60statorpole helicopter direct drive
and probably more messages to come ...
Vriendelijke groeten Ron van Sommeren
I'm the guilty
Hello, I'm the 60-slot DD-heli "dreamer".
My theory of keeping at good power/weight relation for a DD heli motor is based in the following:
A 10 or 14 pole 12 slot motor (LRK or "distributed LRK" winding)
seems to have very good efficiency, air-gap force and power density
at speeds of 8000 to 15000 rpm.
By cascading 5 (5x12 = 60) the optimal speed range should end up at
1600 to 3000 rpm. Simply.
Of course, everything based the same good geometry, tolerances and choice
of materials. For sure it will be demanding to make the parts.
What I understand, going for less slots or poles leads to more material
in the stator to be able to keep down the Ri and efficiency up.
I think Digix is right, the more poles the better but iron losses first and
skin effects second and ESC switching frequency third will set practical limits.
My first problem to overcome is the initial cost for a custom stator design.
I'm very interested tips where to turn here.
If somebody at least could help me with the rawmatertial, I
want 0.2 or 0.35 mm sheets, a few sqr meters will do.
Where I looked, I have to buy 50 to 100 kg minimum.....at like 20 EUR/kg.
Joined Dec 2005
for simplicity i try to find some unusual construction which can easily fit many poles and feed then from one coil. something like stepper motor.
for Pontus Claesson:
I have done done super fast motor tests for research. and seems that you cant run usual steel stators faster than 1Khz
ESC have nearly unlimited speed if compare with that.
Without better magnetic materials it will be little point to make so many poles, since you can get same or better result with some gears.
One untested choice is to use ferrite magnetic, it have very low magnetic loss and can be formed into any shape. its permeability is few times lower, but this can be compensated with much higher speed.
unfortunately I had no luck to find any information about ferrite motors
Dear Digix, please do not forget what I want to do.
I do not want high speed, I want the optimal nb of poles and slots to produce the best efficiency and power per weight unit, at typical head speeds 1600 to 2200 rpm.
It have to be doable with available materials.
One parameter more that have big influence is of course
the stator diameter vs length.
Theoretical, the larger diameter and shorter stator, the
more power from a given motor weight if rpm is
kept fixed. (note: we talk about ring-motors with relativley low tooth height)
I think a somewhat larger diameter is better in my case
but it should also be possible to incorporate the motor
in a helivopter chassie (w/o too much modifications)
Thats why I've landed on stator OD 110 mm, will give
motor OD of 120 to 125 mm.
After almost 2 weeks of thinking , calculating and browsing a lot of forum posts,
I have decided to order custom stators and NO18 material (0,178 mm or 0,007"), in a first small quantity (5 sqm).
I have decided to go down to 48 slots but keep OD=110 mm.
Will have the pattern etched out, good tolerances (0,05 mm),
no sharp edges, no deformation and no altering of material properties
as it is a stress and heat free process.
To not just throw away whats left over of the (in small quantity) extremly expensive NO 18 sheets,
I will at the same time have some more stator models produced (see picture):
9 slot OD 16 mm
18 slot OD 35 mm
24 slot OD 58 mm
36 slot OD 84 mm
If anyone is interested to buy in, send me a private message.
In the first shot, prices and total quantity be about:
2200 pcs 9 slot ( 0,15 EURO/pc)
600 pcs 18 slot ( 0,45 EURO/pc)
250 pcs 24 slot (1,00 EURO/pc)
250 pcs 36 slot (1,90 EURO/pc)
200 pcs 48 slot (3 EURO/pc)
It will take at least 6 weeks from now before I have the stuff ready for delivery.
Please note, even if I sell the complete list above, the profit for me is
still negative, just a way to make it possible to build my dream machine
for a little less!
For each core material composition and thickness, there is a parameter called
"specific core loss" (Watt/kg or lb) and it is given for different flux and frequency.
At a given frequency, iron losses in NO18 is half of for example M270-35A, a material I seen mentioned. (thickness 0,35).
A way to make use of the low losses is of course to run at normal speeds or
to run motors with high nb of poles at higher than normal speeds.
Losses at 1 T in NO18 is about 160 W/kg@2500 Hz and 12 W/kg@400 Hz.
I will think about this..my interest would be something to sit in the front of a rotary engined WWI model..1500-2500 RPM is spot on for me also. Driving a large coarse pitch prop..
Obviously there is plenty of room for the diameter, and a 'thin' motor is also good.
What sort of power are you anticipating?
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