Tobias Heidrich

Effects of current displacement in a PMSM traction drive with single turn coils

The current research concerning hybrid and electric vehicles brings forward several new ideas and concepts for electric traction drives that are explicitly tailored to the requirements of the automotive sector. An alternative approach for winding design is the use of a concentrated bar winding with only one turn per coil, which reduces the effort and volume for insulation material and increases the slot fill ratio up to 80 %. Consequently, traction drives with higher power density, reduced mass and improved efficiency are feasible. The major challenge of this design approach lies in the massive winding bars that can cause effects of current displacement especially for high speeds and a high number of pole pairs. The present paper focuses on the primary reasons for the current displacement (like skin effect, proximity effect and the magnetic stray field) and introduces three possibilities to reduce these effects: conductor splitting, conductor rearrangement and different conductor wiring. Related consequences for winding and stator design are highlighted in aspects of motor losses, efficiency and operating performance.

Increased power density of permanent magnet synchronous machines by use of concentrated bar windings

Due to the current transition to electro mobility, requirements in terms of power density, specific power and efficiency are continually increasing for electrical drives. Thus, to improve these main quantities especially for electric traction drives, new and suitable approaches for motor optimization will be searched. The present paper introduces a new winding and voltage concept, with the aim of reducing passive component volume in the motor. By the use of concentrated bar windings with only one turn per coil, the slot fill ratio will be increased and the insulation effort will be minimized. The comparison with a conventional motor design points out the new concepts advantages. High current load and skin effect represent the primary limits of the design approach.

Design and commissioning of a low voltage 25 kw PMSM traction drive

Electric vehicles require traction machines with a high efficiency, a high power density and a low weight. Not to forget are aspects like a fail-safe motor operation, a safe maintenance and handling and an easy and cost-effective industrial production. Based on these requirements, a 25 kW PMSM was developed as decentralized scalable drive unit for traction applications. In contrast to conventional high voltage designs, the machine has a concentrated winding with only one turn per coil. Thus, the motor voltage is located in an extra-low voltage range, which reduces the effort and volume for winding insulation. Machines with this winding design can benefit from higher slot fill ratios, a simplified winding assembly and an improved recyclability. The present paper deals with the design and commissioning of this low voltage PMSM traction drive. In addition to motor dimensioning, construction process and practical realization, the challenges of winding configuration are considered. The paper is completed by first results of the machine measuring on an adapted test bench.

Dimensioning of ultra capacitors used for range extension in electric vehicles

Electric vehicles (EV) require energy storage with high power and high energy-density. A hybrid-storage-system combining battery (high energy density) and ultra-capacitor (high power density) to supply a motor is logical. This paper will present an efficient way of dimensioning the ultra-capacitor of this system. The optimal size is determined by applying real driving cycles to a dynamics simulation. The dynamics model used for the simulation is explained and the results for different driving cycles are presented. In addition a lifetime estimation for the ultra-capacitor (UC) using available datasheets is performed with the same simulation.

Integrated high-speed PMSM drive with IMS PCB-technology for mobile applications

The design of a permanent magnet synchronous machine with an integrated control and power circuit for sensored field oriented controlled (FOC) operation at a high power density is presented in this paper. To cool down the switching power transistors inside the machine, a single sided insulated metal substrate (IMS) PCB is used for thermal coupling of the power components with the housing of the PMSM by mounting them onto the motor end shield. The most common application field for IMS PCB-technology is the lighting industry with their power LEDs [1]. The utilization in a compact PMSM drive system is a novelty. For the angle and current measuring, the FOC-algorithm calculation and the excitation of the power transistors, a piggyback control PCB is also integrated. The system size and the voltage level are based on application standards for handheld power tools. The paper introduces the machine and PCB design of this new compound system and investigates power limitations and curve progressions such as speed, power and efficiency over torque. Also research on thermal distributions of the drive system are considered.

Development of a decentralized traction drive unit

The paper deals with the decentralized traction drive unit as alternative concept for an electrical drive train. The system consists of a dynamic storage, an inverter and the electrical machine, which form a high efficient separate module. The continuous system power of 25 kW goes back to drive cycle and vehicle analysis that allow a scaling to different vehicle classes by varying the module number. In contrast to conventional electrical drive trains, the system voltage is lower than 60 V. This voltage level is compliant to extra-low-voltage standards for a high system safety and reduced insulation effort. Resulting RMS currents up to 600 A are the major challenge for the system and motor design. Starting with the overall concept, the paper highlights the effects on machine and winding configuration. The development process is completed by measurements of the realized drive train demonstrator and the identification of optimization potential.

System voltage estimation for a decentralized electromotive drive train system

At present, there are two typical electromotive drive train system (EDTS) configurations on the market. On the one hand, there are high voltage systems for conventional cars with system voltages in the range of 400 V - 800 V. In industrial truck and fork lifter applications, there are low voltage solutions with a system voltage of 80 V. A main question at this topic is: “Which system battery voltage is the best solution for EDTSs?” In future, the development-goals of EDTSs are high efficiency, high power density, low costs and system safety [1]. This paper will show the way of estimating the best system voltage regarding the named development goals. The main focus of the paper is on the system efficiency and losses simulation. Therefore a system simulation with a real measured driving cycle input will be developed.