Since the invention of electric motors in the mid 1800s, Motors are being used from industries to our homes to make our lives easier. Now, they are also replacing conventional engines in vehicles. An electric motor converts electrical energy into mechanical energy. The rotating forces are generated by the interaction of magnetic fields. Magnetic fields are produced by either current flowing conductors or permanent magnets.

There are various types of electric motors based on various considerations:

1. Power Source
2. Construction Method
3. Use of permanent Magnets
4. Type of motion Output

A motor mainly consists of two components: Rotor and Stator. As their name suggests, Rotor is the moving(rotating) part of the motor and the stator is the stationary part of the motors. Based upon the arrangement of rotor and stator, there are two types of possible configuration:

1. Axial Flux
2. Radial Flux

The difference in these configurations is due to the axis of rotation and direction of magnetic field. In axial flux configuration, the direction of magnetic field and the axis of rotation are parallel while in radial flux, it is perpendicular.

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The first patent of Axial flux motor was filed back in the 1890s but the major developments are visible since last decade due to availability of strong permanent magnets and advancements in BLDC control mechanisms. Axial flux technology can be applied to any motor configuration such as induction, stepper and even brushed DC.

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Advantages of Axial Flux motor over Radial Flux

Axial flux motors are known for their high power and torque density compared to conventional radial flux motors.As per basic mathematics of motors, In case of axial flux motors, the torque increases in proportion to cube of diameter increment while in case of radial flux, it increases in proportion to square of diameter. Diameter getting doubled means 8 times torque increment in Axial flux motors while 4 times in radial flux motors.

Magnetic flux path is shorter in Axial flux compared to radial flux motors that leads to higher power density. Axial flux motors are also called pancake motors. Considering the disk shaped rotors and stators, these disks can be stacked together to form various configurations of motors. Most common configurations are single rotor single stator, dual rotor single stator and single rotor dual stator.

Yokeless design is also possible with axial flux motors thus significantly reducing the weight of the motor and increasing its power density. To compare power densities, here are specifications of a Permanent magnet axial flux motor developed by Magnax (German axial flux motor company) compared with BMW i3 Radial flux motor:

Axial flux motors are best fit for in-wheel(hub) motors due to their geometry. Here, Axial length and weight are constrained while diameter of wheel gets utilized.

Axial flux motors are still not getting used in Industry due to availability of other alternatives such as induction and radial flux motors. In industries, machines generally run at a short range of rpm where they provide high efficiency. But recent developments in Electrical vehicles require motors that can provide high efficiency over the whole range of vehicle running cycle. Looking at the compatibility of Axial flux motors with electric vehicles, major developments are happening in this technology.

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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.

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