Most efficient electric motor?

[DennisCNC]

What is the most efficient type of electric motor generally speaking? Dc brush, BLDC, Perm Magnet AC, Induction AC? other?


Thanks

[Al_The_Man]

I would plump for PM AC sinusoidal.
Al.

[neilw20]

Efficiency depends on losses.
IMHO when iron losses and copper losses are equal that's as good as it gets.
If windings are solidly packed it will be better because the more copper, the lower the resistance, the lower the copper losses.
As for the iron losses, if too close to saturation losses will go up.
Eddy current losses. Thinner laminations properly insulated from each other help here.
Wire window to cross section of pole. The more amp turns the better.
If you want low friction use air bearings, but take into account the energy to supply the compressed air.
You can make a good or bad motor with any technology.
I like BLDC because you can make really efficient controllers with high efficiency right through the speed range. All above losses still apply. They just add to the controller losses. A well designed controller (any type) will be well above 90% efficiency.