Triple Rewind of Unite 500W Motor

[safe]

Winding Completed

http://www.ebikehub.com/forum/download/file.php?id=397

I'm going to upgrade the motor wires (near the brushes) before I reassemble the motor. (and my fingertips hurt right now) so I still am not to the actual level of motor testing.

For more info:

http://www.ebikehub.com/forum/viewtopic.php?f=4&t=886&p=1636#p1636

 

[skyl4rk]

Thanks for the help, a very interesting thread.

 

[safe]

So far everything is going according to plan. I got the motor assembled late in the day yesterday and tested it at 24 volts and it appears to be working correctly. The no load speed appears to be only 1333 at 24 volts, but since it's a Triple and can pull a lot of amps (with ease) it can produce 800 watts of power output at only 24 volts.

The Stock motor was "sold" as a 36 volt 500 watt motor that had a no load speed of 3000 rpm.

So being able to equal the power output at only 24 volts means that at higher voltage you exceed it.

It's raining today, so I'm not going to be able to do any road testing, but it's looking like tomorrow will be clear... so I hope to confirm all the numbers tomorrow. The main thing to confirm is the no load speed and at 24 volts that's 20 mph on my bike.

It runs really smooth...

 

[beast775]

excellent info safe

excellent post.i will learn alot here.im already looking for a cheap ezip chain drive motor.and will try to rewire.very exciting.

 

[AussieJester]

I dont believe i forgot this, i have a little UNITE motor her safe sitting ona scooter we found on curbside colletions i think it will be a 250watter definately a UNite though!! i can practise on it before i 'destroy' a larger more expensive motor hahaa... I'll rip it out when i have finished the tray im working on and post a pic or two Could perhaps 'donate' it too someone on Moteredbikes who wants to try their hand at an electric...Lil small for my use ...

KiM

 

[safe]

AussieJester, before you get to winding let me know what motor you have and I can run some simulations with the spreadsheets and give you some options about what way to rewind it.

Do you know the exact model number?

Is it a MY1018Z?

...or more like a MY1016?

...the MY1020 series of motors never included a 250 watt version.

 

[AussieJester]

Looks exactly like the MY1016 safe, i cant get to it till tomorrow though to check for numbers its down the side of my house in storage area where i keep my (donor) bikes/steel etc and there is no lighting there unfortunately...shall let you know more tomorrow will take pics of it also

Cheers buddy

KiM

 

[safe]

The MY1016 "should" be identical to my own MY1016Z3 as far as the core. The "Z3" adds the geardown, but otherwise it would be about the same.

It will end up looking like this if you rewind it:

http://www.ebikehub.com/forum/download/file.php?id=373

...I just did a quick analysis of the "other" motor (the one you don't have) which is the 1018Z. My estimate of the change from Single to Triple is this:

http://www.motoredbikes.com/attachment.php?attachmentid=16526&stc=1&d=1238688824

 

[duivendyk]

I can't make any sense at all from this triple wind technique.Somehow the winding resistance is claimed to be reduced when a number of windings are put in parallel on a motor armature.With say,3 windings and the same number of turns per winding, one would have only 1/3 of the resistance,great,but this would be the case if the wire size could be kept the same,but then 3 windings should take up 3 times the original area in the armature slots.So actually the area of each winding would have to be reduced in the same ratio and consequently the resistance of each strand would be 3 times as high as in the original winding.With 3 strands in parallel we are back to the same winding resistance as before.So what's the point of the whole exercise?It remains a complete mystery to me.About the only advantage I could see is that with thinner wire one might get a somewhat better filling factor of the armature slots and thus get a somewhat reduced resistance of the armature windings.Am I misunderstanding what this triple wind scheme is exactly about?.Please elucidate.

 

[safe]

Well, I'm learning too... so here's some feedback from the first testing I did with the Triple wind motor while on the bike.

First of all the motor is powerful... the reduced resistance comes about for the same reason that a series set of resistors has more resistance than a parallel set of resistors... every time you do one of those "interconnects" in the middle of the coil it is like making it more parallel.

If the wire thickness is held constant then all that matters is the turn count to determine the no load speed. Changing the number of winds just changes the resistance and does not effect the no load speed. Life is simple.

However, the thing I just learned is that thickness of the wire matters a lot more than I thought. Let me explain...

My first Triple rewind was with a motor that had 22 AWG to begin with. All I did was change the winding pattern from a Double (Stock) to a Triple and the big reduction in resistance allowed for more power.

So far so good...

The next step was to rewind the 500 watt motor that (as it turns out) actually seems to have been wound with thicker 20 AWG wire. When you go from 20 AWG to 22 AWG the cross sectional area drops by a factor 1.59 and if you square that number you get 2.53 which is the exact amount that the no load speed increased above my anticipated values.

Moral: When you change wire thickness it changes the no load speed and this is a separate calculation to the other things you need to keep track of.

So the factors are:

Wire Thickness
Number of Turns
Number of Winds

...all three interact with each other and form the resistance and inductance behavior of the motor.

The "bottom line" is that it's easier to keep the Wire Thickness constant and then just change the winding pattern from Single, Double or Triple... it's a lot easier that way... the mind can more easily understand what is going on because it's just like dealing with simple resistors moving them from a series connection to a parallel one.

My best advice for this MY1020 500 watt motor rewind would be:

20 AWG

Double Wind (9x2=18 same as Stock turns means same no load speed)

...this in NOT what I just did, but that's what being the "guinea pig" means, someone has to actually be the pioneer and try this stuff first.

------------------------------------

It actually turns out to be a bit of good luck because the bike I want to use this on is geared so that at 24 volts this Triple will work perfectly. So while I missed my original target I have learned some things and the motor is not a total loss.

It's the other rewind I did... the MY1016Z3 that I'm more worried about because the no load speed would recalculate to 8000 rpm and that's getting a little high. I might have to redo that one...