Project Journals > Oztules
It looked simple on paper......
oztules:
It looked like this:
It was not mine, and the bloke that brought it too me asked if it would go again....... I said no, it has burnt out nearly every wire in the alternator head. They are only about $250 dollars on ebay, and that it would be best if we just forgot about it. So he went and bought another, and was happy.
Some time later I decided to pick the thing up and take it to the dump.
Some how i couldn't make myself do that until I had a better look at the actual damage, and what if any thing I could do with it if I really tried.
I have never rewired one of these AVR stators complete before. It had just been drive coils , but never the full monti.
Having decided that I was a slacker, I started to pull the wires out of the stator, to see just how they wired them up...... and it was nothing like I thought.
Each coil had 4 wires going to the next coil group, there were taps going into the coils all over the place for different functions of the AVR and output, 12v circuits and the drive.
It was only that I could not understand how it was done that I .... well just had to carefully unpick the whole thing..... which is very much not easy when you don't know where each wire from each coil actually goes. You need to get the coils out of the stator slots, without breaking them, else we won't know from where they came and went.
Well after countless hours carefully teasing the truth out of it, it appears to look like this... on paper at least.
Simple really when you know isn't it.
So, it's 10 main coils divided into 2 coil groups of 5, each with 25 turns, then another 10 coils in series with this ten coils, but only 2 turns each.
This made up the main stator field. effectively 250 turns (10x25t) of the first string, in series with 20 turns (10x 2t)of supplementary turns... or 270 turns for the main..... why didn't they just make 10 coils of 27 turns..... achieves the exact same thing??, and much easier to wind.
Then there was the 12v winding, which I just cut off, don't want it anyway.
Next was the drive winding. This will provide power to the AVR (automatic voltage regulator) so that it can drive the rotor field up to whatever magnetic strength it needed to maintain the 240 volts.... load dependent. It was three coils of 50 turns.
So there we have it. Simple...... now we have to work out how to wind it easily.
Zubbly showed us a Diamond head winder, which looks the part, but I don't have one, ... so the next best thing is to emulate what it did simply.
I figured the best thing was to get a lump of 1 inch thick particle board..... and use some 4 inch nails.... and make a winding board like this.
It can be seen that this has been used before for this purpose... yes it works well.
We measure the difference between the slots of an inner coil, at their longest point, and that will be that coils width, then the length will probably be about 25-35mm longer than the stator stack. Then the next coil. Establish the difference between those coils size widths in relation with each others coil size, and use that difference to calculate the next width next coil/s groups.
You see the problem with 2 pole stuff, is that the coils at the larger size of the coil groups will be almost on opposite walls of the stator, so measuring the circumfrul distances gets messy, so if you increment at the rate the coils of the inner groups are, you'll be close for the outers.
Leave the height about the same for all groups.
We'll wind the drive coils first, as they are made of spider web, and will slip into the slots like a breeze.... positive experiences help at this time...
It looks like this:
When we take it off the winder it looks like this..... don't forget to wire tie the relevant coils before you remove the nails.
Then place the wire into the slots... easy with thin wire.... make sure you don't mess up the coils orientation, or it will cancel rather than adding voltage to each other.... develop a system so that when you remove the coils from the winder, they are all in the same orientation that you wound them, otherwise you will suffer.... badly....( been there and done that)
Making the paper bits that insulate the slots is a given.. just make sure they don't project above the stator steel, but do go all the way up to the very bottom of the stator teeth. That way when you put the keeper in place, it will push the wire down to where you know there is paper protection, no chance of being against the stator steel itself.
Fashion the excess wire out the ends to give you the desired real estate for the next stage... the main event.
Well we can only post 9 pics per post, so time to move along to part 2 I guess
This is what it looks like to throw away lots of 1mm wire
That comment I made about 27 turns instead of 25 plus 2.....
Well I wound this with 27 turns, and felt pretty smug about it all, and started to fill it into the slots, wrangling different size wire loops with different sized stator slot spacing............and ... and yikes, It hit me.
I had thought that they just wanted to sample the voltage of the output coil, and did that by using a set number of turns out of the total number of turns in the whole shebang....
That is what they wanted, on a transformer thats what we do, but here........ exactly which 20 turns do they have in mind.
If we think about it, each coil within a group has different resistances, different magnetic area, just about everything is different between coils within the group, it is the vector addition of every wire in the group that gives us the output voltage, and every wire sees the moving field differently.... and thats the oh no moment right there.
So nicely wound and thrown out..... it looked so simple on paper too.
It would work to regulate the voltage, but it would not hold the voltage like we expect.
..........................oztules
oztules:
So we have wound a new 5 coils of 25 turns ( not 27 smart turns), and we are putting them in You can see how it's done. first one side then the other. Put in the keeper, and it looks snug as a bug.
keep the coils in order, so that you don't turn one over by mistake.
next coil etc
tidy things up a bit, and it's starting to look the part
Here it is with the 25 turns complete, next the next 2 turns..
You can see the two wires peeking out from the stator slots for the last 2 turns for the 5 coil group.
complete nearly ready for the lacquer
It works ;D ;D ;D ;D
A BigThanks to Zubbly for his insight on how to do stuff..
Actually I fired it up and nothing happened... nadda....then noticed the 240v overloader switch was off... flicked it on and the meter sprang to life.
I was surprised at just how well that AVR system worked, even dumping a 2000w heat gun on, made no difference to the voltage, the hertz sagged, but the voltage remained the same through out the switch on/off/on/off .. nifty
.................oztules
Watt:
Very nice oztules! 8)
Bryan1:
Put's his cold beer down to write this gripe..... :'( :'( :'( :'( :'(
Being one sucker using that nail method did look all too easy at the start for my 4kw motor rewind only to find after putting 2 coil groups of 16 turns of 1.6mm wire some enamel scraped off so out come the wire cutters to start from scratch on MK.2 (attempt ::) ). Was extra careful with the 2nd wire up on the nail board was extra careful on the insertion of the next 2 coils and though with bloody sore fingers YAY I'm getting there......... 8) 8) 8).
Then placing the covers on to ensure the coils would fit in a cry of (I'm gunna wring ya bloody neck MURPHY) the coils are too bloody long and the covers won't go on.. >:( >:( >:( >:(
So there that 4kw motor sits on the shed floor in disgrace and next thing our resident Einstein goes and shows just how easy it is.... :( :( :( :( :(
Days off work are a distant memory and that phone call made before xmas of $300 folding money to get a pro to rewind does seem the least frustrating way to get my 4kw motor conversion finished..
/ end Gripe
Picks up now a warm beer and trudges off mumbling obscene things about how easy the nail method is......
MadScientist267:
I guess that's a twofer then?
I've never done a rewind of this nature, but can imagine that it involves a certain level of "throw something really small,really fast through a tube in the direction of some sucker that needs it"... Hehe
Fun to read about tho! :P
Steve
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