EN50155:2007 / EN50155:2017 Comparisons30th 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.
No change – Still references EN50121-3-2
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
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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