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Old Jan 02, 2012, 02:13 AM
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Can Brushless motors run on 2 wires? Can they work without an ESC?

Can brushless motors work with only 2 wires?

Eg; not connecting the third to an ESC?

Will it still run?
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Old Jan 02, 2012, 02:35 AM
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scirocco's Avatar
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The answer is no, and you can't run a brushless motor off a brushed ESC.

I highly recommend you visit this forum: http://www.rcgroups.com/forums/showthread.php?t=739069 as there are masses of resources for learning about the ins and outs of electric flight that will help you focus your questions.

Another fantastic resource is here: http://homepage.mac.com/kmyersefo/sitetoc.html

And one more: http://www.rcgroups.com/forums/member.php?u=106813
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Old Jan 02, 2012, 03:51 AM
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United States, AK, Fairbanks
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Simple answer: No.

More detailed answer: No.
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Old Jan 02, 2012, 08:20 AM
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Oh I don't know . If you want a detailed but fairly useless answer :
- no ESC, nothing will happen
- ESC and two wires only connected it will never start
....BUT
- if you start a motor with all 3 wires connected to the ESC and then cut one of the wires it will carry on working after a fashion.

So what was it you really wanted to know ?

Steve
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Old Jan 02, 2012, 08:47 AM
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Southern Ontario
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Many folks ask this type of question to avoid spending money.
Take a look take a look at some of these very inexpensive controllers (ESC) from
China:
\http://www.hobbyking.com/hobbyking/s...yKing_ESC.html

or one shipped from US, here is a 25 amp one for less than $11:

http://www.hobbypartz.com/60p-dye-1002-25a-esc.html

Gary
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Old Jan 02, 2012, 08:53 AM
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Quote:
Originally Posted by Nelatonin View Post
Can brushless motors work with only 2 wires?

Eg; not connecting the third to an ESC?

Will it still run?


Hmmm. Brushless because the motor has no brushes and relies on a alternating current provided from the ESC (the ESC converts the battery current from DC to AC) to provide the opposing electro magnet fields in the windings, in the casing. Opposing to the neodymium magnets on the rotor (inrunner in this case) which causes the motion.

All you'll get is a brief jolt in the motor but no spin.
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Old Jan 02, 2012, 10:59 AM
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Quote:
Originally Posted by Masterpiece View Post
All you'll get is a brief jolt in the motor but no spin.
As opposed to the 50 or 60Hz Hmmm you'll get with an AC input to a BLDC motor
The ESC provides electronic commutation of the DC input, based on the feedback the ESC gets from the motors back EMF.
Pete
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Old Jan 02, 2012, 12:41 PM
homo ludens modellisticus
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Quote:
Originally Posted by slipstick View Post
...
- ESC and two wires only connected it will never start ...
Controller may even burn.

Quote:
Originally Posted by slipstick View Post
...
- no ESC, nothing will happen ...
- connect two of the three wires directly to battery and you will cause a minor conflagration: motor and/or battery will go up in flames. A brushless motor is a massive short for DC voltage/current!

Quote:
Originally Posted by pilotpete2 View Post
As opposed to the 50 or 60Hz Hmmm you'll get with an AC input to a BLDC motor
The ESC provides electronic commutation of the DC input, based on the feedback the ESC gets from the motors back EMF.
Pete
More pictures and explanation:
http://www.aerodesign.de/peter/2001/...DY-BL_eng.html (English version)


Full throttle, no PWM chopping






Partial throttle, PWM chopping for lower RPM

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Old Jan 02, 2012, 12:50 PM
homo ludens modellisticus
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The Netherlands, GE, Nijmegen
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Several animations. It's obvious that the three motorwires (phases) are equivalent, but not the same.

http://www.aerodesign.de/peter/2001/...index_eng.html (English)
-> Animation 14-magnetpole outrunner

Two magnetpole inrunner
http://townbiz.com/animations/2-pole_bldc_motor.swf

Four magnetpole inrunner
http://townbiz.com/animations/4-pole_bldc_motor.swf

More
http://townbiz.com/animations/animations.html
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Old Jan 03, 2012, 12:30 AM
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thank you
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Old Jan 03, 2012, 11:11 AM
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It's also obvious that there is NO ac current but pulsed dc.

mw
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Old Jan 03, 2012, 11:59 AM
homo ludens modellisticus
Ron van Sommeren's Avatar
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Thanks Mark for opening that can of worms

Gelukkig Nieuw Jaar Ron
diy motor tipsDrive Calculator
diy motor groupCumulus MFC
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Old Jan 03, 2012, 12:25 PM
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Moab, Utah, USA
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Quote:
Originally Posted by Mark Wood View Post
It's also obvious that there is NO ac current but pulsed dc.

mw
Actually, the pulsed DC does create an AC current through the motor windings. The scope traces that Ron posted display represent the voltage applied from the ESC to the motor, not the current flowing through the motor windings. I have attached a photo of a scope trace that does represent the current through one pair of windings on a brushless motor. The center horizontal line with the hash marks represents zero amps. You can clearly see that the current flow is maximum in one direction (trace is above the zero reference) for 2/3 of the commutation cycle and the current is zero for 1/3 of the commutation cycle. During the next commutation cycle the maximum current trace is below the zero reference indication that the current is flowing through the coils in the opposite direction, i.e. AC current.

Larry
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Old Jan 03, 2012, 02:14 PM
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Isn't this pretty much the same thing that we'd see if we looked at the current flow in the coils of a brushed motor running on DC?
Pete
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Old Jan 03, 2012, 03:59 PM
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Exactly the same, Pete. Very perceptive of you.

Larry
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