Reactive power - Reactive Generator research from GotoLuc - discussion thread

[poynt99]

Looks like it might be core saturation.

The transformer is designed to be as cheap to manufacture as possible, with no regard for efficiency. This is because it is the manufacturer who pays for the copper and iron, but the user who pays for the energy consumed. Thus the iron area is minimised which results in the core being taken well into saturation with result high core losses. The copper area is also minimised, resulting in high copper losses. The heat that these generate is handled by forced air cooling, usually by the same fan that is required to cool the magnetron. The core saturation is not part of the non-ideal classification, it is merely as a result of the economics of manufacture.

http://wiki.4hv.org/index.php/Microwave_oven_transformer

[gotoluc]

Luc.

I see the problem now, and silly of me to have missed it before.

Your MATH trace measurements, i.e. MATH max and MATH min, are not the ones you need to be using. The measurement that you need to use in order to see what the net power is, i.e. net going back to the grid, or net being consumed by the circuit, is the MEAN (average) of the trace. This is a single measurement and will tell us the net average value of the MATH trace. Now, in order to get a relatively accurate measurement of the average power, you need to display about 10 cycles. So get about 10 or more cycles on the display and use "MEAN", not "Cycle MEAN" measurement on the MATH trace.

Test again using this setting, both with CH2 not inverted and inverted. They should produce opposite numbers, for eg. +10VV, and -10VV.

Okay poynt,

below is the circuit under a 10 Ohm 1% 50W Load Resistor at 21.3v RMS = 45 Watts

First shot is standard and next shot is Inverted.

Let me know what you think

Luc

[poynt99]

Okay poynt,

below is the circuit under a 10 Ohm 1% 50W Load Resistor at 21.3v RMS = 45 Watts

First shot is standard and next shot is Inverted.

Let me know what you think

Luc

Luc,

I think something is not right.

First, I don't know if it is just the snapshot itself that is so pixelated, or if the scope itself is really showing such degradation in the wave forms. This might be affecting the measurement. What record length are you using in the scope?

The MATH MEAN value should be the same but opposite polarity when inverting CH2. So that is confirming that something is not quite right.

btw, I performed a similar test today with a Tek scope with just a simple capacitor and resistor in series, to get a phase shift between the voltage and current. I confirmed that the computed power is the same but changes polarity when one channel is inverted.

[hartiberlin]

Stefan, I don't think we are discussing the same topic!

Proper phase of the measurement probes is of the utmost importance in this situation, and it certainly is relevant here.

We ARE attempting to get the input power from the grid, and in order to do that we need to set up the probes as I have shown AND invert CH2 in the scope. Please go back and study my diagrams more; it is very clear as to why this must be done this way in this case.

No you are wrong,
we want to see the power used up by the LCR circuit and this is why the 2nd channel DOES NOT NEED TO BE INVERTED !

If this power is negative on the Math line we can see, that the circuit is just pumping back power into the grid.

How you want to measure it is not current standard and confusing !

Regards, Stefan.

[gotoluc]

Luc,

I think something is not right.

First, I don't know if it is just the snapshot itself that is so pixelated, or if the scope itself is really showing such degradation in the wave forms. This might be affecting the measurement. What record length are you using in the scope?

The MATH MEAN value should be the same but opposite polarity when inverting CH2. So that is confirming that something is not quite right.

btw, I performed a similar test today with a Tek scope with just a simple capacitor and resistor in series, to get a phase shift between the voltage and current. I confirmed that the computed power is the same but changes polarity when one channel is inverted.

Maybe consider what you're wanting to see is not correct?... I've asked other EE and they don't agree with inverting chanel 2.

Have a look at the scope shots below. I've used a transformer that's not ideal for the effect, so it will use more power then it can return. The first scope shot is standard and the second is inverted.

When a circuit uses power, the math will mostly be above the Zero line, like the first scope shot. By inverting Chanel 2 you are making the math do the opposite. I think there is your problem?

Luc