What is an axial flux motor?
Motors can be divided into two categories – radial flux motors and axial flux motors. The radial flux motor is the common and frequently used general-purpose motor in the market.
The axial flux motor is the world’s first motor manufactured by Faraday. With the acquisition of YASA, a world-renowned axial flux motor company by German Mercedes-Benz, domestic and foreign motor companies have begun to focus on the research and development and manufacturing of axial flux motors.
In axial flux, the direction of the magnetic flux is parallel to the machine’s rotation axis, while in radial flux machines, the direction of the magnetic flux is radial.
Difference in magnetic field between axial flux motor and radial flux motor
In radial motor, the flux path is much longer than that of axial motor, as it goes from one rotor pole to the first tooth of the stator, then through the stator back iron to the second tooth until it reaches the other rotor pole again. In contrast to radial machines, axial flux machines have a shorter and direct flux path. It goes directly from one pole to another through the air gap. The magnetic field remains strong along the shorter path, which helps to increase the efficiency and power density of the machine.
Why are axial flux machines more efficient than radial flux machines?
In radial machines, the flux has a two-dimensional path.
Therefore, grain-oriented steel cannot be used in these machine types. In axial machines, the flux path is unidirectional, which allows the use of grain-oriented steel. Due to the higher magnetic permeability of this steel, the iron losses of axial flux machines can be reduced and the efficiency can be improved by 2%.
Technical advantages of axial flux motors
Compared with the conventional radial flux permanent magnet motors popular in the market, the advantages of axial flux permanent magnet motors are as follows:
➢ Volume is reduced by about 1/2.
➢ Weight is reduced by more than 25%.
➢ Efficiency is increased by about 0.5-3%.
➢ Fault-tolerant function:
Dual stator structure, each stator can be powered separately to drive the motor to operate.
➢ Easy modularization and standardized spare parts:
Power can be increased by axial stacking
Leverage
In an axial flux motor, the permanent magnets are placed further away from the center – this allows for greater leverage of the permanent magnets, i.e. more performance output for the same amount of material used in the motor.
More surface area to generate performance output
The rotor is the moving part of the motor, with only one rotor in a radial flux motor and two rotors in our axial flux motor; this creates a larger surface area to generate motor power.
Electromagnetic field
The simpler design of an axial flux motor means the magnetic path (flux) is shorter; and the flux is straight, not curved: these two factors together allow for higher motor efficiency compared to non-axial flux motors.
Higher copper utilization
Up to 100% copper winding utilization, up to 2 times that of non-axial flux motors.
Axial flux motors have less copper windings to return to the core (which avoids the associated drag and friction, resulting in higher power density).
Lower heat generation and higher efficiency
Axial flux motor technology generates less waste heat, which improves motor efficiency.
