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Number of poles from a 3 phase motor
By windstuffnow, Section Homebrewed Electricity Posted on Thu Apr 20, 2006 at 01:39:19 AM MST
Formula?

I have a 5hp 3phase motor that I'm considering either using it as is or pulling the laminants out and rewinding it for a couple smaller units.
Considering using it as is I was trying to figure out how many poles to place on the magnet rotor. The plate on the unit says 60hz 3 phase at 705 rpm 440volt ( kind of an odd ball ). It has 48 slots in the stator. If I pull the windings and rewound it I would most likely use 16 poles. Using the formula; rpm = 120 x freq / poles I get some odd numbers for poles using the rpm stated on the motor. What would the number of poles be considered on this motor if I chose to convert it as is? I came up with 10 which didn't make sense to me. I haven't pulled the wires yet to see how it was wired.
.

Number of poles from a 3 phase motor | 12 comments (12 topical)

Re: Number of poles from a 3 phase motor (3.00 / 0) (#1)
by Warrior on Wed Apr 19, 2006 at 07:50:55 PM MST

Hi Ed,

Three phase motors can be a little hard to understand because there are many ways to wind them. I asked sort of the same question some time ago and Zubby gave me a great explanation. See here:

http://www.fieldlines.com/story/2006/3/30/15714/6613

Good Luck,

Warrior

Warrior__ "Why can't Murphy's Law be used to my advantage??"

Re: Number of poles from a 3 phase motor (3.00 / 0) (#2)
by zubbly on Wed Apr 19, 2006 at 07:56:23 PM MST

hi ed!

thats a 10 pole machine. it is rare. inspection of the winding, you will find that it has coil groups of 1 and 2 coils. (known as odd grouping)

place 10 poles on the rotor and away you go.

the frame size would be equal to approx a 15 or 20 hp by todays standards. will make a lovely gen :)

zubbly

Re: Number of poles from a 3 phase motor (3.00 / 0) (#5)
by windstuffnow on Wed Apr 19, 2006 at 08:28:11 PM MST

Thanks Zubbly! That gives me a starting point anyway. I figured it would make a nice HD alternator, emphasis on heavy. I'm still in the decision stages of this project and using it as is may be a bit overkill.

I like the dual rotor designs, quick and simple, but when your building them for very low rpm high output operation they tend to get big and heavy. Laminants have a considerable more bang for the buck which helps keep them smaller and lighter overall. At least from my past experiences building the axial versions of the slotted silicon stators. I've considered having some reverse laminants cut out and using a large brake drum... which would be ideal for this application.. but that could get pricey.

I haven't done a "motor conversion" as yet so this actually sounds quite fun even if I don't use it on this project.

We'll see...

.
Have Fun! Windstuff Ed
[ Parent ]

Re: Number of poles from a 3 phase motor (3.00 / 0) (#10)
by vawtman on Thu Apr 20, 2006 at 05:06:18 PM MST

hi ed
These conversions with strong mags are incredible at low rpm.You need a big turbine and your planning for that.

Do you have the mags and layout figured out?

You will be happy with it.

[ Parent ]

Re: Number of poles from a 3 phase motor (3.00 / 0) (#12)
by BuddyL on Fri Apr 21, 2006 at 07:56:18 AM MST

I also have a motor that i could use your help on. It is 5hp 3 phase 240 vac made by Reliance textile duty. Ok it has 24 slots 12 wires 2 in hande that make up 6 coils the rpm is 3485 5.6 amps. What i want to know is this a 2 pole motor and worth doing anything with just the way it is. I dont want to rewind it was free so no loss. Hope you can help and thanks! http://www.otherpower.com/images/scimages/3110/Im000941.jpg this is the motor.

[ Parent ]

Re: Number of poles from a 3 phase motor (3.00 / 0) (#3)
by Nando on Wed Apr 19, 2006 at 08:24:30 PM MST

You have an 8 pole motor AS IT IS.
Remember:

RPM = ( HZ * 60 sec)* 2/P

RPM = (60 Hz * 60 Sec)* 2 /8 = 750 RPM less the Slip = 705.

And it seems to be a 3 phase with 48 slots and with 3 phase

Nando

Re: Number of poles from a 3 phase motor (3.00 / 0) (#4)
by Nando on Wed Apr 19, 2006 at 08:28:00 PM MST

Heck I need to check my writing I meant 10 poles and I wrote 8 poles all the way

I have lost my mind, indeed !!

Nando

[ Parent ]

Re: Number of poles from a 3 phase motor (3.00 / 0) (#6)
by zubbly on Wed Apr 19, 2006 at 08:36:54 PM MST

let us know if you find it! ;=)

[ Parent ]

Re: Number of poles from a 3 phase motor (3.00 / 0) (#8)
by Nando on Thu Apr 20, 2006 at 09:12:44 AM MST

Zubbly:

No luck, I tried hard and I can not find it, now my area is a mess with all the papers in disorder searching for it .

I really lost my mind !!!Now !!

Nando

[ Parent ]

Re: Number of poles from a 3 phase motor (3.00 / 0) (#9)
by zubbly on Thu Apr 20, 2006 at 02:36:11 PM MST

i replaced mine with a tomato :)

zubbly

[ Parent ]

Re: Number of poles from a 3 phase motor (3.00 / 0) (#11)
by elvin1949 on Fri Apr 21, 2006 at 06:47:40 AM MST

eggplant works pretty good to.
later
elvin

[ Parent ]

Re: Number of poles from a 3 phase motor (3.00 / 0) (#7)
by kenputer on Thu Apr 20, 2006 at 05:59:12 AM MST

Of all the things I have lost,I miss my mind the most :-) good luck

[ Parent ]

Number of poles from a 3 phase motor | 12 comments (12 topical)

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