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Author Topic: COP 20.00 (2000%) Times, Reactive Power Energy Source Generator,  (Read 303042 times)

listener191

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Re: COP 20.00 (2000%) Times, Reactive Power Energy Source Generator,
« Reply #330 on: September 04, 2014, 11:16:44 PM »
All,

Attached are  prints from a Rigol DS1104Z scope, which has a Math function. A differential probe was used for the voltage measurement and a clamp for current. You can see the RMS values displayed for voltage and current and the AxB function is used to display Watts (peak). So far I have not found a way to apply an RMS value to the Math function.

The shot with in phase V & I is the load.

Barry

TinselKoala

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Re: COP 20.00 (2000%) Times, Reactive Power Energy Source Generator,
« Reply #331 on: September 05, 2014, 12:11:13 AM »
Nice displays. The scope is pretty smart: when you are using a current probe it displays in Amps and when it sees that you are multiplying Amps x Volts it gives you the result in Watts. But why would you want to apply RMS to an instantaneous power trace?  "RMS Watts" really has no physical meaning. It is the _average_ Watts value, not RMS, that represents actual dissipated power over a time interval.

When using active differential voltage probe and current clamp probe, the probes will have slight time delays. This will cause phase angle errors which in turn will affect the instantaneous power calculation. This problem is generally called "probe skew" and many advanced scopes have a probe de-skewing menu and options to correct for these time delays. Here's a short article from Tektronix talking about the issue with their scopes and probes.

http://www.newark.com/pdfs/techarticles/tektronix/Probing_power_measuremets.pdf

Farmhand

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Re: COP 20.00 (2000%) Times, Reactive Power Energy Source Generator,
« Reply #332 on: September 05, 2014, 04:20:59 AM »
All,

Attached are  prints from a Rigol DS1104Z scope, which has a Math function. A differential probe was used for the voltage measurement and a clamp for current. You can see the RMS values displayed for voltage and current and the AxB function is used to display Watts (peak). So far I have not found a way to apply an RMS value to the Math function.

The shot with in phase V & I is the load.

Barry

I think the questions most folks might be wanting to ask are.

1) What was the input power from the wall socket and the power factor there ?

2) What was the output power, or what was the power consumed by the bulbs ?

Those figures would allow folks to gauge to some degree what is going on.

eg. if at the wall socket the power factor is bad and VA and VAR are high compared to Watts in, and Watts in are more than
watts consumed then we could roughly determine the effect and magnitude of VAR at the socket.

I find it difficult to believe that a person would do all that setup and experiment without determining the input and power factor
from the wall socket at the wall socket, and therefore already have a figure of some kind for efficiency, apparent and real powers.

Where was the setup probed for the shots ?

..

listener191

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Re: COP 20.00 (2000%) Times, Reactive Power Energy Source Generator,
« Reply #333 on: September 05, 2014, 08:29:22 AM »
This is exactly the same setup as before with the Owon scope.

The out of phase V&I waveforms were at the input from the source (secondary of transformer). The in phase waveforms were taken across the load.

Farmhand mentioned this before, and by comparing with a voltage sample across a shunt resistor, I demonstrated that the current clamp does not have skew.

The RMS function was applied to the measurements at the bottom of the display for comparison with an energy monitor that is at the input.

The Math function AXB, is a sample by sample calculation and is displaying the power waveforms.

Barry

listener191

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Re: COP 20.00 (2000%) Times, Reactive Power Energy Source Generator,
« Reply #334 on: September 05, 2014, 08:34:44 AM »
Regarding the differential probe. I will check the skew against a grounded probe, but the V I phase looks the same as the previous waveforms taken on the Owon scope.

The reason for the differential probe is so I can measure anywhere in the switching circuit, without probe reference issues.

Barry

listener191

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Re: COP 20.00 (2000%) Times, Reactive Power Energy Source Generator,
« Reply #335 on: September 05, 2014, 08:49:13 AM »
I can apply average measurements to the V&I displayed however, I have not found a way to apply an average to the Math function AXB, so I only have the peak power values. This DS1104Z is a new scope for me, so if anyone knows how this may be done, please let me know.

Barry

listener191

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Re: COP 20.00 (2000%) Times, Reactive Power Energy Source Generator,
« Reply #336 on: September 05, 2014, 10:19:36 PM »
Attached are some results from a single cap variant.

Note: the Rigol scope has bug in the way it handles units for Math functions. In this case it uses the Amps units set on channel 1 unless I change channel 1 units to Watts.
The calculation of (VXA) is appears to be correct.

Anyway power is the main concern for measurement. The scale for power is 20W per division. The source display is showing two divisions forward and one division reverse power. The zero line indicted by the bottom of the switches off period.

The load display shows V & I pretty much in phase and one division of power.

Barry

listener191

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Re: COP 20.00 (2000%) Times, Reactive Power Energy Source Generator,
« Reply #337 on: September 05, 2014, 11:05:26 PM »
These shots are with a 6uF cap replacing a 4uF.

I have opened the switching dead period so the zero line can be clearly determined.

The source shot appears to show almost equal power being returned to the source. The source power measurements show an average close to zero, max 30W min -30W.

The load is showing 16W average.

Barry

listener191

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Re: COP 20.00 (2000%) Times, Reactive Power Energy Source Generator,
« Reply #338 on: September 06, 2014, 01:05:56 AM »
I repeated one of the load shots. This is the one I should have uploaded.

Barry

Void

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Re: COP 20.00 (2000%) Times, Reactive Power Energy Source Generator,
« Reply #339 on: September 06, 2014, 02:34:28 AM »
Hi Listener191. You are doing excellent work on this. Those are really interesting results. Because there have been so many
ideas and possible capacitor and switching arrangements discussed, I am not clear on what switching
arrangement and switching timing you are currently using. Would it be possible for you to upload a 
simplified wiring diagram showing how the caps and switches are arranged in your current setup,
and what your current switch firing sequence is with that arrangement. Only if you have time of course.
I am having a hard time visualizing this...   :)


listener191

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Re: COP 20.00 (2000%) Times, Reactive Power Energy Source Generator,
« Reply #340 on: September 06, 2014, 09:00:43 AM »
Hi Void,

Attached

1. power switch circuit with timing
2. timing circuit
3. zero cross circuit

The cap switch is a variation on a circuit that Mario has already tried.

Barry

listener191

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Re: COP 20.00 (2000%) Times, Reactive Power Energy Source Generator,
« Reply #341 on: September 06, 2014, 09:02:21 AM »
Sorry didn't attach

listener191

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Re: COP 20.00 (2000%) Times, Reactive Power Energy Source Generator,
« Reply #342 on: September 06, 2014, 10:02:16 AM »
Hi TinselKoala,

Attached is a scope shot showing differential v grounded scope probes.

I have shifted the traces vertically so you can see there are two traces, otherwise they align perfectly.

As you can see there is no skew.

Barry

TinselKoala

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Re: COP 20.00 (2000%) Times, Reactive Power Energy Source Generator,
« Reply #343 on: September 06, 2014, 01:01:46 PM »
Hi TinselKoala,

Attached is a scope shot showing differential v grounded scope probes.

I have shifted the traces vertically so you can see there are two traces, otherwise they align perfectly.

As you can see there is no skew.

Barry
Thanks for posting the shot... but.... it's always something. I don't know which channel is the diff probe and which the passive probe, the channels are set to different attenuations, there is at least half a volt DC offset coming from somewhere on one channel, and it _does_ look to me like there is a couple degrees skew. Look at where the zero crossings are, don't try to match peaks. This means, of course, that the baselines for the two channels have to be in the same place vertically... and they aren't.
Further, why isn't your scope actually computing the phase angle between the two displayed signals? I've seen several screens, like this one, where the phase angle computation comes up "asterisks".


ETA: I see why _this_ screen doesn't compute the angle, you are asking it to compute with a channel that doesn't have a signal. One wonders why you haven't asked for the phase angle between the two signals that _are_ displayed.
 
If both probes are hooked to the same signal, shouldn't the voltages agree? Yet one is indicating ten times the voltage of the other.


Please do this if you have a chance. Set both channels and both active and passive probes to the same attenuation, connected to the same sine wave signal from a signal generator at the same frequency as your DUT . Set the vertical positions so that both of the baselines are _exactly_ on the center graticule marker. Set the scope's computations to compute the phase angle between the two signals of interest!

listener191

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Re: COP 20.00 (2000%) Times, Reactive Power Energy Source Generator,
« Reply #344 on: September 06, 2014, 03:14:14 PM »
Hi Tinselkoala,

The Rigol scope is only a day old and so I am still learning its operation.

The differential probe has x20, x50 & x200 selections. I kept the x200 setting as I cant make the comparison with the x10 ground probe, exactly as you requested.

The previous shot before was done quickly as to not disturb my setup, henec the use of Chl2 & Chl3. The rigol measurement functions are over whole cycles so any display that shows less than a whole cycle results in blanked fields.

The phase shift according to the measurement function is 0.865deg.

When I tried to increase my vertical resolution from 20V/div to 10V/div there was an overange situation.

I tried the setup on my old Owon scope and set the max resolution I could, and measured 10us (approx 0.2deg) skew between the probes.

Which ever one you take,  0.865deg or 0.2deg  the skew is under a degree and so has little effect on the AxB (VxA) function computation.

Barry