Re: Power Inverters

On Tue, 13 Jun 2006 22:21:35 GMT, Jim Ford
<jaford@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:

|steviephilips@xxxxxxxxxxx wrote:
|>> An RCD does not need an earth, it measures the difference between the
|>> currents in the line and neutral.
|>
|> Yes it does.
|>
|> So in the case of a supply isolated from earth, such as an inverter
|> powered from a battery, how do you get a current imbalance in L & N to
|> trip the RCD ?
|>
|> If there is an imbalance, where is the missing current going ?
|>
|> How can it go to earth since there is no connection between earth
|> (apart from a slight capacitative effect) and the isolated supply to
|> complete the circuit ?
|
|Good point! With mains, neutral is connected to earth at the power
|station, therefore current can find its way back to the power station
|via 'you'. I guess that because an inverter's output is 'floating' with
|respect to earth there would be an indeterminate PD between its nominal
|'live' and nominal 'neutral', and earth. I say 'nominal' because the
|'neutral' won't be tied to earth and therefore won't be truly neutral. I
|guess that the PD between either of the inverter's output terminals and
|earth would be small with a high source impedance. Who's going to
|volunteer to give it a 'hands on' test?

*NOT* me. Water and electricity mixed produce the oddest results.
--
Dave Fawthrop <dave hyphenologist co uk> Google Groups is IME the *worst*
method of accessing usenet. GG subscribers would be well advised get a
newsreader, say Agent, and a newsserver, say news.individual.net. These
will allow them: to see only *new* posts, a killfile, and other goodies.
.

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