3 phase supply
- Thread starter Avis61
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Why do you need to know?
It depends on the wiring resistance. If you know this, divide it into 400 to get the current.
I'd be reluctant to have them in the same house!
And the impedance of the supply transformer.
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it is one of the questions on the technical assessment i am doing as part of my electrical course the 4 possible answers are(1) twice the phase to neutral value ( 2) 500v ( 3) 230v (4) 3 times the phase to earth value
And the reason that you should go back with an answer given by somebody else because you don't know what you should in order to pass the assessment, thereby passing the assessment when you should not and/or thereby giving your tutors a false impression of the progress you are making is what, exactly?
The question you asked was about prospective short circuit current. These answers (at least three of them, and presumably also the fourth) are all voltages! I don't think you've looked at the same Q and A!
Kind Regards, John.
I don't think he should go back to the people who asked him and pretend that he understands the question and knows the answer.
It's not that ususual. My house has different phases on each of three floors. I've gone to quite some lengths (some people would probably say unnecessarily) to keep the phases apart (e.g. by using ELV for cross-floor control circuits, even lighting control), but I think some people probably get unnecessarily nervous about this. It obviously makes sense not to have different phases (e.g. sockets) close to one another but, in the final analysis, 230V is almost as likely to kill as 400 (or 240V as 415V).I'd be reluctant to have them in the same house!
Kind Regards, John.
The correct answer is
The current that causes immediate tripping of the lowest rated OCPD ( over current protection device ) of the two OCPDs fiited on the phases involved.
But quoting that will make the OP look like a clever clogs and they are not liked.
The current that causes immediate tripping of the lowest rated OCPD ( over current protection device ) of the two OCPDs fiited on the phases involved.
But quoting that will make the OP look like a clever clogs and they are not liked.
Do you think so?
Eh? The prospective fault current might not actually be adequate to produce 'immediate tripping' (tripping within the required disconnection times) of the OPDs - that's surely one of the reasons one needs to determine prospective fault currents?
The prospective fault current is what it is - purely a function of the supply voltage, fault loop impedance and current-supplying capabilities of the source (the latter assumed not to be a limiting factor with mains supplies) - what effect that has on OPDs (if any are present
is surely a totally different matter?It also might be a little difficult answering an MCQ in such terms
Kind Regards, John.
The PSCC is either measured directly if the tester can cope with 400v, i.e. the max value between L1-L2, L2-L3 or L3-L1.
If the tester cannot cope with 400v then the maximum L to N value may be doubled up and used.
P
Paul_C
This is one area where the Wiring Regs. have gradually been relaxed over time, as debated recently:
//www.diynot.com/forums/viewtopic.php?t=283088&start=41
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