Axial vs Radial Flux: Simple as Pie. Or cake. Or Pancake. Motor.

Enln7I was still confused.  It seemed like I understood what the difference was between axial and radial flux motors, but still, the terminology was not really making sense.  I was chatting with John Fiorenza, and suddenly it became clear.  I was getting hung up on the axial vs radial air gap.  Then I found this site and this simple little graphic, above.  SO simple.

The little arrows show the direction of the magnetic flux in each motor.  The axial flux motors have flux that runs parallel to the output shaft – along the axis of the shaft, thus, “axial”.  A radial flux motor has it’s flux running in and out from the center of the shaft – on the radius – thus, “radial”.

The air gap – the space between the rotor and the magnets – can also describe the motor, but when you’re looking at the air gap, think of it as a dimension.  The gap dimension – the distance between the rotor and the magnets – on an axial motor is the same as the direction of the flux – parallel to the shaft.  In a radial motor it’s the distance between the outside diameter of the rotor and the inside dimension of the magnets – again, on the radius.

Here’s what was messing me up.  I was thinking of the air gap as a shape – because I’m a visual guy.  This is what I mean:

Screen shot 2015-06-13 at 3.41.15 PMSo, if you look at it like that, then the air gap is a disk-shaped thing that is perpendicular with the shaft.  Which is radial.  Which is what confused me.  Think of the gap as a dimension, or think of the gap as what the flux crosses, and you’ve got it.

And John Fiorenza?  I hereby convey and anoint upon him the title of “The Most Patient Man in Electric Vehcles”.

Thanks again, sir!


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