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Instrumentation • Electronics


Fig. 1. The Porsche Panamera is designed to be driven in pure electric mode by default up to a speed of 130km/h.


4 Most automotive engineers are familiar with mechanical and electrical vehicle design and testing requirements, but fewer will also know about all the EMC design and testing requirements for conventional, hybrid and electric vehicles.


The silent peril of electromagnetic interference


A


utomotive companies use their own requirements over and above those published in standards to avoid the threat of liability. In-house requirements are typically 10 times


higher than the EU Automotive requirements, often interpreted as absolute minimum requirements. As long as the in-house requirements are met, legislative requirements are just a formality for automotive manufacturers. EMC design is not just about shielding sources


of electromagnetic emissions. Keith Armstrong, principal at EMC specialist Cherry Clough Consultants argues that EMC shielding is costly and adds unnecessary weight when other measures are available by using robust circuit and software techniques. “The result of interference is a delayed,


degraded or false signal,” says Armstrong. “If interference causes a vehicle fieldbus not to


recognise a data packet and it has to be transmitted again, this could be hazardous in safety circuits such as braking. There are hardware and software signal and power integrity techniques listed as good practice in the IEC 61508 international industry standard for functional safety. “A vehicle electromagnetic environment is very


harsh because of electrical activity such as DC motors, sparking plugs and pulses that feeds a fuel injection system. Electric vehicles also produce a good deal of interference from pulse width modulation (PWM) motor drives as a series of continuous spikes and transients.


Steer-by-wire


“Hydraulic vehicle steering consumes a lot of power because the pumps are always running and so is being overtaken by electronically assisted power steering which only uses power when it is needed. In steer-by-wire systems, turning a steering


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