Drive Inverters & Mechatronics

The trend towards decarbonization leads to a rapidly progressing electrification in all relevant transport sectors, like automotive, commercial vehicles and aviation. Therefore highly efficient, compact and reliable electric drive systems are required to meet the application-specific requirements. We work on electric drive systems for mobile applications. Our focus is the development of innovative inverter power electronics and electric machine solutions. We can offer a complete in-house research and development, prototype-realization and testing of electric drives.

  • Development and prototype realization of inverter power electronics
    • Voltage range for automotive applications: 48V up to 900V
    • Output power: up to 1 MW
    • Focus on Siliconcarbide (SiC) and Galiumnitride (GaN) based inverter systems
    • Experience with a wide variety of inverter topologies (Multilevel, Multiphase, etc.)
    • Applications: Traction, fuel-cell air-supply, electric turbochargers
  • Development and prototype realization of electric machines
    • Traction and auxiliary drives for automotive and aviation
    • Complete 3D-FEM design of the electric motors
    • (electromagnetical, thermal, mechanical)
    • Co-simulation tools to calculate machine behavior in combination with inverter (realistic losses, dynamic, control stability etc.)
  • Highly integrated electric drive systems (3D mechatronic integration)
  • Field-oriented motor control software development for various machines
  • In-house testing possibilities with several motor test-benches and a vehicle dynamometer
  • Vehicle integration of electrical drive systems


Inverter Development

The development of efficient, highly integrated and reliable electric drive-systems plays a key role for the electrification of individual mobility.

Automotive axle drive unit with integrated IGBT-inverter

SiC-based traction inverter for mobile applications

Wide-Band-Gap (WBG) semiconductors, like SiC and GaN transistors, offer the potential for inverter systems with highest efficiencies, power-densities and especially switching frequencies far beyond the state-of-the-art. To achieve the combination of highest output powers/currents for automotive or aviation traction application with highest switching speeds, an adapted design of the commutation cell, the power-module and the gate-drive is required.
Fraunhofer IISB develops customer specific SiC inverter for typical automotive voltage levels (e.g. 400V/800V). Fast switching power-stages (>= 20 kV/µs) with output currents higher than 800 Arms have been realized using simulation models and experimental setups. In-house prototype realization and characterization at the IISB motor test-benches can be offered.

© Kurt Fuchs / Fraunhofer IISB
© Fraunhofer IISB

SiC-based inverter for High-Speed Motors (e.g. Compressors, Turbochargers)

High-speed electric motors, like compressors, fuel-cell air-supply or electric turbo-chargers, require highest inverter output-frequencies and therefore higher switching-frequencies to avoid additional losses and torque-ripple within the machine. In order to meet these demands, investigations and product-developments of inverters with wide-band-gap semiconductors are carried out.

  • Nominal DC-link voltage: 400V and 800V
  • Output power: 10 to 80kW
  • 2-level/3-level topology
  • Max. switching frequency: 80-100 kHz
  • Sensorless motor control

Integrated Drive Systems

Mechatronic integration of inverter power electronics in or close to the electric machine offers the potential to reduce costs, required volume and EMC-issues. But this placement of elec¬tronics close to the electric machines also leads to a higher level of thermal and mechanical stress. At Fraunhofer IISB we focus on the development of system architectures and components for electric drives with different integration level. The use of innovative yet production-optimized material concepts and joining technologies enables us to achieve the required robustness.

Electric Machine Development

Fraunhofer IISB offers the design and prototype realization of customer specific electric machines fitting to the application.

Project example: 800 V 175 kW electric machine with 6-phases for automotive traction

Our design process includes a complete 3D-FEM and Co-simulation-based toolchain for the electro-magnetic, thermal and mechanical design and optimization of electric machines. A variety of motor test benches and available inverter solutions allow a complete in-house characterization of the prototypes.

© Fraunhofer IISB
Section of an IPMSM in Ansys/Maxwell
© Fraunhofer IISB
Co-simulation tool for realistic electric machine loss estimation

We cover a broad range of motor and drive applications:

  • Traction motors and auxilary drives for Automotive and Aviation
  • Industrial drives
  • Voltage range: 48 V to 1000 V
  • Power range: up to > 250 kW

Customized motor designs with focus on:

  • Highest power-density
  • Highest efficiency
  • Advanced cooling solutions
  • Integrated solutions with inverter system

Electric machine design based on inverter co-simulation:

  • Simulative coupling of SPICE/PLECS inverter simulation with FEM-simulation of electric machine
  • Realistic estimation of inverter losses for inverter operation, e.g. harmonics induced rotor losses
  • Comparison and optimization of different thermomanagement solutions for rotor and stator (e.g. water-, oil- and air-cooling)

Motor Control Software

A safe and efficient operation of electric drive systems requires the development of application specific motor control software.

Fraunhofer IISB cooperates with the Laboratory for Control Systems of the ‘Technische Hochschule Nürnberg’ in developing and analysis of modular control algorithms addressing for example the machine types listed below:

  • Permanent Magnet Synchronous Motors (PMSM)
  • Induction Motors (IM)
  • Electrically Excited Synchronous Motor (EESM)
  • Brushless DC
  • Multiphase and multilevel topologies

The following solutions are covered by our R&D work:

  • Conventional drive control methods (e.g. field oriented control)
  • Adaptive control of drive systems (e.g. iterative learning control)
  • Sensorless control and high frequency control algorithms, e.g. for high-speed drives (electric turbocharger, fuel-cell air supply etc.)
  • Implementation and testing on in-house developed control-board hardware (e.g. based on Infineon TriCore or SOC/FGPA)
  • Test of the developed drive control systems at the in-house dynamometer facilities

Power Electronic System Robustness

Fraunhofer IISB analyses the dynamics of (thermo)mechanical robustness and optimization of mechatronic products characterized by a consistent workflow of experimental and numerical investigations.

The integration of mechatronic systems into highly stressed spaces demands an indication of product life already in the design phase. External vibrations, e.g. roadway bumps or engine oscillations, excite mechanical structures at their natural frequencies, which may lead to uncontrollable dynamic responses and failures at an early stage. The vibration resistance is further lowered by the operational thermal overlay. Common failure patterns in power electronics are fatigue cracks in solder joints, delamination at material boundaries and fretting corrosion of electrical interfaces. Typically, these robustness failures are electrically detected, but mechanically triggered. In the case of safety-critical devices, failures may have farreaching consequences. These critical load spectra are often found in mounting positions that are unsprung or close to an engine and occur in automobiles, aircrafts or wind turbines.

© Fraunhofer IISB
Robustness evaluation from system to design element

Possible subjects are approached based on the geometric complexity and may comprise different functional elements:

  • Electrical devices: resistors, capacitors, transistors, inductors, transformers
  • Electrical interfaces: connectors, busbars
  • Circuit boards: multilayer, flex rigid

 

We offer the following simulation services:

  • Thermomechanical robustness simulation of customer systems based on material parameters and CAD files
  • Experimental vibration testing on in-house shaker system with 3D laser scanning vibrometer
  • Analyzing the physical response of sinusoidal and random vibration signals
  • Identification of natural frequencies and measuring frequency responses at any location
  • Parameter studies in terms of design, loads and materials
  • Optimizing structural design by minimizing thermomechanical response

 

Smart Nodes for Automated Vehicle Power Supply Systems

Building set for smart power distribution nodes for on-board power supply systems of highly automated vehicles.

HiBord DC/DC with DLC storage

© Fraunhofer IISB
© Fraunhofer IISB
Hardware modules of the smart power distribution node building set
© Fraunhofer IISB
Block diagram of the HiBord DC/DC with DLC storage

Highly automated vehicles as of SAE level 3 lack the driver as a fallback during power failures.

In the research project HiBord, funded by the German Federal Ministry of Education and Research, new on-board power supply system topologies were investigated which can handle faults in the power supply system without full redundancy.

  • Energy flow control
  • Fault isolation
  • Network reconfiguration
  • Local reflexes and global decisions

 

Advantages:

  • Logic module with μC and FPGA for advanced monitoring algorithms and quick fault reactions
  • Scalability by using standardized interfaces
  • Modules equipped with sensors for current, voltage, temperature
  • Different communication options (CAN, Automotive Ethernet, …)
  • Scalable housing and cooling solution due to standardized module dimensions and connectors

 

Modules:

Many modules are available

  • Uni-directional and bi-directional switch modules (12V or 48V)
  • 48V/12V DC/DC converter module
  • Double layer capacitor module
  • Active and passive DLC pre-charging modules
  • Logic module with powerful FPGA and µC

… and more, depending on project requirements

 

Application Example

A combination of an on-board DC/DC converter and a DLC was realized with the building set and is a key component of the HiBord power supply system.
.The system combines a DC/DC converter with a transient power storage and thus can replace a 12V battery in fail-operational scenarios.

Electric Drive Testing Possibilities

Complete vehicle tests and characterizations can be carried out in a temperature controllable (-25°C/+50°C) all-wheel roller dynamometer.

© Kurt Fuchs / Fraunhofer IISB
Motor test bench

A variety of motor test benches up to 300 kW and 1000 VDC-power supply are available at Fraunhofer IISB and can be used for the characterization of electric motors and complete drive systems.

Project Examples

© Anja Grabinger / Fraunhofer IISB

HoskA - 9-phase automotive SiC-Inverter

Within the project HoskA, a SiC-based 9-phase automotive inverter based on B6-powercores was developed. The powercores include the DCB-based powermodules with SiC-MOSFETs and SEMIKRON SKiN technology, the gate driver, the DC-link capacitor as well as current and temperature sensors.

Using three B6 powercores in parallel, a symmetrical 9-phase 150 kW electric drive with a phase displacement of 40 degree of the PMSM was realized. The modularization concept allows also the realization of 50 kW (3-phase) and 100 kW (6-phase) drive systems using one or two identical powercores.

Project partners: Volkswagen Aktiengesellschaft, Semikron, TDK, Liebherr, Federal Ministry of Education and Research, VDI|VDE|IT

Download Product Sheet HoskA - 9-phase automotive SiC-Inverter"

© Kurt Fuchs / Fraunhofer IISB

6-phase SiC-Inverter for automotive application

Siliconcarbide (SiC) MOSFETs offer huge potentials for power electronic systems due to their significantly reduced conduction and switching losses and their capability for highest junction temperatures. Based on this semiconductor technology, a modular and compact 6-phase 800 V drive-inverter for automotive application with a maximum output power of 300 kW was designed and realized. Using four parallel MOSFETs per switch, the system provides a maximum phase current of 150 Arms.

The inverter demonstrates the advantages of SiC-semiconductors on system level:

  • Highest power density
  • Highest (part-load) and drive-cycle efficiency
  • Highest switching frequency
  • Reduced cooling effort

Due to possible switching frequencies of up to 100 kHz, the SiC-inverter is suitable for machines and applications with highest electric frequencies like high-speed traction-motors, compressors and electric turbochargers.
Download Product Sheet "100 kW SiC-Inverter for automotive application"

© Fraunhofer IISB

60 kW SiC-Inverter for Fuel-Cell Air-Compressor

High-speed electric motors like the compressor-motor for fuel cell air supplies require higher inverter output-frequencies and therefore higher switching-frequencies to avoid additional losses within the machine. With state-of-the-art inverter systems (e.g. using Si-IGBTs and Si-diodes) the switching frequency is typically limited to values of 10 to 20 kHz due to higher switching losses.
.In order to meet these demands, a 60 kW inverter system for high-speed electric machines was developed. The use of SiC 1200 V MOSFETs, ceramic DC-link capacitors and a low inductive system design allow switching frequencies up to 100 kHz at reasonable efficiencies.
An overall power-density of the power-stage of >150 kW/l was achieved. This offers the possibility to integrate the inverter directly into the fuel-cell air supply system.

Download Product Sheet " 60 kW SiC-Inverter for High-Speed Drives"

© Anja Grabinger / Fraunhofer IISB

6-phase electric machine with 175 kW for 800 V

Within the LZE-project Fraunhofer IISB developed a 6-phase automotive traction motor with 175kW for a nominal DC-voltage of 800 V. Highest power density with a maximum motor speed of 20.000 rpm.

  • Permanent magnet synchronous machine with buried magnets
  • Specification based on automotive traction motors
  • Usable in 3- and 6-phase connection
  • Segmented magnets
Peak Power 175 kW
Topology PMSM, 3/6-phase
Max. speed 20.000 rpm
Max. torque 230 Nm
Max. phase current 280 Arms
Nominale ZK-Spannung 800 VDC
Stator length 150 mm

 

© Fraunhofer IISB

COSIVU – Integrated 1200 V SiC-Inverter for Commercial Vehicles

Fraunhofer IISB developed an integrated 1200 V inverter in cooperation with the COSIVU project partners. The inverter is used in an electric drive-unit for commercial vehicles of Volvo. The inverter uses highly efficient SiC transistors which raise the part-load and drive-cycle efficiency of the system significantly.

A modular and flexible design allows also the realization of a 6-phase inverter system.

Technical data:

Max. output power 290 kVA
Nom. input voltage range 600 VDC to 800 VDC
Max. phase current 300 Arms
Switching frequency 10 kHz to 16 kHz
10 kHz to 16 kHz Modular B6

 

Project Partners: Volvo Technology, Hella, TranSiC, Sensitec, Nanotest, Elaphe, Swerea, TU Chemnitz and Fraunhofer ENAS

Download Product Sheet "COSIVU"

The work has been performed in the research project 'COSIVU', funded by the European Commission under grant agreement number 313980.

© Fraunhofer IISB

EMiLE

Electric motor integrated power electronics with Smart Stator Teeth

Within the EMiLE project, ten partners from the German industry and research-institutes are working on innovative drivetrain solutions for tomorrow's e-mobility. The project focusses on compact and efficient electric vehicle traction-drives with a high degree of integration of electric machine, power electronics, and gearing, which are perspectively suitable for large scale production. High power density, high efficiency and cost minimization are benefits of the realized Smart Stator Tooth - structure within the drive unit. Each stator segment of the PMSM electric machine has its own individual control and power electronics. The modular system approach can be adapted to different vehicle and drive classes.

Drivetrain with Smart Stator Teeth

Each Smart Stator Tooth (SST) consists of a motor segment and an electronics assembly. Twelve SST form one PMSM stator and the corresponding inverter.
.Each tooth electronic consists of an IGBT full bridge power-module, phase current sensor, current control loop, gate driver unit, and a fault detection block. The stator windings are directly connected to the AC terminals of the power module, thus minimizing space and reducing the number of parts. The pre-assembled SST is fully testable before mounting the complete system.

Novel Control and Safety Functions

The advanced SST control functionalities have two objectives: First, a failure in one phase power module does not lead to a full system failure. Second, after detecting faulty parts, the remaining SST are used to actively compensate the influence of the failure.
l.The SST concept redefines and improves both availability and failure mitigation: The aim is to achieve a safe system state, concerning vehicle stability and passenger safety, without additional hardware effort. At the same time, the availability is increased, which means that partial faults do not stop the whole system.

 

Project Partners:  VDI|VDE|IT, Aix Control, Bosch, Infineon, iSEA RWTH Aachen, Lenze, Siemens, TDK-EPC, VW, ZF

Funding: German Federal Ministry for Education and Research  

Download Product Sheet "EMiLE - Electric motor integrated power electronics"