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Author Topic: Reactive power - Reactive Generator research from GotoLuc - discussion thread  (Read 362121 times)

TinselKoala

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Mine does, and I think most variacs do too. Just saying that they can, but yours apparently doesn't.

I suggest checking with an ohmmeter just to be sure that the two sides are actually completely isolated and that the neutral isn't common to both sides of the isolation transformer. I've seen ones (even Solas) that had the neutral common, so they didn't achieve full isolation after all.

Every Variac I've seen has one terminal in common to both input and output sides, so they don't really isolate.

TinselKoala

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Here is a zip of the original file.

BTW, the load is 15 Ohm 1% 50w resistors connected to 3 Series 12v batteries at 37 volts DC, so no error on power to the load.

It's 1:25am and been a long day, so I'm closing up for the night. I'll pickup more of my 12v batteries from storage tomorrow so we can see how far we can take this.

Stay tuned and please try to find the error as this is too simple!

Luc

OK, the negative math mean is only about one-twentieth of one vertical division (math trace is 200 V-V per div). This could easily be a sampling or calibration error. The "mean" of an approximately sinusoidal waveform like the math result should be approximately zero. In order for human eyeballs to check the scope's math it would be nice to have only three or four full cycles displayed, so that areas above and below the zero reference could be compared by external means.
Since the negative value is so small compared to the overall signal (nearly 800 V-V p-p) I am skeptical that it is real.

d3x0r

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I don't know where the error is, but I see now why the scopeshots are so pixellated, the scope is set to save them at 320x240 resolution. And from looking at manuals it seems that might be as good as you can get. Maybe Poynt99 can give some advice as to how to get better resolution.

Sorry for the distraction, it's not really important, just hard for my old eyes to read your images especially with a lot of cycles and traces displayed.
And personally; my scope (rigol ds10something), the math is done with the value shown on the screen and not what is in the sample buffer... so it's pathetic low resolution like that even though it's 2Msa stored....like the values change if I change the time...




TinselKoala

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And personally; my scope (rigol ds10something), the math is done with the value shown on the screen and not what is in the sample buffer... so it's pathetic low resolution like that even though it's 2Msa stored....like the values change if I change the time...

I think that's why .99 asked for many cycles on-screen. Maybe Luc's Tek also only does math on the screen display too. It's always a tradeoff, I guess. The old Link pc-DSO that was donated to me can do its math and measurements on the entire sample buffer, or just what's displayed on the screen, as the user chooses, but its math is limited and it can't do trace multiplication. Some other scopes I've used, like the early LeCroy WaveRunner 104x,  seem to incorporate the trace offset into the math, so one needs to be very careful about where the baselines are set. Luc is setting them all at the screen center, I think, so that's not likely to be a problem here.

poynt99

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Probably because I open them in windows image viewer and use screenshot pilot and make a png file so I can upload then. This site is not accepting bitmap (Tek regular file format) for some reason.

Luc
According to the manual, you have the following image file format options to save to:

bmp, pcx, tiff, rle, epsimage, jpeg

I would suggest trying tiff and jpeg. I don't see where one can change the resolution though.

btw, nice scope Luc. Where did you buy it?

poynt99

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And personally; my scope (rigol ds10something), the math is done with the value shown on the screen and not what is in the sample buffer... so it's pathetic low resolution like that even though it's 2Msa stored....like the values change if I change the time...
The value changes with the Tek scopes too. Once you have about 10 or so cycles of the MATH trace, the value does not change even if you put more cycles on the screen.

The screen in these DSO's is closely tied to the resolution of the converters. The converters are 8-bit, and there is effectively one for positive and one for negative excursions. So the zero ref line is the LSB and the top and bottom of the screen is the MSB. That's why it is recommended that all your wave forms be placed at the center for best accuracy. You should also try to use most of the "vertical deflection" before clipping.

Until 12 or 16 bit high speed converters are affordable, we just have to live with this limitation.

poynt99

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Poynt-How can we get the power factor of the tank circuit?. If i place my scope across the cap for volts,and use a CSR for amp's,and the two wave forms are in phase,dose this mean a power factor of 1?.
If the wave forms are like that posted (i.e. non-sinusoidal), it might be difficult to get the PF.

To get PF with two sine waves, you first obtain the phase angle (in degrees) between them. Then it is just a matter of taking the COS of the angle with your calculator.

COS 0º = 1
COS 45º = 0.707
COS 90º = 0

poynt99

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Hi everyone,

I uploaded a video which is unlisted. I did this not to confuse other researcher from other sites and so on since this video is related to the discussion going on here.

So here is a test a la TinMan of my best score yet

Link to video: http://www.youtube.com/watch?v=CyoT9I3_93w&feature=youtu.be

I may also have another interesting thing in the works and will share when I confirm the ideal values for maximum output.

Stay tuned

Luc

Luc, isn't your watt meter plugged into the output of your generator?

Never mind. I see that it is plugged into the AC feed to the genset, which is feeding your motor.

poynt99

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Luc
In regards to your last video-something seems not right. Are your DMM's reading rms voltage?. The reason i ask is this.
The prime mover uses 157-158 watt's-with or with out the reactive circuit switched on.
Without the reactive circuit switched on,your exciter circuit meters read this- 167.2volts @ 1.405 amp's. This is 234.916 watt's ??? -asumeing a power factor of 1.
I'm sure most of that is apparent power. And the wave forms are probably similar to your own so the meter measurements aren't going to be very accurate.

poynt99

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Below are the scope shots that acompany the above,but with the reactive circuit in place and running.
By eye-balling it, I would say the PF is pretty close to 0. Obviously it won't be zero because some power is being consumed by the exciter circuit.

poynt99

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Ah man!... things are getting much worse now :o ... I've got 90 watts out and a negative Mean.

Are you sure this is the right way?

I'm running out of water to cool my resistors :'(

See the scope shot

Luc
Luc,

Please confirm what the MEAN power reading is when NOT inverting CH2.

Thanks.

poynt99

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So this is what you want to know?

I have shared that 30 watts is the max I can pull out of my gen. Anything above that and the prime mover has to supply more energy in the standard way.

My generator has a 12uf cap for exciter field. Cap connected and prime mover needs about 158 watts to turn gen at 3500 RPM. If I disconnect the exciter cap the prime mover needs about 100 watts to turn the gen head. Prime mover is 3600 RPM max.

Hope this helps

Luc
I see, thanks.

So the gen exciter circuit requires about 60W. I wonder if that 60W increases as the gen is loaded?

So once you start drawing more than 30W from the gen, the motor power indicated on the meter starts to increase as well, and under 30W the motor power remains at a relatively steady 158W?

Hoppy

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So once you start drawing more than 30W from the gen, the motor power indicated on the meter starts to increase as well, and under 30W the motor power remains at a relatively steady 158W?

So, at this point in the investigation, it would appear that Luc has a system electrical efficiency of around 19% with a fixed load of 15R. This seems rather low, so I imagine that the efficiency should increase to some extent as the load is varied?? Hopefully Luc will plot a loading curve to show where optimum efficiency appears on his setup.

gotoluc

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Hi Luc
Dose your scope have a USB output?-this is how i take my screen shot's.I then open the saved file on the thumb drive in windows paint,and save as a JPEG.They come out just as i see it on the scope.

Hi TinMan,

I'll give it a try. I was saving it on a USB stick then to computer.

Thanks

Luc
« Last Edit: January 06, 2014, 12:50:38 AM by gotoluc »

gotoluc

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Mine does, and I think most variacs do too. Just saying that they can, but yours apparently doesn't.

I'm not using my variac as Isolation transformer. I'm using a real Isolation transformer.

I'm not sure I'm following you there Luc. What are you doing exactly?

What I was doing is using 240v AC through 18uf Series cap through a FWBR in series. The DC of the rectifier is connected to three 12v batteries in series and the 15 Ohm load is connected across the 36v of the batteries.

I made a video demo of it and will soon have it up

Luc