Baldor 3 HP Motor Conversion Assembly

[SparWeb]

Hi everybody,

I hope you guys aren't all sick and tired of "yet another motor conversion" by Sparweb...

I have been slowly working on this one since January.  Not much free time to spend on it, so I hope that finishing it off won't take until next year!



It's a former Baldor 3 HP motor.  The dataplate info says:

• 1725 RPM
• 182T Frame Fan-cooled
• 8.6Amps @ 230V
• 4.3Amps @ 460V
• 40 deg C continuous
• full-load efficiency 82%

Other info:

• 5.0 ohms across phases in Star
• 1.125 diameter shaft
• Rotor Diameter 4.4" OD
• Stator diameter 4.5" ID
• 36 stator teeth

I started out with drawing - pretty anal, I know, but I have fun with this FEMM program and this time it's really paid off.  I came up with a really neat magnet configuration:







Yes, it was very difficult to assemble the magnets like that.  Being unable to screw down the narrow brick magents, I had to glue and clamp them.  Then I discovered that I hadn't mixed the glue properly (or it wasn't any good to begin with) so I had to do a bunch of extra gluing to make certain they would hold.



Then finally the big day of re-assembly.  Did it very carefully so that nothing would get damaged.  Hung the rotor from the ceiling and used a block-and-tackle pulley to lower it slowly.  The housing you see is clamped to my work bench.





And with that, it was time to have fun!  A set of flashing light bulbs always makes for a few chuckles: 



The shaft turns quite easily due to the alternating magnet sizes.  Really pleased with this.

Later I ran it up using my drill press to maintain various constant speeds.  I get an open-circuit DC voltage (rectified) of 37 Volts for every 100 RPM with it connected in series-Star.  In parallel-Star that gives 18.5 Volts / 100RPM.  This would lead to a 24V cut-in speed of less than 130 RPM!!!

That seems to be too slow for the size of blades I plan to use, 10 feet.  For a rotor that size I would like to have a cut-in speed around 160 RPM.  The solution is to use a different connection scheme.  I'm thinking it's time to try out a JERRY connection...

I guess when that's done, I will fill in the end of this story. 

[Rover]

Wow, what a beeast , nice job

[FishbonzWV]

Another fine job Stephen,

I see you made a new rotor with lots of milling. Did you mill the flats to accommodate the 1/2" mags and then the 1" ones in the center? If you did, I see why it took so long!
I can also see in the Femm drawing that alternating the mags should keep maximum saturation of the stator versus a 1" x 1/2" x 1" layout. Did you also model that configuration? Just curious as to the results.
What's your choice of epoxy for the mags?
The last one I did, I filled all the gaps to the tops of the mags just for the extra strength.
I think you are right with the IRP ((Jerry)(speaking of Jerry, where is he)) it should get you closer to the desired cut in.

Hope you get it flying soon.
Bonz

[DamonHD]

That looks amazing!

Rgds

Damon

[TomW]

Stephen;

Pardon me being as thick as a brick but, I don't understand  the layout of the magnets?

Could you explain in terms a tree stump could understand?

Thanks.

Tom

[ghurd]

Looks Great Steven!
G-

[SparWeb]

Sure Tom,

Rule # 1 is that the preferred set of magnets is usually the cheapest.
Rule # 2 is that the more magnets, the more flux you get, and usually the most voltage.

So I went choosing between different arrangements of magnets to find the best coverage, and kept an eye on the dollars because I'm cheap.  Below are the three contenders for which I kept screen-shots.  The first is an arc-segment.  That turned out to be expensive, and the dimensions have to be "perfect" for the right amount of flux.  The second is an 8-magnet arrangment.  I could fit magnets 3/4" thick as long as I only had 8 per ring.  But there are big pie-shaped gaps between each magnet.  So I tried to make smaller magnets work, and found that I could make the best coverage with 1/2" magnets.  This had high flux, but the cogging was going to be pretty bad because 12 magnets line up really well with 36 teeth...

Then I hit upon the idea of using some 1"x1"x1/2" and 1"x1/2"x1/2" mags in alternation.  By doing that 3-D drawing I wrapped my brain around how I was going to machine such a thing, and that's when I decided to go with it.  I could flip the pattern of the middle ring backwards, and its cogging attraction "clockwise" would counter-act one of the other ring's cogging "counter-clockwise".  This plan also turned out to be pretty cheap, like 250$ or something.  I spent a little more on screws and the epoxy was already paid for.  The blank of steel for the rotor is yet another junk-yard discovery.  Got an extra 18" of it, so I can make 6 more if I want!!

To mill the flats, I started with the four rows 1 inch wide for the 1"x1"x1/2" magnets.  Then I clamped it in the vise at the odd 37 degree angle I needed for the next big flats, measured very carefully.  Once that flat was done, it became a process of repeated iterations of clamping against the previous 37 degree flat to mill the next one at 90 degrees to it...  At these angles I could not mill straight across, either.  I had to mill each 1" flat on the ends, then come back later and mill the central 1" flats at the opposite 37 degrees.  With all of those done, I only had the 1/2" wide flats to finish, which followed the same procedure, but turned at yet a different cock-eyed angle.  Time consuming!

Have to talk the boss into getting a 5th axis drive for the CNC....

I guess there are a lot of details left out because I do a bunch of this stuff either on paper or in spreadsheets scattered about my computer hard drive that don't even make sense to me a few months later.

I took some pictures of the machining process so maybe if I can find them it would help.  Here are the FEMM drawings.



ARC SEGMENTS



1" X 3/4" MAGNETS



1" X 1/2" MAGNETS + 1/2" X 1/2" MAGNETS

[SparWeb]

FishbonzWV:

You asked about the glue and here I must confess my shame.

I started by putting the 1x1 magnets on, screwing them down with a dab of epoxy to "for insurance".  I had grabbed a bottle of laminating epoxy that I like to use for my wood blades.  Talk about using the wrong stuff!  I didn't notice that things weren't working as I was screwing down the big 1x1 magnets, but when I got to the 1 x 1/2" magnets, I had 5 or 6 on and was working on the 7th when one I thought was done curing, popped off and LEAPED onto its neighbour!  Uhhh.  Started taking several off and others wouldn't let go, but still didn't trust the glue.  Then the full reality of what I had done struck me and I realized that the laminating glue will not hold in high temperatures, but I wouldn't get many of these magnets off without breaking them.

So....  what to do?  I found the strongest, toughest, and most temperature resistant types of epoxy data sheets and went around trying to find suppliers.  Eventually an old hand aircraft mechanic I know let me borrow a pot of his stuff.  I even went to the trouble of bonding sample pieces of steel together, cooking them in my toaster-oven for 2 hours, and pull-testing just to make sure that the epoxy would hold.  Very impressed by the results, by the way.  The plating will come off before the epoxy lets go.

So that epoxy is the grey stuff you see filling the gaps between many of those magnets.  I'd recommend it to everyone (Hysol EA934.NA) but it is EXTREMELY expensive and very toxic.  Mere mortals such as I should not be playing with these kinds of matches.

[Rover]

That was wood stump explanation?... ( I must be a rock, someday I'll be a stump).

I was interested in the odd arrangement as well.

[SparWeb]

Good point.

"Cram on as much magnet as possible"  That's about all I really needed to say.
The rest is just details about how to make it.

[12AX7]

Hello!

Your conversion looks very impressive! 
I'm sure I've heard Zubbly say the same exact thing "cram as much magnet as possible"
Two real quick questions.
How much $ do you have invested (if you don't mind)
How many hours?
and maybe one more,  ever consider doing a Zubbly rewind?

ax7
Mark

[SparWeb]

Thanks for your comments (everyone)  I'm flattered.

Time? Cost?  You think I'm a injuneer or sumthin.   

I think I spent over 350 dollars (CAD or USD doesn't matter these days) on the magnets mostly, the materials and the old motor were free.  I'm including my search for better epoxy though I didn't use what I bought, because it didn't "fillet" well inside gaps.

Time is almost impossible for me to work out.  I spent many hours with the simulations and drawings.  Still poke at them from time to time too because I'm not done yet.  In the shop I easily spent more than 20 hours on the lathe, milling machine, fussing about the press getting the cylinder onto the shaft, and tapping all the holes.

Now I'm about to take it apart again so that I can re-connect the stator star-point wires.  That will take as much time as it takes to get done.  After that I'll put a connectors box on the side.  Do you also want to include the time it will take me to build the hub for the shaft and the mount for the tower?  The cost of any project is usually decided at the moment you decide that "enough is enough".

I've never seriously considered re-winding the wire.  There is always enough in there and so far there has always been one connection scheme or another that would suit.

[willib]

Hi Stephen , could you describe the setup a little more where you are cranking the alt by hand?

I see that you have a RPM gauge of some sort on there.

Are the three bulbs connected to each phase? cuz it looks like one is really bright , one is sort of bright and the front one is off ?

what is the meter reading? point 344 what ?

Just curious , and keep up the good work,

PS i don't think we will ever get tired of reading about peoples projects

[SparWeb]

Bigger version of the test photo:

http://www.sparweb.ca/3_Gen_MoCo/Baldor/Tests/Baldor_CrankTest1.jpg

That's just fooling around, there.  I don't remember how fast I was turning it, and I can't see the screen of the bike speedo in the picture either.  I think it said 0.344 Amps.  Sounds about right for a set of 40-watt bulbs.  Each bulb is across a separate phase.  I made the 3-bulb rig just for kicks a while ago.  I was going to use it as a demonstration piece but it wasn't done in time.  Anyway, the 3 bulbs light up in succession and you can see the "rotation" speed up as you crank faster.  Kids please do try this at home.

Anyway, the real scientific    tests just had the meters plugged in, with no fancy light tricks.  The stock motor has 9 of the 12 phase wires coming out of the connection box, meaning that the Star Point is hard wired and tied up with the rest of the windings in the stator.  I will find it and cut it and crimp+solder separate wires to each of the 3 star point wires to make # 10, 11, and 12 available for connections.  I've decided this generator needs a Jerry connection, and I can't do that if I don't separate the star point.

Sometimes I crank by hand but usually I have a pulley on the end of the shaft.  Wrapping a string around the pulley, and tying weight to the string, the weight will make the shaft turn at a relatively constant speed.  With the shaft turning, I can pay attention to the meters ticking off volts and RPM simultaneously.  That's how I derived my figure of 37.3 volts per 100 RPM figure.

Since I first posted I've finished up a much more detailed diary entry on my personal website:

http://www.sparweb.ca/3_Gen_MoCo/Baldy.html

So for those what want to read more, I can offer them the story up until here, in more detail and with more pictures.

[dave ames]

Steven,

thanks so much for sharing your work!           

another top notch presentation... love the magnet arrangement, reminds one of the chevron shape of the magnets in the early F&P's.

hope readers appreciate the time and effort it takes to document a project such as this? supper duper job as always with even more details in your diary!

i always come away with something useful from your work and your postings!

cheers, dave

[SparWeb]

Dave,

Thanks for the kind words.

I just added details of the wiring connection changes.  Maybe you'll be interested in that, too.
Most of the details on my own site, but here are some pictures:









For completeness' sake, let me summarize that I was making extra wires come out to the connection box.  The added wires are numbers #10, 11, and 12 in the standard three-phase motor scheme.  If you look up the means of connecting three-phase motors, you will see that in order to use Delta or Jerry connections, you need these three separate wires.

[ghurd]

I second Dave's assessment.
You do have a way of explaining complicated or confusing things in clear and understandable terms. (cough-cough-hint-hint-cough)





 

[SparWeb]

...cough-cough-hint-hint-cough...

I hear ya-

Well, whaddya THINK I was doing, spending so much time writing and illustrating this?
I'm hoping to have the "how-to" part of a FAQ done once I have this written out.

There are also many basic issues that we will always refer back to Zubbly, partly because we still love him, but mostly because he did understand it better than I do. 

[adaml]

Steven,

Another masterpiece conversion - fascinating as ever.  Thanks for the excellent post/write-up.

[SparWeb]

To be continued:   http://fieldlines.com/board/index.php/topic,143680.0.html