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Electric General Discussion
› need some help understanding electric heli's
10-25-2004 02:51 AM  13 years agoPost 1
Cobraman

rrApprentice

USA

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Ok guy, Im going to be gettin a electric heli here soon, probally a hornet II. I was wondering if you use a governor on them, and or can you? If not how do they do 3-D without a governor or and idal up setting on it? There seems to be something that i dont undersant here and im not sure what. Maybe its just a brain fart LOL. Thanks guys

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10-25-2004 05:12 AM  13 years agoPost 2
Saint728

rrProfessor

Honolulu, Hawaii

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You can either use a governor or you can use a regular throttle curve and set it up that way? The choice is up to you. I use a regular throttle curve even though I have a governor mode on my ESC. I think it's easier to adjust the throttle curve and fine tune it to your liking with the non governor mode.

Take Care,
Cheers, Patrick

Check the hotties in my Gallery
http://rc.runryder.com/helicopter/gallery/9019/?all=photo

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10-25-2004 08:13 PM  13 years agoPost 3
Razmo

rrKey Veteran

Chicago

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Cobraman,

Just to clarify what Saint728 meant, most ESC's (electronic speed controllers) come equipped with governor mode software so no external governor is needed. You have the choice of using either the governor software or a throttle curve as Saint728 mentioned.

Raz

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10-26-2004 02:14 AM  13 years agoPost 4
Cobraman

rrApprentice

USA

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ok thanks

ok thanks guys,,, im just getting into electrics and im kinda anxious to get started. I didnt realize the ESC for electric had governor built in. So whats some of the brand names of some good ESC? thanks again guys

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10-26-2004 03:08 AM  13 years agoPost 5
KnimRod

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Central Michigan

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Just FYI, there is no governor mode for a brushed motor. Only brushless motor systems offer the governor option.

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10-27-2004 01:24 PM  13 years agoPost 6
askman

rrApprentice

willamette valley,​Oregon

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well, there are several different brand of esc.

these are fairly common:

Hacker/Jeti.
Castle Creation
kontronics
Schuelze

CC stuff is most common in US and most used in smaller helis. cc10 or 25.

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11-14-2004 12:59 AM  13 years agoPost 7
darrens

rrKey Veteran

United Kingdom

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You will notice brushless motors have 3 wires. So i am told, one of these feeds back the info regarding RPM to the speed controller and this is what the govener uses. I fly a brushless set up on an Eolo in govenor mode and it works great. you just set the throttle % to what you want and this sets the head speed. e.g Normal mode at 70% may equal 1600rpm, Idle up 1 at 80% 1700rpm and so on.
With brushless and 8000mah lipos on my machine I get an average 20-25 min run time. You'll love it when you get it!

He who dies with the most toys is the winner!

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11-14-2004 12:40 PM  13 years agoPost 8
rscamp

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Ontario, Canada

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Brushless DC motors have three wires because they are actually three phase, synchronous, permanent magnet AC motors. The three phases, which are energized by pseudo sine waves 120 deg. apart produced by the brushless speed control, create a rotating magnetic field that pulls the rotor around.

Sensorless controllers use other means (back EMF or the like) to sense rotation and provide commutation timing. Sensored controllers get their commutation timing from hall sensors in the motor.

Rob

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11-14-2004 06:37 PM  13 years agoPost 9
KnimRod

rrApprentice

Central Michigan

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Brushless DC motors have three wires because they are actually three phase, synchronous, permanent magnet AC motors. The three phases, which are energized by pseudo sine waves 120 deg. apart produced by the brushless speed control, create a rotating magnetic field that pulls the rotor around.
Actually, Brushless DC motors are not AC motors per se. The motor system operates from DC current. A brushed DC motor is internally commutated from a DC current applied to three motor windings through brushes and a rotating commutator. A brushless DC motor operates on the same principle except the commutation is performed externally through an electronic commutator (The ESC). The fact that the brushless DC motor mechanism has three phases of electrical impetus is no different than the three phases of impetus within the brushed DC motor.

This has been covered before in some detail: http://www.runryder.com/helicopter/t81091p1/

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11-14-2004 07:50 PM  13 years agoPost 10
rscamp

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Ontario, Canada

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I guess you missed the term "pseudo".

Rob

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11-14-2004 11:17 PM  13 years agoPost 11
TMorita

rrApprentice

SF Bay Area, CA

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I'm gonna be at a dead horse...but they are AC motors.

Let's say you have three wires coming out of a motor, and it's wound delta. So you have WIre A, B, and C.

Between A and B you have Phase 1, between B and C you have Phase 2, and between C and A you have Phase 3.

So now you power the wires in this order:

ABC
+--
-+-
--+
+--
-+-
--+
...

If you look at the Phase 1 (across wires A and B), then on the first clock it winds up being powered A+ and B- then on the next clock A- and B+
.
So, from the motor's perspective it is seeing AC because the current flows first in one direction, then the opposite direction for each set of windings.

Toshi

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11-14-2004 11:33 PM  13 years agoPost 12
KnimRod

rrApprentice

Central Michigan

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Sorry Toshi. That's just wrong. It aint a motor without a commutator. You can beat the dead horse all you want but it wont make a brushless DC motor an AC motor.

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11-14-2004 11:53 PM  13 years agoPost 13
rscamp

rrVeteran

Ontario, Canada

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KnimRod.

If you fed three phase AC to a brushless "DC" motor, would it run?

If so, why? If not, why not?

Rob

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11-15-2004 12:05 AM  13 years agoPost 14
KnimRod

rrApprentice

Central Michigan

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Probably not. The same could be said for running a DC motor from an AC current.

The brushless DC motor is commutated in almost the same fashion as a brushed DC motor. Speed is predominantly a factor of voltage and it is a function of the brushless ESC to commutate the motor at precisely the correct rotor angle. The ESC (commutation) is synchronized to the motor not vice versa.

If you could attach an oscilloscope to the windings of a brushed DC motor, you would see an almost exact correlation to what the brushless ESC provides to the windings of a brushed motor. The only difference is that a brushed motor uses brushes and the brushless motor does not.

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11-15-2004 12:37 AM  13 years agoPost 15
rscamp

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Ontario, Canada

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It would work if the frequency was synchronized to the rotor speed though, would it not?

Rob

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11-15-2004 02:02 AM  13 years agoPost 16
KnimRod

rrApprentice

Central Michigan

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What's your point? There is indeed a way to synchronize the frequency. It's built into every brushless DC motor speed control.

For all practical purposes, a brushless DC motor is useless without the commutation from the ESC.

I really didn't set out to debate this issue. I only wanted to set the record straight. A lot of people a whole lot smarter than me have already defined the difference.

From the "Handbook of Small Electric Motors", section 5.1:
"Brushless direct current motors (BLDC) are so named because they have a straight line speed-torque curve like their mechanically commutated counterparts, permanent-magnet direct-current (PMDC) motors. In PMDC the magnets are stationary and the current carrying coils rotate. Current direction is changed through the mechanical commutation process. In BLDC motors the magnets rotate and the current carrying coils are stationary. Current direction is switched by transistors. The timing of the switching sequence is established by some sort of rotor-position sensing."

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11-15-2004 11:20 AM  13 years agoPost 17
rscamp

rrVeteran

Ontario, Canada

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I dont' disagree with your point. My point is, we're getting hung up on the name. It is common practise to call these DC motors but they could just as easily be called AC because of the way they work. The way they create a rotating magnetic field is almost exactly like a three phase AC motor, the only difference being the field frequency is timed to rotation. The current in our high power controllers is even ramped to form a "pseudo" sine wave...

Rob

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11-15-2004 03:44 PM  13 years agoPost 18
KnimRod

rrApprentice

Central Michigan

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Yes, but by using that logic, you would also have argue that all DC motors are "AC" since they all use a rotating magnetic field and their "commutation" results in the reversal (alternating) of current in the windings.

My point is, that a "brushless DC motor" is just that. It's not an "AC motor" and it's not a "brushless AC motor" which have rather unique definitions and performance parameters of their own.

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11-15-2004 08:45 PM  13 years agoPost 19
CRAZYKEV

rrVeteran

Cincinnati,Oh -​U.S.A.

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If you run power through the brushless motor the output works exactly like an alternator in your car. The current running through a brushless is alternated through the three wires. I have seenand talked with one of our runryder members who uses an AXI brushless motor as an alternator (not generator) on his gasser photo heli to power the cameras and accesories

Kev

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11-15-2004 09:41 PM  13 years agoPost 20
darrens

rrKey Veteran

United Kingdom

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With my weak 3 wire discription, I never once assumed to open this can of worms!!!! Gentlemen, corners please!

He who dies with the most toys is the winner!

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