Inductive Power Transfer

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

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

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

• Research project in cooperation with the Chair of Electron Devices (LEB) and further chairs of the Universität Erlangen-Nürnberg
• Fraunhofer Institute for Integrated Circuits IIS

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

• Research project in cooperation with the Chair of Electron Devices (LEB) and further chairs of the Universität Erlangen-Nürnberg
• Fraunhofer Institute for Integrated Circuits IIS

Project Targets

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

Challenges

• Inductive power transmission with medium power (>100W) 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

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