Brushless motors

[Craig Spence]

Hi all,

I just tried to wire up a 170w brushless motor and brusless esc + li-po batt to my plane and just as I got the mount sorted out and all was going well I connected everything up and the prop turned the wrong way, GUTTED. But what was even worse was I tried to do something I used to do on brushed motors which was unsoldier the ends at the motor, change them round and resoldier them, problem solved prop turning the right way. Well thier are three terminals on brushless motors and I cant unsoldier them at the end so I chnaged the wires at the end (of the speed controller) the battery connects to (not thinking it through). When I connected the battery the speed controller smoked OPP's, I belive I shorted it. Well the battery is fine because im useing it, the speed controllers messed up (I think, well its binned anyway) and I think the motors fine too (again not sure, but have faith).

Can anyone tell me what went wrong and how do I reverse the motor direction without blowing something up (pictures and diagrames will help lol).

Oh and why do brushless speed controllers come with no on and off switch?.

Cheers all. 

[winchweight]

It's very easy, there's three leads running between the esc and the motor, you just swap any two leads. The two leads (red and black) from the esc must go to the corresponding leads on the battery, but the motor leads are interchangeable.

[Frank Skilbeck]

Just swap round any two of the three wires between the motor and ESC. Changing the battery wires around is a sure fire way of releasing the magic smoke.

Some brushless ESC's do come with an arming switch, but if you are using lipo's you must always unplug them as they will still be supplying some power to the ESC and will eventually be drained below the 3v per cell limit and irrevocably damaged. 

[Craig Spence]

Hi Shaun,

the principle remains the same then im just an idiot ha, oh well it wont happen again, live and learn.

Cheers.

[Craig Spence]

Hi Frank,

thanks for the info mate like I said before the principles the same I just never put much thought into it, oh well, ive took the mistakes on board and it wont happen again (he sais lol).

Cheers.

[Former Member]

[This posting has been removed]

[Myron Beaumont]

Maybe its time  I put my foot in it again ,this time  regarding 3 wires to  the motor..I bet many folks think -"how come you can switch any two wires to change the direction of rotation ?" I'll try to explain ( & I bet there are plenty of experts who can do it better )   Dont think of the set up as a "reversing switch"   I could go into sinusoidal waveforms that might confuse some  (even me ) so I won't !   Here goes   ?

-Our mains power supply is -single phase ie  max plus to max minimum  both parts counting as power  YES  ! in regard to the reference to a datum/mean value ie zero on a normal x -y graph !  & it happens 50 times every second   50 Hz its called ( 60 Hz in the USA I think )

With 3 phase AC flow two lots of "single phase type "sources are superimposed on each other so to speak .& spread over the same ONE cycle ie one of 50 on our mains 3-phase supply to industrial factories etc. who need max power ! So far so good Eh ! (I hope )

Now then ---Imagine the graphical representational form of what you have happening ie max to min more than just once ( like the mains 50 times a second) & then alter your starting point on your "x" axis for 3 phase running  - a brushless motor for instance powered by an ESC capable electronically of understanding DC and putting out two lots of "single phase" power.together  Got it ? Its not anything to do with magic or flukey maths !

If you move the starting point  ie the ESC connections anyway at all (it has to be two wires of course at a time -You cant move just one !)  then basically each move alters the initial event that determine the direction of the motive force to complete the cycle of a complete revolution of the motor .Phew!

Like I said --- Ready for put downs !

[Former Member]

[This posting has been removed]

[Craig Spence]

Hi Eric, thanks for the help,

the receiver is fine and the battery as well but im not sure about the motor as I have to get a new speed controller to find out lol! but im sure its fine, as Phil Wood said the esc probably protected the motor (or at least I think thats what hes saying).

Cheers.

[Craig Spence]

Hi <a href="http://www.modelflying.co.uk/localiser/member.asp?sp=&v=1&MemNo=958" title="Visit Myron Beaumont member profile">Myron Beaumont</a>,

thanks for explaining a little but ill be totally honest with you and say I probaly didnt understand most of what you said lol!. I may be stupid but ive tried lol!, but thanks for the effort.

Cheers.

[Craig Spence]

Hi Phil I think I get what your saying and it helps a little as well as being a little reasureing.

Cheers.

[Robert Bromwich]

HI

Myron very close with 3 phase explanation but just as it says there are 3 single phases (you said 2) in there

Its easy, mains voltage is AC 230v (50hz) so every 50th of a second the voltage goes upto 230v then drops down to -230v this is why its called  Alternating Current (AC !) on a 3-phase system this happens 3 times in a second but at different times in that 50th of a second. Of course then there are 3 power cables all giving out 230v these are Brown,Grey,Black and Neutral Blue not forgeting Earth !

yes you are right about the USA bring 60hz but there voltage is only 110v

Rob

[Myron Beaumont]

Robert     Silly me of course I meant 3 not 2  Thanks for correcting my mistake -could make it even more confusing to comprehend

[Nik Harrison]

A very easy way to understand the 3-phase problem is to use an equilateral triangle.  One with all three sides the same.  Each phase wire from the ESC to the motor can be numbered 1, 2 & 3.  This will represent the order the phases switch.  Draw a triangle on a piece of paper and place the numbers 1,2 & 3 on the points of the triangle.  Just place them randomly.  Now count from 1 to 3 and the direction you count round the triangle will be clockwise or anti-clockwise.  That is the direction the prop will go.

To change direction, interchange any two numbers - example swap 1 & 2.  The direction will now be the opposite way round.  Easy eh!

[Myron Beaumont]

Nicholas   Much better than my explanation 

Myron

[Craig Spence]

Hi Nicholas,

that info is very to the point and very helpfull, thanks alot for the lamens explanation.

Cheers.

[Pete Rieden]

Myron, Rob and Nik have given good explanations of 3-phase AC motors, but I feel moved to point out that they don't describe what's going on in our brushless motors because they are NOT 3-phase AC motors. Our brushless motors are DC motors and are identical in all respects to brushed motors except in the minor detail that the commutator is electronic rather than mechanical. Most specificly the speed controllers do not drive the motors with sinusoidal AC - they just switch DC on and off in either the forward or reverse polarity for each pole of the stator as required (plus some chopping to regulate the speed).

There are three wires and three sets of poles in the stator simply because this is a rather effective coil configuration - most brushed motors are wired in a very similar way but you don't see it because it's in the internal connections between the commutator and the windings. There are other viable configurations involving lesser and greater numbers of pole connections.

[to be continued]

PDR

[Pete Rieden]

[Continued due to message length limit]

A simple way of visualising what's going on is to imagine the three "phases" as the sides of a triangle. Voltages are applied to the three corners to produce magnetic fields along the sides (don't worry why or how - the clever bit comes next). The speed controller then chanes the voltages so that each bit of magnetic field moves around to the next side. This is repeated, so that the magnetic field seems to rotate around the triangle. If you then place a rotor (with permanent magnets stuck to it) in this rotating filed the rotor is pulled around with the field creating a rotating motor.

That's a simple way of visualising it - it's not strictly true because there's some "clever stuff"(tm) involving using different numbers of rotor and stator poles which makes it work better, with a net result that the field is actually rotating twice as fast as the motor, but you don't really need to know this unless you're interested. The point is that if you swap any two of the three connections to the corners of the triangle the direction the field rotates in will be reversed - it's just like looking at the triangle from the back. So it's that simple.

£0.02 supplied,

 PDR

[Myron Beaumont]

After all this you'e not going to believe that my EDF only runs in one direction now --BACKWARDS !! I've swapped the three wires & all that   Simply fed up with the whole scenario and will sell the lot & get back to proper modelling  ie no foam- no fire risks -longer engine powered flights ETC   For what I've spent so far & not even flown I could have bought a couple of top brand four strokes .& I shall re- convert a couple of models back to engines as they used to be originally -NO probs

VERY Grumpy Myron

[Bruce Richards]

You should only swap any 2 of the 3 wires not all three.

[Myron Beaumont]

Peter    Thanks for reply  Sorry if I sounded a bit p    d off but I really am

I never swopped all three at once for the very reason you've explained & that I'm perfectly aware of  &.I've only ever used gold 4mm connectors for everything. I simply just dont understand it . It doesnt make an ounce of sense to me at all .Just a culmination of a long hard struggle that has not worked out .

[Craig Spence]

Hi Peter,

if I blew my brushless esc would the motor still work the battery and receicer do fine.

If your wondering what the circumstances are they are explained in this thread but basically i tried to get the motor to turn the other way but instead of swaping the wires at the motor end i did it at the end of the speed controller which connects to the battery hence blown esc oopps.

Any feedback appreciated.

Cheers.

[Nik Harrison]

Myron,

If you have done all the bits that have been suggested and it still only rotates in one direction only, then I would look at the ESC/motor combination.  You do not mention whether the ESC has been set up specifically for your motor.  That is the timing or in-runner/out-runner etc.

Try a different ESC as it is the ESC that decides the direction of rotation bases in information that it detects from the motor.  When switching on, the motor does a shuffle and this is the ESC trying the workout what to do to drive the motor in the "correct" direction.  Maybe that calculation is not working with your combination.

Just a thought.

Craig,

The battery, motor and Rx should still be fine after the ESC was turned to toast.

The battery would survive a brief  "short" as it destroyed the ESC.  The motor is at the "other end" of the ESC and probably did not feel a thing.   The Rx can be tested using a regular battery, but it unlikely to have suffered as the ESC has a voltage regulator in it that would have help protect it.  Good luck.

[Craig Spence]

Hi Nik,

thanks for that info its reasurring to say the least the battery and receievr are working fine as im still useing them in my plane, it was just the motor I was worried about.

Ill find out soon enough though as im buying a new brushless esc and now I wont have a problem wireing it together, cant wait to see the difference, although a bit worried as im not 100% on the brushed set up yet ie.. flying, I suppose I could just take it easy once its airborne.

Cheers Nik.

[Craig Spence]

Hi Peter,

I have a Spectrum DX6i and im not a hundred percent but I cant remember if ive ever seen that in the manual, could it be known as something else?.

Cheers.