Andreas Möckel

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.

Modeling and power flow analysis of cascaded doubly-fed induction machines

In this paper, a modeling approach for a brushless doubly-fed induction machine is proposed using an equivalent system of cascaded doubly-fed induction machines. A Steady-state and a transient model are developed and the results show a good agreement to measurements conducted on a set of two 1.5 kW doubly-fed induction machines. One main aspect of this work is the examination of the electrical and mechanical power flow of the combined machines with regard to the required inverter size.

The brushless doubly fed induction machine as generator for small hydro power - machine design and experimental verification

This paper presents the brushless doubly fed induction machine (BDFM) as an alternative choice as generator for small hydro power plants. Looking at this application, the BDFM offers many advantages, mainly the fact that a speed-variable operation in a convenient speed range is possible with a fractionally-rated inverter without the need for slip rings and brushes. An introduction to analytic modeling of the brushless doubly fed machine is given by using an equivalent circuit model, and a machine design process is shown. At first, the main dimensions of the machine and its rating are discussed considering the tangential stress in the air gap. Afterwards the parameters for the equivalent circuit are derived from the machines geometry. Because of the complex fields in the BDFM, the well-known calculation approaches for standard machines have to be extended. The model and the design process are verified using finite elements simulations and experimental tests with the implemented prototype machine on the test bench.

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.