Axial gap technology

My experience with axial gap technology is that its success is largely dependent on the application. To achieve the torque densities necessary for minimizing the amount of amorphous magnetic material (due to its high cost per kg as compared to laminated steels), the resulting electric machine designs tend towards higher pole numbers. To compete with the same applications with induction or PM machines with lower pole numbers, axial gap topologies generally require higher carrier frequencies in the variable speed drive that feed. This is to minimize ripple in the current waveforms and the resulting torque ripple at the shaft. The VSD drive size tends to be larger to accommodate the switching losses at the higher PWM carrier frequencies. I must say, though that the torque to inertia ratio of these machines are generally good and might be quite successful in spindle drive applications where high speed in positioning applications demands a premium.

Generally speaking SMC has two application advantages compared to laminations. The eddy currents are very low and the parts can be shaped more freely. However hysteresis loss are a little higher, therefore the combined iron losses will be higher at low frequencies and lower at higher frequencies. Making SMC interesting for high speed applications. The strength varies at least a factor 4 depending on the powder/production method used. And in the old SMC materials the strength is also a function of temperature, because they are bonded by a plast binder. The new materials are much more robust because the binding is ceramic.

SMC has much lower loss than 0,5mm thick laminations from 200Hz and above, which is almost always the case in EV applications. A factor 2 or 4 on the iron loss will definitely matter not only on the power consumption, but also on heat transportation, which is critical in EV's. Thinner laminations are very expensive therefore SMC can also compete on price. The SMC part will not rotate, therefore the speed will not have any influence on the centrifugal force. Mechanical strength demands are the same as for "normal speed" SMC motors, which have existed for many years without problems. I agree that the first SMC materials had mechanical problems, but not the new materials, they are very strong.