Quote: Originally posted by DaveWr on 09/11/2011
Quote: Originally posted by subaqua on 08/11/2011
Quote: Originally posted by vealmike on 17/10/2011V * A does not necessisarily = W. More accurately, it's Volt-Amps. Google "power factor".
Yes, 240V from the centre to any of the three phases, or 412V between phases.
Complicated stuff, electron herding.
actually 230V is the nominal voltage to earth which gives 400V phase to phase when multiplied by 1.732 which is sq root of 3 . hence RMS Root Mean Sq . gives the same power calc results as an equivalent DC voltage. peak voltage will be 0.707 times higher than the RMS value.
in camping terms not overly significant on overloading a circuit .
I love "Sun Sparkies" . 2 months on a domestic course and then let loose in the real world. keeps me in business especially on sunday afternoons when they try and change the light fittings. in reality it makes a mockery of the reason HMGovt introduced part P and really grips a lot of apprentice trained sparkies who did a full 5 year apprenticship .
for a tiny prize ( ok non existant) can somebody tell me the significant size device being withdrawn in January 2012 .
Steve W MIET
I suggest you go back to college. RMS has nothing at all to do with the square root of 3!!!
Just check it out, it depends on waveform shape. Also peak voltage for a sine wave (approximates to mains) is 1.414 times RMS, which is the square root of 2.
BSc EE
Post last edited on 09/11/2011 16:45:46
another reason to not use the internet on a mobile. poor editing functions now i am back on a real internet connection.
. The RMS (root mean square) of the peak voltage of a sine wave is about 0.707 times the peak voltage. Recall that the sine wave represents a changing voltage, and it varies from zero to some positive peak, back to zero, and then down to some negative peak to complete the waveform. The root mean square (RMS) is the so-called "DC equivalent voltage" of the sine wave.
The voltage of a sine wave varies as described, while the voltage of a DC source can be held at a constant. The "constant voltage" here, the DC equivalent, is the DC voltage that would have to be applied to a purely resistive load (like the heating element in a toaster, iron or a clothes dryer) to get the same effective heating as the AC voltage (the sine wave). Here's the equation:
VoltsRMS = VoltsPeak x 0.707
The 0.707 is half the square root of 2. It's actually about 0.70710678 but numbers that small at the voltages i work with are not that important in the grand scheme. 3 decimal places is sufficient.
but thats all theory stuff - sadly the general advice given by sun sparkies is largely concerned with practical application and the lack of understanding can be very dangerous. one of the best i heard was about RCD protection and how it protects against overloading on campsites .
I would write a proper guide to camping electrics but in this day and age with frivolous lawsuits it just isn't worth it.
and no its not Token meters. its a protective device size
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camping since I was a kid
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Topic: EHU - maths
