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Re: Input Power Measurement
Subject: Re: Input Power Measurement
Date: Tue, 27 May 1997 06:20:51 -0700
From: Bert Hickman <bert.hickman-at-aquila-dot-com>
Organization: Stoneridge Engineering
To: Tesla List <tesla-at-pupman-dot-com>
References: 1
Tesla List wrote:
>
> Subject: Input Power Measurement
> Date: Mon, 26 May 1997 23:42:39 -0700
> From: Skip Greiner <sgreiner-at-wwnet-dot-com>
> Organization: Greiner, Ltd.
> To: tesla list <tesla-at-pupman-dot-com>
>
> Hi All
>
> It is obvious to all that any given transformer can be run in excess of
> its rating. Thus, a 1kva transformer may be run with 2kva input and
> live. This does not mean that the TC is being run at 1kva since the
> transformer is rated at 1kva.
>
> How can the actual input power to the TC be measured????????
>
> We can know the input voltage, I think, since most of us run from the
> mains (except those that insert a variac and transform the mains voltage
> up to 130v or 140v). We can still measure the output voltage of the
> variac, I think, and therefore know the input voltage.
>
> BUT....how can the input current be measured. I seriously doubt that it
> is sinusoidal. There are ac ammeters, several different types which give
> an indication. Is there one type of ammeter, the reading of which could
> be multiplied by the voltage as obtained above, which would give an
> input power which all of us could use for comparison purposes?
>
> I have a commercial instantaneous reading wattmeter. Does it provide any
> usable information? For instance....if I compare the input power to two
> different systems which use different types of input
> transformers....will I indeed be able to say that one system is more
> efficient than the other?
>
> Any suggestions would be appreciated.
>
> Skip
Skip,
While precise measurement of input wattage is quite difficult due to the
non-sinusoidal input currents, the wattmeter should provide a useful
relative comparison when the systems are run at similar break rates.
-- Bert --