FW: Coil Efficiency (and true wattmeter)
From: richard hull[SMTP:rhull-at-richmond.infi-dot-net]
Sent: Wednesday, June 25, 1997 6:20 PM
To: Tesla List
Subject: Re: Coil Efficiency (and true wattmeter)
>I agree. Can you suggest a simple way to measure the capacitor voltage?
>Regarding wall plug power; who knows how the distorted and pulsed
>waveforms are affecting our ammeters and wattmeters. To solve the
>problem, I suggest that we all build the optical isolator wattmeter
>suggested by Dave Sharpe of the TCBOR. Dave has I believe posted
>info on the results of the project...and I believe accuracy was within
>5% which is a lot better than any typical meter, because this optical
>isolator device gives an accurate representation of the true
>instantaneous power delivered to the load even with a wandering
>input voltage and a non-linear, reactive load. The max power input
>for the circuit is 1300 watts, but maybe this can be "upped" using
>appropriate shunts. I haven't built one yet, but I don't really think
>there's any choice, unless someone can suggest something simpler
>of comparable accuracy.
>Maybe Dave will add some more info here about his unit.
Agreed! Dave Sharpe's submitted wattmeter is waveform/power factor
insensitive and will give absolute true watts consusmed at the plug!
I measure the capacitor voltage with a capacitive divider system and the
tank or cap current with a Pearson wideband C.T. Feed one into each channel
of a DSO scope. Use AXB math function and the resultant wave worm is the
time ordered instantaneous record of wattage in the tank. It is vastly less
efficient than anyone would imagine and the losses are huge (make that
beyond belief (as I have stated many times before on this list.) Wall power
is just a loss we must live with with current gap switches and other
materials used by the cloiler. The H2 Thyratron allows good watt efficient
performance, but is not as robust as the lousiest spark gap and is not
capable of remaining on for the desired time in lightly coupled systems.
Also, my work has shown that the instantaneous impulse power in the hottest
systems is below that calculated by the classic surge impedance equation due
to the voltage rapidly dropping as the current rises. This indicates
substantial losses in the switching device and tank circuit components.
Also in the power tranny, I would imagine.
Malcolm is right about the loses.
Richard Hull, TCBOR