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Old Jun 11, 2011, 11:02 PM
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mattyhawk's Avatar
Oxnard, Ca
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Here is some prop data. All done with a Hobbywing 120A HV ESC, Turnigy 4S 5000mAh 20C batts (2 in series). This is a different ESC than I did with the no load tests.

APCE 10x7
31.43V
33.85A
1063.9W
13,000RPM

APCE 11x5.5
31.51V
34.36A
1082.6W

APCE 13x6
30.28V
57.71A
1747.4W

After playing around in motocalc, it shows like a confirmed 475kv. Still seems like the kv is wrong.
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Old Jun 11, 2011, 11:44 PM
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Here is the change I made:

After un-soldering the connections, I used the terminates with the light blue arrows as E1, E2, E3 (refer to picture on post #12) and were soldered together. S1, S2, S3 are the ends with red arrows pointing at them and they were the ESC phase wires.

BTW, it is difficult to see which is the correct terminate end in the middle. On the motor I have, the ends of the two winds, (S1 and E3) come between the same tooth on the stator. The strand closest to the hammerhead is the E3 and the furthest back is the S1.
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Old Jun 12, 2011, 07:09 AM
Jack
USA, ME, Ellsworth
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I'm not sure that anything is wrong here, Matty. The Kv thing is not really an exact science the way we measure them (often called the "raw" Kv rating).

If you used the same methods to get the 900 Kv you measure at the start as you are getting now, and did not actually remove any turns from the motor, I think it would be reasonable to expect to get the 520 Kv (900 x .58 = 520).

But other things can enter into it too I think, like minor differences in the lengths of the winds, the crossings and arrangements of the wires as they leave the windings and are terminated, etc., etc.

And the fact that the winding scheme table says that 8 poles, and the ABC wind is "not the best choice" is a factor? Maybe it is even the way you hold your mouth when you do the testing?

As one of the newesy guys into this I agonized over a lot of the details like how to measure Kv's, the arcane mathematics and theory discussed in places like the beginners guide to electric motors, and numerous web pages.

And in the end I think I've become pretty philosophical about just believing in the numbers I get and adjusting turn counts to get results relative to that. I've come to using the raw Kv I get from no load testing as a starting point and basing adjustments on just that using the predictions from Manuel_V's Turn Calculator 5 spreadsheet. That gets me results that I am happy with even if they are not dead on accurate.

I'm still not sure if motor winding is a predictable science or an art.

Jack
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Old Jun 12, 2011, 09:57 AM
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Thanks jack. I am trying to be realistic about the results here and your post helps me to have confidence in that. You just can't argue with consistent testing methods (right or wrong is another story) and the consistent results I get on this motor. The fact that motocalc was relatively in agreement with my findings on the prop suggests I am not too far off. The only conclusion is I made an error in my initial test of the unadulterated motor. In any case, with optimal airflow, it will hold >1700w for 15 sec with only a 5*C increase in temp. That has promise for the >2300w I want to cram down it's throat to get a H9 Sundowner to 130mph on 8S.
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Old Jun 12, 2011, 12:49 PM
Jack
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Your more than welcome, we're all learning something here I think.

Is the H9 a pylon racer?

That low temperature rise is encouraging for sure. That is one of the most telling things when I test a motor, I always look at that first.

At any rate you might have to really push it or settle for short duration bursts to get 2300W out of a 370 gram motor. That would be over 6 Watts per gram for that motor.

Jack
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Old Jun 13, 2011, 12:25 AM
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Very true, i will be bursting that motor. It is designed for 8s and 90a, so we will see how it does. If it gives up the ghost, I'll just rewind like I originally planned. It helps I have the motor in direct airflow with cowl ducting and the motor has the built in fan since it's for a heli. It is important to note, the motor was in direct airflow with no cowl for the test, but the small rise in temp was comforting. I tend to use in flight telemetry with temp and amp draw to take my motors to the very edge of life, throwing efficiency out the window. It's a fun challenge for me, kinda like what the NHRA guys do with the top fuelers.

Yeah, The hangar 9 sundowner is a pylon style pattern plane, 50 size. They safely go to 140mph, but that's about it.
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Old Jun 13, 2011, 03:09 PM
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So I took out the plane today with the t600. Good news. Plane was consuming 60a constant both in the air and static on an APC 12x12, so about 2000w. Nice thing is temp rise.

Ambient temperature was about 22*C.

Motor in air for a 10 sec burst speed run never went over 34*C in flight. On the ground after landing, it peaked at 42*C. I was measuring at the front of the motor, directly on the motor windings by the stator tube. I don't know if it's a 2500w+ motor, but it is happy as a clam at 2000w.
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Old Jun 13, 2011, 03:44 PM
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Tell your father in law and he'll deem you worthy if his daughter, finally

Vriendelijke groeten Ron
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Old Jun 13, 2011, 06:16 PM
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Quote:
Originally Posted by Ron van Sommeren View Post
Tell your father in law and he'll deem you worthy if his daughter, finally

Vriendelijke groeten Ron
Finally!
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Old Jul 05, 2011, 11:46 PM
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mattyhawk,

i wonder if i am on the right track here or not. but after studying this i have a question.

in the delta configuration one strand or group of wire is wound around 4 cores and is conected to the esc at each end.

so this means that that strand is capable acording to hobby king of having 90amps ran through it and a voltage drop across it of 29.6v or 8s wich is a lot..

but now you have the motor conected in a star configruation.

in the star configuration there you take 2 strands or groups ot wires each are wound around 4 cores and hook one of the ends to the other. this makes the 2 strands in series.

i am no ee so this is why i ask. since there are 2 loads or strands in series the voltage drops across each so when you put an 8s across the total of the 2 winds the one strand only sees 4s but is capable of 8 so should you not be able to hook more voltage to this motor in this configuration.

that is keeping the amps and heat down in the 90 amp or less range i would think you should be able to go to an 10 or 12s and theoretically 16s but am not sure and would realy like to know.
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Old Jul 06, 2011, 07:00 AM
Jack
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I'm not sure that you have the connections right as you describe them there, I do better with images of the two:

http://www.bavaria-direct.co.za/models/motor_info.htm

But the Delta and Wye terminations, at the same turn count, are really apples and oranges as you compare them for use with the same propeller. The RPM and current drops for the Wye but the torque goes up.

So depending on the prop being used and the plane (wing loading, drag, etc.) and considering that going from Delta to Wye can let you use a lighter battery, it is too complicated to predict say which is best. You may have to try them both in flight to really figure it out.

This is quoted from that same link, to reverse the situation (look at if from the Star vs Delta viewpoint) the factor is that going from Delta to Wye would lower the RPM and current by a factor of 0.58.

DELTA vs STAR (WYE)

For the same number of turns and wire thickness:

DELTA gives 1.73 higher power and amp draw than STAR

DELTA Kv (RPM) = 1.73 higher than STAR Kv while the Kt (torque) = 1.73 lower

With a STAR connection, 1.732 less turns need to be wound to get the same power (and Kv) as with DELTA

In case you're wondering: 1.73 = sqrt(3)

Jack
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Old Jul 06, 2011, 08:48 AM
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i agree with you on all of this as i read the manual also.

motors i always thought were rated in max voltage because of the relativity with amps. higher voltage same prop = more amps. i no there are other parameters but for simplicity we will go with this.

but my friend says that they have a max voltage because the break down of the wire or insulator from the fields. not exactly sure on this as he did not give a great explanation.

so here is why i am wondering if you can run more voltage..

look at the delta wind in your example. let say this motor config is rated at 3 molts max. if you put a voltage drop of 3 volts hooked to the first connection and the last connection currant should flow threw the blue wire run though its coils then to the other end it only sees 3 coils, there is a voltage drop across each wind so if the motor can only handle 3 volts max. each coil is only seeing 1 volt a piece. so each coil is rated at a max 1 volt. now i no that current can run threw the red wire an the the green one in this connection but it is my understanding that current flows threw the least resistance so i think that flow direction is very negligible. but i am not sure because i am no ee.

now look at the star motor. make the 3 volt connection from the red to the blue wire. that same 3 volts sees 6 coils of wire. each coil of wire only sees .5 volts. but we had predetermined that each coil could handle 1 volt max so we should be able to hook 6 volts to this connection then each coil will see the 1volt max.

your example also divulges something else to me which i had not thought of. the coils become much closer in the star configuration. thus the flux fields will be closer to each other counteracting what i have just been wondering about in the first place so it might be a wash.

sure would like to no. its very interesting..

later Andrew K
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Old Jul 06, 2011, 10:38 AM
homo ludens modellisticus
Ron van Sommeren's Avatar
The Netherlands, GE, Nijmegen
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Quote:
Originally Posted by jackerbes View Post
... The RPM and current drops for the Wye but the torque goes up. ...
Torque per Amp่re (Kt) goes up, not torque by itself. In SI units Kt x Kv = 1

Quote:
Originally Posted by jackerbes View Post
... So depending on the prop being used and the plane (wing loading, drag, etc.) and considering that going from Delta to Wye can let you use a lighter battery, it is too complicated to predict say which is best. ...
Rewind a wye terminated motor with 1,73 (= sqrt(3)) as many winds and terminate it in delta. You end up with same motor. Wye has the advantage of not having (parasetic) recirculating currents because it is not a closed circuit as delta is.

Quote:
Originally Posted by 57sailplane View Post
... motors i always thought were rated in max voltage because of the relativity with amps ...
Current depends on load (prop size). Current is what counts, current kills (heat). Not voltage, not power (Watts). Voltage determines rpm and as long as motor does not break down mechanically, you're okay. Insulation can withstand few hunderd Volt. Motor can run at any voltage as long as you keep current down by reducing the load (prop pitch and diameter).
Motor current in Brushless Direct Current (BLDC) type motors wants to go up squared with voltage, and cubed with Kv.

Quote:
Originally Posted by 57sailplane View Post
... look at the delta wind in your example. let say this motor ... ... then each coil will see the 1volt max. ...
A motor is not a simple resistor (or several resistors), neither are the coils. Otherwise current would go up linearly with voltage. There's also induction to consider PLUS the fact that it is a three-phase system. See these pictures and links:
http://www.rcgroups.com/forums/showt...0#post18686818
And
www.consult-g2.com -> course

Quote:
Originally Posted by 57sailplane View Post
... else to me which i had not thought of. the coils become much closer in the star configuration. thus the flux fields will be closer to each other counteracting ...
The (laminated) iron captures the flux, that's what the iron is for, no flux outside the iron. Lamination reduces eddy currents. A massive stator would give very poor performance, motorwise, and excellent performance stove-wise.


Vriendelijke groeten Ron
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Old Jul 06, 2011, 11:33 AM
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Wow Ron, I was going to respond, but your explaination is perfect, and more knowlegable than mine.

On the topic of actual tested data for the motor, I think I have found the max for the modified motor, which seems to be about 3700W. The 90A max from HK is not too far off. Any higher current, I would expect the efficiency to drop hard.

I recently (last weekend) ran the modified motor at 10S at 94A, 12x12 APC with fair to good cooling. Remember, this motor has semi-ceramic bearings in it. With multiple 15 second pulls for 3 minute flight, the motor temperature increased to 30-32*C max in the air with ambient at around 21*C. After another 15 second WOT pull, I landed imediately and found a peak of 45*C increase on the ground.

This is really a very nice motor, one of the best out of the box motors I have found from hobbyking.
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Old Jul 06, 2011, 04:10 PM
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thank you ron,

your explantion puts me back to the way i origanally thought about motors.. keeping an eye on the amps and over heating. the rise in voltage raises the amperage when you keep the same load....

so are all motors wound with such high voltage insulation?

thanks, andrew K
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