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View Full Version : Strange little motor rewind – 2210?


wingnutt
12-31-2009, 05:17 PM
I am at a loss on this one. An FB gave me a motor he picked up off of ebay which he could never get any decent power out of. I am not sure what size class it fits into and I hope someone here can shed some light.

Description –
The motor is an outrunner that has light blue anodizing and a black flux ring. There is a label on it marked with “KV (some Chinese symbol) / 1000 RPM/V”. The motor also came with a backside AXI type prop adapter and an ‘X’ mount as well. Opening it up, I found the following:

Stator Size: 22.7mm OD X 9mm Thick X 10mm ID for Bearing Tube
Stator Teeth: 12
Magnets: 14 Count and 10mm long
Wire: 4-5 strands of 31Ga
Termination: Delta

The drill press test gave a kV of 1017, so that at least was close enough. I tried a GWS 9x5HD prop and it pulled 8A on 3s and pulled 12A on a 9x7.5E APC. Something was just not right here. Even an OK 1000kV motor should pull almost twice the current on these props.

Rewinding –
I am really not sure how many turns or exactly how many strands were used on this thing since the windings were ‘secured’ to each other with CA and were so thin that I kept breaking strands. I will give the benefit of the doubt and say 5 strands even though it was acting like it had only 4. It took some time to free the windings from the stator without tearing up the decent powder coating.

As far as how to rewind it to get near 1000kV (for a glider or 3D), I am not sure. The stator is 9mm wide, but the magnets are 10mm long. So is this a 2209 or a 2210 class motor? My best guess is that it is a 2210. So using Dave North’s thread of rewinding a 2210 and 2213 I figured either a 13 turn LRK terminated Delta or an 8/7 turn adLRK wind terminated Wye would do it. Using 24Ga on the 13 turn LRK left too much open space, so I wound it with 22Ga and the 8/7 aDLRK. This should give me the power handling and the low throttle response I am looking for. After winding the cogging feels MUCH better and shorting two leads makes the motor much harder to turn than when tried with the original wind.

I hope to get a chance to throw it on the drill press today for the resulting numbers. As soon as I do, I will post back.

If anyone has dealt with this motor before, please share what you know.

wingnutt
01-01-2010, 04:33 PM
And the answer is...

It is acting like a 2209. The 8/7 adLRK gave a kV of 1220. So i will need either a 19 turn (10/9) Wye, or a 32 turn Delta to get to 1000kV.

Dang!

wingnutt
01-05-2010, 01:16 PM
Finished the rewind yesterday. Decided on a 10/9 adLRK wind with 24Ga which should result in 950kV. There is a bit more open space than I would have liked, but it is a free motor and am curious as to what it is capable of. Will try to test today or tomorrow to be sure.

wingnutt
01-11-2010, 02:40 PM
Got to test the motor some with the 10/9 adLRK, Wye wind. The drillpress test came up with a 976.5kV (2.275 VAC average from 2985rpm). when testing it with a freshly charged 2200mAh pack and a GWS 9x5HD prop, it pulled 9A @ 8500rpm giving 23.2oz of thrust. Not too bad, but still could be better.

My requirements for this motor have changed now. Instead of needing to spin a 9x5 folding prop, it needs to spin a 8x4.5 folder. So, I think I will go back with a 1235kV wind by using 13 turns per tooth Delta and 24Ga wire. This is equal to the original 8/7 Delta wind with 22Ga, but should still yield a lower Rm. Only testing shall show.

wingnutt
01-27-2010, 09:18 PM
I rewound it with 10 turns of 24ga wire per tooth terminated Delta.

Measuring it on a drill press at 3000 rpm, I got
1.402 V
1.405 V
1.407 V
This averages out to 1.405 V. Calculating kV I get (3000/1.405) / 2^0.5 / 0.95 = 1590kV. This is all well and good, so I hook it up to my test system and with 12.28V of input to the ESC I get a no load current of Io = 1.4A at 19710 RPM.

Calculating Rm from this should be Rm = ((Vin – (RPM/kV)) / Io. Entering my data into the formula gives an Rm = -0.085. Negative Rm? Looking back, I see that reverse calculating kV with 19710 RPM / 12.28V = 1605kV. So either my kV calculation is off or my RPM measurement is off. Double checking everything I get the same measurements. I am figuring that the “0.95” figure is not too accurate.

Rm a different way –

Using my newly constructed, Lucien designed milliohm meter, I find a DC resistance of 0.055 Ohms. We know that Rm is dynamic, so I tried measuring it dynamically. Chucking the motor shaft back into the drill press, I measure a generated voltage of Vg = 1.407V (same as before). While the drill press is still spinning, I connect a 5 Ohm, 1% resistor between the leads. This gives me a load voltage of Vl = 1.390V. Now the winding resistance while running should be Rm = Rl * ((Vg/Vl) – 1) = 0.0612 Ohms. I still think this is rather low, but believe it is due to only testing at 3000 RPM. I will chuck the motor into my Dremel and test it at a range of RPMs and see what I get.

So what I want to know is, how accurate is the “0.95” factor in the kV equation and is a motors Rm in a generator mode the same as in motor mode? Any ideas?