variable field motor demo

link to variable filed motor, windings move in/out of the stator to adjust speed also torque I assume, anyone care to explain this
phenomenon? I vaguely remember it being discussed many years ago but I've not seen it put into action before.
video link is to solar car racing team from japan
[youtube]https://www.youtube.com/watch?v=xzVmjNd1wLM[/youtube]

whatever said:

link to variable filed motor, windings move in/out of the stator to adjust speed also torque I assume, anyone care to explain this
phenomenon? I vaguely remember it being discussed many years ago but I've not seen it put into action before.
video link is to solar car racing team from japan
[youtube]https://www.youtube.com/watch?v=xzVmjNd1wLM[/youtube]

Click to expand...

whatever,

This is just a method of field weakening, also called flux weakening. Not sure exactly what it's called, but I refer to it as displacement field weakening. More common methods do not involve physically misaligning the rotor and stator but involve timing. The results are the same; a reduction of the field flux present in the armature.

The generated voltage (often called BEMF) is proportional to flux and RPM. So reducing the flux causes the RPM to increase to maintain voltage. Also, torque is proportional to flux and armature current. So when flux is decreased (weakened) to increase RPM, it also reduces the torque per ampere.

major

Neat! Looks expensive. If its just a method of field weakening, would there be some advantage to doing it mechanically vs controller? Could this mechanical method be used in addition to controller timing or do both methods reach some practical limit of diminishing returns?

DanGT86 said:

Neat! Looks expensive. If its just a method of field weakening, would there be some advantage to doing it mechanically vs controller?

Click to expand...

1) Slightly more efficient
2) No massive deceleration if the controller glitches for a second