How Does the Dyson Motor Work?

[rob77]

so for what its worth, i've never run across a shaded pole motor with a variable air gap. meaning, the air gap across the section after the shorted turn is the same as the rest of it.

those two would be mutually exclusive i believe... either shaded pole or asymmetric air-gap. and actually a shaded pole would not make too much sense in a brush-less DC motor.

[amyk]

Technically it's not a DC but an AC motor.

yes correct, brush-less DC motors are technically AC motors.. everyone knows that, yet everyone calls them brush-less DC motors and technically the brush-less DC motors are the closes relatives to stepper motors. and technically stepper motors are also AC motors... aren't they ?

the reason for that might be that a brush-less DC motor requires a controller to be operated (which does the switching and also might do sensing of rotor position), therefore the motor and the controller can be considered as a single unit - and that unit is fed by DC.

Unipolar steppers and switched reluctance motors can be driven with DC, there's no reversal of the current through the windings. On the other hand, something like this Dyson motor is clearly being driven with an AC waveform.

I found an examination of another Dyson motor, one from their vacuums:

https://www.experimental-engineering.co.uk/dyson-dc35-digital-teardown/

In this image you can clearly see what looks like an asymmetrical (and rather large) pole gap.

[rob77]

Unipolar steppers and switched reluctance motors can be driven with DC, there's no reversal of the current through the windings.

no there is no reversal of current in one winding, but the reversal of magnetic field is achieved by a second winding (technically a center taped winding in a unipolar stepper)
so i would disagree with that statement... it's like saying a full-bridge driven transformer is fed by AC , but a push-pull driven is fed by DC.. the difference between those transformers is exactly the same as between bipolar and unipolar steppers.

On the other hand, something like this Dyson motor is clearly being driven with an AC waveform.

correct, it's a brushless DC motor, therefore it's fed by AC.

I found an examination of another Dyson motor, one from their vacuums:

https://www.experimental-engineering.co.uk/dyson-dc35-digital-teardown/

In this image you can clearly see what looks like an asymmetrical (and rather large) pole gap.

interresting teardown, thanks for sharing the link !

[KalleMp]

Technically it's not a DC but an AC motor.

yes correct, brush-less DC motors are technically AC motors.. everyone knows that, yet everyone calls them brush-less DC motors and technically the brush-less DC motors are the closes relatives to stepper motors. and technically stepper motors are also AC motors... aren't they ?

the reason for that might be that a brush-less DC motor requires a controller to be operated (which does the switching and also might do sensing of rotor position), therefore the motor and the controller can be considered as a single unit - and that unit is fed by DC.

Unipolar steppers and switched reluctance motors can be driven with DC, there's no reversal of the current through the windings. On the other hand, something like this Dyson motor is clearly being driven with an AC waveform.

I found an examination of another Dyson motor, one from their vacuums:

https://www.experimental-engineering.co.uk/dyson-dc35-digital-teardown/

In this image you can clearly see what looks like an asymmetrical (and rather large) pole gap.

There is a Hall sensor for the motor in the picture at the same site mentioned by amyk.

It looks like a Siemens SLIC-HALL TLE 4945L device.

The rotor may have an asymmetrical magnetic field (one pole larger than the other perhaps) or the stator pole asymmetry may have something to do with it.  However I think it would be a good idea for someone with a good long recording memory scope to examine the waveforms to the H-bridge, and from the stator winding and Hall sensor.

While the impeller on these is somewhat directional there are many simple/cheap aquarium water pumps with straight vanes that are self starting in either direction I still believe it would be instructional to find out how Dyson selects or determines the designed direction to get the best efficiency.

The best would be for a simple circuit that could drive the motor with the H-bridge signals and the Hall Effect feedback without the Dyson legacy battery issues.  Having a small circuit that could take any power tool battery pack and run it down to 18V as fast as selected would make the vacuums recyclable and the fans repurposable.

[KalleMp]

Found some interesting of a Dyson motor from a Fan I think.