Inductive Power Transfer

For wireless charging, coils are installed in roads or parking areas. These coils use a magnetic field to transfer electrical energy inductively to a receiver coil in the vehicle's underbody. This allows cars, buses, delivery vans, and trucks to charge while stationary or – on appropriately equipped routes – even while driving. Since no physical connection is necessary, the technology can be installed on a wide variety of areas, such as roads, parking lots, depots, or bus stops. This allows vehicles to charge "on the side," reducing long downtimes at traditional charging stations and the need for very large batteries.

A similar principle is used for inductive charging of smartphones and also in many kitchens with induction cookers, where heat is transferred to the bottom of the pot via a magnetic field.

Wireless systems are flexible, discreet, low-maintenance, and also suitable for autonomous vehicles, as no manual plugging and unplugging is necessary. They can also serve as a common charging platform for entire vehicle fleets.

In conductively charged vehicles, the contacts can wear out or become soiled. These problems do not occur with inductive charging systems. Furthermore, the vehicle does not need to be plugged in. This is a major advantage, especially for autonomous systems. A vehicle can drive to its parking space independently and charge there. No plug is necessary.

Wireless charging while driving has further advantages: It reduces dependence on critical battery raw materials by making it possible to reduce battery sizes. In addition, vehicles are not charged at high power at rest stops, but rather draw moderate power. This stabilizes the grid and increases the overall efficiency of the system. One further efficiency advantage over conventional electric vehicles is that battery losses can be eliminated and the transmitted power can be fed directly into the motor. 

Inductive: Energy transfer without cables via a magnetic field. This type of energy transfer requires a transmitter and receiver coil. Examples include wireless charging of smartphones or electric toothbrushes.

Conductive: Direct connection via plugs, rails, or current collectors. This technology requires a physical connection to the vehicle.

No. The coils are only switched on at the exact moment when an inductively charged vehicle drives over them. At all other times, the coils are switched off. 

According to SAE J2954, 85 kHz is specified for inductive energy transfer in road traffic. 

Yes, there are already pilot projects in various countries such as Sweden, the USA, France, and Germany. In France, there is a test section on the Autoroute A10 south of Paris, and in Germany on the A6 highway near Amberg (Bavaria). 

Visually, hardly at all: the induction coils are invisible, lying a few centimeters below the asphalt surface. Only inconspicuous control cabinets (so-called management units) at the roadside control the coils. On the motorway in France, these management units are installed underground and are therefore invisible. Anyone driving on the road will not notice any difference.

The power supply is segmented. The control cabinets (management units) are spaced 100 meters apart. This results in a maximum cable length of around 50 meters per section (between the control cabinet and the coil).

The system complies with the limits set by the Bundesnetzagentur (Federal Network Agency) and also meets the stricter requirements of the IEC 61980 product standard for inductive charging. These limits must also be met during dynamic operation. 

No. The system on the test track is only active when a suitably equipped vehicle is driving directly over the charging coils. The highest field strengths occur in the immediate vicinity of an actively charging vehicle .

The relevant limit values are:

• ICNIRP 2010 (EU): 27 µT
• ANSI IEEE (US – with a focus on implant safety): 1.63 mT (= 1,630 µT)

The system is largely silent. Only during operation may a quiet humming sound occur in the control cabinets, similar to that of a refrigerator.

Yes. Stable charging performance is possible even when driving at speeds above 120 km/h. However, it should be noted that the amount of energy transferred is related to the driving time on the charging section. 

Yes, the system is applicable with both construction methods.

Yes. It can be installed almost invisibly in busy areas such as bus terminals, taxi lanes, or parking lots and enables charging even during short stops (so called “snack charging”).

Yes. Neither snow nor ice interfere with inductive energy transfer. The system can also be used in tunnels or on bridges. However, for reasons of cost and system optimization, the coils are not usually installed continuously in tunnel or bridge areas. 100 % coverage of a route is not necessary: vehicle batteries can easily cover unequipped sections of the route.

No. To use inductive charging systems, electric vehicles must be equipped with receiver coils and the required electronics. These components are necessary to pick up the electromagnetic field generated by the road module and convert it into electrical energy. 

Yes, but they are so far only used pilot projects and test facilities.

The calibration procedure and billing have not yet been finalized. However, there are ongoing funding projects (without IISB participation) that are addressing this issue.

Only authorized vehicles that are recognized by a contactless charging system can draw energy.