AC motors

[Phil the drill]

I recently came across a reference to the Rabbitool AC electric motor, and a further note about it having been licenced to Sanyo. I'm curious to know a little more about these motors and their controllers. The use of an AC motor on an ebike appears to make a lot of sense (so long as it doesn't need a 10 mile mains lead ). I have never noticed any ebikes that are advertised with this technology, but I'm surprised that this is the case if the technology exists, especially as on the face of it it offers many potential advantages (much wider torque spread, more effeciency, much better potential for regenerative charging etc.)
Anybody out there able to enlighten me further about this?

Cheers, Phil

 

[flecc]

The Rabbitool AC motor was first used for Electric bikes as the Motorised Wheel, marketed in the USA by the Birkestrand Corporation, and the main intention of the design was to provide for regeneration. I don't think it was particularly successful and was later licenced to Sanyo.

When Giant Bicycle stopped using the Panasonic motor unit on the Lafree series, their e-bike division looked around for a motor that could be marketed in a cheaper bike and adopted that Sanyo motor in the budget Giant Suede, but without regeneration.

They later changed course to go upmarket again with the New Twist 1 and 2 bikes, both with regeneration. However, the performance wasn't very good, the regeneration was so poor it was difficult to detect, and being a regenerative motor it has no freewheel so is somewhat unpleasant to pedal without power due to the drag. The result was these being widely dicounted by dealers to get rid of them.

The motor has now appeared in new guises in the Twist Freedom and Twist Express, gaining a freewheel at last and losing the worthless regeneration, hopefully with better performance as well.

So all in all history hasn't been very kind to this AC motor.
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[Blew it]

You've already got one

That magical controller on your machine is running your DC hubmotor on three phase AC !

 

[john]

AC motors usually work by induction. As the Rabbittool motor has permanent magnets it is not of this sort. I suspect that this is just a brushless DC motor of the kind used on most bikes now. These are sometimes referred to as AC by suppliers to distinguish them from the more traditional brushed DC motor.

 

[flecc]

I doubt if true AC induction motors would match our latest Hall motors for small size combined with the same power and useful torque characteristics.
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[Phil the drill]

Hi Thanks everyone for the replies and info. It appears the original hype was obviously as over optimistic as we've come to expect !

Phil