What is my stator voltage delivering?

[freejuice]

Hi everyone,

 I need some help, I have made a stator for my 12 inch machine that uses  1x2x.5 n42 magnets and I was just doing some testing for voltage on each of the phases etc.

Here's are my three questions:

  Using my cheap-o radio shack multimeter, each phase was hitting 300 volts AC..that was with the negative lead ground to the machine and the positive lead on the bare wire coming off my stator....even if I used the neagative lead from the multimeter on a one of the phases and the positive lead from the the multimeter on one of the phases it was still reading 300v AC.

  What would be the conversion to DC if I use the standard 1.4 loss through the rectifires?

 What is my watt rating from this?

 What are my amps?

  Oh, dont ask me the exact rpms I was just spinning it by hand...it was maybe somewhere around  150-200 rpms

 Thanks for your help!

[freejuice]

Just one more question...it appears that voltage is very high, since I'm more of a machinist than an electrican...was I reading the 300V wrong?

[ghurd]

I am guessing this is a 3 phase machine?

And it has 6 wires leaving the stator?

And you were measuring One phase of 3, not 2 of 3 phases wired Star?

Measuring one phase, then wiring in Star increases the voltage by a factor of 1.73.

So 300V x 1.73 = 519V AV.

Converting to DC, rectification increases the voltage by a factor of 1.4.

So 519VAV rectifies to 726.6VDC.

Subtract 1.4V for the diode losses, leaving 725.2VDC.

Not sure what you are trying to do, but that is too many volts for about anything I can think of.

G-

[freejuice]

Hi Thanks for the info,

 Its probalby more of me not reading this multimeter correctly. I have tried to sit down and find some info on reading a multimeter correctly since my last post

 I then took some more readings from this stator arriangment:

 9 coils wired in star with three leads coming off the stator for 3 phase.

 I then took one lead from the multimeter and place it on one of the stator leads and the other lead from the multimeter and place it on another lead from the stator and it gave me about 400ma ac after a good spin by hand...is this 4.0 volts? I checked each phase this way by "hopping" around with my multimeter across all three stator leads and each phase gave about 400ma after a good spin by hand.

 Am I checking the stator correctly?

[freejuice]

Hi Ghurd,

 I think I'm starting to get a grasp on this, if I assume a few things from your post:

First,I will assume the 400ma ac is the same as 4.0 volts that I am geting from each phase when I check across two of the three leads, from my 3 phase, star wired stator.

 Second, if I assume correctly I can apply the 1.4 volt gain in DC conversion and add it to my output abilty which would bump my DC output to 16.8 volts...please tell me I have this correct! )

[ghurd]

It is not 1.4V.  It is a factor of 1.4.  100VAC will rectify to 140VDC.  

Like 100 x 1.4 = 140

You are doing something very wrong with the testing.

Not sure what you mean by 400ma AC being 4V.

If it is a meter like I expect it is, set the meter to 200V AC.  Try it again.

If you are measuring 400ma of current, shorted, with a 12" disk and those magnets, then something is very wrong there too.

And 400ma is current.  Not voltage.  They are no more interchangeable than age and weight.

G-

[freejuice]

Hi G.

The mulitmeter I have only has settings for 10, 50, 250, 1000 AC

 So I too a digital mulitmeter and still got 400 milivolts ( I missled you with the MA comment ..groan sorry, forgive me I'm  more machinist than eleectrical guru.

 However the rotors are 11 inches in diameter That was the largest dimater I could spin on my lathe in my workshop. Yet the magnets are 12 n42's 1x2x.5 on both rotors I machined the rotors to a thickness of about .430 thousandths maye .002 runout.... The stator is about 14.inches in diameter with the center of the coil in the same realtionship of the magnets ( The magnets pass through the center of the 9 coils) Each coil is 14ga wire single strand with 65 turns.

 Do you think I should be getting more voltage from this setup? If so how much what would you consider the target voltage?

 The top rotor can be adjusted down some more say. .200 thousadths or less howerever the bottom rotor is about 3/16 of an inch or .187 from the stator at is current postion

[ghurd]

Yes, should have more than 400mV at 150-200RPM.

No idea what target you were aiming for, but 0.4V is a long ways from anything I can imagine it would be.  

I figure you should have 10VAC minimum, regardless.

If the meter is not the problem...

Is this a by the book PMA?  Possibly the coils are not properly connected.

Not really enough info for me to guess at possible problems.  I am not very good with dual rotors anyway.

Give us the details.

Who's book and which design?

Magnet and coil count?

etc.

Someone else will be able to give more information if they have something to work with.

G-

[poikkis]

I think that you can´t really measure ac voltage from the generator.

The frequency (200 rpm -> 3.3 HZ) is way too low to the meter wich is ment to measure of frequency 50-60 Hz.

Use diodebridge and rectified your genny ac output to dc and try measure DC voltage.

Poikkis

http://www.poikkis.net

[freejuice]

Hi G,

 I used the plans for on this machine from this website.  The only thing I modified was the rotors diameter, they ended up being 11 inches in diameter to be able to fir my lathe, and the rotor was a little thicker, finishing up at .430. I used 12 n42 1x2x.5 magnets on each rotor in the NSNSNS, etc setup.

 The stator was 1 inch in diamter smaller than listed for the 12 inch machine to get the position correct for the coil placement.

It was 9 coils with 65 windings of 14 ga wire ( essex brand double insulated stuff)

 They were wired in three phase, in a star setup.

 I check each one for continuity before I checked the stator..everything ok.

 after assembly I can short two leads and it turns hard and cogs, likewise when I short all three leads it turns very hard but does not cog. likewise, if I dont short it out it turns very freely.

 I can get some more adjustment from the top rotor...maybe 150-200 thousandths more but

[Janne]

Hi,

The frequency will be higher than 3.3Hz, since there are more poles than 2, i assume there are 12 poles.

As to the lack of voltage, one possibility might be a reversed coil in a phase, or 2.

[ghurd]

The shorted testing sounds correct.

Leaving (no offense) "operator error" using the meter.  Could be a faulty meter.

It could be something else, but figuring out how to correctly use and read the meter seems like the next logical step.

The 400mV is only 25% of a AAA battery.  (Also AA, C, and D batteries)

Can you put a 12V car tail light bulb on 2 phases, and give it a spin?

If it lights more than a very dim glow, you have more than 0.4V (400mV).

It will chug or pulse due to the pulsating flow of current.  ('Cogging' is due to magnets pulling toward a section of iron usually in the stator, technically it does not cog)

Light bulb testing does not tell anything useful, except you have more than 0.4V.

G-

[freejuice]

Hi Janne,

I remember making sure the coils were the right side up.... They stressed that often here in the web site. I checked and double checked even triple checked when I wired, twisted and soldered up each phase..... even when I glued it, with super glue to the fiberglass mat to keep it in postion before pouring the resin, in fact I checked everything one more time before I poured it to make sure.....I must have checked the wiring and how the way the coils were postion in regards to how the wire came from the inside or outside of the coil in relationship to right side up at least 5-6 times! )

 I bet I'm reading  that mulitmeter wrong! Like I say I can machine just about anything, but I'm as good on electrical ti the point of wiring up my house years ago. It even passed they counties Inspection!

 However my multimeter is a new but the old analog type of meter like the name brand "Simpsom or Samson" was before th digital days!

 I have it set on 50 ac but the scale ( which is where Im probably reading this thing wrong is showing me an 8 when I spin it fast by hand. ( I gave up using the cheap-o radio shack pocket size version digital multimeter I have)

 I'm off to do a light bulb test if I can find one!      

[Flux]

I suspect your alternator is ok. I am fairly certain it is your meter or your means of using it.

Firstly I am not convinced that you have the meter on the right range. mA shouldn't come into this. You are trying to measure volts not current.You need the meter leads plugged into the sockets marked common and volts, there will be separate holes for current measurement.

Firstly set your meter to 10v dc and see if it will read 1.5v off a single cell battery. If this works then change it to ac volts For a cheap nasty meter you seem to have too many ac volts ranges I suspect you may still be on the dc range.

Anyway when you have located the ac volts range then try again. If you still get virtually nothing I suspect your meter.

If you can understand how to do this fit a 3 phase rectifier and measure dc volts out of the rectifier, if your meter reads a battery on the dc range then it should read the dc volts from the rectifier. It will probably go off scale on the 10v range with any reasonable speed. If the 10v range works then move it to a higher range and you can soon see if that is working.

I think your alternator will light a car headlamp bulb on hand cranking when connected to 2 leads ( 1 phase). It will be hard to turn and feel lumpy. If you have the rectifier fitted it will light the lamp on the rectifier output and be harder to turn but not lumpy. If it passes the lamp test you have to sort out how to use a meter.

Flux

[freejuice]

HI Flux, Ghurd and everyone!

 I just ran the lamp ( lightbulb test) I could only find a 12v light bulb from out of my tractor. I hooked up two leads off the stator to the bulb and gave it a spin....as you folks say it felt lumpy but it sure was bright! SO I'm thinking everything is good with my stator/rotor setup. So now I need to get a book "meter reading for dummies"! )

 The mulitmeter ( analog style)has only two places for the leads + & -

However when I set the meter on 50 AC and spin the rotor fairly fast by hand it gives me a reading of 8 on the scale, however just above this 8 is another number 40, so my question is this: If I have the meter set on 50AC that would say the meter would read up to 50 volts AC, correct? Then the number I was reading as 8 volts was actually 40 volts correct?

Since I have passed the light bulb test, and the Meter is set on 50AC and if my hunch is correct about reading the meter correctly this time, I can say each phase is generating 40 volts AC? for a total of 120 volts AC?

PLeeeease tell me I fianlly correct in all of this )

If I am indeed finally correct in all of this, I need to go back and review Ghurds power calculations when it rectifies into DC voltage

[Flux]

If the meter is 50v fsd ( full scale) and has numbers 0 to 10 then yes 8 will be 40v.

Usually there is a scale with 5 or 50 on a meter with 50v range to make things easier but if not then direct % of the full scale figure.

Flux

[Perry1]

Age and weight may not be interchangeable but they do seem to be proportional for some reason.

Perry

[bzrqmy]

Here is a video of my generator with a rigged up rectifier and a hand crank.  It's running a cooling fan from a motorcycle and an automotive head lamp.

http://www.youtube.com/watch?v=MJ_LGubuS1o