Alternator numbers are in!

[freejuice]

Ok Folks  thanks for putting up with my earlier posts...that was a great help!

Here's some numbers off on my generator to play with and to get feedback from you folks:

 It is a 11 inch diameter, 24 1x2x1/2 (inch) N42 magnets with 9 colis wired in 3 phase star configuration of 14ga. 65 turns. The stator gap is about 3/16 of an inch per side:

 Here what I got off of it today:

Each phase gave me 44 volts and 4.5 amps AC with a very good spin by hand( check me out here to see if I was doing it right) I took a 12 volt headlight from my tractor and used it as a load. I hooked the headlight's two wires to two of the phases  and place the amp meter around only one of the wires going into the headlight...that's how I came up with the amp reading...hopefully this method was correct. I did not check both wires ( two of the three phases) at the same time through the amp meter.( It was one of those amp meters which clips around the wire).

Sooo I'm thinking I simply take all three phases which produced 44 volts and 4.5 amps and add them up for total voltage and amperage...which end up being 132 volts at 13.5 amps...so I multiply these two together to get watts which ends up being 1782 watts...that seems high...is my math off? Do I calculate just from one phase alone?

Second question, What keeps the rotor "free" turning when all three phases are hooked up? Is it the bridge rectifier, electrical cable length etc.?

[ghurd]

The alternator needs to be turned at several RPMs while connected to a battery to do any meaningful testing.

Without 2 of 3 primary variables known, nothing else has any real meaning.

I can get 1A from a AAA battery for an hour.

I can make a circuit to get 100V from a AAA battery for an hour.

I can not make a 100W bulb light for 1 hour from a AAA battery.

Example?

You can barely lift 250 pounds.  (open voltage)

You can walk stairs for up 10 stories before you are too tired to keep going.  (shorted amps)

You can not walk up 10 stories of stairs carrying 250 pounds.

"free" turning?

Power is being removed from the system to charge a battery.

The power comes from somewhere.

There is no "free" turning if power is being removed.

When all 3 phases are connected, there is less vibration, or lumpiness in the rotation.

This is due to the power being removed from the system at a more even (smoother) rate.

G-

[freejuice]

Hi G,

 Thanks again, I see it needs to be set up as a complete system: generator- rectifier-battery to get any real results and rotated at various rpm's.

So do I measure from each phase indivually and crunch the math for each phase, or would I measure from the DC side after the rectifier to find out how many watts it will generate?

[ghurd]

Either would be a great start.

After the rectifier is easier.  I do not see a whole lot of point in calculating what 'might' be coming out of the rectifier if it can be directly measured.

It is a 3-ph PMA.  Measuring the output of all 3 phases makes sense.

It is a battery charger.  Measuring the output into a battery makes sense.

G-

[freejuice]

Thanks G,

  You are a wealth of knowledge!

 One more question about the stator:

 I see that they often use 2 strands of 14 ga wire when making a coil, where as I used only one strand for making each coil.

 What is the purpose behind this, does it reduce the amount of force it takes to turn the rotor ?

For example, when I spin the rotor by hand, without anything hooked up to the phases it turns freely, however when I hook up the 12v light bulb to it, I can feel some slight resitance from the rotor when turning it by hand, in other words it takes a little bit more force from me to turn it by hand. So my hunch is that the two strands of wire in each coil reduces the force it takes to turn the rotor....(I might be completly off base in this hunch, but it would appear that if I can keep the rotor turning as easy or freely as possible it would be a benefit to help generate rpms in the wind)

[ghurd]

It is easier for the current to flow in 2 strands, same as it is faster and easier to fill a 55 gallon drum with 2 hoses?

Less ohms of resistance increases efficiency.  Increased efficiency means it is easier to turn with the same output.

"without anything hooked up to the phases it turns freely" because no power is being made.  It is available, just not being removed from the PMA.

"when I hook up the 12v light bulb to it, I can feel some slight resistance".

Yes.  The extra force to turn the PMA is to make up for the power being removed and supplied to the light bulb.

The extra force is the power in the bulb.

Connect 2 bulbs and it will be twice as hard to turn.  And it will have to turn faster to supply double the power.

G-

[imsmooth]

You don't multiply by three to get the total wattage.  If you have 44v @ 4.5A for one phase (phase to neutral) of a three phase system connected in STAR you do the following.

Multiply one phase by 1.7 to get the AC voltage: 1.7 * 44vac = 74.8vac

Now, multiply the voltage by 1.4 to get peak DC: 104.7vdc

Now, multiply by your current, 4.5A to get wattage: 471W

IF you are getting your 44v by measuring phase to phase voltage (connected between two of the phase leads) then just multiply by 1.4 and then the 4.5A to get:

44v * 1.4 * 4.5A = 277W

The only thing I am not sure of when one does this calculation is if the peak dc volts are used or just the RMS value.  I wouldn't mind someone clearing that up.

[imsmooth]

Following up a point of ghurd's above, when I did my wattage calculations, I connected my load after the rectifier/cap bank and measured the dc volts and amps, and just multiplied the two together.

[freejuice]

Hi Johnathan and Ghurd,

Great, things are much clearer!

Jonathan your wrote"

"IF you are getting your 44v by measuring phase to phase voltage (connected between two of the phase leads) then just multiply by 1.4 and then the 4.5A to get:

44v * 1.4 * 4.5A = 277W"

 That' exactly what I did, measured across two of the three phases, or as you said "Phase to Phase"

 So the one more question and I hope to give you folks a break....i'm wearing you guys down!

 If the watts is 277, ...that is total output of all the phases combined correct?

 Yes I have to get my bridge retifier built and do as you and Ghurd say to do, just measure the volts and amps on the DC side.

 Is there any reason why folks use individual rectifiers for each phase on these PMA's other than amps or price?

Is something like these I see on ebay ok to use?

http://cgi.ebay.com/Diode-Bridge-Rectifier-60A-1200V-Model-60MT120KB_W0QQitemZ180394212726QQcmdZView
ItemQQptZLH_DefaultDomain_0?hash=item2a00553d76&_trksid=p3286.c0.m14

[Flux]

To measure power out of a battery charging alternator it is easiest to use the dc values. The dc voltage is virtually peak, but with a slight ripple. A moving coil or digital multimeter will measure dc mean( this is what batteries see) so dc volts a dc current is power. When charging it is battery volts x current.

You will struggle to do any meaningful measurements on the ac side when feeding a rectifier and battery.

When an alternator is supplying a 3 phase resistive load then the power is root 3 x v line x I line x power factor. This is the normal way most alternators are loaded for other than wind applications. Another way to look at 3 phase power is that it is 3 times the power per phase and you can measure it that way for a star load..

If the 3 phase are not balanced then with conventional loading you need a 2 or 3 wattmeter method but none of this is of any interest for wind machines.

The voltages you mention are correct in the above example but I wouldn't take any notice of the current figure.

By phase I suspect he means line voltage so there is no need for the 1.73 factor.

Loading a single phase into a lamp and measuring the current gives no indication of what it will do into a battery ( assuming he intends to charge a battery). The whole thing is very vague and I am even more suspicious after reading the last part of the question, which fortunately Ghurd has answered. If it becomes free turning we are back to the over unity issue.

Flux

[freejuice]

Hi Flux,

 Thanks for the info... I guess I really need to get my bridge rectifier built and wait and see. Sorry for any possible confusion abot "Free turning" I'm throwing out there to any of your folks...this is my first PMA and I'm not an electrical guru, nor to good with the terminology. The " free turning" concern came from me thinking the generator would not give me any kind of resistance when turning it when something like a car lamp was connected to it )...I'm on a big learning curve!

[Flux]

A car lamp is a load and it will make it hard to turn at any speed.

Perhaps what you were thinking of was start up under wind conditions. With a battery and rectifier there is no load on the alternator until the thing is generating a voltage equal to the battery voltage. It then starts up off load during the time the prop is stalled and the prop is out of stall by the time you expect it to produce power.

This is why it is very difficult to get machines to start with heaters as a load rather than battery charging.

Yes get your rectifier and then try it into a battery and you can then decide what it is likely to produce. At least you have proved that it will work and do something.

flux

[imsmooth]

This is exactly the one I have.  It has proved to be very robust and I have no problems with it.  If you plan to generate a lot of power connect the back to a heat sink with some heat sink silicon paste.

[garison]

I have been reading a lot of different postings and I'm not understanding

that after the ac is rectified there is more power in dc dont you loose power though the diodes. sorry also a rookie turbinite.