Fraunhofer Institute for Integrated Systems and Device Technology IISB
Fraunhofer Institute for Integrated Systems and Device Technology IISB

Inductive Power Transfer

At Fraunhofer IISB, we are at the forefront of researching and developing inductive power transfer (IPT) technologies. Inductive power transfer enables fully contactless – wear- and spark-free – energy transmission, providing maximum operational safety. This is especially important in dusty, humid, or rotating applications where traditional connectors fail prematurely. Therefore, this technology creates added value in wide range of applications, for example:

  • Inductively dynamically powered electric vehicles (cars, vans, and even heavy-duty vehicles) with reduced battery volume/weight and transmission powers of up to 300 kW already achievable today while in motion. To put this into perspective: approximately 100 kW is required for trucks to drive continuously at 80 km/h on flat terrain without additional charging stops.
  • Inductive stationary charging of electric vehicles with power classes according to SAE J2954 from WPT1 3.6 kW, WPT2 7.2 kW, WPT3 11 kW, and WPT4 22 kW. Higher power classes for stationary systems up to the MW range are technically possible and are the subject of ongoing standardization.
  • Customized auxiliary power supplies (e.g., 48 V to 48 V or 24 V to 24 V) for applications with very high insulation requirements
  • Non-contact connectors for demanding environmental conditions
  • Power supply for moving or rotating electrical loads

Our mission at Fraunhofer IISB:

We are the independent European research institution for the development and evaluation of contactless energy transfer technologies and a driving force for new value creation.

We develop and implement complete stationary and dynamic IPT systems – from FEM simulation of the inductive transmission system to the analysis, simulation, and design of the required power electronics, through mechanical integration to the implementation and testing of fully functional demonstrators. In addition, we develop process and testing technologies for IPT systems.

Questions and answers about inductive charging 

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  • 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.

Focus Topics

StruFuFako
Inductive Charging for Electromobility
Inductive Ball-Bearing
Inductive Plug
Wireless Office
HF-Generator for Inductive Heating

StruFuFako – Lightweight Underbody with Integrated Wireless Charging

Research Project StruFuFako – Structural, function-integrated Vehicle Components based on Fiber-Reinforced Thermoplastics

Integration of an inductive receiver coil in a lightweight component for a compact self-driving vehicle for next-generation urban mobility.

StruFuFako is a joint R&D initiative that develops a weight-optimized underbody module for battery-electric vehicles. The component combines fibre-reinforced thermoplastic structures with a 3.6 kW inductive charging coil and an intelligent thermal management system–all manufactured in a single process step. The fully integrated solution is expected to lower overall vehicle mass, cut part count and production effort, and enable 3.6 kW wireless power transfer at a system efficiency of 96% for future small, light, autonomous passenger transportation vehicles for inner-city areas.

Project Targets at Fraunhofer IISB

  • Dimensioning of vehicle and ground coils, resonant circuits and power electronics
  • Optimization of coupling, efficiency, and EMC for varying air gaps and misalignments
  • Development of a mechanically and thermally robust coil carrier for direct embedding in the composite structure
  • Laboratory build-up, assembly and validation of the inductive charging system

Challenges

  • Maintain high magnetic coupling and EMC compliance despite variable air gaps, misalignment and road clearance
  • Embed coils and ferrites in the composite without compromising crash safety or recyclability
  • Control heat in a sealed, thin underbody module exposed to road debris, water, and temperature cycles
  • Achieve automotive cycle times and robust bonding between metals, composites and electronic parts in a single process step

Project Partners

Research project in cooperation with

  • Centrotherm Systemtechnik GmbH (Coordinator)
  • ElringKlinger AG
  • LIA GmbH
  • HK-Präzisionstechnik GmbH
  • Fraunhofer ICT

Inductive Charging for Electromobility

IPT system for electric vehicles enabling fully autonomous, hands-free charging and next-generation self-driving vehicle mobility

Our inductive charging system employs small air gaps between the transmitter unit and the vehicle coil, enabling scalability, very low material usage, high efficiency, and minimum stray fields.

 

Download Product Sheets as PDF:

Not only the increase of electric driving range, but also the improvement of user comfort is a crucial point for the success of battery electric and hybrid electric vehicles. In view of ergonomic and practical aspects of the charging process, wireless charging is a consecutive step for the development of charging infrastructure. We developed an inductive charging system for battery electric vehicle in order to facilitate an autonomous charging process without any user interaction. This approach leads to a tremendous improvement of user comfort and facilitates the necessary technology for an ubiquitary charging concept.

Project Targets

  • Design of a position tolerant wireless charging system
  • Transmission power of 3.7 kW (scalable  up to 11 kW)
  • Charging without user intervention (“autonomous” electric driving)
  • Wireless communication between primary and secondary side

Challenges

  • Selection of a suitable coil geometry and arrangement
  • Optimization of the coupling coils to reduce the system losses
  • Safe and efficient operation of the charging system

Results

  • extremely compact vehicle side coils (diameter of a CD)
  • 94% system efficiency up to the battery
  • Integration of a low-rate and robust information transmission channel (max. 3.5 kW)

Project Partners

Research project in cooperation with the Chair of Electron Devices (LEB) and further chairs of the Universität Erlangen-Nürnberg

Inductive Ball-Bearing

IPT system to transfer electric power in small moving components – contactless and wear-free

Our contactless inductive power-and-data transfer system delivers up to 20 W to a rotating ball bearing, offering a scalable, wear-free, and environment-resistant alternative to cable-based solutions for fast-moving parts.

 

Download Product Sheets as PDF:

The ability to transfer power in small moving systems is required for a wide range of applications such as wind power systems with electronics integrated in the rotor blades or highly-automated Industry 4.0 production platforms. The goal of the project is to develop a technology for the contactless transfer of power and data in small moving components in harsh environments.

The IPT technology enables synchronous machines to receive their rotor‐excitation current completely contactlessly and brushlessly, allowing the use of wound‐field rotors instead of rare‐earth permanent magnets. By eliminating the rotor magnets, it reduces dependence on critical raw materials, lowers component costs and supply-chain risks. At the same time, wireless excitation provides precise, dynamic control of power factor and machine performance without wear‐prone brushes or slip rings.

Project Targets

  • Realization of an inductive energy transfer for fast moving components
  • Transmission power up to 20W
  • Wireless communication of information as well as higher data rates for the transmission of sensor & actuator information

Challenges

  • High integration level of the coupling coils
  • Realization of a rotating transformer with metal parts in the surrounding
  • High mechanical conditions

Results

  • Demonstration of the functionality of the rotating application (ball-bearing with shaft)
  • Practical robustness tests & simulations of electronic assemblies beyond the normative measuring range
  • Near field transmission at high frequencies including alternative capacitive transmission systems with differential directional coupler
  • High-quality digital modulation and thermoelectric optimization of the crossover

Project Partners

   

Inductive Plug

Inductive power transfer offers the capability to inductively (contactless) transmit power in moving components. The technology could be used as the basis for robust inductive plugs in food processing facilities or the chemical industry or as a simpler and safer way to provide electricity to agricultural machinery attachments that need robust plug solutions.

Project Targets

  • Realization of an induction plug for special environmental conditions
  • Transmission power up to 1000 W
  • Easy handling
  • High robustness
  • High efficiency

Challenges

  • Due to the requirement for high compactness only a small power loss can be dissipated (high efficiency necessary)
  • Integration into a small assembly space

Results

  • Demonstration of the functionality
  • System design (across all applications) for magnetics and power electronics with improvement of the performance and simulation methods
  • Practical robustness studies and simulations of electronic assemblies beyond the normative covered measuring range

Project Partners

Wireless Office

A battery and a receiving / transmitting unit for the inductive energy transfer were integrated into a roll container. The battery storage is charged at the socket (optionally inductive). The DC voltage network can be supplied wireless or by cable through the roll container.

 

 

Download Product Sheets as PDF:

Project Targets

  • Next generation of desks without any visible connections - „Clean Desk“
  • Higher flexibility of the desk

Challenges

  • Inductive power transmission with medium power (>100 W) in the area of protective low voltage leads to high currents
  • Providing a stabilized voltage for the desks DC voltage network

Results

  • Very compact power transmission system (150 mm x 150 mm x 40 mm)
  • Representable air gaps up to 20 mm
  • Transferable power <150 W

Project Partner

BACHMANN GmbH

HF-Generator for Inductive Heating

The performance and toughness of a CoolMOS™ transistor in high frequency clocked bridges should be shown by the example of a HF-generator for inductive heating.

 

© Fraunhofer IISB

Project Targets

Development of a HF generator with an extremely high efficiency for inductive heating.

Challenges

  •     Output power ~ 1 kW
  •     Working frequency 100 - 500 kHz
  •     SMD power transistors
  •     Input voltage 230 Vac
  •     Absolute operational safety under all load conditions

Results

For the generation of an HF-power of 1 kW in the frequency range up to 500 kHz, the generator was realized as a resonant half-bride converter. Each of the both half-bridge switches consist of two parallel connected CoolMOS transistors (type SPB20N60C2 - 190 mOhm, 600 V). Thereby the generator achieves an efficiency of more than 97%. Due to the low power loss, the power transistors could be mounted in SMD technology and heated by the circuit board.

A special control method ensures resonant commutation under all conditions (even transits).

Project Partners

Infineon AG

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