Author Topic: 100w induction single phase motor conversion  (Read 10861 times)

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isacp

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100w induction single phase motor conversion
« on: March 19, 2015, 03:41:19 PM »
Hi!

I wanted to start some project, so i thought a small windturbine would be fun to make. I´ve found a nice 15-20 years old single phase induction motor in a old grinder. I´ve tried to read as much as i can on this forum but every conversion from induction motor to pmg is on bigger 2 or 3 phase motors. So i have some questions to ask if someone would be so kind to answer. well here we go.

First, is it possible to convert a single phase to a pmg?
Second, what do i do with the capacitor should i leave it untouched?
It is a 4 pole motor does that meen that i should put on 4 rows of magnets on the rotor.
And last is it possible to generate power to charge, say a car battery?

Greatful for any kind of response // IsacP

Flux

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Re: 100w induction single phase motor conversion
« Reply #1 on: March 19, 2015, 05:06:59 PM »
Yes single phase will work but it does have different characteristics but at the small end that may not be an issue.

In fact you have a 2 phase motor and if it is a capacitor run motor you can rectify both phases and sum the output. If it is a capacitor start motor, depending on the start mechanism you may or may not benefit from the start winding.  If it relies on the start winding resistance for starting torque it may not help. You should get some idea by the % of space used for the start winding, if it uses reasonable space and has wire similar to the run winding then it may contribute significantly. If the start winding is tiny and wound with thin wire then it may not be worth using it.

Yes a 4 pole motor does need 4 magnet groups ( 4 poles) on the rotor. You may be able to use the winding as it is or you may need to re-group the coils depending on the speed you run it at. You are probably looking at a fairly small fast prop so it may be a bit high on voltage side to use the original winding un modified.

Flux

isacp

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Re: 100w induction single phase motor conversion
« Reply #2 on: March 20, 2015, 03:46:50 PM »
Thanks for the answer. im not sure what you meen with starting windings. As i can see all the windings are the same size, well i added a picture, maybe someone can help me indetify what kind of single phase motor this is.

I rather not do the rewinding, feels like its a bit to complicated for me right now.

Isacp

Flux

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Re: 100w induction single phase motor conversion
« Reply #3 on: March 20, 2015, 05:10:29 PM »
Your motor looks to be a capacitor run motor. The 2 windings are likely identical and to reverse rotation you connect the capacitor to the other phase. The 2 windings are in fact a 2 phase motor but the phase is shifted from single phase by the capacitor.

If you separate the common winding and bring each winding out with its 2 leads you can rectify each phase separately and connect the dc sides of the rectifier in parallel. You have virtually the equivalent of 3 phase and should get 50% more rating than from a basic single phase winding.

I agree about the messing about with connections, that is not always easy, I find most people accept this without much question, but I personally would prefer to start with a scrap motor, strip the windings, do a test coil and then wind to suit the job in hand.

If it is a 110v motor it may match 12v reasonably well but if higher voltage it probably won't be near ideal without messing with the windings.

A 100w motor is small so we are probably looking at something near a 4ft prop so you can match things to some extent by choosing the prop tsr when you have some figures from the motor.

Flux

isacp

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Re: 100w induction single phase motor conversion
« Reply #4 on: March 21, 2015, 01:25:09 PM »
Damn! My motor is 220v since i live in sweden... ive looked around and it seems tricky to do a rewinding good. And everything is so small in my motor. Do you think i can rewind it? Is it possible you can walk me through it? i think thats my only option with this motor at least...

electrondady1

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Re: 100w induction single phase motor conversion
« Reply #5 on: March 21, 2015, 01:48:22 PM »
maybe rewind the next one.
what about a step down transformer to bring the voltage down to what you can use

isacp

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Re: 100w induction single phase motor conversion
« Reply #6 on: March 21, 2015, 02:19:39 PM »
Do you think that would work? What is the price for that kind of transformator You think?

As i said it would be awesome to not do winding on my first try. What voltage can i expect to get out of my small motor if coverted 220v 2.5 A ? So i can look into price for transfo.

Isac

OperaHouse

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Re: 100w induction single phase motor conversion
« Reply #7 on: March 21, 2015, 02:40:19 PM »
I always think higher voltage is the way to go.  You will never do better than a factory wind.  Electronics is the way to go, not a transformer.  Then the cut in speed can be set and adjust power point for wind speed.

isacp

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Re: 100w induction single phase motor conversion
« Reply #8 on: March 21, 2015, 02:54:37 PM »
Well there is ofcourse better ways. But how expensive will they be. I dont want to put out to much money. But you guys think its possible to use my motor and just modify the capacitor WWithout spending to much money?

Flux

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Re: 100w induction single phase motor conversion
« Reply #9 on: March 21, 2015, 03:12:32 PM »
Try converting it and see what you get. If you get a decent amount of magnet in there you will be looking at about 200v at 1500 rpm. It may suit a 24v battery as it stands with cut in about 200rpm.

Yes transformers are possible and so are buck converters but I think the simplicity of direct charging is well worth a try before adding complications on such a tiny project.

Flux

isacp

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Re: 100w induction single phase motor conversion
« Reply #10 on: March 21, 2015, 04:20:55 PM »
Okey. Thanks all for the feedback! Really appreciate it.

I will try to convert it as you said. Can you please tell me more detailed what i should do with the capacitor. i have no experience doing that. Am i supposed to just cut of the wires from the capacitor and connect them to the other wires?

Flux

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Re: 100w induction single phase motor conversion
« Reply #11 on: March 21, 2015, 05:18:33 PM »
You don't need the capacitor.

You have 2 windings electrically at 90 deg ( 2 phase winding)  One wire of each phase is internally connected so that you only have 3 wires coming out. When used as a motor the common connection is connected to the supply neutral, one  other winding is directly connected to live and the third is connected to live via the capacitor. To reverse rotation you connect the live to the other side of the capacitor.

Ideally for what you want you need to separate the internal common link so that you have 4 wires coming out ( 2 from each phase). You then connect each phase to a bridge rectifier and connect the rectifiers in parallel on the dc side.

I suspect that in real life it will work just as well if you connect the existing 3wires to a 3 phase rectifier just as you would for a 3 phase motor. This will save you having to break the internal link between phase. The rectifier will conduct in an odd mode but I don't think it will make any difference.

Flux

isacp

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Re: 100w induction single phase motor conversion
« Reply #12 on: March 22, 2015, 11:44:17 AM »
Okey so i lifted the stator out and disconnected the capasitor and noticed i have 4 wires coming out + earth. Two was leading to the capasitor red and yellow, and two is going out brown and blue as normal. The red and brown is coming from one side and the yellow and blue from another.

 I guess it wasent build as you did guess. But isnt this better? shouöd i just connect each side to  separate rectifiers and then connect them parallell to the future battery?

Thanks Isac

Flux

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Re: 100w induction single phase motor conversion
« Reply #13 on: March 22, 2015, 03:20:29 PM »
Probably the best approach is to fit the magnets and get it to generate, then you can use a meter to actually measure which of the leads belong to each winding.

Flux

isacp

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Re: 100w induction single phase motor conversion
« Reply #14 on: March 22, 2015, 03:46:25 PM »
Will do that. Thanks for all help! Ill be back when i have fitted the magnets. Well thanks again for your time and patience.

ISacp

isacp

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Re: 100w induction single phase motor conversion
« Reply #15 on: March 23, 2015, 03:26:47 PM »
Is there any problems with drilling holes for the magnets, will the fact that the magnets are buried affect the power on the magnets? thought it would be easier to just drill.

Isacp

Flux

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Re: 100w induction single phase motor conversion
« Reply #16 on: March 23, 2015, 05:22:30 PM »
It's ok to drill a shallow hole to locate the magnets but you will loose flux if you go too deep. It may be ok to sink a 12mm magnet in to 3 or 4mm but beyond that things start to suffer badly. If you go in full depth you will have a very serious loss.

Flux

isacp

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Re: 100w induction single phase motor conversion
« Reply #17 on: March 30, 2015, 01:59:53 PM »
Hi! im back again.

Now i have fitted the magnets, got my hand on small neos for nothing at all. they are 6 in diameter and 4.7 high, in mm ofc. I printed a cage in a 3Dprinter in school and drilled the holes and then glued the magnets with some superstrong epoxy, which i now regret because it will probably be impossible to remove the magnets if i want to. Here is some pics



8712-1

As you can see i used a cold beer upside down to prevent the epoxy to set to fast. to keep track on the North or south side of the magnets i just took a bunch and painted one side red so i knew not to put that side down, it worked very well.

The motor is cogging a little bit but not so much, i guess i can fit one more row of magnets in each pole, but i will do that later if its needed.

So i used my screw driver and turned the rotor and got a lightbulb to shine (WOHO! super happy.). Then i removed the capasitor and tried on those wires as well and it worked fine.

i have bought a multimeter today and measured resistance between the wires and here is the result.
So Brown and Blue is main wires and Red and Yellow is from capacitor, (brown and red comes from one way and blue and yellow another)

When i measure the resistance between the different wires i just dont understand the connections.

Blue-Brown -    30 ohm
Blue-Red -        130 ohm
Blue-Yellow -    1 or 0 ohm
Brown-Red -    100 ohm
Bronw-Yellow - 30 ohm
Yellow - Red -   130 ohm

And the light bulb was not shining when i connected the yellow with the brown or blue wire but it worked when i connected yellow with red, or blue with red and so on.

Im studying mechanical engineering and have only taken one course about electricity so im very green in the subject as you notice. i´ve tried to figuer out myself how it all work but i just can´t i need some help from someone to explain it for me. Please have patience with my slow brain. Appriciate all input.

Isac

Flux

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Re: 100w induction single phase motor conversion
« Reply #18 on: March 30, 2015, 05:11:53 PM »
You seem to be progressing well.

From your readings it looks as though the yellow is internally connected with the blue. The run winding is from Brown to blue and is 30 ohms. The start winding is from brown to red and is 100 ohms.

Your lamp should light from the main winding brown to blue and should also light from the run winding when connected to brown and red.

You should also get some light between red and blue from the sum of both windings.

Try your meter on ac volts and see if you can measure volts from brown to blue and also from brown to red.

When you rectify to dc you should get most of your power from the main winding and a useful contribution from the start winding.

To try tests with a rectifier, ignore the yellow wire and connect a 3 phase bridge rectifier with the ac connections to brown blue and red. The dc output from the rectifier will be your voltage at the speed you are turning it at.

Flux

isacp

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Re: 100w induction single phase motor conversion
« Reply #19 on: March 31, 2015, 05:34:09 AM »
Okey now i have done some tests on ac V with my tiny screw driver no idea what rpm. I tried all connections to get a clear view.
brown blue 75V (run)
brown yell 75V
red blue 130V
Red yell 130V
röd brown 95V (start)
Blue yell 0V (Obviously paired)

This gave me a bigger understanding. As you said blue yellow is connected since it is zero. And all connection is the same with blue and yellow wire. So it doesnt matter if i use blue or yellow. you can also see that the start winding has higher V than the run windings.

Well just wanted to air my numbers. I have ordered  a 3phase bridge rectifier, it will be delivered before thw weekend i hope. I'll be back with new progress then.

Thanks again flux for your priceless help!

Isac

hiker

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Re: 100w induction single phase motor conversion
« Reply #20 on: March 31, 2015, 01:29:18 PM »
looks great..........
WILD in ALASKA

isacp

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Re: 100w induction single phase motor conversion
« Reply #21 on: April 08, 2015, 11:08:34 AM »
Ok. Got my 3phase bridge rectifier now. I tried it on and got around 12v for every 100rpm.

does that mean that i should run my generator at abit higher so i get like 14v to charge it or can i run it at higher voltage and then connected to a battery the voltage will drop and the current will rise. I have reed that on a couple of threads on this forum. But does it really work like that?

If i got a 4 foot (1.2m) diameter prop in 5m/s wind and 100 rpm it will mean i will have a tsr on 2.5  if i understand it right.

Flux

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Re: 100w induction single phase motor conversion
« Reply #22 on: April 08, 2015, 11:51:50 AM »
It will start charging as soon as the rectifier output goes above battery voltage, so the cut in will be slower on a low battery than on one reasonably well charged.

Because of the resistance ( and reactance) in the windings the charging current will increase gradually as the wind picks up and although you will cut in at near 100 rpm you will need several hundred revs to get decent charging current.

Your machine would better suit a 24v battery and start charging from about 200 rpm, the same charging current will then give you double the power. It will work at 12v but it will need to be a high solidity prop to produce enough torque to drive it without stall.

I haven't checked your tsr figure but it seems likely to be right. If you copy Hugh Piggott's 4ft prop that runs at about tsr 5 and would be fine for you working at 24v. I suspect it will stall at 12v.

You could try 4 or 5 of those nasty bent tin blades sold on ebay to get a lower tsr but unless there is some fundamental reason why you need to stick to 12v I would use Hugh's 3 blade wooden prop as a starting point.

Flux

isacp

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Re: 100w induction single phase motor conversion
« Reply #23 on: April 08, 2015, 03:23:08 PM »
I have done the math again. I get 4 tsr if i calculate in 3 m/s with 200rpm and 2.5tsr if i calculate with 5m/s. Either way i found hugh's pdf with step by step instructions but with 7 tsr. how do i calculate what measures i should change to if i want to have 4 or 2.5 tsr. Or is it anyone else who has already done the job for me?



Isac

Flux

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Re: 100w induction single phase motor conversion
« Reply #24 on: April 08, 2015, 04:26:15 PM »
I think the example prop Hugh has on the site is tsr7, that suits many alternators. The details of the 4ft prop are probably in one of the recipe books, but he has a spread sheet on the site that lets you find the angles and dimensions for props of various tsr.

I think the spreadsheet is on the old site, not the blog.  It's near bedtime now but I will see if I can find the link tomorrow.

Flux

isacp

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Re: 100w induction single phase motor conversion
« Reply #25 on: April 09, 2015, 05:18:34 PM »
Okey. Ive looked at hughs homepage now. Cant find anything about the 4tsr blades. Im wondering, because this is as small windmill, cant i use those pvc blades i have seen alot of people making. If i use thick pvc, is it much losses? And can i decide the tsr on pvc blades? Thanks.

Isac

Flux

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Re: 100w induction single phase motor conversion
« Reply #26 on: April 10, 2015, 03:16:31 AM »
Many people seem to have some sort of luck with pvc blades, wouldn't hurt to try and if the thing looks promising you can fit better blades later.  They are probably not as good as the better bent tin ones but should get you started.

If you go to http://www.scoraigwind.com/ and go right to the bottom you will find links to old stuff.

Somewhere right at the bottom is a picture that said trip to Sri Lanca 1999 or similar. just above this is the link to the blade calculator spreadsheet.

Flux

Janne

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Re: 100w induction single phase motor conversion
« Reply #27 on: April 12, 2015, 11:27:11 AM »
Fun looking project.
Finland exports lots of good stuff, but Lapin Kulta is not one of those.. that's almost like exporting water :)
Nothing's as easy as drilling a hole in the wrong place

isacp

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Re: 100w induction single phase motor conversion
« Reply #28 on: April 19, 2015, 02:25:59 PM »
Haha well janne thats why i use it as a glue holder!

I have cut out my pvc blades now just as test. Did it from 110mm dia pvc pipes and just did a shape i thought looked nice. The huvhub i think i will print in 3d, just because i can.

I did try to measure the amps on my generator and it seems to be really low. When i connect the generator to a lamp of 11watt and spin it so i get 24volt it is barely glowing at all. Why do i get so extreme low amps? Is it anything i can do about it?

Isac