the Otherpower.com Discussion Board || 3-PH Conversion Question Star or Delta

Front Page - [Homebrewed Electricity-- (wind) (solar) (hydro) (steam) (controls) (storage) (mechanical)] - Classifieds - Site News
Everything - Newbies - [Remote Living-- (housing) (heat) (light) (water)] - Rants & Opinion - Diaries - Our Products

3-PH Conversion Question Star or Delta
By ghurd, Section Homebrewed Electricity Posted on Sun May 7th, 2006 at 03:24:31 PM MST
What to Expect if I Keep Going?

Hey Everybody,
Made a AC conversion.
3-ph, 3600RPM, 1/3HP, 10 ohms per phase, factory coils.
Laptop hard drive magnets, in half.
Star, at about 425RPM shows open volts at 12VAC. 25RPM per Volt DC.
Is that going to be 425RPM for 10VDC Delta? (17/1.7) Meaning 575RPM for 12V cutin?
Star is making 1A into a battery at an unknown RPM, maybe 500RPM? Seems to peak out, possibly partly due to slippage in the drive setup.
Star ohms with 10 ohms per phase, is that 15 ohms?
12V (battery) + 15V (1A x 15 ohms) = 27V and 27 watts in the coils.
And Delta, 12V + 10V (1A x 10 ohms) = 22V and 22 watts in the coils.
Delta needs 5V less in the coils when making 1A.
(25RPM / Volt Star) x 1.7 = 42.5RPM per volt.
So at 1A it needs 212 less RPMs(42.5 x 5) than it it first seems? Comparatively.
The air gap is, well, huge.
Any idea if doubling the magnets will be a much help given the relative large surface area of the poles? There is room. (Hi Zubbly!)
Yes, 3600 is not good. No, I can't spin it under load with any accuracy, won't attemp it loaded in the lathe. Not sure of the open volt RPMs because the lathe knob says 200-----1500, looks like 425 on the knob.
Let me have it. How am I thinking about this wrong?
Would it be worth the effort to try Jerry Rig Delta, doubling up the magnets, or is this beating a dead horse?
G-

3-PH Conversion Question Star or Delta | 10 comments (10 topical, 0 editorial)

Re: 3-PH Conversion Question Star or Delta (3.00 / 0) (#1)
by Flux on Sun May 7th, 2006 at 11:08:12 AM MST
(User Info)

Yes you are right about the cut in speed in delta.

If 1 phase is 10 ohm then star resistance is 20 ohm Equivalent delta resistance will be 1/3 or 6.7 ohms.

With small magnets and a large air gap, resistance may have little to do with determining the output, but delta will still give more current.

The slipping drive doesn't make your calculations any easier.
Flux

Re: 3-PH Conversion Question Star or Delta (3.00 / 0) (#2)
by zubbly on Sun May 7th, 2006 at 05:13:02 PM MST
(User Info) www.zubbly.com

hi Ghurd!

it sounds promising. before trying to make any more calculations on output, i would do my best to try and add some more mags in there to reduce that airgap. shoot for an airgap between 1/32-1/16 of an inch. your voltage will come up much sooner with less rpm required.

what voltage is the motor on the name plate? how many mags per pole have you put on the rotor? do your best to get your test setup running without any slippage. got any pictures?

zubbly

Re: 3-PH Conversion Question Star or Delta (3.00 / 0) (#3)
by ghurd on Sun May 7th, 2006 at 07:26:23 PM MST
(User Info)

Thanks Guys!

Driving it without slippage at a known speed will be a problem, at least in the very near future. Shaft too large for the drill press, lathe seemed somewhere between `unsafe' and plain stupid.
Glad to hear the resistance numbers will be better. Sometimes the more I think about it the worse it gets.

Brand new GE, 5K19MG42, 1/3HP, 3450/2850, 220V, 60/50, `FJU' (?)
Cont, USA. 18 slots.
With 16 magnets per pole, averaging ~0.625x0.375". Very close to 1/8" thick. Zero cogging.

I filled the first to go in 2 rows around with double magnets and it does fit.
Given the inconsistency of the shapes, 1/32" is out of the question. Unless a smaller magnet is used for a 3rd layer? Bet I can find something that fits. He-he.
Expected it to work better or not at all. The ends, etc, will be cleaned up later.

Any more thoughts, except wishing you didn't see the photo?

Perhaps it should be re titled "How to Ruin a Good Motor and 250 Hard Drives".

G-

Re: 3-PH Conversion Question Star or Delta (3.00 / 0) (#4)
by powerbuoy on Sun May 7th, 2006 at 07:48:52 PM MST
(User Info)

Interesting to say the least ... I was wondering when I read 16 magnets per pole ... now I know why ...

[ Parent ]

Re: 3-PH Conversion Question Star or Delta (3.00 / 0) (#5)
by dinges on Sun May 7th, 2006 at 11:08:33 PM MST
(User Info)

OMG! And I thought I had a nice collection of HD magnets.

I notice there's something missing in this picture: hot glue?

That cage won't win a beauty prize, but maybe it's mechanically much better than it looks. Think I like the look of Zubbly's conversions better though ;)

What I might be worried about is some of the Nickel-plating, that's already separating at places, coming of in small pieces and finding its way in the rest of the motor, damaging wires, etc.

Looking forward on hearing updates on the project, esp. results.

PS: I just found the perfect stepper: 2.8V/2.2A. 5.6V/coil and two completely separate coils. This one should actually give me 10W output, after some quick measurements. Think 'VAWT'. Won't even need slip rings, grin.

Peter.

[ Parent ]

Re: 3-PH Conversion Question Star or Delta (3.00 / 0) (#7)
by ghurd on Mon May 8th, 2006 at 06:56:45 AM MST
(User Info)

A word about hard drive magnets.
Do Not put much effort or money into getting FREE HD magnets!
Click Wondermagnet.com at the top and buy some magnets. It's cheaper!
Between gas, several sets of torx bits, shipping, several days of disassembly, these broken and mis matched magnets cost a lot more than good magnets.

I was quoted $186,000 for a well fitting aluminum cage. (kidding)

When the magnets are snapped, the coating begins peeling. Used a small razor knife to peel off any that was loose. A layer of water-PROOF epoxy is over the entire magnet.
Epoxy was on everything. Try fitting that many neos close together without epoxy getting everywhere.

Good luck with the stepper, looking forward to those results.
G-

[ Parent ]

Re: 3-PH Conversion Question Star or Delta (3.00 / 0) (#9)
by ghurd on Mon May 8th, 2006 at 08:35:05 AM MST
(User Info)

(I save hot glue for the fancy projects)

[ Parent ]

Re: 3-PH Conversion Question Star or Delta (3.00 / 0) (#6)
by zubbly on Mon May 8th, 2006 at 04:55:52 AM MST
(User Info) www.zubbly.com

hi Ghurd!

well it may not be the prettiest thing to look at, but then again neither am i. LOL

just a thought, you could try using steel shim stock glued on top of the mags to close the air gap up some more. i haven't done it myself but it should work.

even if you only end up with a few amps output it will add up over time and better to have some juice in a batt than none at all. every little bit gained is 100% more than you had. the experience itself is the real value you gain.

if you leave the air gap as is, or add shim stock to reduce it, you could always heat shrink a pop bottle over the rotor to get a bit more guarantee that the mags will not be coming off.

have fun!
zubbly

[ Parent ]

Re: 3-PH Conversion Question Star or Delta (3.00 / 0) (#8)
by ghurd on Mon May 8th, 2006 at 07:41:34 AM MST
(User Info)

I will go with stacking more magnets. The long stack of thin ones near the top measure 0.040".

This is the largest one I ever tried.
The hope was for 60W-ish. And a 12V or 24V cutin not as low as I usually get (have made some dandy 10W PMAs that would be great for Jerry's truck).
I will assume Jerry Delta will be the only option when I get gap smaller unless someone thinks otherwise.

I was thinking heat shrink tubing, totally filled with epoxy. Bad idea?
Never had any problems with too much heat... go figure.

How much power could this one make, with factory coils, if properly done?
What magnets would be good? I was thinking 2x 1/2x 3/16" (if they are made) will be a nice fit. More magnet in less area. And easier.
I do happen to have a spare to ruin later. ;)

G-

[ Parent ]

Re: 3-PH Conversion Question Star or Delta (3.00 / 0) (#10)
by ghurd on Wed May 10th, 2006 at 07:32:19 AM MST
(User Info)

I doubled the magnets. Got the gap down to about 1/16".
Quite a jump!

Amps are up to 1.6A into a full battery, the drive is still slipping.

Open volts at the same RPM went to 19V AC, 27VDC. The knob was not adjusted.
Jumped from 25RPM per volt to 15.75RPM per volt. Still in star.

Adjusting the RPMs for 12VDC showed the speed knob is no way to check RPM. It is not even close enough for a guess.

If 425RPM was correct, star cutin is now 200RPM, delta
Can feel a bit of cogging now, about like a tin stepper motor. Certainly not enough to have an adverse effect.

The second layer of magnets is easy to add.

Some of the first layer magnets still had some of the other pole left.
I believe it would be a good idea to remove the center 10% of 2 pole per face HD magnets from now on.

Delta cutin is about where I want it!
I came up with 330~360RPM for large Rich H blades. Not sure if thats right...

I'm calling this one done after changing it to delta.

Thanks guys!
G-

3-PH Conversion Question Star or Delta | 10 comments (10 topical, 0 editorial)

Menu

� create account
� How to use the board
� FAQs
� search the board
� Google search the board
� Old Otherpower Board

Login

Make a new account

Username:

Password:

Total Views

��147 Scoop users have viewed this posting.

Related Links

� magnet
� Also by ghurd

You must be a registered user to post here. It's easy and free, and the link is on the upper right side of your page.
All trademarks and copyrights on this page are owned by their respective companies. Postings are owned by the poster, but may be deleted or moved at the ADMIN's sole discretion. The Rest � 2003 Forcefield.
You can Email the board ADMIN here. PLEASE include the username you signed up with!