Advances in EMC Measurements on Railways. Origins of EMI in Railways

Advances in EMC Measurements on Railways

Origins of EMI in Railways

Difficulties With Railway EMC Measurements

• (Fast) Moving EUT• Large EUT• Complex Radiation Propagation Mechanisms• Poor Control of Measurement Environment• Transient Emissions

– from traction motors– from power supply arcing

The Measurement System

• Three Spectrum Analysers giving:– constant monitoring of a chosen frequency range

• Two Further Spectrum Analysers:– to detect transient emissions (amplitude & repetition)– set to single frequency (zero span)– wide input bandwidth– two analysers allow for test site variations and

spurious radio signals

• Camera:– to record an image associated with each plot

Transient Detection

• Tuned Receiver / Spectrum Analyser– good dynamic range– readily available in EMC laboratories– good response when wide bandwidths

chosen

• Fast Sampling Oscilloscope– All signal information can be captured

instantaneously

Transient Detector 1 (350MHz)

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30

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100

0 5 10 15 20 25 30

Time (seconds)

Rec

eive

d L

evel

(d

Bu

V)

Transient Detector 2 (360MHz)

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90

100

0 5 10 15 20 25 30

Time (seconds)

Rec

eive

d L

evel

(d

Bu

V)

Variations in Emissions

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5

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35

0.1 0.105 0.11 0.115 0.12 0.125 0.13 0.135 0.14 0.145 0.15

Frequency (MHz)

Re

ce

ive

d L

ev

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(dB

uV

)

Vehicle 1

Vehicle 2

Vehicle 3

The System Aids In:

• Measurement of EM emissions from railway systems dynamically

• Separation of continuous and transient events– Increasingly important as digital communications

become more widespread

• Rapid assessment of rolling stock characteristics• Monitoring and assessing variations and

degradations