Manufacturing Challenges of a Modular Transverse Flux Alternator for Aerospace

Abstract

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.

A Review of Transverse Flux Machines Topologies and Design

“…Aircraft and spacecraft (M) [96][97][98][99]. Two 160 kVA TFMs have been proposed for aerospace applications [96,97].…”

“…A high torque density and good thermal performance are key aspects in the design process: for this application, liquid cooling is not suitable due to safety, mass, and maintenance restrictions [97]. Besides, a fault-tolerant TF alternator has been proposed for an aerospace power generation system [98]. Another TFM has been proposed for the position control of a spacecraft [99]: apart from low mass and power requirements, motors for spacecraft applications should have a high reliability, very long operational life over a wide temperature range and hard vacuum and immunity to space radiation.…”

“…C-core TFMs benefit from lower losses and higher torque at the cost of a more challenging manufacture [84,97]. • Claw-pole stator [8,16,25,87,95,98,[122][123][124] or claw-pole stator and rotor [85,86]. Compared to a radial machine and a mutual flux path TFM with the same volume, the claw-pole TFM offers higher torque densities and its weight is lower.…”

“…Similar to PMs, the skewing can also be applied to the stator [19,99]-even with more than one step [19]. Tooth pitching [98] imitates the coil pitching of radial flux machines. Pole shaping can also be applied both to the stator [114] and rotor [112,117], as well as pole width adjusting [98].…”

“…Tooth pitching [98] imitates the coil pitching of radial flux machines. Pole shaping can also be applied both to the stator [114] and rotor [112,117], as well as pole width adjusting [98]. Magnetic shunts can make up for a short distance between the adjacent magnet to reduce cogging torque [127].…”