This paper presents the manufacturing challenges of a transverse flux alternator for an aerospace application. For fault tolerance, four independent isolated phases are required to deliver a specific power at low speeds, whilst at over speed, there is a strict limit on the short circuit current. A transverse flux machine (TFM) was selected due to its high inductance combined with the modular nature of separate phases lending itself to fault tolerance. The stator consists of pressed soft magnetic composite (SMC) segments. The authors explore the electromagnetic, mechanical, and assembly design challenges of the machine. It is shown that mechanical design aspects of the segments are of equal importance to the electromagnetic design and optimization. Simple design choices have allowed the same component to be used as all the stator segments, despite the requirement of a 90° electrical phase difference between phases and a tooth offset of 180° electrical within each phase.

In this paper, a permanent magnet alternator which presently relies on magnetic slot wedges is redesigned to give lower iron loss. The new segmented stator design is used as the basis for a validated loss studycomparing bonded lamination stacks with those held together with a punched notch. Segmentation is shown to improve the production process, reduce losses and remove the need for wedges, whilst not significantly altering the acoustic performance. In the first series of prototypes, however, where notching is used to secure lamination packs, the process is shown to have adversely affected material properties of the nickel iron laminations and overall measured losses increased. In the second prototype, with thinner laminations and glued stacks, iron loss predictions and measurement agree and are less than the present slot wedge design.

In this paper, a permanent magnet alternator which presently relies on magnetic slot wedges is redesigned to give lower iron loss. The new segmented stator design is used as the basis for a validated loss studycomparing bonded lamination stacks with those held together with a punched notch.Segmentation is shown to improve the production process, reduce losses and remove the need for wedges, whilst not significantly altering the acoustic performance. In the first series of prototypes, however, where notching is used to secure lamination packs, the process is shown to have adversely affected material properties of the nickel iron laminations and overall measured losses increased. In the second prototype, with thinner laminations and glued stacks, iron loss predictions and measurement agree and are less than the present slot wedge design.

In this paper, 28 slot-18 pole and 24 slot-20 pole permanent magnet alternators (PMA) with soft magnetic composite slot wedges are designed and compared. Power lane separation required due to fault tolerance requirements, means the proposed machines initially do not produce balanced phase voltage and currents, resulting in high ripple on the rectified power output. The alternators are optimised using 2-D finite element analysis (FEA) to get smoother DC power waveform. It is shown that the power ripple might be reduced by about 12% and un-balanced windings can be significantly balanced by thickening up the SMC slot wedges between the sub-machines. Furthermore, no load loss analysis has been conducted at rated speed and it is shown that 28s18p machine generates lower loss on no load condition compared to 24s20p single layer PMA.

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