Axial flux motors - The new hope

axial flux motors are considered the ultimate future of electric vehicles and most importantly of electric aviation because they have a high torque to weight ratio which is ideal for aircraft companies like rolls royce and magnex have intense research and development in progress on these motors interestingly the first ever electrical generator developed by the genius michael faraday was an axial flux type you can see the axis of rotation is parallel to flux lines however it never got its day in the sun back then based on the orientation of magnetic flux electric machines can be divided into two types first is the radial flux motor which is used in 99 of applications today and second is the axial flux motor in a radial flux motor the magnetic flux is perpendicular to the axis of rotation in an axial flux motor the magnetic flux lines are parallel to the axis of rotation now let's see how the axial flux motor actually works the axial motor's operation is based on the interaction between the permanent magnet and the electromagnets when coils are energized they become electromagnets the most common design of axial flux motors have fixed coils and freely rotating permanent magnets here the mortar's coil arrangement is shown when a direct current supply is given to one of the coils it gets energized and becomes an electromagnet when coil a gets energized in this way the s pole of the rotor is attracted to the stator's opposite end pole simultaneously the like poles repel the tangential component of these two forces is shown here the tangential force components make the rotor rotate when the rotor aligns with coil a the net force acting on the permanent magnet becomes zero will the rotor motion stop at this point the rotor's speed or the inertia effect causes it to travel ahead of the perfect alignment angle during this time the next coil b gets energized because of the same forces of attraction and repulsion the rotor then reaches near to coil b later coil c gets energized after that in the next half rotation coil a energizes again but this time with the opposite polarity just by changing the supply directions the process constantly repeats and the rotor continues to rotate however in this operation you can see two coils are always dead these coils drastically reduce the motor's power output here's the trick to overcome this problem we simply have to pass the opposite polarity current through the second coil to ease the understanding let's focus just on the nearest pairs of magnets you can see that at the stator side two south poles are together the combined effect of these two poles will be here and based on this we can have an easy force analysis here again a net tangential force is developed the combined effect produces more torque and power output from the rotor interestingly this process also ensures that the motor has a constant torque output the question is how will you decide which coil to energize to get continuous rotation for this purpose we use a smart electronics controller the sensor determines the rotor's position and based on this information the controller decides which coil to energize theoretically the rectangular pulses like this produces a constant torque output for the axial motors however in practice when you suddenly switch on or switch off a phase current ripples will be produced in the other two phases thus the torque quality will be affected the best solution to overcome the issue is to gradually kill or raise the phase current resulting into a pattern like this let's compare the axial flux motor with the most commonly used motor the radial flux induction motor the first differentiating factor is the flux flow path in the machines if you compare the magnetic flux pattern of both the motors you can see that the axial motor's flux flow path is much more dense and shorter when compared to the induction motor to confirm the flux paths let's take help from the fea here is an fea result in em works 2d software paired alongside solidworks the interaction between rotor and the stator magnetic field generates torque here some field loops rarely interact with the rotor on the other hand in the axial motors the majority of the flux lines lie in the useful work area to generate torque for this reason the axial flux motor gets a higher density of flux thus generating a higher torque output from the same size of the motor the second differentiating factor is the larger diameter in axial flux motors the rotor magnets can be located further away from the central rotating axis this larger radius allows the motor to generate more torque made clear by this simple torque equation however if you try to increase the diameter of the induction motors the rotor's inertia will increase which can lead to the motor sniffing up huge currents during the start axial flux motors keep this issue under control as the rotors already have less inertia there you have it a 200 year old motor is currently the most powerful and efficient motor of our day these lightweight motors are the best choice for electric airplanes in aviation every ounce you save is a boon the ion bird craft developed by rolls-royce uses three such motors by yasa these motors are powered by 6000 lithium ion batteries and a smart electronics controller with an incredible efficiency level promise of more than 96 percent and their compact size axial flux motors can even become a good choice in electric cars we hope you enjoyed this video please don't forget to be a part of the lessex team thank you

Channel: Lesics

Views: 1,282,740

Rating: 4.9078741 out of 5

Keywords:

Id: 8EEVPVNJHjM

Length: 6min 38sec (398 seconds)

Published: Tue Sep 28 2021

Reddit Comments

[u/lpisani]

Interesting. With axial motors being the choice of electric aircraft says a lot. The motor they highlighted in the video showed just over 96% efficiency. Plus they mentioned that, with the same size motor, the axial produced more torque. All positives. It just confirmed for me based on previous research that hub motors are definitely the way to go. Most OEMs use radial because it allows a design that parallels their traditional ICE layout. Changing 100+ years of design is scary. They don't want to be too disruptive. Even dinosaurs evolved or died, though. Their choice.

[u/LevelTo]

Check this out

[u/What_2000]

I am a big fan of HUB motors. I read about them like 20-25 years ago. Have to admit I started to nod off after about 2 minutes. Still interesting.

[u/RadRunner33]

Very interesting.

[u/stockratic]

That was very interesting. The physics was a little over my head. :)

[u/iVoid]

I don't think lordstown's hub motors are axial flux motors though. In fact any production hub motors I've ever seen are radial flux motors.

Axial flux motors are cool because they can be made really thin (like a pancake), but they have their own limitations. Saying axial flux motors are also known as hub motors is oversimplifying it, and misleading.

[u/Crusher-4-you]

Having background and a double graduated in Electrical Engineering I love this video, thanks for sharing.

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I feel like this is the future too, there could be some challenges but we are moving away from traditions (like from gas to EV, from traditional batteries to solid state, who thought? )

[u/SomeGuyNamedPaul]

WKHS uses axial flux permanent magnet motors for their current products.

[u/rightlywrongfull]

That's great. Maybe the people working at Lordstown can get new jobs selling these!