Minor mistakes on first stator ...

[stoichiometry]

I just finished molding my first stator last night!  It's a Homebrew "heavy duty" for the round magnets, wound for 12 volt.  When I took the stator from the mold, I noticed two things this morning.  (1) My stator is a little thick (9/16 average and 5/8 in some places), and (2) my superglue job (fiberglass bits superglued to legs of coils) didn't hold when I compressed the mold and some are slightly lopsided after being compressed within the mold.  Also, during mold compression, one or two coils are askew by a few degrees. 

Do you think my two stator errors will significantly hamper the output of the turbine?  Also, will the AN style washers be thick enough or should I buy several extras to accommodate the 'extra' thickness?  Thoughts??

BTW -  The molding was fun and relatively easy - for anyone interested, the two part fasco 110 epoxy glue is highly recommended.  It is temperature resistant (300+ C), has about  a 20 minute working time, and works like peanut butter.  It can be squeegeed and is a nice product for casting. 

Kindly,
S

[DanG]

I dislike opening my mouth AFTER folks have done the work - I wish we'd all collectively learn to talk ideas out before acting on them.  I know, its a stretch

The 300°C range of maintaining physical strength is good only if it can reach every wire wrap.

One of the basic tenants of potting coils is fix every wrap so it won't heave and subside with every magnet pass - the factory insulation is good but not that good, over time arcing will develop where wraps have chaffed against each other.

If you could find a method to coat the wires-in-hand as the coils are laid up that peanut-butter compound might be a step up for mechanically stronger stators. VE resin pours nearly water-like thin and may still allow air pockets in the coil cores but it really wicks in, and has a heat distortion temperature above 180°C...

[stoichiometry]

"... I wish we'd all collectively learn to talk ideas out before acting on them.  I know, its a stretch ..."

Ouch -- nice jab.

I'd bet my wires are at least as well coated as if I'd molded in VE.   I am less concerned about this and a bit more concerned about a couple of the coil legs being a bit out of square (relative to the path of the magnets) and also wondering if I should be prepared to deal with the extra overall thickness.

  As you note, it's a good idea to talk about ideas before acting on them.  So, before I continue, I am  trying to determine what to expect, in practice, from a stator that has a couple of legs out of square.  If it's 10%, it's probably not worth the time and expense of building/buying a new one.  If it's like >40%, I'll probably buy some new magnet wire and recast.

[fabricator]

It sure won't affect the out put by 40%, if you are running star it'll likely be less than 10%, there have been lots of stator pics posted here where the coil spacing was visibly inconsistent, one I remember was from one of the workshops, that mill went up and worked fine.

[DanG]

Not intended to be a jab, likely more a misplaced muse on our low-tech human nature that was  definitely learned from my own personal history!

Slight errors on coil alignment probably not discernible power-output at the work load totals - but would be seen in the waveform shape and timing, some extra ripple after the rectifiers; extra noise and vibration maybe - unless the coil legs are seriously offset enough the end loops are under the swept path.

The small stator thickness variations is non-issue output wise... maybe give a handy magnet crash tattle-tale warning rub area if your bearings or stator mounts get screwy as the total magnet air gap likely will be huge in comparison to the 0.125" difference or 0.0625" high-spots on each face if you align the stator to the centers of the coils.

Thanks for posting, looking for pictures

[dlenox]

I'd guess that the stator coil connections are star?  If so not so bad, but it may make a bigger difference if they were connected in delta.

I've heard that when doing delta the coil placement is more critical.

Dan Lenox

[ChrisOlson]

I'd guess that the stator coil connections are star?  If so not so bad, but it may make a bigger difference if they were connected in delta.
I've heard that when doing delta the coil placement is more critical.

For delta coil placement, shape and phase timing is absolutely critical.  You're delivering power to one leg with two groups in parallel and the sine waves from the two coil groups have to exactly match or it won't work right.

For this stator in question here, I have my doubts that a slight mistake in coil spacing or geometry is going to make any measurable difference in output.
--
Chris

[Flux]

Don't worry , it will be fine. The slightly thicker stator means you will need to run with a bit bigger air gap but I bet you will still need to increase it unless you have an incredibly short cable run.

The slightly misplaced coils will have no detectable effect on a star winding, it's turns and flux linkage that matters not leg position.

[stoichiometry]

Photos ... kinda ugly I know.  Last night, I banded them with some extra glass to make the rim where they are to be mounted a bit more rugged.  THis caused some of the unsightly surface imperfections. 

Oh ... one more question -> The wires of the first leg are *really* close to the first anchor hole.  Any recommendations on how to insulate it from touching the anchor bolt?

[Flux]

I assume you have already done the metalwork and can't move the stator hole.

From the picture it doesn't look to be touching, you may have room for a piece of heat shrink sleeving over the mounting bolt and it wouldn't hurt to fit a couple of insulating washers under the steel washers where it clamps the stator.

As long as it doesn't physically touch and water doesn't get in you need very little clearance at low voltage.

Just one other thought, could you drill another set of fixing holes and find a point where you can get them all in with better clearance?

Flux

[DanB]

yes, so long as you get it bolted up without hitting copper, and you've made the connections correctly it'll likely be just fine.  (it might even work better!!!)
It looks fine...  it is a pretty forgiving design.