An Air-Cooled YASA Motor for in-Wheel Electric Vehicle Applications

Abstract

In-wheel motors present a range of opportunities for innovation in electric vehicle design as the torque produced at each of two or four wheels can be controlled individually. A high aspect ratio (large radius, short axial length) motor is required to fit within the wheel. Due to its location, liquid cooling of the inwheel motor is difficult and undesirable, but a high power density is required to reduce the mass-which is particularly important as it is unsprung-and fit the space envelope. Furthermore, a high torque density is required to eliminate the need for a gearbox. These constraints create a real challenge for the design of a machine for this application. An axial field machine using a Yokeless and Segmented Armature (YASA) topology is designed to fit these requirements as such a machine has clear advantages when considering the high aspect ratio. A soft magnetic composite (SMC) material is utilised to carry the flux in its non-planar path without incurring excessive losses or requiring a lamination design which is difficult and expensive to manufacture. A novel cooling arrangement involving heat-spreading elements on each armature segment is employed to improve heat dissipation and hence power density. The design, analysis, manufacturing, and testing of the motor is described in this paper to verify the concept against the requirements outlined above.

Comparative Study of Dual-Rotor Slotless Axial-Flux Permanent Magnet Machines With Equidirectional Toroidal and Conventional Concentrated Windings

“…It has the merits of high torque density and efficiency thanks to the high slot fill factor. In [12], [13], the cooling systems of the YASA machines are investigated to improve the power and torque density.…”

SMC Development Guidelines for Axial Flux PM Machines Employing Coreless Rotor Structure for Enhancing Efficiency Based on Experimental Results

“…Therefore, axial flux machines (AFMs) are often used for flat PMSMs [3]- [14]. In recent years, many research groups have conducted investigations into AFMs from the perspective of structure, such as the number of stators and rotors [4], [5] and pole/slot combinations [6], [7]. However, there have been almost no investigations into the characteristics of soft magnetic composites (SMCs) suitable for enhancing the efficiency of AFMs.…”

Design and Analysis of a Novel Axial-Radial Flux Permanent Magnet Machine with Halbach-Array Permanent Magnets

“…The two kinds of structure have different merits. For example, YASA machines with drum windings can eliminate stator back iron, which can reduce material and volume [19,20]. As for the topologies with toroidal windings, they have the same length of winding ends for concentrated windings and distributed windings.…”