COP 20.00 (2000%) Times, Reactive Power Energy Source Generator,

[listener191]

Hi Mario,

I measure current on the scope with a current clamp and it is sitting on the feed to the load from the transformer, so what you see in my scope shots is what you asked for.

The discharge pulses are largely within the same period as the charge pulses, so current is definately flowing back to the source, so the load sees current in both directions resulting in 11W.

Note: this scheme is not the most efficient, as the timing of the discharge has to be set so the discharge voltage exceeds the sine falling edge voltage. The parallel/series arrangement allows the discharge to start at the peak of the sine, (their current discharge waveforms look like 3 caps in series not 2).

OK hypothetically...

My scope shot shows about 20mv RMS so 20 x 0.01A= 0.2A, close to what I measured with the meter. Divide by 2 as only half is input, (probably should do a power calculation by area).

So the input power is 0.1 x 150V 15W approx. The other half is being returned so say -13W as the discharge current waveform is less in area. So we generate 11W for 2W supplied.

How do we meter this correctly as both meters are seeing the 0.2A as regular AC sine , where as 50% of the flow is in a different direction?

Barry

Barry

[TinselKoala]

Sorry, wrong thread, oops.

[TinselKoala]

@listener: I think you should discontinue the wattmeter and use scope measurements throughout. Proper phase angle measurements along with your instantaneous V and I measurements will tell you the true story of the input and output power.

The current clamp you are using should be explored carefully. Some will introduce phase shifts of their own, and digital ones like Bill Alek uses have timing delays built in that can cause erroneous phase angle measurements if not corrected. Does your scope have a "probe deskew" facility?

I don't want to get into some controversial discussion but you might want to consider my opinion on this: the idea that reactive power is somehow "returned to the source" has always bothered me. If you set up some mirrors so you get many receding images of your face, is the image being "returned to the source" when it's reflecting back and forth from one mirror to the other? There are times when reactive power indeed does get "returned to the source" and I have the exploded mosfets to prove it, and it sounds like you do too. But in an ideal reactive power system the reactive power "circulates" without being _dissipated_ in the source, it just bounces back without hurting anything or really having any effect except to exist as stored power in the reactive system. I think.

Trying to get a bunch of mosfets marching in neat rows can be very difficult. For good synchronization I've used such tricks as multifilar gate phase transformers (primary driven by mosfet driver, secondaries to mosfet gates in anti-phase) or even fully controllable H-bridge controllers by Intersil like the HIP4080AIP.

[listener191]

Hi TinselKoala,

If you run a straight resistive load on AC and monitor with my current clamp, the voltage and current waveforms are in phase, so I am sure there is no skew however, I will take a scope shot of the same phase shifted waveform, montoring voltage across an in line shunt resistor, just to demonstrate that they are the same.

I have not damaged a MOSFET since I have kept the current below 1.5A.  Experimenting I was exceeding the SOA of the P12NM60's.

Each MOSFET has an individual driving totem pole pair fed from a common floating +15V source. The totem pole pairs share a common op amp drive, however I can connect individual isolated drive circuits for each MOSFET, which would  allow only one device to be switched for charge or discharge.

I want to try and run at what can be considered a useful power level, so IGBT's are the way to go.

I think you are right about using scope measurements, I just wish my scope had some more flexible math functions.

Barry

[listener191]

Hi TinselKoala,

Attached are scope shots of shunt monitored current versus clamp monitored current and shunt monitored current against voltage.

As you can see, my current clamp does not skew phase.

Barry