On 3/15/2013 7:28 PM, fotajoye wrote:
This article talks about a prototype non-inverter, 23 phase, multi-microcomputer controlled AC motor design: http://www.goauto.com.au/mellor/mellor.nsf/story2/60F68FBFB8ABF2CECA257B2E001BCD49
The description is interesting, but seems to have left the reporter with a few misconceptions.
The new motor is claimed to be 95% efficient, but that is pretty much the usual efficiency of any electric motor of similar horsepower. The comment about normal motors being 70% efficient applies to cheap consumer grade motors under 1 horsepower.
This is an axial flux motor. This is less common than the usual radial flux motor, but is still a pretty conventional design.
Putting microcomputers in motors is also not revolutionary. Huge numbers of motors already do this.
The one interesting aspect mentioned is that it has 23 phases. There are lots of polyphase (more than 3 phase) motors, but they usually have some even number of phases. I've seen 6, 8, 12, and 24 phase motors, for example.
The odd number of phases makes me guess that this is a more-or-less conventional brushed DC motor, with its commutator replaced with switching transistors. It is common to have DC motors with an odd number of commutator bars and rotor windings. Such motors have been built before, but the advantages weren't enough to compensate for the higher price of all the power transistors (each one of which has to carry the full motor current for part of the rotation).
I don't see any particular need for a microcomputer in the rotor, as the current in the windings of a typical brushed DC motor is a simple square wave. And since all the windings are in series, they can't really be controlled individually.
There was a company in Canada working on a "chorus" motor that sounded somewhat similar. The Chorus motor was a conventional induction motor, but with something like 24 phase windings in the stator. These stator windings were wired like 8 3-phase motors. They had 8 3-phase inverters driving them. The claim was that the large number of parts was offset by being able to use small inexpensive TO-220 transistors instead of big expensive modules. And, each could be run as a simple square wave inverter, with the sinewave synthesized by running them at different phase angles relative to each other.
It will be interesting to see if any more details come out about the Australian motor, so we can tell if it really is something different, or just a reinvention of something that's been done before.
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