EN50155:2007 / EN50155:2017 Comparisons

30th November 2017

EN50155:2007 / EN50155:2017 Comparisons

A new version of the defacto railway standard  EN50155, for electronic equipment hit the streets in October 2017.  The review below helps to provide a quick overview of some of the key differences between the 2007 and 2017 versions

a) Operating Temperature

There are now 6 operating temperature classes, OT1 & OT2 for passenger and driver compartments, OT3 & OT4 for equipment in technical cabinets and OT5 & OT6 for special applications.  OT3 (-25 to +70 degrees) should be taken as a general requirement unless otherwise specified.

There is also more onus placed both on equipment manufacturers and end users to define exactly what temperatures the equipment should operate in and what constraints should be observed.

b) Shock and Vibration

No changes here – EN61373 is still the reference standard.

c) Relative Humidity

The new standard now references EN50125-1.

d) Battery Voltages

Details of additional battery voltages of 28V and 36V have now been referenced.  There is also tighter definition of the power supply ranges.

e) Interruptions in supply voltage

Better definition of a supply interruption with the addition of a new class (S3 – 20mS)

f) Supply voltages for rolling stock powered by combustion engines

New section, closely defining what ripple factor is likely to be seen on supply voltages

g) Supply change over

No changes here.

h) EMC

No change – Still references EN50121-3-2

i) Reliability

The requirements for proof of reliability for end user equipment is much more thoroughly defined, but needs to be agreed between the end user and supplier of equipment.

j) Useful Life

Previously the useful life of all equipment was deemed to be 20 years, but there are now 5 classes which can be agreed between end users and suppliers starting at 5 years.

k) Insulation coordination

Unless otherwise defined by the end user EN50124-1, pollution degree level 2 will apply.

l) Capacitance to ground/earth

This is a new clause suggesting that earthing capacitors should always be class Y1/Y2 and be limited to 10nF

m) PCBs

All PCBs should now comply with IPV-A-610 class 2 minimum.  The use of single side PCBs has now been prohibited.

n) Protective coatings

More precise definition with 3 classes of coating depending on the application with reference made to IPC-A-610

o) Type testing

Low temperature start up, cyclic damp heat and EMC tests are now mandatory.  There is also a new type test called “Power Supply test”.  This covers the following:

  • Supply Variations
  • Temporary supply dips
  • Interruptions of supply
  • Supply change over

p) Dry heat thermal test

This is now more fully defined and performed over 3 test cycles.

q) Voltage withstand test

The test duration for routine tests has been reduced from 60 secs to 10 secs.

r) Design Guidelines

There is now a comprehensive annex  (F) with suggested derating factors  for a range of electronic components and includes suggested limits for the values and types of capacitors fitted between ports and ground/earth  (10nF max class Y1 or Y2)

John Stone – Relec  Electronics – 30/11/2017

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