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Re: Tube Coil Wattage?
From: FutureT-at-aol-dot-com[SMTP:FutureT-at-aol-dot-com]
Sent: Saturday, November 15, 1997 2:57 AM
To: tesla-at-pupman-dot-com
Subject: Re: Tube Coil Wattage?
> From: Andrew Chin[SMTP:chinny-at-ozemail-dot-com.au]
> Wouldn't the power of the coil be equal to the power drawn from the
> mains?
This is input power. But some people what to calculate or measure
output power which is always less than input power due to losses.
> Granted, a Tesla coil is far more efficeint than a conventional
> transformer (>100%), so maybe you could say that the power of the coil
> is at LEAST the power drawn from the mains?
All transformers and coils are less than 100% efficient. You may be
thinking of *peak* power which can be higher than the input power,
but average output is always less than average input power due to
losses. Efficiency is always based on average power.
> If a Tesla coil was a conventional transformer, then power calculations
> would be so much easier. All you would need to do is use the power
> formula, Power=current x voltage. A transformer will change current and
> voltage, but the input power will always equal the output power. (For a
> 100% efficient transformer of course)
That power formula only works if you have a unity power factor, which
usually we do not. Tube coils do not create the strong peak power
pulses that spark gap TCs produce. The easiest and probably the
best way to gauge "efficiency" of a TC is by comparing input power
to output spark length. I wrote efficiency in quotes because this is
not a true engineering definition of efficiency, but it *is* a practical
solution, that is used by most coil builders. Attempts to measure
the true efficiency are fraught with difficulties, and tend to lack any
practical application for most coilers, but offer benefits when the
efficiency of one *section* or another of the TC is measured for
efficiency. For example, the efficiency of the TC power supply can
be measured by comparing the energy that ends up in the caps,
with the energy that is drawn from the wallplug. This subject of
how to measure coil efficiency was
previously discussed to death and beyond on this list, you may
wish to peruse the archives for more viewpoints.
John Freau