A Novel Poly-Phase Outer Rotor Homo-Polar Transverse Flux Machine using Ferrite Magnets

A Review of Transverse Flux Machines Topologies and Design

“…In any case, the number of PM pieces per pole (2, 3 or 4 usually) and the ratio of side to main PM width must be chosen carefully [75]. Other configurations use an axially magnetized PM ring between two iron cores (Figure 8b) [67,85,86,116,117] or are directly in contact with the air gap, thus eliminating the intermediate iron cores [118,119]. If that is the case, PM segmentation must be considered to prevent high eddy currents in a solid PM ring [85].…”

“…The sectorial arrangement consists of grouping together all the phases in the same rotor and stator stack, resulting in a less bulky design [113]. In this case, the electric and magnetic circuits are not decoupled, which results in lower power and torque densities [116].…”

“…Figure 11 depicts the torque-speed and power-speed ratings of some TFMs found in the literature [6,8,67,69,71,72,80,81,90,93,95,104,109,113,116,122,131], both for TF motors and generators. As shown in Figure 11a,b, most of the reported TFMs have their ratings up to 100 Nm and 2 kW: in Figure 11c,d The efficiency is a key aspect of modern electric drives, and it is closely linked to the machine losses: they are formed essentially by copper losses, iron losses, PMs losses, stray load losses and even housing losses (for example, if it is made of aluminum, eddy currents can be induced) [129].…”

“…In [86], it is said that TFMs benefit from an efficient cooling due to their lack of endwindings, lower PM temperatures and no hot spots in the ring coils. According to [116], cooling is more tedious for outer rotor TFMs. For aircraft applications, liquid cooling is not suitable due to safety, mass, and maintenance restrictions [97].…”