A continuing challenge for electric motor manufacturers and motor users is delivering more shaft power while using less input power, which simply put means increasing the motor's efficiency. Motor efficiency improvements extend the life of battery-powered products, save on energy costs and reduce the amount of heat that can cause damage and increase in-field service and warranty costs. Higher power efficiency also means lower internal power losses.

1. Copper winding (function of conductivity of copper and the resistance of the stator coils)
2. Coulomb friction (brushes, bearings and shaft seals, etc.)
3. Viscous friction (bearing lubrication, certain materials damping characteristic as a function of speed)
4. Hysteresis (magnetic memory in motor's soft iron members)
5. Eddy currents (primarily soft iron losses caused by material type and thickness of laminations, material induction levels, commutation frequencies. Losses vary as a function of speed squared)
6. Windage (aerodynamic effects due to motor geometry and speed)
7. In most applications, the copper winding losses are the largest contributor to an inefficient motor. These losses are computed by multiplying the input current squared by the winding resistance of the stator. The conductivity and resistance of copper are among the lowest per foot of any current carrying material. Only at higher speeds do eddy current losses become significant.

I think I found my answer. I think.

Sorry for the triple post guys.............

Specs on the NEU 1515 series are as follows:

MODEL RPM/V V Range Max Current Draw
1515/1Y 2200 7-25 100
1515/2.5D 1700 7-40 100
1515/1.5Y 1500 7-35 85
1515/3D 1360 7-45 85
1515/2Y 1100 7-50 75

So a 1515/1Y Has a recommended Voltage range of 7-25V and as expected (in part) the voltage range increases as the # winds increases. (and the current draw falls)

Procharged, yea that's some good info.

My understanding of iron losses is that they increase with the frequency of eddy current generation. Everytime the poles intersect eddy currents are generated. In a higher pole motor the intersections are occuring faster for a given RPM than in a lower pole motor.

Yes, lower Kv generally permits higher voltage which in turn results in lower current.

High current is an enemy of efficiency. Ohms law shows that the voltage drop over a given resistance is lower for less current drawn. ie. if you are pulling alot of current, you are loosing more power to circuit resistance. This is why power distribution is done at high voltage.

If you run a lower kv motor then it is in the effecency range.

Hey guys, R/C equipment aside, I thought we couldn't pass approx. 30 volts due to it's potential to cause some serious damage, even death, if a mishap were to occur. Any other info on that?

I myself never heard of that. I have in the 40s on one truck. The spark is loud on first hook up.

I know in Germany one requires some special permit to work with more than 10S systems...

That's kinda low. If you mean death by electrocution; personally, I don't "feel" anything less than 60-65v, and even then, it's a very faint tingle. It's not voltage that kills you, it's current. And it takes ~15mA to kill someone. And given our bodies are in the 10-15 Mega-ohms of resistance, it would take quite a bit to produce 15mA of flow. There are other factors in this, but I won't continue rambling. :)

Yes we know it's current, a by product of voltage. In the above post Aragon mentioned the 37v threshold, and that is what rings the bell. There has to be a reason for the permitting requirement. You have to remember somebody may have wet hands, or drive through water, or something of the like.

Why would they make an esc for 12s lipo or even 15s lipo?
15s lipo is some powerful voltage. Now that would make a car zing.

To fill demand. Heli and plane guys are running upto 15S these days. High current is a very bad thing in a 3D heli, so HV is a must for high power setups (>2kw).

While there may seem to be many people wanting high-V systems out there, the vast majority of truck/car systems still run relatively low voltage systems. Most of the electric vehicles are still designed to use NiMH cells, so the replacement lipos are still between 2s and 5s. Manufacturers are going to build for the majority, not the minority. Until more electric vehicles start using high voltage the choices for ESCs that can handle that will be a niche market.

True. In fact I've taken 2-3 50,000 volt hits in my life. All from high-performance 1:1 scale ignition systems.

I've also taken several 120v hits hits while rewiring electrical systems in buildings. The 50,000v hits tingle.....they take away feeling for a minute or two whereas the 120v hits (higher current) hurt more and tingle less. .....if that makes sense to you all.............

So yes, it's the current that gets you!

I think the escs will grow to fit the demand. As more electric make the speed
record more will want to be part of that.