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Industrial Electrical Engineering and Automation © Sabine MarksellElectromagnetic Compatibility Problems in Automotive Applications Problem Pulse Width Modulation, PWM Long, unshielded cables AM-band on the radio
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Industrial Electrical Engineering and AutomationLund University, Sweden
Electromagnetic Compatibility Problems in Automotive Applications
Sabine Marksell
© Sabine Marksell Electromagnetic Compatibility Problems in Automotive Applications
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Outline
Problem Suggested solutions Implementation Experimental results Conclusions
© Sabine Marksell Electromagnetic Compatibility Problems in Automotive Applications
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Problem
Pulse Width Modulation, PWM Long, unshielded cables AM-band on the radio
© Sabine Marksell Electromagnetic Compatibility Problems in Automotive Applications
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Suggested solutions
Shielded cable Current return through conductor Randomly varying switching frequency
Increasing the gate resistor
© Sabine Marksell Electromagnetic Compatibility Problems in Automotive Applications
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Implementation
Shielded cables Shield grounded in both ends
Current return through ground plane Connectors mounted at both ends of ground
plane Randomly varying switching frequency
Switching frequency 10 kHz :250: 40 kHz Gate resistor
3 and 330 respectively
© Sabine Marksell Electromagnetic Compatibility Problems in Automotive Applications
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ExperimentsSet-up
© Sabine Marksell Electromagnetic Compatibility Problems in Automotive Applications
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ExperimentsTest site
© Sabine Marksell Electromagnetic Compatibility Problems in Automotive Applications
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ResultsReference set-up
Switching frequency: 20 kHz
Gate resistor: 3
Current return through cables placed on ground
Unshielded cables
• Reference set-up
© Sabine Marksell Electromagnetic Compatibility Problems in Automotive Applications
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ResultsShielded cables
Switching frequency: 20 kHz
Gate resistor: 3
Current return through cables placed on ground
Shielded cables
• Shielded cables
• Reference set-upUnshielded cables
© Sabine Marksell Electromagnetic Compatibility Problems in Automotive Applications
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ResultsCurrent return through ground plane
Switching frequency: 20 kHz
Gate resistor: 3
Current return through ground plane, cable placed on ground
Unshielded cable
• Current return through ground plane
• Reference set-upCurrent return through conductor
© Sabine Marksell Electromagnetic Compatibility Problems in Automotive Applications
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ResultsCurrent return through ground plane
Switching frequency: 20 kHz
Gate resistor: 3
Current return through ground plane, cable placed 11 cm over ground
Unshielded cable
• Lead-in cable 11 cm above ground plane
• Lead-in cable placed on ground plane
© Sabine Marksell Electromagnetic Compatibility Problems in Automotive Applications
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ResultsRandomly varying switching frequency, RPWM
Switching frequency: 10 kHz :250: 40 kHz
Gate resistor: 3
Current return through cables placed on ground
Unshielded cable
Fix PWM(dBA/m)
Random PWM(dBA/m)
Frequency (kHz)
Peak Quasi Peak
Peak Quasi Peak
20 52.1 51.5 43.8 37.5
40 47.2 46.9 39.0 31.9
60 39.7 38.5 39.5 24.1
120 31.7 32.2 39.4 24.0
• RPWM • Reference set-up fix switching frequency
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ResultsUsing a 330 gate resistor
Switching frequency: 20 kHz
Gate resistor: 330
Current return through cables placed on ground
Unshielded cable
Gate resistance Rise time Fall time
3 545 ns 38 ns
330 1.42 s 94 ns
• 330 • Reference set-up3
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Conclusions
The current return should to the greatest possible extent be through a conductor
Varying the switching frequency gives good results in the switching frequency range
Using a high value of the gate resistance mitigates the disturbances in the higher frequency areas