Small wheel hub motors

Hummie · July 26, 2016, 3:59pm

my analysis tells me to listen to what these people say.

http://vedder.se/forums/viewtopic.php?f=6&t=6&start=10

Hummie · July 26, 2016, 4:05pm

I’m saying yes they get converted to amps or something like that. sign up on vedders thing and ask those guys how it works or read the whole thread.

you do not get a cooler motor from more voltage that much is true, the details I cant explain

Hummie · July 26, 2016, 4:07pm

you dont have to sign up for anything and just read it. then maybe you can explain. the fact remains no cooler motors with more volts. INfact more likely the opposite as the no-load speed is now further away and more inefficient unless going faster

Hummie · July 26, 2016, 4:09pm

go tell vedder. this is a repeat conversation i’ve had a couple times. sometimes people freak out and tell me I’m an idiot. best you go to the source and shoot them not me

brams · July 26, 2016, 4:20pm

@devin
I think that @Hummie just misread the Vedder explanation.

Vedder simply illustrate the Amps * Volts = Watts equation, at the same Power (Watts) the heat is the same regarding if you add more Volts or Amps. Example : 10A * 3.7V = 37W and 1A * 37V = 37W. The heat is the same, the balance is different. You have to keep in mind that heat is generated by the losses in the motor, and this heat is calculated in Watts.

Now, Vedder never stated that amps convert to volts, that simply basic knowledge of electricity.

PB1 · July 26, 2016, 4:22pm

@Hummie and @devin just to confuse you and very much oversimplified: it’s the VESC that converts volts into amps, not the motor.

brams · July 26, 2016, 4:26pm

Seriously stop saying confusing stuff like that. VESC does not convert volts into amps. It controls (like any ESC) the 3 phases of the motor. The VESC just warms up at higher current.

Seriously it’s not magic, again it’s just electricity.

Nordle · July 26, 2016, 4:28pm

and it’s the esc wich stays cooler as the voltage becomes higher, not the motors

brams · July 26, 2016, 4:35pm

devin:

heat could be addressed by limiting amps, running motors as close as possible to %85 of no load rpm at full throttle on the flats (this would set your optimal kv based on mechanical load / wind resistance on the flats), air vents, active cooling such as forced air, choice of motor materials (this option affords about %60 of max potential power, but at about the theoretical max [%85] electrical to mechanical conversion efficiency).

to get the most power (and most heat without sacrificing power) from your motors on the flats, you would target kv so you are running at %50 of no load rpm at full throttle on the flats (because of wind drag, etc). (%100 of max potential power, about %50 electrical-to-mechanical conversion efficiency vs %85 max)

running at about %70 no load rpm at full throttle on the flats strikes somewhat of a balance between max power and max electrical-to-mechanical conversion efficiency at full throttle (about %90 of max power vs %100, and about %70 electrical-to-mechanical conversion efficiency vs max %85)

How do you calculate those numbers? Also why 50% of no load rpm would produce 100% of max power?

brams · July 26, 2016, 4:44pm

Have PMDC and BLDC the same performance curve?

PB1 · July 26, 2016, 4:56pm

@brams of course it does, in an oversimplified way.

Input of an ESC is DC voltage and current. Output is AC voltage and current. And they do not to be the same. So this is a conversion.
I can write more later, in the train commuting right now…