Comparation Radial GO and Axial  motors technology

There is a powerful promotion of the superiority of the axial  electric motor over others. But this is far from the truth. Let's compare the two types of motors radial and axial in detail. We will use two most popular axial motor producers YASA and Emrax with the different motor contractions and compare them with our motor technology.

Winding

It is not a secret that axial motors have much more complicated construction than radial. The main problem is fixing the coils. There are two most popular ways of fixing coils with the core inside. Like in Emrax motor, fixing coils from the bottom with aluminum rectangular tube and like in YASA motor, fixing coils from the top with the plastic structure. In all cases, epoxy for bonding coils with contraction. In the Motres design, the coils, together with the teeth, are inserted into the stator and rigidly fixed. In the Emrax contraction, the aluminum fixture between the coils significantly reduces the fill factor and increases the eddy current  losses from the coils AC current. For the axial motor the whole wire is involved in the creation of the torque, in radial only wire on the slot produces torque. For YASA motor end-winding produces the same torque per wire length like slot winding due to anisotropic SMC structure. For Emrax motor end-winding produces less torque then slot winding due to oriented GO steel structure.

Magnetic system

The magnetic system of these two types of motor is different. Axial motors use standard axial polarization magnets. It has big eddy current losses on the magnets and needs to make segmentation to reduce it. It will increase magnet cost. Emrax to reduce losses in the magnets back plate, produce it from the same lamination GO steel like stator. Motres use tangential polarization magnets array with GO steel teeth. It produces a higher magnetic field in the gap then Halbach magnets array and reduces eddy current losses in magnets. For assembly this magnets construction no need glue and possible to remove magnets if need to make magnetization.

Cooling

YASA motor direct oil cooling system is the most efficient with comparison to Emarx and Motres but is more difficult and expensive. To seal coils from the environment they need to increase the gap between magnets and the stator core. It will highly reduce motor performance. Emrax uses an aluminium rectangular tube for fixing coils for the cooling system. It is very close to the wire and effectively removes heating from it. But decrease wire fill factor and increase eddy current losses. For air cooling the axial motor is possible only with open contraction like stanad outrunner motors. Motres use a standard liquid cooling system with the case outside the stator. Motres air cooled motors don't have a case outside the stator. It used direct stator cooling with high surface lamination.

Sealing

Due to construction of the axial motor it is very difficult to seal it.Good sealing like IP67 will produce high frictional losses or increasing construction weight. For a radial motor it is not a problem.

Performance

All information and photos provided in the article is taken from free sources on the Internet
https://www.youtube.com/watch?v=HFY0cNRQjHA
https://www.e-motec.net/yasas-high-efficiency-axial-flux-motors-are-extending-ev-range
https://build-its-inprogress.blogspot.com/2017/05/emrax-motor-teardown.html
https://www.beyondmotors.io/research/emrax-compariosn-axial-flux
https://www.emworks.com/ckfinder/userfiles/files/Axial%20Flux%20Motor.pdf
https://www.emobility-engineering.com/rolls-royce-spirit-of-innovation/