12 ft turbine waveforms

[Seekscore]

I was playing with my turbine and decided to get some pictures of the output waveforms. This picture is at cut in speed. Looks pretty sweet. This was built a few weeks ago at the Otherpower command post with Dan and George. I am looking forward to getting it up and going. I was spinning this at around 120 RPM.

Mike

[SparWeb]

Now hook it up to rectifiers and a battery.  Gets chopped up pretty good!

[Seekscore]

I'll see if I can get pictures of the rectified output this week.

Mike

[Flux]

If you scope the dc output with no battery it will have about 6% ripple but fairly good dc. If the battery is connected it will be the battery volts and dead smooth.

I think what Sparweb was hinting at was that the ac into the rectifier that you showed as the near ideal waveform will be chopped into a virtually unrecognisable mess.

It will be good practice to look at these various waveforms but in real life it is just interest, you will see nothing that is of any real use.
Your particular alternator has a near perfect sinusoidal waveform, most air gap machines are fairly good between terminals if star connected, you could have a look at the voltage of one phase if you can get at your star point but if it was Dan built I suspect the star point is not available. The phase voltage is also fairly reasonable in many cases but will have some harmonics which are cancelled in the star connection.

Flux
Flux

[Seekscore]

Here is a picture of the rectified output of the machine. It is what I would expect to see. The first picture is of the output of each phase. The second is a picture of the output of all three phases ran thru 1 Meg Ohm resistors in place of the battery or dump load. I am not sure I understand what you are saying about how it gets chopped into a virtually unrecognizable mess. Are you referring to what is happening inside the coil if it wasn't configured for a star pattern? These pictures are exactly what I would expect to see for a three phase rectified output and the ripple DC that is fed into the battery or dump load.

V/R,
Mike

[SparWeb]

[qupote]...ran thru 1 Meg Ohm resistors in place of the battery ...[/quote]

That's the key difference.  There's virtually no current in a Meg Ohm resistor.  Once a couple of amps flow, either through a battery or a resistor less than 5 Ohms, then you will see other frequency vs. current and switching "bounce" effects happening.  But they are invisible when only a milli-amp of current flows.

Hey these screen-captures may also come in handy because questions about the wave-form come up from time to time.  Now that you've posted a few pix they make for a useful reference when explaining what happens when the output is rectified.  EG:  the root-mean-square of a sine wave is the peak divided by 1.41.  But when it's not sinusoidal, like the rippling DC as you show, the RMS is is only a little bit less than the peak voltage.  Your pictures illustrate that well.

[Seekscore]

Thanks for your explanation. I tried to run it through a lot less resistance but it was too hard to spin by hand. Once I get it up on a tower and operating, I'll see if I can get more pictures. I took it apart this morning after I got the pictures so I can go get it powder coated. Hopefully, I'll get it flying in the near future.

Mike

[Ungrounded Lightning Rod]

Thanks for your explanation. I tried to run it through a lot less resistance but it was too hard to spin by hand. Once I get it up on a tower and operating, I'll see if I can get more pictures. I took it apart this morning after I got the pictures so I can go get it powder coated. Hopefully, I'll get it flying in the near future.

Mike

Even running it through a lower resistance won't do all that much to foul up the waveforms.  The fun comes when you hang the battery (or a big capacitor with a shunt resistor) on the output of the recitifers.  The current happens mostly in bursts near the waveform peaks and the restive voltage drop of the current in the alternator coils and drop wiring is subtracted from the beautiful sinusoidal waveform.

[willib]

Mike could you describe the machine in some detail?
number of poles and coils
Diameter of rotors?
Magnet dimensions ?
thanks

[Seekscore]

It is a 24 V, 12' machine. 12 coils of 4 in hand 16GA with 16 magnets. Magnets were 2' round, 1/2" thick. Rotor was 15" round. Here are some pictures of it when we made it at the Otherpower shop. The first 2 pictures are my machine.

http://fieldlines.com/board/index.php/topic,143348.msg964108.html#msg964108

I think they made a similar one at a workshop and Dan posted some info from it as well.

http://fieldlines.com/board/index.php/topic,143480.msg965551.html#msg965551

Mike