industrial electrical engineering and automation lund university, sweden electromagnetic...

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