3hp Motor Conversion Update

[andyman5002]

Hi all, I just thought I would just post a quick note on my motor. Things haven't really moved much I have been on holiday and just got back to work on it. Not much done today, just stripped it down and had a nosy around. Here are some pics:

Much bigger bearing housing than last time, the whole thing is massive, it looks to be very well built.

Theres the rotor, very big plenty of room for my mags, not sure what size im going with yet, I was thinking of 1/2inch dia by 1/4 discs. I've still got to work everything out yet.

There's the wiring, not sure how to use this yet as my 3 phase knowledge is limited. How would I connect my rectifiers to that??

There's the main motor assembly, very well built. The stator has 36 slots on it.

So far the project looks promissing and should hopefully make a good genny. It bears a very strong resembalance to Zubbly's 'production run' motor, almost all of it seems exactly the same except the voltage/current ratings. His voltage is higher but my current is higher. Like Zubblys it is IP55 rated, so it should be water proof??

Zubbly if you read this could you give me some word on that motor you had, how well did it work out? I couldn't seem to find any follow up of that one.

I dont think this motor has even been used yet, or it has had very little use, everything seems new and clean. I think it was a great ebay bargain at £10.

This time everything is going to be done by the book. Going to use Zubbly's method of creating a cage for the mags. Mag wise I'm not sure how many rows yet but I'm going with multiple disc mags on 10 degree skew, am I correct in saying that one pole should fit inside one coil??. One thing I have noticed is that the shaft is a lot harder to turn than the last motor I had, but I think the bearings were badly worn on the last one.

Any thoughts/comments on how I should proceed would be great.

Thanks Andy

[kitno455]

post pic of nameplate, esp. rpms and volts/amps

allan

[andyman5002]

Here is the nameplate

Andy

[dinges]

Have you tried to weigh it? Mine comes in at a hefty 35 kg; that's 28kg for the housing, and 7 kg for the rotor. Heavy stuff. All the other specs of my motor are the same as yours.

[vawtman]

Hi Andy thats a much better motor.

 3hp 4pl.Nice

 Did you have mistype when saying this motor turns harder.

[andyman5002]

Vawtman, not sure what you mean about mistype, but the shaft on the motor seems to be harder to turn by hand than the last motor, probably due to the size of the rotor and the new bearings.

Dinges how is your conversion going?

Andy

[dinges]

"Dinges how is your conversion going?"

The same as last time (see my diary). I.e., no new work done. My mate with the machine shop is still too busy with real work. Guess I'm last on the priority list

Anyway, the magnets have arrived. I use 20x10mm round ones, N42. Ordered from Supermagnete.de; need 40 of those magnets. Would have ordered from the Dans, but shipping overseas is not really an option.

Looks like it'll be a few more weeks before work will continue on the 3HP conversion.

[powerbuoy]

Try this one ...

Powerbuoy

[zubbly]

hi Andyman!

the reason i never posted any further info on my 3hp conversion is because that is the unit that fell with my whole tower last year.  destroyed the prop and bent the shaft. i will put a new shaft in it someday. never got to get it under load, but is was a beauty of a unit and would have worked very good.

i used a total of 60 3/4 round by 3/8 inch thick mags in that unit.  15 mags per pole.  basically i maxed out as much mag as i could do.

your unit does look very similar.

my original rotor diam was 4.222 inch. the stator lam length was 4.343 inch.

if you put a tape measure inside the stator bore (with the tape flat against the stator bore), and measure the total width of 7 stator teeth, that will work out good for your pole width. use as many as you can in the length of the pole.

my mag spacing was 22MM centres for both length and width of the mags within the pole. you must be extremely accurate in marking out the mags for the 22mm spacing. there is no room for error or you will be drilling a hole patially through the other hole.  depending on your skill, 23mm spacing may work better for you and a little easier.

output voltage of the original winding was 78.5 volt at 300 rpm star connection 1 circuit and 45 volt delta connection 1 circuit. the original winding was 230-460 volt, 1 and 2 circuit star. i added the 3 extra leads to make it 1 and 2 circuit star and delta.

right now you have 6 leads in your connection box that is connected for star. by switching those cross links across from each other, you will have delta connection.

hope this helps,

zubbly

[powerbuoy]

concerning the IP55 question ... the book says dust and water jet compatible ...

In case this motor will be exposed to wind and weather, we always put some additional sealer on the endbells and siliconed the connection box up to the top. We also used sealed bearings.

Powerbuoy

[andyman5002]

Ok guys, I thought I should run my mag ideas past you for some advice. I have worked it out that I can fit 15 mags per pole if I use the following specs:

Grade 42 Mags 15mm dia x 8mm Discs

 3.75 mm horizontal spacing

 2.3 mm vertical spacing.

 52 mm wide poles

This will give me 3 rows of 5 mags per pole totalling 60 mags, with comfortable spacing in between.

The only thing im a bit concerned about is the depth of the mags. Are they big enough to get some decent power?

Also my calculations are to place the mags on the only the part of the rotor where the iron laminations are, as there is an aluminium edge on it, this wont help flux??. Is this correct? There are also some balance weights on the rotor, little washers, these will come off once machined, is this a problem?

The overall length of the rotor is 112 mm and the part with the iron lamination is 90 mm

Once all of this has been sorted out the mags will be ordered or not if they are no good.

So any thoughts on this configuration would be great.

Thanks Andy

[dinges]

Andy,

I was facing this choice: 48 magnets 15x8mm; or 40 magnets 20x10mm (all round magnets).

I had calculated the total volume of the magnets, it appeared that with the 20x10 magnets I had much more volume. Don't remember the figures exactly, but according to Zubbly's rule, I'd get abt. 700W with the 15x8mm ones, and abt. 1100-1200W with the 20x10 ones. Don't take the exact power-figures as a fixed thing, it's what you end up with when using Zubbly's rule. The most important thing here is that with the bigger magnets (even though fewer of them) I had much more magnetic material in the rotor, thus more power. Over 60% improvement.

See if you can fit the 20x10 magnets in, how many, and how much magnetic volume you end up with.

My rotor is 89mm diameter; total length was 150mm, of which 120mm is actually available for magnetic material. (the stator is 120mm long too) Seems my stator & rotor are a tad longer than yours, but not much (8mm).

BTW, figuring this part out has so far been the hardest part of my conversion... Took a lot of sketching and calculating. AutoCAD is great for making quick sketches to see if it'll all fit.

[dinges]

Oops, my rotor is actually quit a bit longer than yours: 120-90=30mm. Strange. Is yours of larger diameter than 89mm? Both motors claim to be 3HP...

Or maybe your motor is more modern, thus has 'modern' ratings... Mine was built in the '60s by a very well known Dutch motor manufacturer (Dordt Electro Motoren Fabriek, Dordt EMF). Very respectable company. Motor was originally used on a lathe.

[andyman5002]

The rotor is about 11.2 cm long including the aluminium rim on the outside with the balances on it. But the part with iron in is only 90mm long. The diameter is only 90mm as well. It does seem to be a very new motor so not sure. What do you think about the mag choices?? Also how was the order from supermagnete.de, did you get them delivered to the UK?

Andy

[dinges]

No, I'm in The Netherlands. Have no complaints about Supermagnete, I've ordered about 4-5 times from them now. Only, the first orders were without VAT, as they were shipping from Switzerland. Nowadays, they ship from Germany. After payment is made, the magnets usually arrive within 2-3 working days.

Already thought you were ordering from supermagnete, judging by the size of the  magnet you intend to useg (N42 15x8mm). I would have liked them to have 12x10mm and 17x12 too, would have made my life much easier. Anyway, I had the option of using 15x8 or 20x10, as I've explained.

Also, the N42 means a bit stronger field; I think that most Americans (Dans; Zubbly too?) use N35. This would mean an extra 20% field strength; modifying Zubbly's rule from 150W/cubic inch to 180W/cubic inch, I think.

Very strange that your motor has a much shorter rotor & stator, at the same diameter. Both claim to be 3HP. I think mine is 3 'old school' HPs, and yours is 3 'modern marketing, push it till the edge' HP ?

[andyman5002]

Sorry I didn't see your previous post about your magnet choices. It seems that I will be limited to about 900 watts with my current choice if my maths is correct which it probably isn't. Hmm not sure what to do, I had hoped to do better than that. But I suppose it will match my small blades.

The magnet choice is limited, If I used 20x10mm mags then I would only get about 700w I think because I have to stay within the 52mm pole width. The only way to get more would be to get 15mm diameter but deeper ones. I don't really want to go much deeper because I'm afraid it will fall apart.

Hmm bit of a problem, I think I will have to look around to see what other mags I can find or stick with 900W. In reality I probably wont even get 900W.

Andy

[vawtman]

Andyman what size blades are you planning?

 I think if you have the knowhow to follow Zubblys 12pl that would be ultimate.On my 5hp 4pl i needed to spin it at 800rpm to get 130v now with a 12pl thinkin and hopin i could reach the same voltage at 1/3rd the rpm.

 I never tried the cage encasement method.

[andyman5002]

HI vawtman, If it requires rewinding im afraid I wont be doing it. I would like ot just use stock windings, I may just use the mags i said before. Blade size I was thinking about 6-8 foot. What magnets did you use for your conversion, what was the air gap?

Andy

[Flux]

Motor conversions are not really my thing, but I have been thinking about the choice of magnet.

The ideal things are curved magnets and with them 1/4 " thick and an air gap of about 1mm (.040"), you should get a gap density of about 1T. As the teeth are a bit smaller than the slots in most cores you will have the teeth well saturated. The total gap density will still increase with the teeth saturated but the gain will be small for a large increase in magnet thickness and with very thick magnets you will not get much beyond 1.1T in the gap.

Assuming that other shape magnets can be got down to about 1mm air gap (which should be possible with multiple circular ones) then there seems little point in using magnets much more than 5/16 thick.

You loose a lot by having round magnets which have a poor stacking factor. I doubt that you can make this up much by using thicker magnets due to the tooth saturation.

I suspect the main aim should be to pack the magnets as effectively as possible. As long as you have a minimum thickness of about 5/16" I think you can consider area rather than volume as the determining factor in deciding the output.

With larger non curved magnets you will not be able to maintain the 1mm gap so there is a need for thicker magnets, but you gain by having the full surface area rather than a poor fraction with small circular magnets.

Zubbly's watts out per volume of magnet may be a reasonable guide but increasing volume by choosing magnets that are longer than necessary may be wasting magnet material.

There has been a lot of interest in motor conversions lately, but everyone talks about output. I would like to see figures of iron loss, how it is affected by flux density and also how output is affected by flux density. Is absolute output everything or do you achieve it at a larger cost in magnets and at the expense of lower low end efficiency.

Room for lots of decent research.

Flux

[vawtman]

Andyman i think even Zubbly would say you need around 12ft to help break the initial cog.

 My mags are arc segs and the airgap was 1/16th.

 Notice i said was, they were just removed and finding a new home.All 16 of them plus 8 more on 3hp Sparky.

 Mag size aprx 1in x 1 1/2x 5/16 n48 naughty boys.

 You wouldnt have skew the stator if caging allthough its fun.

[andyman5002]

I don't think I will be able to make such big blades due to my area, the neighbours will not be happy. I will have to just see how it goes with my small blades and wait for high winds, I may make bigger ones in the future but 12 foot blades for 900W is it worth it, are 12 foot blades not capable of more?

I think I will go with the mags I said before in light of flux's input as they seem to meet the minimum 5/16 thickness. Flux do you think it would be better to just try and cram in another mag on top of the aluminium rim so it fills the stator width?? Because If i just place them on the iron lams then there is little of the stator filled? I know that they are supposed to be placed on an iron base to improve flux flow or something, but could it improve output? This way there will be more magnet area?

Andy

[vawtman]

Hello Flux

 I know your not fond of conversions but its a cheap way to start out and learn.

 Your last paragraph of iron loss and how it affects flux density.How could this be calculated?

 I know im the reason you added the word {decent }but its all in fun.

 Apparantly there arent many flying yet.

 Im gonna play awhile and see how things go.Thanks

[Flux]

The iron loss can't be calculated simply and we would never have the data on the core material if it could.

I was hoping that someone would actually measure it along with efficiency at various points. Perhaps it is not as easy as with a dual rotor and it would most likely be someone with a big lathe that would be able to do this.

Measuring torque is the fun bit and without a torquemeter coupling or mounting the stator on bearings as in a dynamometer, the simplest way would be to swing the shaft in a lathe, with tailstock support if needed and measure the torque reaction on the stator with a spring balance ( scale?).

It is the alternator input that needs matching to the blades. Once someone had done a curve the figures may be good enough to give others some idea of the input load from the output tests .

Flux

[Flux]

I assume the iron bit of the rotor is the same width as the stator, it is the stator width that you need to consider. There is no point in adding magnets outside the stator width, but if at least half the magnet is within the stator width it will still help as long as part of it is still on the iron core of the rotor.

If you are limited to smaller blades then you can make up the output to some extent with more speed so slightly less magnet may not be an issue.

Flux

[andyman5002]

Ok thanks flux, I just measured the stator and you are right it is the same length as the iron on the rotor, for some reason I thought it was larger. I think I will just go with the mags from before. One more question im hoping someone can answer. When you skew the magnets should one skewed pole fit inside the main coil? Or should the pole just be the width of the coil and the skewed pole will enter and exit the coil at different times?? Hope this makes sense?

Thanks Andy

[Flux]

Not sure I understand. The skew depends on the number of slots and needs to be such that the displacement over the width of the rotor is the same as the pitch from one slot tooth to the next. ( 10 deg in rotary angle for a 36 slot core) . This will not be the angle of the magnets across the rotor.

For 3 phase the pole width is about 2/3 of a pole pitch, so your total magnet area will be about 2/3 of the circumference. ( magnets 2/3, gaps 1/3). Hope this makes sense.

If it means you get more magnets in then you can exceed 2/3 with the magnets. You make less use of the magnets if the poles are too wide but you gain up to the point where the thing is covered in magnets. I wouldn't go to extreme but if you gain a row of magnets by exceeding the 2/3 then go for it.

[dinges]

Andy,

Have you read the Zubbly pdf-file? You'll see that the skewed magnet (the extreme two points of it) overlap the legs of the coil a bit; I.e., an unskewed magnet should sit inside the coil, but when it's skewed, it can extend/overlap a bit:

http://www.otherpower.com/images/scimages/253/magnet_skewed_between_coil_legs.jpg

I tried a quick search for the link to the full (part 1, 2 & 3) Zubbly conversion pdf-file, but can't seem to find it now. Hope someone else can help, or search yourself. It's explained in detail there. BTW, Zubbly's document should definitely be in the FAQ!

"For 3 phase the pole width is about 2/3 of a pole pitch, so your total magnet area will be about 2/3 of the circumference. ( magnets 2/3, gaps 1/3). Hope this makes sense."

Flux, I didn't know that and it was something I had wondered about a few times. Some guys fill the rotor to the brim with magnets. I have made a few sketches, and if you do fill the rotor completely up, you will get voltage cancellation (thus, less output, or, as you put it, non-optimal use of the extra magnets). Seems that in my rotor, I have about 2/3 filled with magnets too. Didn't know of your rule, just had to figure it out myself & make some sketches. Glad you confirm.

[dinges]

Zubbly,

Whilst perusing your photouploads I came across pictures of a car alternator that you modified with Neo magnets:

http://www.otherpower.com/images/scimages/253/130ampalter1.jpg

I can't seem to find the story about this alternator; did you write a story about it, and if so, where to find it?

[andyman5002]

Ok there is a lot of new information there. I read somewhere that it had to fit into a coil or something. Zubbly said 7 sator teeth, which that diagram shows, that was the diagram I was looking for i think. I thought the pole, clump of magnets, was just skewed on a 10 degree angle and that was that. But then I thought that this may cause cancellation because the pole will not be totally inside the coil, and will partly be in another one, but zubblys diagram seems to show this. Im going to have to re-read all of this for it sink in. I haven't read zubbly's PDF, and I agree it should be in the FAQ.

There is a lot for me to learn yet

So it seems I have gone just over this 2/3 rule with my 52mm pole widths. Im not clued up on the term pole pitch either . I think I will do some reading later on today. Also if the pole should not be skewed 10 degrees, how do you calculate the correct angle?

Im sure I'll get there in the end, its very interesting learning all of this and I would like to thank everyone for their help.

Thanks Andy

[dinges]

That 2/3-rule is a guideline; a few mm won't kill you. Besides, converting motors to gennies isn't a science, more like an art (at the moment, at least. Hopefully more hard data will turn up in the future).

Flux said it, but I'll say again: the 10deg skew does NOT project onto the rotor. See this discussion (lengthy!) for more info:

http://www.fieldlines.com/story/2006/6/15/19126/8190

http://www.fieldlines.com/story/2006/6/18/11456/6477

If you skew by one slot, you should be fine. IMO, it should be a tad less than one slot, but this is probably nitpicking. Put the rotor in the motor, put a mark on it at the left under one slot, at the other end under the next slot, and draw a straight line on the rotor. That's your skew angle, NOT the 10 deg (with 36 slots, as in your case).

The good thing is, you'll have to really mess up to end up with something that does NOT generate electricity. But the less cogg, the better, of course.

[andyman5002]

Thanks for the links they have cleared quite a lot up with my skewing concerns. I have done as you said and the skew angle seems to be 5 degrees. Which seems the same as the skew on the aluminium slots on the rotor. It turns out that I also measured the pole width incorrectly. I measured from the edge of the top the of the stator slot not the horizontal leg, so it works out to be 50mm now. I should still be able to use the same configuration of mags though.

I have been reading a lot of conversion posts mainly ones with aluminium cages. My question is that some seem to have the cage flush with the mags, and others seem to have the mags protruding 3-4 mm out of the top of the cage? Which is better or does it have no affect on performance at all?

Thanks Andy

[dinges]

I don't think whether the magnets protrude from the aluminium cage or not matters. The aluminium is basically invisible to the magnetic fieldlines; it's only there for the mechanical support of the magnets.

The steel core, however, is very important to complete the magnetic circuit, as you probably already know. It's also the reason that you need an aluminium cage and not a steel one, otherwise many of the magnetic fieldlines would be shorted & not go to the stator: a waste of expensive magnets.

If your new skew angle is the same as the original rotor, that should be fine.

I prefer to have my magnets slightly recessed in the aluminium cage, so that when I shove the rotor into the motor, the magnets can never touch the stator core. Also, when I slide the rotor in, I wind the rotor with layer of paper, to prevent scratching of the rotor. Not really necessary, but when you've got a shiny aluminium rotor, I want to keep it shiny. And yes, I know no-one will ever see the rotor when it's in place. Call me obsessed

[andyman5002]

Thanks for clearing that up dinges. I didn't think it would really matter because it is aluminium, I suppose its what they had available at the time. I can understand not wanting it scratched, after all it was a lot of hard work.

After doing the calculations again, there seems to be plenty of room between my mags, not sure if its too much, I read some where that zubbly likes a gap of about 1mm between each mag, mine have 3.75mm horizontal gaps and 2.5mm vertical gaps. If I could get 16mm diameter mags it would be better. But then again I need to take into account my blade size. I think I will be lucky to see 900 watts out of this unit with my mag choice and blades, shame really seems a waste motor potential.

Thanks Andy