Invisible danger?

Electromagnetic fields in the car matter

(Bild: Mercedes-Benz)

Some people don't sleep with their cell phone next to their bed, others feel uncomfortable near high-voltage power lines, and still others don't want an induction stove or microwave in their home. Radiation of any kind can cause people anxiety. Even cars are full of electrical components that produce magnetic fields. How dangerous is the radiation for passengers?

What few people know: In an electric car, we are constantly surrounded by magnetic fields. Produced by many servomotors, for example for the seat adjustment or the power windows. But above all from the high-voltage drivetrain with its huge battery and powerful electric motor.

But how dangerous are these fields? Doesn't the Federal Office for Radiation Protection (BfS) warn on its website that strong static magnetic fields can cause dizziness, nausea and a metallic taste?

It is Dr. Martin Reuter's job to ensure that no harmful radiation is produced in a Mercedes. The electrical engineering graduate is responsible for the electromagnetic compatibility (EMC) of electric drives.

(Bild: Mercedes-Benz)

Compliance with limit values is not mandatory
"We take the issue very seriously and consider it from the development of a vehicle right through to its release," says Reuter. The recommendations of the BfS, which in turn refers to the WHO, serve as a basis. The World Health Organization evaluates all medical research and publishes limit values as recommendations via the International Commission on Non-Ionizing Radiation Protection (ICNIRP) for radiation exposure from cell phones or mobile phone masts, but also in electric cars.

However, the WHO is not a governmental organization. Therefore, these values have no legislative function. Manufacturers can, but do not have to, adopt them. For Reuter, this is not a question: "Mercedes takes the issue seriously and of course adheres to these limit values."

His team examines the EMC in its own test building in Sindelfingen. The manufacturer has invested 50 million euros here to test antenna systems and the up to 250 electronic components used in a car. The S-Class, for example, contains over five kilometers of cable. "We make sure that the radio doesn't buzz when the electric motor is running or the windscreen wipers are switched on." The engineers therefore have to carefully insulate all cables and e-components and shield them from each other.

(Bild: Mercedes-Benz)

Hardly any differences between e-cars and combustion engines
"In principle, however, there is very little difference between electric cars and combustion engines. Both have the same critical sources of magnetic fields, such as seat heating, air conditioning, assistance systems or loudspeakers." In an electric car, there are also electric units such as the battery, motor or on-board charger. However, studies by the BfS show that the magnetic fields depend less on the electrical power of the electric motors than on the position of the battery, the cables and the power electronics. To reduce radiation exposure, Mercedes therefore installs cables and e-components as far as possible in the underbody or engine compartment, i.e. separated from the cabin by a layer of metal.

In addition, the field energy decreases disproportionately with increasing distance. In free space, the magnetic field is only a quarter as strong at twice the distance. Insulation or shielding can even reduce it to a tenth. "Just a few millimetres more distance from cables or wires makes a big difference here," says electrical engineer Reuter.

Impairment possible despite harmless values
This is confirmed by a BfS study. It shows that magnetic fields are distributed very differently in cars. The highest values usually occur in the front footwell, while they are significantly lower in the head and torso area of the passengers. Some measurement results showed the highest values in the rear, especially when the battery and wiring of the electric car are located directly under or behind the rear seat. However, even in the worst-case scenario, none of the vehicles tested exceeded the limit values. Even the maximum immissions were around 30 percent below the ICNIRP reference value.

Two combustion engines were also examined for the study. In the Audi A4 and VW Passat, the engineers detected a similar level of radiation in the front footwell as in the e-car. The causes lay in the motor of a ventilation fan and its wiring. At the highest power level, the measured values were even above the recommended reference values in one case. But here too, the magnetic field measurements did not provide any indication of a potential hazard. Not even for wearers of pacemakers.

Nevertheless, owners of electric cars complain from time to time that they feel uncomfortable in their vehicles. That their arms or legs tingle, that they quickly get a headache. Although there is no direct physical cause, physicist Reuter does not simply dismiss such observations. Scientific studies would confirm such phenomena. Just the fear of gradual poisoning, for example by exhaust fumes from a factory or the proximity of a nuclear power plant, can give people stomach pains or make them feel unwell. (SPX)