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Home✈️Aircraft🚁HelicopterHelicopter Main Discussion › Learn something new everyday on electric motors?
07-23-2012 10:35 PM  8 years ago
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Wedge77

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St. Charles Missouri USA

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Learn something new everyday on electric motors?
So Im putting my electric 640 together last night, and i bolt up the motor and am checking the lash on the pinion and main gear. the first couple times i spin the head, it feels really good.. after a few minutes im double checking it, and i grab the wires from the motor and hold themm in my palm as i spin the head again. this time the head feels almost like the mesh is locked up? REALLY hard to turn and the faster I tried while looking at the mesh, the harder it got. so i sit back, look at it again, grab the frame this time, and give her a spin and its easy again. Now im scratching my head. after a few minutes, the wires are going back so I grab them again, hold them in my palm and the head is really hard to turn.. seems holding the 3 wires coming from the motor together while spinning it.. is producing some sort of electrical current through the motor and acting like a brake.. Im not up on brushless motors that much yet, so kinda took me by surprise, anyone else ever find this.. and what cause it?
JR NEX E8, 12 cell
Goblin 630, 12 cell
Vibe 50N Fbl
Century E640 Fbl, 12 Cell
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07-23-2012 10:40 PM  8 years ago
Solmanbandit

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Tucson , AZ

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Never heard of it or have had it happen to me. Was the esc plugged in?Trex 700E / Trex 500 ESP - Ikon/ HD 500 - Ikon 2/ Goblin 500 Ikon 2
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07-23-2012 10:58 PM  8 years ago
dkshema

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Cedar Rapids, IA

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If you try to spin the motor with its terminals shorted together it will be difficult to turn.

When you turn the motor, it is acting as a generator (coil of wire passing through a magnetic field will do that every time), creating a voltage at the terminals, and there is current available.

Normal behavior, don't fret. Go fly.
-----
Dave

* Making the World Better -- One Helicopter at a time! *

Team Heliproz
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07-23-2012 10:59 PM  8 years ago
scott011422

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Sycamore, illinois

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Yes, this is 3 phase cogging. All 3 phase motors should do this. A 3 phase motor is a generator that you run power to. So, as you turn the motor shaft, you are generating a small amount of current. Shorting the wires together creates a small magnetic field. Actually, if you were to turn that shaft with a power drill, you would probably see some arcing between he wires.
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07-23-2012 11:03 PM  8 years ago
McKrackin

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Lucasville,Ohio

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That's a BLS motor on the back of my nitro.
The tail gear drives it and it generates the power to run my electronics and charge my RX pack.

I literally never use the word literally right.
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07-23-2012 11:24 PM  8 years ago
Egroeg

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Cyprus

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If you touch the 3 phases together, the motor will definitely turn harder because the current generated will act against the magnetic field of the turning magnets.
On sailplane motors, you want the BRAKE ON feature when using folding propellers because the wind will otherwise keep the prop spinning and the centripetal force will keep the prop open which obstructs the plane during flight.
By selecting brake on,in the programming of the ESC that keeps the motor hard to turn when throttling down which forces the prop to close.
This is basically shorting the phases through the ESC .
No Pitch...No Fun!
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07-23-2012 11:27 PM  8 years ago
Egroeg

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Cyprus

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@McKrackin , hi I have seen this before.
Does A)reduce power to the rotor.
B)needs a regulator of some sort.
C)how d' you hook up the motor onto the rotating shaft?
Thanks.
No Pitch...No Fun!
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07-23-2012 11:31 PM  8 years ago
McKrackin

rrProfessor

Lucasville,Ohio

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@McKrackin , hi I have seen this before.
Does A)reduce power to the rotor.
B)needs a regulator of some sort.
C)how d' you hook up the motor onto the rotating shaft?
Thanks.
PM sent
I literally never use the word literally right.
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07-24-2012 05:54 AM  8 years ago
GetToDaChopper

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Las Vegas , NV

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i would like to know all that to MK ?    ▲
  ▲ ▲
▲ ▲ ▲ One of a Kind !!!
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07-24-2012 06:48 AM  8 years ago
adamsz06

rrVeteran

Geilenkirchen Germany

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What kind of output are you getting?R.I.P. Roman
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Home✈️Aircraft🚁HelicopterHelicopter Main Discussion › Learn something new everyday on electric motors?
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