Re: Re: Power saving unit?

[Anthony R. Gold <ukha@xxxxxxxxxx>]

On Sat, 08 Aug 2009 04:11:07 -0000, you wrote:

> --- In ukha_d@xxxxxxx, Vargster <vargster@...> wrote:
>>
>> I think this http://www.powergard.ca is similar tp
the one that appeared on
>> the BBC news website.
>> Any chance it might sctually work then? And thereby save on the
elecy bill?
>>
>> Lee

It's snake oil!  Yes, there can be theoretical savings from slightly
reduced current in your house wiring and so a tiny reduction in IR losses
through heating, but don't expect that to cover the cost of the gadget.

> I'm sure one of the electricians can explain this better, but it seems
to be trying to alter the power factor - which is a 'fake' measure of your
consumption..
>
> power factor is a hound of a thing to explain...
>
> basically the power numbers you would get in a DC environment, where
simple rules like power = voltage * current hold true, and the AC world are
different.
>
> AC voltage traces out a sine wave - the current flowing in the circuit
also follows a sine wave.. what's a little counterintuitive is that the
current and voltage sine waves are not always in sync.
>
> if your circuit only contained simple components with just resistance
the current and voltage would be in sync.
>
> As soon as you add inductance and capacitance into the circuits, then
the current and voltage slip out of sync... and the calculation of the true
power consumed becomes more complex - and the ratio between your
theoretical Volts * Amps power, and the *actual* power being consumed is
your power factor.
>
> Power meters make assumptions about your power ratio, as do
electricity providers - devices like this may reduce a bill in the short
term (bt almost certainly not by much - a few percent tops), but they won't
affect the actual amount of power being used in any real sense: the same
amount of coal/gas/whatever will need to be used to generate the same
amount of juice - it will just read differently on the meter in your
premises.
>
> If this is pants, please - I'd welcome a better explanation from
someone who relaly 'gets' power factor. I always feel that my understanding
is a bit tenuous...

I understand power factor correction but I don't see how that translates
into helping domestic consumers when their tariffs in kWh and their power
meters already measure in true kWh values.

Industrial and commercial users have an incentive to correct power factor
both to reduce the sizes of their own plant (where sizes of cables and
switches are based on current) and also by avoiding power factor reactive
charges (usually for average PF worse than 0.9) from energy suppliers.

Tony


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