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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)
20
30
40
50
60
70
80
90
100
0 5 10 15 20 25 30
Time (seconds)
Rec
eive
d L
evel
(d
Bu
V)
Transient Detector 2 (360MHz)
20
30
40
50
60
70
80
90
100
0 5 10 15 20 25 30
Time (seconds)
Rec
eive
d L
evel
(d
Bu
V)
Variations in Emissions
0
5
10
15
20
25
30
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
el
(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