Tech explained: Electromagnetic Compatibility Testing

Electric hypercars like the Rimac C_Two are changing the game in more ways than one. Not only do they have the accelerative capabilities to rearrange your internal organs, but they are forcing manufacturers to invest in new high-tech development facilities.

That is because of a process known as Electromagnetic Compatibility Testing. While the test itself is nothing new, the way it is conducted, and the engineering required to pass the test with a high-powered electric vehicle is a whole new ball game.

Electromagnetic Compatibility Testing is, on the face of it, a straightforward undertaking. It measures the electromagnetic signals a car emits, and how that vehicle reacts to the same invisible forces being sent back from various pieces of technology and infrastructure. For something like a VL Commodore, it would have been a walk in the park. The most advanced fully electric vehicle ever built? Not so much.

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If you’ve ever seen a hypercar in the flesh, and whipped out your phone to take a photo, the reason your handset hasn’t turned into an expensive pocket weight is because of EMC testing. While the Bugatti Chiron has more wiring than a JayCar, it also uses a good old fashioned combustion engine to make its power, meaning its electromagnetic emissions are relatively low when compared to something like, say, the 1408kW all-electric Rimac. If Rimac didn’t put the C_Two through the rigorous EMC testing and homologation procedure, it could drive down the street frying traffic lights and wiping the laptops of passers-by.

While the Rimac is an extreme example of why the procedure is necessary, regular cars have needed to complete EMC testing in order to receive homologation for a while now. The increased demands of in-car connectivity such as WiFi hotspots in the cabin, along with autonomous driving systems, digital radio, and car-to-x infrastructure has made EMC testing more rigorous. As an example of what a ‘regular’ car is now fitted with, the Mercedes-Benz S-Class has more than 200 control units on board, and more than 5 kilometres of wires.

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The EU approved standard – ECE R10 – must be achieved for a vehicle to be homologated and sold in Europe. As in many disciplines, Rimac is pushing further and setting more rigorous goals to achieve.

In order to pass EMC testing, Rimac had to begin working on the problem during the earliest stages of development. All high and low voltage systems on the C_Two, including the battery, inverters, powertrain and more, were fitted with solutions such as filters and Y-capacitors that dampen electromagnetic outputs. During EMC testing the C_Two is driven at a selection of varying speeds on a rolling road within a Semi Anechoic chamber, and subject to varying levels of electromagnetic radiation – from a mere 20MHz, all the way to 20GHz.

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The car is bombarded sequentially with antennas, using different directions and polarisations to simulate varying levels of electromagnetic force, and testing is repeated with different combinations of on-board electronic systems activated. Finally, everything from the C_Two’s wipers, navigation, radio – the whole lot – are activated, and the maximum amount of radiation sent its way in order to ensure it performs in a ‘worst case scenario’ setting.

EMC testing is understandably incredibly complex, and immensely challenging for a car like the C_Two to complete. So much so that after completing its first round of electromagnetic evaluation late last year, Rimac’s engineers had to return to Croatia to make further changes. If you ever manage to snap a pic of the C_Two on your smartphone without it bricking in your hands, you’ll know they’ll have done the job.

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IN HOUSE

While Rimac uses external contractors to conduct its EMC testing, automotive giant Mercedes-Benz completed construction in 2019 of a new technology centre in Sindelfingen dedicated to in-house electromagnetic homologation. The cost? A cool A$78 million. More than 200 Mercedes employees staff the facility.

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RECEIVING LOUD AND CLEAR

No longer does a vehicle have a single antenna that simply does the job of receiving AM and FM radio. Bluetooth, sat-nav, central locking, and more all require antennae fitted to the vehicle to work. With the introduction of 5G, cars will require two or four antennae to do the job previously conducted by one. EMC testing allows companies to ensure that these antennae will be able to receive the information they need so you can keep tuning into Smooth FM on your commute to work.

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SHIELDS UP

There’s no need to put on your tin foil hat just yet, but in our modern society electromagnetic waves are everywhere. Between radio, television, and wireless internet, this invisible force is inescapable. To ensure EMC testing is conducted as accurately as possible, the facilities are shielded using metal to prevent outside interference disturbing the results.

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STIRRED UP

Mercedes-Benz’s new EMC testing facility (see above) uses a unique system designed in-house. Instead of placing different antennas around the room and repeating the test for different directions, a trio of large mechanical “stirrers” are housed within a reverb room. These spiral structures rotate at between 10-120rpm and constantly distribute electromagnetic waves, allowing Mercedes to test for the effects of radiation from different directions and with different polarisation simultaneously.

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