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        Discussion Can Brushless motors run on 2 wires? Can they work without an ESC?

#1 Nelatonin Jan 02, 2012 02:13 AM

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?

#2 scirocco Jan 02, 2012 02:35 AM

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

#3 C₄H₁₀ Jan 02, 2012 03:51 AM

Simple answer: No.

More detailed answer: No.

#4 slipstick Jan 02, 2012 08:20 AM

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

#5 Gary_Canada Jan 02, 2012 08:47 AM

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

#6 Masterpiece Jan 02, 2012 08:53 AM

Quote:

Originally Posted by Nelatonin (Post 20295163)
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.

#7 pilotpete2 Jan 02, 2012 10:59 AM

Quote:

Originally Posted by Masterpiece (Post 20296666)
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

#8 Ron van Sommeren Jan 02, 2012 12:41 PM

Quote:

Originally Posted by slipstick (Post 20296452)
...
- ESC and two wires only connected it will never start ...

Controller may even burn.

Quote:

Originally Posted by slipstick (Post 20296452)
...
- 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 (Post 20297707)
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


http://static.rcgroups.net/forums/at...r-3-phasen.gif



Partial throttle, PWM chopping for lower RPM

http://static.rcgroups.net/forums/at...last_Motor.gif

#9 Ron van Sommeren Jan 02, 2012 12:50 PM

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

#10 Nelatonin Jan 03, 2012 12:30 AM

thank you :)

#11 Mark Wood Jan 03, 2012 11:11 AM

It's also obvious that there is NO ac current but pulsed dc.

mw

#12 Ron van Sommeren Jan 03, 2012 11:59 AM

Thanks Mark for opening that can of worms :D:D:D

Gelukkig Nieuw Jaar ;) Ron
diy motor tipsDrive Calculator
diy motor groupCumulus MFC

#13 Lnagel Jan 03, 2012 12:25 PM

1 Attachment(s)
Quote:

Originally Posted by Mark Wood (Post 20307721)
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

#14 pilotpete2 Jan 03, 2012 02:14 PM

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

#15 Lnagel Jan 03, 2012 03:59 PM

Exactly the same, Pete. Very perceptive of you.

Larry


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