Thomas Bäckström

Analytical design and analysis procedure for a transverse flux machine

A transverse flux machine (TFM) offers a higher specific torque and power density than a conventional radial flux machine, though at a cost of a poorer power factor. This paper provides an analytical approach to dimension an application-specific TFM and analyse its performance for first order calculations. Important features of TFMs are also outlined to facilitate an understanding of its operation and design. The design is explained with reference to an arbitrarily chosen application; a TFM wind generator. Only a surface mounted, single sided, outer rotor TFM generator design is treated. The method can however be equally applied to other types of TFMs, with proper adjustments of the analytical models.

A novel drive strategy for hybrid electric vehicles

Based on research work on a double-rotor integrated energy transducer (IET) for hybrid electric vehicles, this paper introduces a novel drive strategy by removing one resolver from the drive system and short-circuiting the IET in hybrid operation mode. Control methods for different operating modes are introduced, finally, a Matlab/Simulink program is created to verify the drive strategy.

On finding compact motor solutions for transient applications

Applications such as emergency breakers, protective devices in explosive environments, emergency exit openings, etc., fall into a broad category that can be grouped under the general term transient applications. There are cases in which a motor is to be operated only for a short duration. The use of standard procedures to select or design a motor for these transient applications, will most probably result in an over dimensioned and an over-sized motor. An alternate approach is hence required. This paper provides guidelines on how to select an off-the-shelf motor and when necessary, on how to design a new motor for such applications. A design example is also provided, and the analysis is verified by building and testing a prototype. It is found that with some derating calculations, an off-the-shelf selection can yield an induction machine solution. However, there may be cases where the selection is not compact enough. In such cases a new permanent magnet motor design is required and a BLDC motor is a realistic choice from a cost perspective. It is found that for such applications, the most critical design factor is to avoid magnet demagnetisation. The thermal loading is not a design factor owing to the very small application times involved. However, a thermal check on the obtained design is always advisable.