Author Topic: K55 ceiling fan motor  (Read 39094 times)

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rustkolector

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K55 ceiling fan motor
« on: August 31, 2010, 07:15:49 PM »
I have an Emerson K55 200 RPM 1 phase, 120v, 0.9 amp ceiling fan capacitor motor. This is unlike the normal fan motors found here in that it has a standard laminated "internal" induction rotor like any typical induction motor. The stator has 36 slots with 4 rows of 9 coils each progressively spanning two slots. There are 4 wires connected to these coils . Red, brown, and two white wires. Red to either white wire is 57.4 ohms, brown to either white wire is 57.4, red to brown is 115.0 ohms.  White to white wire is .01. My goal is to rectify the output to provide a constant 13v output via an external voltage regulator.

I plan to fabricate a new rotor from steel with 18 poles using ceramic or neo magnets. My input speed will be a near constant 600 RPM which might be a bit high for the end voltage I am looking for, but unfortunately it is a fixed direct drive arrangement. I was expecting to find 2 rows of coils in this motor (for some unknown reason) and the 4 rows has me a bit confused. My guess is that this motor is wired with all 4 coil rows in series with two common center tap wires, but I am not sure just what the coil schematic would look like.

What would be the best way to wire this stator/rectifiers to the end goal of 13vdc output???

Jeff




joestue

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Re: K55 ceiling fan motor
« Reply #1 on: September 01, 2010, 12:48:56 AM »
Keep it the way it is. at 600 rpm you should get plenty of voltage out, rectify it to 120-350 vdc and pipe it into a 12 volt smps.
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dave ames

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Re: K55 ceiling fan motor
« Reply #2 on: September 01, 2010, 03:15:17 AM »
Keep it the way it is. at 600 rpm you should get plenty of voltage out, rectify it to 120-350 vdc and pipe it into a 12 volt smps.

cool !

 i need a whole bunch of those, any links?

ghurd

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Re: K55 ceiling fan motor
« Reply #3 on: September 01, 2010, 08:07:12 AM »
I expect it is multi-speed, and that causes problems.
Most of the coils will not make power because they will not be properly laid in the slots in relation to the magnets.
After diagnostics, pretty sure it will require a lot of Snip&Solder to the existing coils, or a rewind.

The first step is to get the 4 wires ends in the open so you can see where they go.
Carefully cut the strings and tape to get a better look.
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rustkolector

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Re: K55 ceiling fan motor
« Reply #4 on: September 01, 2010, 11:49:41 AM »
Ghurd,
I found more info on this motor this mornning. It is designed as a single speed 200 RPM motor with two series windings connected with a center tap (two white wires). Series capacitors are used to control the voltage to the windings for different motor speeds. Making up each of the two windings (red to white or brown to white) are two adjacent sets of 9 coils (18 total) connected in series. They are laid in the slots overlapping and adjacent to each other. Each individual coil spans two of the total 36 slots coil slots, so the two adjacent coils of each winding spans three adjacent slots. Hope this description makes sense to you. I will also try to post a photo of the stator. Thanks for any assistance.

Jeff






I inserted your photo please go read the photo posting sticky in site news
Kurt
« Last Edit: September 01, 2010, 01:03:36 PM by kurt »

ghurd

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Re: K55 ceiling fan motor
« Reply #5 on: September 01, 2010, 12:33:44 PM »
I think a photo from above would help... a lot.

I can't quite see how single-phase overlapping series coils is a great idea.
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rustkolector

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Re: K55 ceiling fan motor
« Reply #6 on: September 01, 2010, 12:44:05 PM »
Ghurd,
After looking at the attached photo my slot references may be a little off, but the photo shows the coil arrangement.

Jeff

rustkolector

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Re: K55 ceiling fan motor
« Reply #7 on: September 01, 2010, 12:48:51 PM »
Ghurd,
I haven't figured out yet how to have the photo displayed in my post. You can vies it by clicking on the attachment K55 winding.jpg at the bottom of the post. 

Jeff

ghurd

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Re: K55 ceiling fan motor
« Reply #8 on: September 01, 2010, 01:06:11 PM »
That's a new one on me!

I think it must have the series coils not overlapping each other, which looks possible but it will be difficult to figure out for certain.  Rows 1 and 3 are one string, rows 2 and 4 are the other?  Hard to put what I envision into words.
I think it would make a PMA if the 2 sets were separated and rectified separately, and with 18 magnets.

The problem will be that 57 ohms per phase and the massive turns per phase.
It will make a whole lot of volts, but not many amps. (by "not many amps" I mean less than 1A is my bet)

I doubt you can get in deep enough to do the "snip&solder" to reconfigure the coils.  I know I would not even try to get that deep.

Attempting to display the pic here...
« Last Edit: September 01, 2010, 01:08:03 PM by ghurd »
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ghurd

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Re: K55 ceiling fan motor
« Reply #9 on: September 01, 2010, 03:21:54 PM »
This one is stuck in my head!

I would be tempted to try a rewind.
3-ph, 12-pole, 2 round neos per pole, 36 overlapping coils, individually rectified phases.

It looks pretty small.  Might be difficult to get much effective volume of magnet in there with 18 poles.
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rustkolector

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Re: K55 ceiling fan motor
« Reply #10 on: September 01, 2010, 05:53:18 PM »
ghurd,
I don't need more than about 40-60 watts of power out of this system at 13v. If I can get 0.7 amps or more AC out of each winding (~60v), I should be good. This is not a project where I am after power as much as a voltage source.  I was planning on two separate AC circuits and then combining the rectified output for added amperage. I will check with my new information source to see if we can discern the way the coils are wired. I don't think at this point that I am up to doing a complete rewind on this project, although I intend to attempt a rewind on a future project.

Assuming that the coils are overlapped 1-2 and 3-4, what do you suppose the output would look like with 18 magnets, and how wiide should the magnets be? If wound 1-3 and 2-4 how wide should the magnets be? Would these coils be wound alternating right - left or all the same?

Thanks for all your help. I will post any new information that I find regarding the winding arrangement.

Jeff                   

ghurd

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Re: K55 ceiling fan motor
« Reply #11 on: September 02, 2010, 09:17:21 AM »
I really doubt it will make 0.7A from each phase at 13V or more, with the coils as they are.
I think you would be doing pretty darn good to get 0.5A out of each phase, without some serious coil reconfiguration that looks to be nearly impossible.

Not sure where the 60V came from, unless you are thinking of trying some electrickery solution.

Sounds like #27 wire, and 0.7A may be pushing the wire's limit in this situation.

If you can't see the direction they are wound, there is a way to run maybe 0.3A DC through one phase and check the polarity to deduce the winding directions and relations.  Could do it with a old, cheap, unregulated 12V DC 1A wall wart.

If coils 1-2 are in one phase, and coils 3-4 are in the other, there would be an awful lot of cancellation, to the point where I would not even try to use it (that's bad, because I'll try to make a PMA out of almost anything).
I can't imagine why they would have wound it that way, so I doubt its an issue.

The look of the output will be based on the load, and you have not specified the load.
The output amps to a battery would look quite smooth.

How wide the magnets should be on something like this is a black art.  Usually educated guessing based on previous projects.

Leaving the coils as they are, I would try to just cover 2 teeth (including 1 slot) and a tiny bit more, with round magnets.  Neo.  2 magnets per pole, slightly skewed.
The length/thickness of the magnets can screw up the plan.  It they are 2" long, then there is not enough room toward the center of the rotor.
Small motor with 18 poles and 36 slots is a recipe for a cogging monster.

Rewinding to 3-ph would be a lot better.  More efficiency, less resistance, magnets could be laid out to greatly reduce cogging.

Guessing you intend to drive that with a diesel?
There would be a Very long list of easier ways to get 50W at 13V, and 1st on my list would be starting with a much larger motor.
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rustkolector

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Re: K55 ceiling fan motor
« Reply #12 on: September 02, 2010, 02:14:32 PM »
ghurd,
I appreciate all your insight and assistance. To answer a few of your questions, I am a model builder. I sought out this forum for much needed information on generators related to my hobby of building scale model working internal combustion engines of the early 20th century. I hope you guys don't mind my intrusion on this forum. My latest model is a 1/10th scale model of a 125 hp Bruce-MacBeth natural gas stationary engine commonly used in 1915 for on-site power generation. The engine is nearly complete except for painting and a cooling system. It is running pretty well at 600 RPM. With this little engine I plan to drive a working model of a vintage 75kva open frame AC alternator. I prefer that my models do something other than just run, and a working generator providing electro/mechanical power or light interests onlookers. I have included photos of the model engine and the actual generator I plan to model, hopefully using the Emerson K55 motor stator. The iron rotor, shaft, and outboard bearing will be fabricated. The magnets in the rotor will be wrapped with string to simulate coil windings and fake exciter brush rings will be installed. The 13v output will be used to drive ~.30 amp 12v computer cooling fan, and an array of 12v lighting load for now.

The K55 is rated at 0.9 amps at 120vac. I was hoping to get near that, but I really only need about 40 watts from the combined rectifed ouput. The dc voltage will be controlled with an external dc regulator. I mentioned the 60vdc per phase figure because another ceiling fan generator builder told me that he got 122vac out of his generator at 600 RPM. It was only a guess on my part.  

The magnets would have to be 1" long to match the stator lamination length. 18 poles would be near scale for the prototype. I would like to use rectangular magnets so they can be wrapped to closely simulate pole windings. Hopefully I can skew them slightly since severe cogging would be undesirable while starting the engine. The magnets will be approximately .375-.500" thick N to S. The rotor pole layout may likely determine the magnet width. The K55 stator laminations are 5.50" dia. and the rotor will be about 3.20" dia. I hope to know next week just how the K55 coils are wound. I found a helpful contact at a fan manufacturer that uses Emerson motors. Hopefully it will be 1-3 and 2-4 as you suggested they would be. Rewinding is beyond my electrical comfort zone just now, but I am working on it.

That is my project, and I certainly appreciate the help. I will post the winding arrangement when I get the information. Thanks again.

Jeff

« Last Edit: September 02, 2010, 02:23:24 PM by kurt »

ghurd

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Re: K55 ceiling fan motor
« Reply #13 on: September 02, 2010, 04:19:28 PM »
Please don't clutter the board with amazing projects.
(kidding).
Very nice.

By the magnet being 2" long, I think you could interchange that with 2" thick, or 2" deep into the center.
Big magnets sound good, until there is not space down toward the axle.  Or until the factory rotor falls into a stack of washers on a rod.  I have had both occur more than once.

It is Always easier to conserve than make power.
Consider reducing the load.
LED bulbs in frosted globes are just as impressive to the novice onlooker while using a tiny fraction of the power. (and can get them on ebay for $5)
Look for a fan with similar CFM at a lower current.  I expect you can find something that only uses 100ma.

I have NO doubt the other guy achieved 122V, but I doubt he achieved 122V and 0.5A at the same time.
That's the problem.
The volts are easy, but volts and amps at the same time are very difficult to get from something with that many turns and that much resistance.  Trust my failures on that one.  Simply the amps are what I would consider out of reach. 
There are deeper issues, especially concerning the coil inductance in something like a cieling fan motor.  There will be a point where the output current simply goes flat.  This chart is of something that weighs 11 pounds and with far less issues than you have,
except (combined total) I expect your will flatten out before 0.7A,



If you use a single rectangular neo per pole, the gap will increase and the flux will decrease.
http://www.otherpower.com/images/scimages/2050/Gap.gif

Dude.  If you built that thing, I bet you can rewind the motor to 12 pole 3-ph.  I am not saying it would be quick and easy.

I am not sure about the aesthetic requirements, but I still think you would be infinitely better off starting with a different motor.
AND decreasing the load.
AND adding a battery, even if it is a tiny battery.

Which brings up the issue of voltage control.  It may be a relatively simple issue with a fixed RPM and known PMA.

There is more than one way to skin a cat.
If you are dead set on making the K55 into a PMA wired as it is, at 600RPM, might even be able to use a pair of 120:18(?) transformers.  No clue if that is a good idea, it is simply a thought.

If you get near Pratt U in NYC, you should stop for a look at their stuff.
Impressive and very friendly.
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rustkolector

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Re: K55 ceiling fan motor
« Reply #14 on: September 02, 2010, 11:32:24 PM »
Ghurd,
If I could find a nice short stack 5-5.25" dia motor stator with more than 6 poles I would consider putting this K55 ceiling fan back together and hanging it in my garage. I have looked for quite some time and K55 is the best fit so far for the basis of this model. More amps would be nice because the engine will run smoother with a little mechanical load on it. If you have any good motor stator candidates I would consider it. Do you know of any good websites that show step by step rewinds?

Relative to the K55, the lamination depth is only 1". I was thinking that by using the two separate windings with an estimated 0.5 amp ac at 50 vac each (25 watts x 2 = 50 watts). Rectification and regulation losses of about 20-25% would give approximately 35-40 watts output.  Am I being too optimisitc?

Jeff

joestue

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Re: K55 ceiling fan motor
« Reply #15 on: September 03, 2010, 05:35:36 AM »
Relative to the K55, the lamination depth is only 1". I was thinking that by using the two separate windings with an estimated 0.5 amp ac at 50 vac each (25 watts x 2 = 50 watts). Rectification and regulation losses of about 20-25% would give approximately 35-40 watts output.  Am I being too optimisitc?

Jeff

no, it should be able to produce a hundred watts
from the way you describe the windings it sounds like a short pitched 12 pole 2 phase motor, in which case 12 magnets covering something like 2.6-3 teeth is about right, but if it is wound as a standard induction motor then you need 18 magnets, but still two phases.
18 pole sounds more plausible, because its a 200 rpm motor, and 50% slippage is normal.
I've forgotten how to do the two phase math, but at 600 rpm you should be able to get more like 180vac out of that motor, in which case a .9 amp load per phase should get you 120 vrms per phase, or about 200-240 watts total. in reality the windings won't be able to dissipate 57 watts times two, so a .5 amp load per phase is more reasonable, and that will get you about 140 watts.
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ghurd

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Re: K55 ceiling fan motor
« Reply #16 on: September 03, 2010, 11:38:58 AM »
Do you know of any good websites that show step by step rewinds?

I was thinking that by using the two separate windings with an estimated 0.5 amp ac at 50 vac each (25 watts x 2 = 50 watts). Rectification and regulation losses of about 20-25% would give approximately 35-40 watts output.  Am I being too optimisitc?

Between a quarter mile of #27 per phase and the inductance limiting, it sounds optimistic to me.

Apparently it wouldn't take you long to make an 18 pole rotor and try it?
Might find a pair of transformers will help.
IF you can find the wire that jumps from coil #9 to #10 in at least one phase, separate the halves and parallel them, that will help.  Both phases would be better.

Maybe then if it does not do what you want, try a rewind?
I am not aware of anywhere having more or better info than right here concerning rewinding motors in alternators.
A simple mental start would be to look at a single rotor Ed made for the idea of how the coils lay in.
http://www.windstuffnow.com/main/alt_from_scratch.htm
Then look at the FAQ about converting motors,
http://fieldlines.com/board/index.php/topic,143568.0.html

With that motor, 3-ph 12 poles, and your machine skills, I think it would be pretty easy.
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rustkolector

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Re: K55 ceiling fan motor
« Reply #17 on: September 03, 2010, 10:13:04 PM »
In starring at this stator today pondering the machining issues, I discovered that this stator is wound rather strangely, at least to my limited knowledge. It would appear that each set of what I originally thought was a row of 9 coils, is actually one coil  laid in the slots in a serpentine fashion. In other words, if you were able to extract one of these 4 coil groups and lay it out on a flat surface, the winding bends in the wire bundle would look like dental molding. Each 180 degree bend reverses direction on the next bend instead of forming a 360 coil loop. To show it simply, it would look like this:   nununu   without the spaces in between (please pardon the lame illustration). So, what kind of winding is this, and does it present any new issues? 

Jeff

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Re: K55 ceiling fan motor
« Reply #18 on: September 03, 2010, 11:23:56 PM »
This machine is wound as a two-phase, 18-pole induction motor.  The capacitors shift the phase between the two sets of coils - and control the speed by causing the phase shift to be something other than 90 degrees and the excitation of the two coils to be unequal, increasing the "slip" of the rotor (and causing extra losses).  If it were running at 90 degrees the synchronous speed (at 60 Hz) would be 400 RPM and the operating speed a few percent lower.

While the rotor may look like a regular squirrel cage, expect it to be non-optimum for a near-synchronous motor.  But a magnet rotor for the conversion should be just fine.  One magnet every two stator poles.

I'd expect the output to be limited more by the saturation of the stator pole pieces than by the thin wire.

The winding is "serpentine".  Nothing special, just another way to do a winding.  (What matters is the way the current runs in the sections of wire in the slots, not what it's doing in the sections bridging between them.)  It's in two sections, offset by a half-turn, so the wire running between the slots will fit in better.  You may be able to find and cut the wire where the winding turns around to split each coil in two for rehooking in parallel, to halve the voltage and double the current.

ghurd

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Re: K55 ceiling fan motor
« Reply #19 on: September 04, 2010, 10:59:15 AM »
What ULR said.

Usually, all the connections to everything are in the same general region.

Regardless of the plan, first need to get in deep enough to separate the phases, which is probably where the white wires go to.
Need to get under the taped sections.

Once you are that deep, may be pretty easy to see where the "jumper wires" are.
The jumpers will look like a single wire that was not placed in correctly.  If they are out where you can see them, they usually stand out from the rest.

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rustkolector

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Re: K55 ceiling fan motor
« Reply #20 on: September 04, 2010, 02:14:39 PM »
ULR,
Not sure I understand this fully, but I am trying. Are you saying I have to isolate the two windings (of two coils each in series),  or do I have to isolate all four coils? The two windings of 4 coils are in series, and the two white wires appear to be wired to the center of those two windings. Why can't I use one white wire and a red or brown wire to isolate an individual two coil winding? I sense it isn't that easy....

The baked varnish is rather heavy where the leads come out and is doesn't cut very easily. Hate to go in there very far.

Jeff


ghurd

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Re: K55 ceiling fan motor
« Reply #21 on: September 04, 2010, 02:31:55 PM »
You could use one phase like that,
but to use both phases, will need to separate them.
They joint together where the white wires go.

Think about it like Red goes into one phase
Brown goes into the other phase
And White is where they all come out.

Factory is probably-
Red-Coil-Coil-White&White-Coil-Coil-Brown ?

At the minimum, will need to change it into-
Red-Coil-Coil-White
and
White-Coil-Coil-Brown

The core saturation and inductance will limit the current through the coils.
Lets say that happens at 0.25A.
Each phase can make 0.25A for a total of 0.5A.
Breaking each phase into 2 halves, them paralleling them, will allow the current to go up to (0.25 x 2) (2) = 1A.

This is pretty much the only way to get much output amps from it-

         Coil
Red<        >White
         Coil


            Coil
Brown<        >White
            Coil


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rustkolector

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Re: K55 ceiling fan motor
« Reply #22 on: September 05, 2010, 01:40:50 PM »
ghurd,
Thanks. I think I might be able to get to the white wire center tap of the two windings, but i'm not sure I can find the winding center taps. It is pretty tight in there and the wire is small. I still have one nagging question. If the two white wires are common to the center tap of the two windings, why must they be split apart if the AC two windings are to be paralleled through rectifier circuits. It would seem (in my little mind) that you would still have two separate AC circuits feeding two paralleled rectifier circuits.



Jeff

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Re: K55 ceiling fan motor
« Reply #23 on: September 06, 2010, 02:53:29 AM »
ghurd,
Thanks. I think I might be able to get to the white wire center tap of the two windings, but i'm not sure I can find the winding center taps. It is pretty tight in there and the wire is small. I still have one nagging question. If the two white wires are common to the center tap of the two windings, why must they be split apart if the AC two windings are to be paralleled through rectifier circuits. It would seem (in my little mind) that you would still have two separate AC circuits feeding two paralleled rectifier circuits.



Jeff

The white wires aren't going to the center taps of the coils.  They're going to one end of each coil (and they're joined).  You have to unhook them from each other to separately rectify the two phases and parallel them, to get both half-cycles of each phase of the waveform rectified and efficiently delivered to the load.

The center tap of each winding is just a place where the wire, after doing half the winding, either makes a U-turn or skips ahead two extra slots before doing the other half.  If you can find that you can separate the two halves of each winding and reconnect them in parallel, to double your current (and halve your voltage).  With a device like this you'll probably want to sacrifice voltage for current, unless you want to down-convert from 200ish volts at something in the ballpark of an amp.

rustkolector

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Re: K55 ceiling fan motor
« Reply #24 on: September 08, 2010, 10:21:57 PM »
Ok, I will try to carefully dig into it and see what I can find. I am pretty sure I can get to the white wire junction. I am trying to complete another item on this project just now but will get in there very soon and will post what I find. Thanks for everone's help. As you can no doubt tell, I need it.

Jeff

ghurd

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Re: K55 ceiling fan motor
« Reply #25 on: September 09, 2010, 12:46:48 AM »
Be gentle.
Try not to 'kink' the wires.  When bending, try to make the bends slow sweeping curves.
Be extra careful where they are glued down, or where the string holds them tight.  That's usually where... uh... the bad things happen.
Those little wires only bend so many times before they snap.

They usually give you an inch or 2 of extra wire to work with.  Its less than it sounds like.
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rustkolector

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Re: K55 ceiling fan motor
« Reply #26 on: September 14, 2010, 10:59:00 PM »
Ghurd,
Found some time today to dig inside the K55 windings. Luckily, I was able to get to all the center taps without incident. I can now isolate and reconnect the 8 leads. Now to get some leads soldered, or crimped to them to bring them out. Those are really small wires in there. I will start looking at magnets now for the rotor. Any ideas on how to layout the magnets to minimize cogging on this small 18 pole rotor?

Jeff

ghurd

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Re: K55 ceiling fan motor
« Reply #27 on: September 15, 2010, 01:08:04 AM »
I do not really follow any set mathematical pattern.
I usually use the 'stripes' in the armature for the format, and they do not always work out to the same one.

If it was mine, I would use 2, 3 or 4 round neos per pole, depending on what fits.
I would follow the armature stripes, or offset to one side or the other from the top to the bottom.
I almost always offset from one side to the other.  Like the top neo is to the left of stripe #26, and bottom neo is to the right of stripe #27?  Or vice versa.
Your situation is a bit different due to the pole and slot count, and size.
Might try to make the top neo even with one side of the slot, and the bottom neo 2/3rds across the other side of the same slot.


Do Not go cheap and try to use paper thin neos.
The total cubic inches of magnet is proportionally related to the power generated under good circumstances.
The air gap between the neo face and laminates is important too, and more important than in the larger machines (IMHO).
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joestue

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Re: K55 ceiling fan motor
« Reply #28 on: September 15, 2010, 02:33:02 AM »
As you now have 4 coils you have two options, go for a 2 phase, 18 pole machine and parallel the two sets of 2 coils, or, go for a 2 phase, 12 pole machine by putting the adjacent phases in series. (this would be known as a 2/3 pitch iirc) the emf would be higher, closer to a sine wave, but the resistance is higher.
End result of the second configuration is less power, but less iron loss and skewing the core or magnets to reduce cogging would be more effective.

If you are looking for good performance from this motor you will need to replace the rotor with a steel pipe or a solid block of steel, the air gaps behind the magnet (aluminum filled void in the existing rotor) only increase the volume of magnet required to get that .6T air gap flux or higher. If you are looking to play around with different configurations you might try getting something like 36 bar magnets, this would let you play around with the configuration. as this is a small motor i doubt you even need 1/8th inch thick magnets, provided the air gap is about 1mm, if its two or three mm then of course you will need something like 1/4th inch thick magnets.
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ghurd

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Re: K55 ceiling fan motor
« Reply #29 on: September 16, 2010, 11:34:08 PM »
(this would be known as a 2/3 pitch iirc) the emf would be higher, closer to a sine wave, but the resistance is higher.
End result of the second configuration is less power

He already has too much EMF, the huge resistance is already killing the output, and the load is not sensitive to the wave form.

Perhaps we should help Jeff get some power from a system that he understands before throwing a confusing lower output system into the works to muddy the waters.
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joestue

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Re: K55 ceiling fan motor
« Reply #30 on: September 17, 2010, 08:36:18 AM »
i thought he was going to use an smps... we've already determined he'll have to rewind it if he wants more than 50 watts out of it at 13 volts.. and that's at like 50% eff, which means its going to get pretty hot.
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rustkolector

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Re: K55 ceiling fan motor
« Reply #31 on: September 25, 2010, 12:26:38 PM »
I am planning on how best to make the new K55 alternator rotor. The old rotor is 3.228" diameter x 1" wide lamination. I was thinking of a solid cast gray iron rotor using (18) 1/4" x 1/4" x 1" neodymium magnets epoxied in place. I would like to use 3/8" x 3/8" x 1" magnets, but the rotor diameter will place them too close together, I think. The rotor would have 18 flats machined to mount the magnets as close to the stator laminations as practical. The 36 slots in the stator are .080" wide with .185" wide stator teeth.

With the stator teeth being narrower than the magnets, what kind of cogging should I expect?

Should I skew the bar magnets slightly?

Will plain epoxy secure the magnets well enough to avert any problems if speed is kept under 1000 RPM?

Thanks for any insight or experiences.

Jeff

joestue

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Re: K55 ceiling fan motor
« Reply #32 on: September 25, 2010, 01:51:12 PM »
Try to skew the stator if you can, it keeps the air gap consistent. i don't think you need .25 inch thick magnets, if the air gap is very close, i don't know how much of a premium .125 magnets have over .25, but it would be easier to order 18 more, and just mill the rotor down some more.
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