Why Does My Rewound Alternator with Copper Wire Not Generate Power?

[odbob]

TL;DR

trying to rewind an existing Chinese alternator

Hi, I am trying to rewind an existing Chinese alternator, it comprises of rotor with 12 magnets and 18 poles (stator), the original design produced virtually no power , aluminium windings have been removed and I have replaced with copper 20 gauge wire, 7 turns per pole, I spin it and nothing, why ? can anyone help me, should I just chuck it in the bin or what

 

[odbob]

I should add, that I am not bothered about voltage, more important the some power is produced at whatever voltage

 

[Baluncore]

That is surprising.
We need a diagram of the wiring, and a picture of your stator terminations.
Is it a two-phase, or three-phase stator?
Does it have a rectifier?

Maybe your meter does not work.
Maybe the magnets are not real.
You may have not connected the new stator windings correctly.

 

[jrmichler]

We need more information in order to help you.

Maybe it has bad rectifiers.
Maybe you are trying to measure an AC voltage with the meter set on DC.
Maybe you made a bad connection.
Maybe you shorted a winding to the stator.
Maybe you did not spin it fast enough.
And more.....

A photo or two would also help.

 

[odbob]

thank you to both of you, I will try to answer best as :-

Baluncore
diagram, I have simply wired these in 3 sets of 6 coils and star connected them, so three phase at present, can be disconnected and wired in which way way is suggested
no rectifier
meter works fine, any way, two meters
the magnets appear quite powerful for size, supposed to be rare earth magnets
the windings can be connected any way that you suggest, happy to cut and join
JRMitchler, no probs there, ac measurment
no shorts on windings
spin created by electric drill, at least 600 RPM
it says file image invalid, whatever that means ? will try later

 

[odbob]

 

[Baluncore]

meter works fine, any way, two meters

The alternator had poor output before the rewind, and now it has poor output. Such a weird thread must involve an oversight or false assumption.

What is the meter's make and model number ?
Is the meter set to measure a low AC voltage ?

 

[odbob]

I also have an Oscilloscope, I think that I will go and try again, although it's raining hard here, so may have to leave till tomorrow, but thanks for the prompt reply, regards

 

[Baluncore]

The poles should all be wound with the same sense. The centre of the star appears to have one winding with the opposite winding direction. The phasor diagram will not be symmetrical.

The 12 magnets on the rotor make 6 pole pairs, for three-phase that requires 18 poles to be wound on the stator.
18 is divisible exactly by 6, but it looks like you have one unused pole on the stator, why?

 

[sophiecentaur]

View attachment 324151

That wire looks very shiny so I ask whether it's enamelled (sorry about the possible insult but we're problem solving here). If it is enamelled then were those joins scraped clean when soldered? I can't see but any port in a storm and apologies once again. The picture is very fuzzy.

 

[odbob]

That wire looks very shiny so I ask whether it's enamelled (sorry about the possible insult but we're problem solving here). If it is enamelled then were those joins scraped clean when soldered? I can't see but any port in a storm and apologies once again. The picture is very fuzzy.

please ask the most basic questions, I'm 80 and too old to get insulted, that said, I think that you have a valid question, yes it is enamelled copper wire, no, they are not yet soldered, just twisted together but I think that I scraped enough off for good connection, but thank you, I will check, regards

 

[sophiecentaur]

I've been there too many times to discount absolutely anything.
It's an excellent habit to state the obvious when at sea. The skipper may just have failed to spot that rock we're heading for so best to point it out to him.

 

[Baluncore]

I tried to number the stator phases. There is a problem somewhere.

 

[odbob]

The poles should all be wound with the same sense. The centre of the star appears to have one winding with the opposite winding direction. The phasor diagram will not be symmetrical.

The 12 magnets on the rotor make 6 pole pairs, for three-phase that requires 18 poles to be wound on the stator.
18 is divisible exactly by 6, but it looks like you have one unused pole on the stator, why?

well spotted, I will change that, the original number of wired poles was 39, but because I wanted to use heavy duty winding, this was not possible to repeat, I didn't think that leaving out every other one would be a problem, bearing in mind that this was my first attempt at playing with windings in this way, note also that I have two sets of 6 and one set of 7, maybe I should remove the seventh coil ?

 

[Baluncore]

The pitch of the magnets on the rotor must be the same as the cycle of windings on the stator. More windings on more poles will produce a greater voltage. You may be getting total cancellation by winding every second stator pole. Use thinner wire during testing the phase position of the stator windings.

Identify the orientation of the magnets on the rotor by feeling for the poles with an iron rod, needle or wire. 12 bipolar magnets make either 12 or 24 poles, depending on the orientation of mounting on the rotor.

Draw up a diagram of the rotor magnet poles, showing N & S, against the three repeated stator poles. Make sure the same magnet poles are passing the same phases at the same time. Make sure there is a N&S passing over each set of three windings.

 

[Dullard]

7 Turns? You may need a micro-volt meter.

 

[Baluncore]

7 Turns? You may need a micro-volt meter.

7 turns times 6 windings per phase = 42 ; the answer to the universe and everything.

 

[odbob]

The pitch of the magnets on the rotor must be the same as the cycle of windings on the stator. More windings on more poles will produce a greater voltage. You may be getting total cancellation by winding every second stator pole. Use thinner wire during testing the phase position of the stator windings.

Identify the orientation of the magnets on the rotor by feeling for the poles with an iron rod, needle or wire. 12 bipolar magnets make either 12 or 24 poles, depending on the orientation of mounting on the rotor.

Draw up a diagram of the rotor magnet poles, showing N & S, against the three repeated stator poles. Make sure the same magnet poles are passing the same phases at the same time. Make sure there is a N&S passing over each set of three windings.

I think that you have now answered my original question, ie, should I just chuck it away, so in the bin it goes, but thanks for all your very valuable help, think I'll now get back to my caring duties and maybe buy a wind turbine that actually works, but really, thank you, you have been very patient with me

 

[gary350]

It is much easier to use a parmenant magnet motor as a generator. What voltage do you want? How many amps do you want? The electric motor on a kids electric car or kids scooter makes a great generator geared 20 to 1. You can change the generator voltage very easy with a transformer. There are a lot of products in the land fill that people trash that have electric motors. I have a wind mill that it built several years ago.

I also have a factory built motor like the motor your building all the coils are in series. I took it apart once, the generator has 6 coils in series with 6 magnets. Output voltage is 12v. Toy electric motor is 12vdc but as a generator not sure what the voltage will be, maybe 12v.

 

[sophiecentaur]

TL;DR Summary: trying to rewind an existing Chinese alternator

I spin it and nothing, why ?

If it's really 'Nothing" then I suspect the reason must be trivial. Everything dead is a service engineer's dream cos it's probably a fuse or an open circuit

To get three phases to cancel exactly would imply the whole thing is perfectly made but just assembled wrong. What do you get if you disconnect one coil or even two coils. There's no reason why a single coil should have zero volts output even with a magnet waved about near it. So what voltage do you actually get?

 

[Baluncore]

There are 39 stator poles shown in the picture.
For 3 phases, there will be 13 possible coils per phase.
That does not synchronously tally with 12 magnets on the rotor.
There must be 13 bipolar N·S magnets on the rotor, making 26 rotor poles.

One magnet, with two magnetic poles, will face each repetition of three phase-coils. Here are the first two full cycles of the 13, in half pole steps.
Stator; phase. – Rotor polarity
pole 1; phase 1. – mag North
–
pole 2; phase 2.
– mag South
pole 3; phase 3.
–
pole 4; phase 1. – mag North
–
pole 5; phase 2
– mag South
pole 6; phase 3
. . .

 

[odbob]

It is much easier to use a parmenant magnet motor as a generator. What voltage do you want? How many amps do you want? The electric motor on a kids electric car or kids scooter makes a great generator geared 20 to 1. You can change the generator voltage very easy with a transformer. There are a lot of products in the land fill that people trash that have electric motors. I have a wind mill that it built several years ago.

I also have a factory built motor like the motor your building all the coils are in series. I took it apart once, the generator has 6 coils in series with 6 magnets. Output voltage is 12v. Toy electric motor is 12vdc but as a generator not sure what the voltage will be, maybe 12v.

thank you, I have thrown it away, not worth bothering any more, as you say, there are plenty of motors out there, but mechanically coupling them to the Chinese blade assembly would be the bigger problem, I am not bothered what voltage just need something that will give me 100 watts at a reasonable speed of 600 rpm, will just wait to see if one comes along

 

[gary350]

Most of the used electric motors have gears on the shaft. Buy a matching gear 20 to 1 ratio from Browning or Boston Gear. Put the large gear on your wind mill blade. If wind mill turns 100 rpms generator will run 2000 rpms. Wind mill blade rpm and average wind speed where you live will determine the best gear ratio. Experiment with generator to learn minimum rpm to maintain full voltage. I worked in engineering 40 year.

I have all the stuff to build a wind mill with a 1 hp permanent magnet motor that I never used. 12v will run a 12v to 120v inverter if you need 120vac, I even have the inverter new in box from Harbor Freight. It seemed like a good idea years ago, now this stuff needs a new home. I never had a great plan for this project it was just a fun project. If you don't live too far from me you can have the permanent magnet motor free, come get it. I am 30 miles south of Nashville TN. Are you in USA?

 

[odbob]

Most of the used electric motors have gears on the shaft. Buy a matching gear 20 to 1 ratio from Browning or Boston Gear. Put the large gear on your wind mill blade. If wind mill turns 100 rpms generator will run 2000 rpms. Wind mill blade rpm and average wind speed where you live will determine the best gear ratio. Experiment with generator to learn minimum rpm to maintain full voltage. I worked in engineering 40 year.

I have all the stuff to build a wind mill with a 1 hp permanent magnet motor that I never used. 12v will run a 12v to 120v inverter if you need 120vac, I even have the inverter new in box from Harbor Freight. It seemed like a good idea years ago, now this stuff needs a new home. I never had a great plan for this project it was just a fun project. If you don't live too far from me you can have the permanent magnet motor free, come get it. I am 30 miles south of Nashville TN. Are you in USA?

thanks for the information, your offer of a freebee is welcome but I live in the UK, rather a long way away but thank you

 

[Rive]

7 turns per pole

It looks very ... spacious there. How was the original turn count and thickness?

Usually the cross section reserved for the windings is in sync with the sum of all copper possible (for saturation) and such extra space would mean serious 'underwinding'
I have no experience with chinese designs, though...

 

[odbob]

It looks very ... spacious there. How was the original turn count and thickness?

Usually the cross section reserved for the windings is in sync with the sum of all copper possible (for saturation) and such extra space would mean serious 'underwinding'
I have no experience with chinese designs, though...

thanks but I have thrown it in the bin

 

[Rive]

thanks but I have thrown it in the bin

Exact type of the device, then? Maybe some pictures online somewhere?

On an experimental approach: I would just fill up those winding spaces there, with finer wire ...

 

[sophiecentaur]

7 Turns? You may need a micro-volt meter.

I wondered about that too. Wire that thick would be for many amps. I'd expect SWG 28 or thinner and then you can get a usable number of turns. I wonder what the original alternator was wound with. I'd expect no more than a couple of Amps at 12V - based on the performance of my little Wind Turbine.

 

[Rive]

A visual reference of 'how it should be done':

Mind the full windings and wire thickness!

Though by eyeballing it the supposed power is few times higher than the one in #6
Another one, with thicker wires (but still with full windings)