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Old Oct 03, 2013, 01:42 PM
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Originally Posted by jrb View Post
Smoke if you hook an outrunner up the 12VAC 3 phase power -- nope.
Yes, but it will also not run, at least not on 50 or 60Hz AC.
Anyone who thinks that a simple PM motor is a functional AC motor is quite mistaken.
Pete
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Old Oct 03, 2013, 01:59 PM
jrb
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Originally Posted by Lnagel View Post

Whatever

Larry
Exactly!
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Old Oct 03, 2013, 02:35 PM
An itch?. Scratch build.
eflightray's Avatar
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How Brushless motor ESC works?

Why not make one and learn as you go along --

seven diy brushless ESC designs
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Old Oct 03, 2013, 07:39 PM
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Originally Posted by Lnagel View Post
Both brushed and brushless motors have three coils that are moved through a magnetic field when spun by a drill press. That magnetic field will induce an identical AC voltage in the shape of a sine wave in those coils regardless of whether the motor is brushed or brushless. T
Most mechanically commutated DC motors (the small ones used for RC) are 2 phase (two windings) as this is much simpler for commutation (just two plates on the shaft). Very large DC motors might use more windings but this does make the commutator more complex.
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Old Oct 03, 2013, 09:14 PM
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Originally Posted by desertstalker View Post
Most mechanically commutated DC motors (the small ones used for RC) are 2 phase (two windings) as this is much simpler for commutation (just two plates on the shaft). Very large DC motors might use more windings but this does make the commutator more complex.
That may very well be. I don't know how many coils are normally used in most small brushed motors. All I know is that I was surprised to see that the small Mabuchi 380 motor I pulled apart had three coils. But it really doesn't matter how many coils are in any given motor. Any coil spinning in a magnetic field is going to have an AC voltage induced into it. It doesn't matter if there is one coil in the motor or if there are a dozen coils in the motor. It also doesn't matter if the motor is brushed or if the motor is brushless.

Larry
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Old Oct 04, 2013, 12:09 AM
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Originally Posted by desertstalker View Post
Most mechanically commutated DC motors (the small ones used for RC) are 2 phase (two windings) as this is much simpler for commutation (just two plates on the shaft).
Every RC brushed motor that I have seen (except a toy that I had as a kid) has 3 commutator sections.

Simple motors with 2 sections sometimes need a kickstart to get running.
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Old Oct 04, 2013, 01:10 PM
jrb
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Nice chart that shows PWM and how it simulates a voltage that varies when it doesn't vary in voltage.

Also, the right hand half of the VFD schematic sure looks an ESC & BL motor.
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Old Oct 04, 2013, 02:42 PM
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You have posted a drawing for a variable frequency drive.

Brushless DC motors used in RC applications don't work this way.

In the brushless motors that we use, only one phase (2 wires) is active at a time.

The PWM frequency is fixed and there is a circuit in the ESC which determines armature position by sensing the back EMF created in the unused phase which then allows the ESC to switch windings (commutate) at the appropriate time.

As has been stated numerous times, the only real difference between a brushless DC motor used in RC and a brushed motor is the technique used for commutation.
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Old Oct 04, 2013, 02:53 PM
An itch?. Scratch build.
eflightray's Avatar
South Wales U.K.
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A Google search on - 'how does a brushless motor controller work'

and one of the many answers --

http://www.anaheimautomation.com/man...otor-guide.php

just to give someone a chance to tell a brushless motor manufacturer they are wrong as well
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Old Oct 06, 2013, 10:56 PM
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Originally Posted by Martyn McKinney View Post
Every RC brushed motor that I have seen (except a toy that I had as a kid) has 3 commutator sections.

Simple motors with 2 sections sometimes need a kickstart to get running.
Bah your right, 3 sections 2 brushes. For some reason my brain decided 2 brushes meant only 2 windings
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Old Nov 04, 2013, 11:51 AM
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I was doing some research as well, and it turned out that searching for "Brushless DC Motor Control" is much more effective than searching for ESC, because you can find professional Electrical Engineers explain the principles in details.
My best find is a two-sessions YouTube video, "Brushless DC Motors & Control - How it Works":
Brushless DC Motors & Control - How it Works (Part 1 of 2) (10 min 33 sec)

Brushless DC Motors & Control - How it Works (Part 2 of 2) (7 min 23 sec)


Particularly interesting is the way the undriven coils are used to measure the speed, from Wikipedia, http://en.wikipedia.org/wiki/Brushle...electric_motor
"Because the controller must direct the rotor rotation, the controller requires some means of determining the rotor's orientation/position (relative to the stator coils.) Some designs use Hall effect sensors or a rotary encoder to directly measure the rotor's position. Others measure the back EMF in the undriven coils to infer the rotor position, eliminating the need for separate Hall effect sensors, and therefore are often called sensorless controllers."

This is my very first post in rcgroups. I felt the urge to write this because of the many different confusing opinions I saw in this thread. Personally I think that opinions should always be backed up by some kind of proof or references, especially when a technology is so widespread that plenty of information is available everywhere.
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Old Nov 04, 2013, 02:58 PM
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rlambert,

Well done. First post too.

Looks like you won't need to ask anything at all, on motors at least, but don't ask anything other than the most simple question on this or any other 'amateur' forum, as plenty of misinformation is available too.

'What a load of crap' or, more politely from another poster, 'respectfully you are all wrong'. I don't have a clue how they work, and reading this does not help at all. So I have decided that they can work however they wish to, as long as they do work. But I think I would believe your reference.

Ask 'Who keeps them up?' That's good one. It's either Newton or Bernoulli. You will then get a long discussion as to whether God wears a green robe or a red one, and you will still be undecided at the end. Meanwhile the pilot gets us from London to New York in a few hours and he doesn't know either. Nor does Mr Boeing.
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Old Nov 04, 2013, 03:05 PM
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Use translate option.
http://aeromodelismoelectrico.blogsp...na-un-esc.html

Manuel V.
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Old Nov 04, 2013, 06:53 PM
Wake up, feel pulse, be happy!
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United States, AK, Fairbanks
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Quote:
Ask 'Who keeps them up?' That's good one. It's either Newton or Bernoulli.
I was under the impression it was Schrodinger.

I was not under the impression it was Schrodinger.
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Old Nov 04, 2013, 07:14 PM
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Originally Posted by C₄H₁₀ View Post
I was under the impression it was Schrodinger.

I was not under the impression it was Schrodinger.
Love it!
Made me remember an very old video. There's this mad scientist. There's this cat, legs in an X, claws deep in the corners of a box. Doesn't want to go in.

PS: your post means you have been observed. Now you must make up your mind.
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