Re: Coil Efficiency (and true wattmeter)
From: Jim Fosse[SMTP:jim.fosse-at-bjt-dot-net]
Sent: Saturday, June 28, 1997 12:42 AM
To: Tesla List
Subject: Re: Coil Efficiency (and true wattmeter)
On Thu, 26 Jun 1997 15:14:02 -0500, Tesla List <tesla-at-pupman-dot-com>, you
>Sent: Thursday, June 26, 1997 4:01 AM
>Subject: Re: Coil Efficiency (and true wattmeter)
>> Agreed. I think that's where a lot of false figures are coming from.
> >In many cases the waveforms are terrible. However, I have scoped
>> transformer primary currents using a very low value resistor in series
>> and probing across it with an isolated scope which not only shows
>> waveform but peak current as well. For an RMS figure, a bit of
>> calculus can be used. A valve scope is a must for a running coil.
> > I like your idea better though. The thought of a blown up scope
>> makes me blanch.
>Can you give any idea of the results you've obtained using calculus to
>figure the input power compared with an ordinary wattmeter, and how
>different the results were with different break-rates? For instance,
>(I'll just make this up) suppose wattmeter read 1000 watts at a low
>break-rate, did calculus results show (let's say) 700 watts, in other
>words a lower figure? And if wattmeter read 1000 watts at a high
>break rate, did calculus method show (let's say) 500 watts, or an
>even lower figure? Intuition tells me to expect these kinds of general
>results...but since I don't trust my intuition very much, I'd be interested
>in your general findings...ballpark of course.
Last month I bought a Yokogawa Hokushin Electric single phase
watt meter surplus (unfortunately, it is just used enough to have it's
model number scraped off the label;). It's a dual scale 12/24 Kilowatt
wattmeter. I've wound a current transformer for it that scales it to
1.2 Kilowatts for use around the house and have been thinking of
winding a current transformer to scale it to 12kW. Has anyone
verified a wattmeter's accuracy on a tesla coil? Say, verses an