The very first axial flux motor was invented back in the 1830s by Nikola Tesla. In principle the axial flux motor is same as the radial flux motor but with inherent topology differences. The magnets and winding are placed axially on the disk of rotor and stator such that the flux path is always parallel to the shaft unlike its counterpart radial flux motor where the flux direction is perpendicular to the rotating shaft.
Thus because of its topology we can place the rotor and stator in a disc form due to which less space is required overall giving it less form factor than conventional radial flux motors which are heavy and bulky in size.Axial flux motors can be used anywhere but we’ll discuss in detail the application where definitely the axial motor is more preferred than its counterpart radial flux motor.
In the EV industry electric motors could be broadly used as inwheel/hub or mid-drive/inrunner type.
Typically, in the hub motor configuration, the outer motor body rotates while the shaft remains stationary, making it easier to place the tire around the body of the motor, which is how a typical hub motor design works. In the majority of bicycles, the hub motor is now preferred. Many companies are launching the concept of electric cars with hub motor in their wheels.
A radial flux motor is not the best choice for an inwheel/hub motor configuration because it takes up more axial space, whereas an axial flux motor is best suited for an inwheel configuration because it is a disc type motor and thus requires less axial space. When it comes to torque and efficiency, the axial flux motor outperforms the radial flux motor by a wide margin.
The axial motor, when compared to the radial motor, offers better torque and efficiency in the same form factor. Axial flux motors can also provide high efficiency across a wider range of rpm than any other motor. Recently Mercedes Benz has acquired one of the prominent axial flux technology company to use the axial flux motor in their upcoming cars. Renault also bought major stakes in Whylot, a french axial flux motor. With the advent of electric vehicles in recent years, the axial motor is quickly becoming the industry’s next big thing.
Permanent magnet motors have been used in wind turbines for decades; in wind turbines, we need a generator motor that can provide a substantial level of energy output at typical low rpm.
Achieving the high power output at relatively low rpm is a challenging task because at very low rpm the amount of magnetic flux cutting the stator coil per second is less and the change in magnetic flux gives rise to the potential difference which in turn causes current flow across the load.
As a result, a considerable variation in magnetic flux is required to obtain higher output power. Because the existing radial motors are unable to mitigate this problem, the engineers have increased the size of the motor itself in order to obtain a larger delta in flux. However, this solution is not economically viable.
The problem can best be solved by the axial flux motor in order to achieve the maximum flux change in a given form factor; the dual stator and single rotor configuration can be used.
Currently the larger drones require a powerful motor with very high energy density. For a given input power it should be able to give maximum thrust. As we have discussed, the axial flux motor offers high power density as compared to any other motor therefore these motors make sense in the aviation industry also. There are many new companies which are using axial motors in their drones.
Recently YASA, which is a pioneer in axial flux motor technology has built a motor for a Cessna aircraft and has successfully tested it.
Elevators require a low rpm high torque motor. Today, there are companies which are using axial motors in the elevators. The reason being that more torque could be taken out of an axial flux motor as compared to any other radial motor. A dual rotor single stator configuration axial flux motor could be used to get the maximum torque at low rpm.
Axial flux technology is going to change the consumer tech towards more efficient and slim designs such as in fans and other applications. Considering the high volume of sales in consumer tech, We are looking at huge impact from this technology.
Looking at the current trend, Axial flux motors are on their way to mass adoption. With the advancement and maturity in technology, we would be finding axial flux motors in other industry verticals also.
At Naxatra Labs , We are developing high performance axial flux motors for electric vehicles. We aim to bring it into mainstream industry and disrupt the existing status-quo, and become the leading axial flux motors suppliers in the Indian electric vehicle revolution.