I unearthed a conspiracy theory :)

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I admit its a bit far fetched but if he is a conspiracy theorist, he's not very good at it. It seems a bit duller than contrails etc.

its not misleading

let me clear something up - i didnt mean the utility companies are doing this all the time or overnight...

i meant that the supply voltage USED to be about 240-250V, (older appliances are rated 250V) (in like the seventies or whatever)
now, the supply is 230V - all new appliances are rated 220-240V, NOT 240-250V


see?
its not something u'd need to keep on doing, just lower the voltage once.



as to what i will do, nothing - because heres the genius part (as i have already explained)
you could get around this by introducing a line-interactive transformer with UPS/power smoother to your supply - but it would have to go BEFORE the mains meter, which you cannot do because this remains the property of the utility company and tampering with it is against the law (no surprises there)

thats why its genius.



unless you would advocate breaking the law?

or you could somehow get the utility board to install a digital meter that calculates P=IV so that you get charged fairly

From http://en.wikipedia.org/wiki/Mains_elec ... by_country (for the UK):
I had line voltage graphs for the previous five years and they were all pretty constant at 240v like the one I posted earlier.

I know what you mean, but, I'm almost certain that here in America, we use watts as the units for measurement. I might have to check though, I could be wrong.

sorry, its just that my grandad told me, and he was a sparky for 6 decades, what would he know?

He should update Wikipedia, since that part of it is apparently incorrect. Alternatively, post links here to supplement or correct what Wikipedia asserts.

Last edited by Cornflake on 26 Aug 2011, 1:58 pm, edited 1 time in total.

What he ought to have known is that one valid demonstration trumps all rumors and opinions. Besides, power-regulation technology has advanced considerably since the early 1950s when power-generation adjustments were made by hand every few minutes or so. Nowadays, computers can fine-tune power levels and power factors to within a percentage point and in less than a second.

In your grampaw's day, this would have been incredible, if not impossible.

We use Watts, Volts, Power Factor (or PF), Ohms, Hertz, and Amps (or Amperes) for measurement of power, potential, instantaneous phase angle (between volts and amps), impedance, frequency, and current, respectively.

Watts
= Volts x Amps x PF
= Amps x Amps x Impedance x PF
= (Volts x Volts x PF) / Impedance

Here's a useful diagram:



To find one of the values in the center (P, I, E, or R), use the formulas on the outer ring. The works for DC only, though.

Power factor is determined by the cosine of the phase angle between voltage and current, and increases as the impedance load becomes less resistive and more reactive. It is also the ratio between real power (P or W) and apparent power (V times A). PF = cos(W / (V x A)). So, while the power being generated remains constant at the source, changes in the load impedance can change the power factor, and unless the measuring equipment takes into account the PF, any measurements of voltage, current, or power will be inaccurate, at best.

If a 60W incandescent lamp is given 120V, its current will be 0.5A, and its PF will be 1, because an incandescent lamp is almost purely resistive.

If a purely inductive motor rated at 0.08 horsepower (about 60W) is given 120V, then its current will also be about 0.5A, but it will seem to draw no power, because its impedance is purely reactive, and its PF will be zero. Thus:

W = 120V x 0.5A x 0 = 0

In the real world, rated PF could range anywhere from 0.4 to 0.95, practically speaking.

This is why knowing the PF is so important in an AC power system - rating power consumption in Watts is inaccurate, while rating power consumption in "___VA @ ___PF @ 60Hz" (Volts times Amperes at a specific power factor at 60 Hertz) is more accurate from both an engineer's and consumer's perspective.