

Jan 22, 2014, 08:46 AM  
Germany, BY, Gräfelfing
Joined Jan 2003
420 Posts

Because of the search of a high efficancy elektric motor i have a little test modelmotor .i yoused this motor to slide different backiron materials outside the windings no need to change any thing on this motor.So i can select + and  of different materials.
So first i slide now some air outside and check the motor running with this freeflux system. Motor has a 2 pol rotor from neodym 22mm dia and 30mm long. Winding is 5 turn of 245 x 0,1 litzwire ,to get low eddy current in the wire and now i have switcht to parallel wind of this litzwire with 5 turn each phase . Internal resistance is 0,004022 ohm ,no load amps are 3,2 amps.The coils are y terminated to get no circle circuite amps. So kv = 7860 rpm . I run this motor on 1 cell 3,6 volt to mesure no load amps. Flux calculating show on the surface of the rotor we have 0,560 tesla ,at 0,5mm distenz= 0,52 tesla,at 1,0mm 0,48 tesla,at 1,5mm 0,44 tesla,at 2mm 0,41 tesla,at 2,5mm 0,38 tesla ..... at 5mm 0,27 tesla. So you see the flux is very low.but low flux will give low fluxrelated los. 
Jan 22, 2014, 09:15 AM  

Quote:
The same argument seems to hold for bearing friction as well. So what sort of actual physical motor losses are accurately represented by the constant, unvarying Io in the 3constant motor model? Are there any, or is the constant Io a purely mathematical convenience with no direct connection to any actual physical energy loss mechanism in motors? Flieslikeabeagle 

Jan 22, 2014, 09:32 AM  
London UK
Joined Jun 2006
100 Posts

Quote:


Jan 24, 2014, 07:17 AM  

Hi
The best graph is to represent Io x Vin versus rpm See the picture for the Scorpion SII 4020 family (3 windings, 3 Kv) At no load, the copper losses are ridiculously low BB losses and aerodynamics drags are probably(?) also very low Conclusion : curve is not linear A good regression is an order 2 polynomial Louis 
Jan 24, 2014, 02:04 PM  

Quote:
with the formula Wo = K V^(3/2) you have only one degree of freedom (K) with the formula Wo = A + B rpm + C rpm^2 you have three and the formula is respecting hysteresis losses + eddy currents losses generally A is very small Louis 

Jan 25, 2014, 04:59 AM  

Quote:
As a comparison Scorpion SII 4025520 weight 341g measured Kv 526 rpm/V Rm 0.0164 ohm On 11.1V Io = 1.5A On 22.2V Io = 2.2A Louis 

Jan 26, 2014, 04:16 AM  
London UK
Joined Jun 2006
100 Posts

Regarding simple modelling: https://www.academia.edu/1360191/Bru...Fixed_Wing_UAV

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