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How does a brushless motor work?

Old 07-18-2006, 05:04 PM
  #76  
cap85king
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Default RE: How does a brushless motor work?

If you go onto www.wikipedia.com and search "brushless motor", they have all kinds of motor info, a lot I didn't understand, (Wikipedia has long articles). Here's the "basic" info from the site:

A brushless DC motor (BLDC) is a DC electric motor that uses an electronically-controlled commutation system, instead of a mechanical commutation system. (The rest of this article assumes the reader is familiar with the principles of electrical motors.)


Because of induction of the windings, power requirements, and temperature management some glue circuitry is necessary between digital controller and motor.
The poles on the stator of a two-phase BLDC motor. This is part of a computer cooling fan; the rotor has been removed.
B=Magnetic Flux. It is uploaded as SVG, the vektor-graphics-format, that anybody can edit.Three subtypes exist:

The three-phase AC synchronous motor type has three electrical connections
The stepper motor type may have more poles on the stator.
The reluctance motor has all its poles on the stator, and a magnetic core on the rotor.

In a conventional (brushed) DC-motor, the brushes make mechanical contact with a set of electrical contacts on the rotor (called the commutator), forming an electrical circuit between the DC electrical source and the armature coil-windings. As the armature rotates on axis, the stationary brushes come into contact with different sections of the rotating commutator. The commutator and brush-system form a set of electrical switches, each firing in sequence, such that electrical-power always flows through the armature-coil closest to the stationary stator (permament magnet.)

In a BLDC motor, the brush-system/commutator assembly is replaced by an intelligent electronic controller. The controller performs the same power-distribution found in a brushed DC-motor, only without using a commutator/brush system. The controller contains a bank of MOSFET devices to drive high-current DC power, and a microcontroller to precisely orchestrate the rapid-changing current-timings. Because the controller must follow the rotor, the controller needs some means of determining the rotor's orientation/position (relative to the stator coils.) Some designs use Hall effect sensors 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. (The BLDC motor has a trapezoidal backemf, while a brushless AC motor has a sinousoidal backemf.)

BLDC motors can be constructed in two different physical configurations: In the 'conventional' configuration, the permanent magnets are mounted on the spinning armature (rotor.) The stator coils surround the rotor. In the 'outrunner' configuration, the radial-relationship between the coils and magnets are reversed; the stator coils form the center (core) of the motor, while the permanent magnets spin on an overhanging rotor which surrounds the core. In all BLDC motors, the stator-coils are stationary.

[edit]
Comparison with brushed-DC motors
BLDC motors offer several advantages over brushed DC-motors, including higher reliability, longer lifetime (no brush erosion), elimination of ionizing sparks from the commutator, and overall reduction of electromagnetic interference (EMI.) BLDC's main disadvantage is higher cost, which arises from two issues: First, BLDC motors require high-power MOSFET devices in the fabrication of the electronic speed controller. Brushed DC-motors can be regulated by a comparatively trivial variable-resistor (potentiometer or rheostat), which is inefficient but also satisfactory for cost-sensitive applications. BLDC motors need a more expensive integrated circuit, called an electronic speed controller, to offer the same type of variable-control. Second, when comparing manufacturing techniques between BLDC and brushed motors, many BLDC designs require manual-labor, to hand-wind the stator coils. On the other hand, brushed motors use armature coils which can be inexpensively machine-wound.

BLDC motors are considered more efficient than brushed DC-motors. This means for the same input power, a BLDC motor will convert more electrical power into mechanical power than a brushed motor. The enhanced efficiency is greatest in the no-load and low-load region of the motor's performance curve. Under high mechanical loads, BLDC motors and high-quality brushed motors are comparable in efficiency.

Old 12-26-2006, 10:52 AM
  #77  
cujo_77
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Default RE: How does a brushless motor work?

I found this and I think it easily explains how a brushless engine works.
http://electronics.howstuffworks.com...less-motor.htm
Old 01-11-2007, 11:32 PM
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Default RE: How does a brushless motor work?

please pass this around!!!If anybody comes across a person named BRAEDON ROLLER or FREEMAN DO NOT buy from him!!! He will rip you off to no end. Hes a liar a cheat and will lie and lie to saying he is shipping you products and wont do so. I repeat DO NOT BUY FROM BRAEDON ROLLER or freeman!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!His email is [email protected] His Address is PO Box 393 Morongo Valley ,CA 92256
Old 01-12-2007, 02:16 AM
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irishpunk1977
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Default RE: How does a brushless motor work?

If anybody comes across a person named BRAEDON ROLLER or FREEMAN DO NOT buy from him!!! He will rip you off to no end. Hes a liar a cheat and will lie and lie to saying he is shipping you products and wont do so. I repeat DO NOT BUY FROM BRAEDON ROLLER or freeman!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!His email is [email protected] His Address is PO Box 393 Morongo Valley ,CA 92256
Old 01-13-2007, 10:17 AM
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Ron v. Sommeren
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Default RE: How does a brushless motor work?

/* deleted */
Old 02-06-2007, 01:30 PM
  #81  
JCORLEY
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Default RE: How does a brushless motor work?


ORIGINAL: Matt Kirsch

A popular myth that I fell victim to myself. Turns out that even though the ESC does switch the polarity back and forth on the various phases of the motor to make it turn, it's still putting out DC voltage. It's similar to AC, but the wave is a "square" type. Unlike AC, where the voltage gradually changes from maximum + to minimum -, producing a "sine" wave, this switched DC changes from full + to full - instantly.

The picture below kind of shows what I mean. This is what you'd see on the screen of an oscilliscope if you compared true AC to what the brushless ESC is doing, sort of, kinda, maybe
would this be the same as pwm and what changes with rpm height or width
Old 02-16-2007, 03:18 PM
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Default RE: How does a brushless motor work?

With PWM the longer the "on" time the higher the effective voltage, resulting in increased RPMs, this part of a brushless ESC is essentially the same as in a brushed controller, though brushed controllers tend to use a lower frequency for PWM.
The PWM is performed before the commutation/switching part of a brushless ESC, the PWM is the means used to control the speed by varying the effective voltage provided to the motor. With PWM the width of the pulse increases as the throttle is increased until the the DC voltage is "on" all the time at full throttle, this is the opposite of an AC Thyristor type control/dimmer that cuts off the voltage at variable levels to reduce the average voltage.
Brushless motors are commutation mode motors just as any brushed motor, only the mechanical commutation has been replaced by electronic commutation provided by the controller.
True AC motors do not have a Kv rating, as they are controlled by the frequency of the AC current, not the voltage applied. No AC motor on line or mains current can exceed 3600 RPM (60Hz) and induction type motors "slip" about 50 RPM below their synchronous speed at no load. Thats why brushed series wound motors are used for so many applications on AC, it's the only way to get 30K RPM out of your Dremel tool or any other appliance that requiers higher RPMs than AC motors can provide. Series wound brushed motors while used mainly on AC today, are classed as "universal" motors as they will run on AC or DC, brushed permanent magnet motors on the other hand run only on DC.
Regards,
Pete
Old 03-30-2007, 04:55 PM
  #83  
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Default RE: How does a brushless motor work?

rotflmao
ORIGINAL: bil2

Scott, these guys are ALL wrong. Actually there's a bunch of tiny midgets that run back and forth inside the motor when you flip the switch on/off. The confusion arises because they run in a RECTANGULAR square trapizoidal sinusoidal rectal shaped direction, thus leading to MAGIC! (The easiest explanation is always the correct explanation. Magic works.) No thanks are necessary. Bil2
Old 06-16-2007, 12:32 PM
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Default RE: How does a brushless motor work?

Great thread thanks answered all my questions
Old 07-24-2007, 11:23 AM
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Default RE: How does a brushless motor work?

To correct something that was posted early on in this thread, Voltage does not flow. Current does.
Old 07-29-2007, 01:22 PM
  #86  
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Default RE: How does a brushless motor work?

Wow, I never really knew what operated it because of the 3 wires running out the back. Good question to ask.
Old 08-16-2007, 11:34 PM
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mambamax
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Default RE: How does a brushless motor work?

im going to invest in the ''momba max'' brushless sistem anyone that can tell me if the pastic gearing will work? or do i have to upgrade to alloy?



MAX
Old 08-16-2007, 11:38 PM
  #88  
mambamax
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Default RE: How does a brushless motor work?

im selling my revo anyone interestid?
Old 08-16-2007, 11:40 PM
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mambamax
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Default RE: How does a brushless motor work?

i ask only 375 for a well running revo
Old 11-06-2007, 03:03 PM
  #90  
shinob1
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Default RE: How does a brushless motor work?

In regards to running two brushless motors on one rc ESC, it is not possible in either series or parallel. However, while it might be more expensive, two brushless motors on two ESC does work. If you have a programmable controller, you can set it up however you want, linking two channels to run on one stick, and trimming just the channels to get a "close match", i.e. both pulling/pushing at near the same rpm, or you can run each on its own stick, which i find personally to be quite fun, it opens up a new world of possibilities. Just remember if so inclined, you can only use one ESC as the BEC, otherwise you will ruin electronics, so make sure your set up properly that way. You will also be heavier because you will be flying with two battery packs as well, i guess it might be possible to split on pack, but that jsut seems like a bad idea to me. As for limits yes there are some. RPMs (to many and things break/shatter... like you magnets... sob), HEAT (to much and you will demagnetize your magnets... again... sob) are the most common two. As for torque, its not like on brushed motors, which is why you find most brushless motors to have a Kv rating and not a turn rating. You torque depends on how much power, i.e. Amps, you can supply to your motor. However, the higher the Kv, the hotter it will run. If you are in the car area you might find it helpful to invest in a temperature gauge (Venom Temp here personally).
im going to invest in the ''momba max'' brushless sistem anyone that can tell me if the pastic gearing will work? or do i have to upgrade to alloy?



MAX
And for the guy who asked about a mamba and his plastic gears, you can use plastic, but when they wear out and they will, replace them with something quality, otherwise you will keep eating up transmission repair costs.
and for sigman, yes if i understand you correctly that is how its done, but there are screws you have to loosen too. You should be able to go to horizonhobby.com and find out for your motor specifically. I think I've taken up enough space now....
Old 11-06-2007, 03:22 PM
  #91  
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Default RE: How does a brushless motor work?

Hi shinob 1,
Good post, but one small quibble, turns and Kv are directly related, higher turns = lower Kv. Axi and many other motors give the number of turns in there numbering eg. Axi 22-12-34, 34 turns 720Kv.
To my knowledge BLDC motors are the only non- brushed motor to have a Kv rating. True AC motor do not have Kv ratings, their no load RPM is determined by number of poles per phase, frequency and the degree of slip in the case of asynchronous induction motors. The Kv rating is normally only associated with motors that run under the principle of commutation, traditionally only applied to brushed motors, but now with the development of BLDC motors sometime in the early 70's, also to motors without brushes.
Pete
Old 11-07-2007, 09:42 PM
  #92  
shinob1
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Default RE: How does a brushless motor work?

Thanks Pete for the clarification on that. I didn't mean to separate them like that. In my experience, and I run RC cars and planes, brushless motors are listed with Kv rating, especially on the aircraft side. Sometimes they only list a turn rating, or they'll provide both. I just wanted to emphasize that point that when talking brushed motors, on given motor size, say 550, it will lose torque as the turn rating decreases in value and gain an increase in rpm. (because a turn rating does involve torque, and when viewed properly the turn rating on brushless motors is really saying it is equivalent/surpasses a NN-turn brushed motor for the kv range... that make sense?) The wind (single, double, triple, and quad), as I understand from a hobby RC perspective, helps to determine where on the rpm range the motor will have the highest torque. Yes there is more to it, but generally when determining how many winds of a given turn would be chosen for a specific car/truck/boat/plane, it is where in the rpm range the torque is needed that will decide. But when dealing with brushless motors, again from a hobby perspective, the motor has close to the same torque through the entire rpm range. The way they wind the wires determines the Kv. The torque comes from the ability to supply the amps needed to spin the rotor load, more easily done in the brushless arena. Clearly I am not a physicist, but I do try to be knowledgeable where my investments are concerned. Please correct me on anything I may have portrayed obscurely or inaccurately.
Old 11-19-2007, 05:45 PM
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Default RE: How does a brushless motor work?

Has anyone here built a b/l from a kit - were you happy with the results - any issues.... [sm=spinnyeyes.gif]

Has anyone tried a kit from these guys?? thanks BD

http://www.innov8tivedesigns.com/
Old 11-20-2007, 04:28 AM
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Default RE: How does a brushless motor work?

I've been following this thread and all the techno babel is good to know info... (depending on your level of schooling in that sort of stuff)

But, (Please, LESS Techno-Babel) what are the difference between and InRunner or an OutRunner????
I see tht the can and venting are different and some of the InRunners I have seen have what looks to be ridges along the outside (Heatsink???)
Old 11-20-2007, 02:48 PM
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bil2
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Default RE: How does a brushless motor work?

The difference between the INrunner and the OUTrunner is easy.
Without techno-babble, the OUTrunner does this: the outer case (aka can) spins. The prop/ adaptor is bolted on the case.
On the INrunner, the shaft going through the middle spins. The outer case stands still.

The difference this makes is that the OUTrunner is swinging those magnets (inside the case) around. The weight of them spinning creates a lot more torque. Since you have a lot of torque, you don't need a gearbox to spin the prop - it can be bolted directly to the spinning case.

On the INrunner, you almost always have to use a gearbox to gear down the motor, thus creating the torque needed to spin the prop. Gearbox=unnecessary complications, noise, breakage.

Hope this helps,
Bil
Old 01-15-2008, 05:37 PM
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shinob1
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Default RE: How does a brushless motor work?

Having weight spin does not create more torque...? (Physics)
Old 01-16-2008, 09:35 AM
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Default RE: How does a brushless motor work?

I wonder why the original radial engines - you know, the ones where the engine spun, and the crankshaft remained in place? - why they went away? Was it torque? (yes - physics).
Ever ponder why your front wheel drive vehicle has "torque" steer? More horsepower = more "torque" steer? I suspect it has to do with "torque."
Maybe it should be called "inertia" but its not, its called "torque."
Old 01-16-2008, 02:37 PM
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Default RE: How does a brushless motor work?

The WWI rotary engines disappeared for good reasons. As they had greater rotating mass than a radial engine, they created more gyroscopic progression. The rotary engine was not able to be throttled, they ran at full power and they "blipped" the ignition on/off to control power for taxing and landing (wow, sounds sorta like PWM controlling our electric motors)
I've been to Old Rheinbeck, so I've had the pleasure of hearing them actually run[8D] ,Ah, the sweet smell of Castor oil in the morning
Pete
Old 01-17-2008, 02:03 PM
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shinob1
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Default RE: How does a brushless motor work?

Let me say it again. Outrunners do not gain additional torque from having the can and magnets spin simply due to weight. In physics torque is a measure of how much a force acting on an object causes that object to rotate. One more time, outrunners do not gain additional torque from having the can and magnets spin simply due to weight. Nor am I familiar with any sort of combustion engine that rotates around its crank shaft. Radial engines are simply pistons arranged in a circle, which connect to a central hub. The hub goes around and around (not spinning though)... Rotating the crank shaft...Not the engine... Rotary engines (Wankel) are different... As they use a spinning rotor that performs the tasks of a conventional piston engine at different times in the same housing. (That is a really vague explanation, go look it up) If its easier, a Harley two cylinder is the same concept as a radial, just two pistons. where as lawn mowers, at least mine anyway, has a rotary engine.... Do I need to delve any further?
Old 01-17-2008, 03:17 PM
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shinob1
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Default RE: How does a brushless motor work?

oops... It would seem flat head pistons are the choice for lawn mowers...

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