What is three phase?

Erbas said:
Succint explanation of the difference ...

Single phase 230v shock ... "ow, bugger"

Three phase 415v shock ... "aaaaaaarrrrrrgggggghhhhhhh" <smoulder> <shake> <die>

Ask me how I know! (I managed to narrowly avoid the final stage though)
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Not sure about that. A three phase system shock is most likely to be from phase to ground not from phase to phase, so a single phase shock can kill you just as dead.
It's a mystery to me why earth leakage circuit breakers, ELCB's, or residual current devices, RCD's, which trip as soon as the tiniest current is detected going to ground, via someone's body for example, are not mandatory. Normal breakers only trip for a direct contact of the supply wire to ground. When I worked as an amusement arcade engineer in my student days, my life was saved several times by ELCB's. It's funny that places of work have better safety equipment than our homes!
 
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CreakyDecks said:
It's a mystery to me why earth leakage contact breakers, ELCB's, which trip as soon as the tiniest current is detected going to ground, via someone's body for example, are not mandatory.
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Not mandatory where? They are in domestic installations - as of the 17th edition of the regs, all circuits have to be protected by an RCD unless they come under a very small number of exceptions. The earlier 16th edition required them for certain situations, and in practice electricians found it easier to protect the lot rather than separate the circuits, so you got RCDs on all sockets and sometimes on the whole house.

Pete
 
prv said:
Not mandatory where? They are in domestic installations - as of the 17th edition of the regs, all circuits have to be protected by an RCD unless they come under a very small number of exceptions. The earlier 16th edition required them for certain situations, and in practice electricians found it easier to protect the lot rather than separate the circuits, so you got RCDs on all sockets and sometimes on the whole house.

Pete
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:) About time too. I have to admit I haven't read the 17th edition because I don't get my hands dirty any more :)
 
CreakyDecks said:
Not sure about that. A three phase system shock is most likely to be from phase to ground not from phase to phase,
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Not when you're working on a live 3 phase lift motor power cabinet :o

And to be tecnhically pedantic, a shock between one phase and ground would effectively be, correction would actually be, a single phase shock - the fact that the supply is three phase would be irrelevant (exepting that a 3ph supply might well be more likely to deliver a lethal current even between one phase and ground before something trips due to higher capacity circuit protection and slower RCD's if indeed RCD's are fitted)
 
Thank you to those who have provided enlightenment and my apologies to those that think I have corrupted the sanctity of a boating forum. I asked the question as I saw reference to a 3 phase electrical cabinet in a boatyard adjacent large boatsheds. The explanations above lend me to think that the cabinet must be a supply box to the boatsheds.

Fear not that I shall venture practically in to three phase; I'm happy with 12v (well 12.4v to 14.4v to be more precise!)

Thanks again

Rob
 
Robih said:
Thank you to those who have provided enlightenment and my apologies to those that think I have corrupted the sanctity of a boating forum. I asked the question as I saw reference to a 3 phase electrical cabinet in a boatyard adjacent large boatsheds. The explanations above lend me to think that the cabinet must be a supply box to the boatsheds.

Fear not that I shall venture practically in to three phase; I'm happy with 12v (well 12.4v to 14.4v to be more precise!)

Thanks again

Rob
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Almost certainly to provide power to large motor driven machinery. As other people have said a big advantage of three phase is the constant power (and torque) provided to things like cutting tools. Nowadays with advances in electronics you can get similar smooth power delivery from single phase using DC motor drives.
 
CreakyDecks said:
Almost certainly to provide power to large motor driven machinery. As other people have said a big advantage of three phase is the constant power (and torque) provided to things like cutting tools. Nowadays with advances in electronics you can get similar smooth power delivery from single phase using DC motor drives.
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Not always, three phase is also used for distribution on a large marina or in your street at home your next door neighbour could be on a different phase which potentially can give you 440 volts. This is why if the generating co loose a phase not all houses in the street are off
 
3 Phase the definition (s)

Phase 1: The elation you feel when you become the owner of a boat

Phase 2: The mixed emotion of the love hate relationship you have with the boat.

Phase 3: Similar to phase 1, the elation you feel when you sell the boat.

The shock is what you get if you are silly enough to count the cost of the 3 phases.
 
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