Reactive Generator Research for everyone to share

[gotoluc]

I've attached an image of my test bench - just for info...

Luc, I'm not sure what I should be looking for...

The capacitors don't seem to 'tune' anything - as I said - you just need 'enough' (for me, about 30uF) to correct the power factor, and any extra makes no difference.

Using less than enough (less than 30uF) - and the phases diverge. With about 5uF or less they're 90 degrees out. At this point there's very little power being delivered to the load, but my variac still draws some power (10-12w).

For my 13w in (to 'light' the bulb - one part of filament goes dull red), I get about 20v across the 50ohm bulb. (I know a bulb's resistance changes when it gets hot - but I'm not letting it get very hot.) I'm not sure if my DMM reads peak, or RMS, but either way the output power is 9watts or less. (8.8 if RMS, 6.3 if peak, I think)

So, with any amount of caps, it looks clear that I'm getting less out than I'm putting in.

So, questions:

1) Do you have a cap switch box - so you can change values while the circuit is running? If not - how do you do it?

2) Have you found that the phase is 90 deg out with very low capacitance, and converges as capacitance increases, to a plateau?
  i.e. Do your results concur with mine?

3) It seems to me that a resistive load *requires* the phases to be together... I think the very definition of resistance means that the power has to be 'used up' (converted to heat). It's possible that an inductive load would be different. What do you think?

Regards
Tim

Hi Tim

I'm quite sure your 50 Ohm load on the Primary is too high of Resistance. If you use the Primary side for load (like you are) then try a 10 Ohm Resistor.  If you chose a load on the Secondary side, then try a 1k Ohm.

If you chose to experiment with a cap on the Secondary it would need to be a small value, like 0.66uf or less. A small cap value on the Secondary is enough to maintain a phase shift on the Primary without adding a cap to it.

All kinds of interesting things to play with

All the best

Luc

[tim123]

Here are some images showing the scope, meter & bulb, at various capacitance settings.
- The voltage from the variac is constant thoughout (40V).
- Yellow is Channel A - which is before the MOT
- Blue is Channel B    - which is before the Bulb

You can see the phases converge, and the voltage at the bulb increases, as does it's brightness.

You can see a maximum phase shift is obtained, and the adding more caps makes little difference.

[tim123]

Hi Tim,
well done.
Maybe you can also try to measure voltage and current BEFORE the Variac with your scope...

Hi Stefan, thanks
  I'm new to measuring current & phase etc. and I must admit I don't really understand a lot of this... Would you be able to do a diagram showing where and how you would make the measurements? How many probes would it require ideally?

I know how I'd do it - but then I usually trip out the house RCDs... It doesn't improve my son's xbox experience

I don't think I have any low-value high-curent resistors for a shunt. I may have to buy a couple.

Can you already verify that the power factor does not change at the input when you load the output ?

Sorry, no. Could you please explain how you would test this? Do you mean perhaps a variable resistor as a load?

What pahse angles do you get between current and voltage ?

Hopefully the previous pics demonstrate this...

I'm still a bit confused by the idea of using a shunt to measure the current vicariously...

I know that in a tank-circuit, the current is at a maximum when the voltage is at zero, and vice-versa...

So would you use a shunt in parallel with the tank to measure voltage, and one in series to measure current?

Are you on a 230 Volts 50 Hz system or 60 Hz 120 Volts system ?

230V - 50Hz.


Regards
Tim

[tim123]

Short Update: Using a Universal Motor as a Load...

Now I have tuning... I replaced the resistive load with the motor from a vacuum cleaner, and now it has a sharp tuning point at about 40uF.

It seems to be most efficient when the voltage at the motor is maybe 25 degrees behind the source (phase difference). The voltage is higher than the source at this phase / capacitance.

I also tried removing the MOT, so the circuit is just the capacitor bank, and the motor, and it seems to behave almost identically. More tests needed though.

It doesn't seem to be improving the efficiency though... The motor runs much better on DC...

[hartiberlin]

Hi Tim,
well done and thanks for the pics.
Did you use the circuit diagram that Luc redraw from yours one ?
So was this with the secondary of the MOT shortcircuited ?

Does your digital Watt meter have the possibility to show
power factor together with the input Watts ?

What kind of light bulb did you use ?
a 60 or 100 Watts type ?
This is probably to low in resistance to really see the differences, so it would probably be
better to start with a 25 or 40 Watts incandescent bulb.

Regards, Stefan.