Originally Posted by ViorelX
Very interesting and very good news that such 24N28P motors are finally available on the market. So far I have got a few pieces NX-4008, with 24N22P configuration from hobbyking:
They are good motors too. I have rewound them, put on EasyGlider and tested with large propellers (13x11 up to 18.5x15). They perform good. On 13x11 propeller I put up to 250W input power (Kv=1000rpm/V and 2s battery) and get excelent speed and climb rate. On 18.5x15 (and Kv=500, 2s battery) I use no more than 100W average input power (for several minutes of run whitout heating) and still get good climb rate and appropriate cruising speed. The greatest thing I get with this large propeller is efficiency: with a 2s 2.2Ah I can fly up to 1h. Last time I flew with 16x13 Aeronaut CAM propeller with the Kv=500 motor and 2s battery. I get satisfactory climb rate (maybe 3-4m/s) and best battery life.
I don't have devices for dynamic measurements and I have no idea what their efficiency is, but I'm very interested to find more about.
I am happy with these motors from Hobbyking, but I am a bit frustrated that they have only 22 magnets and I don't understand why they are not produced with 28magnets, to perform even better on such large propellers.
Your measurements above reffer only to magnetic loss on no load run. I am wondering about the level of magnetic loss both as a function of speed and load, and of course the overall efficiency as a function of speed and load.
The iron losses are not depending directly of the load.
Iron losses depend of rpm (not linearly)
Copper losses are Rm Amps^2 (Joule effect)
+ some ESC losses