Originally Posted by mjsas

Any cheap motor from China will be rated at 98% or higher, some may even get up to 90%.

Keep in mind that max efficiency only occurs at one operating point. All motors suck when operated at some weird point. It is possible to smoke any motor. Trying to get that last percent is a waste of time and money. Spend the money on better batteries.

That is not really true. A few percent improvement in efficiency allows you to use a much lighter motor for the same application. If you have one motor with 90% efficiency and another with 80%--and both are run at 1000 watts input--it is easy to see that the 80% efficient motor will have twice the heat to dissipate. It will need to be larger and heavier to do the same job without cooking.

FYI--just because a motor is"rated" for 98% does not mean that it comes even close.

Efficiency does matter!

Steve Neu

Ah right, the iron that holds the magnets in place, rather than between the windings, gotchya!

And I've seen the difference 5% efficiency makes when talking 80 v 85%. I can pump 30% more power into it, for the same temp rise. Large difference there!

Originally Posted by Odysis

Ah right, the iron that holds the magnets in place, rather than between the windings, gotchya!

No, the iron that surrounds the windings. Instead of being fixed to the can like a slotless motor, it's fixed to the shaft. It's a brushless coreless design.

Greg

Originally Posted by sneu

That is not really true. A few percent improvement in efficiency allows you to use a much lighter motor for the same application. If you have one motor with 90% efficiency and another with 80%--and both are run at 1000 watts input--it is easy to see that the 80% efficient motor will have twice the heat to dissipate. It will need to be larger and heavier to do the same job without cooking.

FYI--just because a motor is"rated" for 98% does not mean that it comes even close.

Efficiency does matter!

Steve Neu

My comment was satire meaning that, well, the same thing you said.

Heat is only one thing that limits a motors power. According to your analysis a 99% motor would make twice the power of a 98% motor or weight half as much. In the real world the difference would be about nothing. And would you believe either rating?

Originally Posted by mjsas

My comment was satire meaning that, well, the same thing you said.

Heat is only one thing that limits a motors power. According to your analysis a 99% motor would make twice the power of a 98% motor or weight half as much. In the real world the difference would be about nothing. And would you believe either rating?

Given that I have tested quite a few motors--both good and not so good I have a pretty good idea of what can be expected from most motors. Getting a hobby type iron core motor into the low 90s efficiency is about all you can hope for. The truth for the "sport" grade motors is a fair bit lower.

Steve Neu

Hi Friends,
in my opinion the best efficancy bldc motor is the flywheel motor/alternator from Prof.Dr.Richard Post , http://worldwide.espacenet.com/publi...396186B1&KC=B1 .
Only two pole for low switching frequenz,no iron flux carry parts only the magnets and the magnets can be laminated for low eddy current,for highest magnetic flux they use a Halbach array sending all flux inside the rotating ring,vacuum to get no aerodynamic loss and 2 two phase coil made from lize wire also to keep eddy current so low as possible. This wining combination can reach astonishing 99,6 -99,8 % efficancy.

I am with Steve,the Tango has very high possible efficancy but the low copper fill will limit this to the lower amp side.Also in the switching mode at part throttle there are lots of eddy current induced in the rotating solide back iron.It has to be made from laminated silicon steel or ferrite for high eff. .

For highest power to weight and efficancy we build motors with every flux seeing part from laminated material. Mean laminated magnets 1mm sheet ,laminated magnet back from 0,2mm or better 0,07mm cobalt iron ,lize wire and very good flux design for low loss.

Steve Neu and Hans Lehner produce the highest efficancy model electric bldc motors in the 95% region. You must only drive them in the high eff.window.