IEC 61373 part of EN 50155?
It is referenced by it. EN 50155 calls on IEC 61373 for its shock and vibration requirements, so compliant equipment is usually tested to both.
How long does IEC 61373 testing take?
Typically a few days. The long-life test alone usually runs for five hours in each of three axes, plus the functional and shock tests.
Does IEC 61373 apply to trackside equipment?
No. It covers equipment on rolling stock. Trackside equipment is qualified under other standards.
We supply railway computers and displays with their IEC 61373, EN 50155 and EN 50121-3-2 documentation, and configure mounting, storage and connectors for the category the installation needs as standard.