Fusing the mains
Fusing the mains
(OP)
OH, my three-phase is rusty...
In North America, we typically get 120VAC off one phase, with one side referred to as hot (line) and the other as neutral (reference, typically held close to earth ground by the power provider). A single fuse gets installed on the hot side. If we want 220 VAC, we use two phases, so each 120VAC has a common reference of the earth ground and adds to 207VAC (close enough for horseshoes), and each phase gets fused.
In Europe (or most of the rest of the world), you typically have 240 VAC. Is that set up as a line (hot) and neutral, or as two phases?
And on to my real question. When running off the mains in Europe, do I need to fuse both wires at the power inlet? I have seen IEC320 power entry modules with a single fuse and a double fuse; is this why?
In North America, we typically get 120VAC off one phase, with one side referred to as hot (line) and the other as neutral (reference, typically held close to earth ground by the power provider). A single fuse gets installed on the hot side. If we want 220 VAC, we use two phases, so each 120VAC has a common reference of the earth ground and adds to 207VAC (close enough for horseshoes), and each phase gets fused.
In Europe (or most of the rest of the world), you typically have 240 VAC. Is that set up as a line (hot) and neutral, or as two phases?
And on to my real question. When running off the mains in Europe, do I need to fuse both wires at the power inlet? I have seen IEC320 power entry modules with a single fuse and a double fuse; is this why?





RE: Fusing the mains
If you use all three phases, you need to fuse all three of the phase lives (but still not the neutral), and get 415ish volts between phases.
I can't think of anywhere in this part of the world where we use just two of the three phases.
A.
RE: Fusing the mains
RE: Fusing the mains
On a related topic, a colleague suggested fusing the live and the neutral, in case someone manages to plug into the mains backwards and swaps live and neutral. I'm thinking that is a bad thing if the real neutral fuse blows first. Is that good practice or bad practice?
RE: Fusing the mains
Keith Cress
kcress - http://www.flaminsystems.com
RE: Fusing the mains
RE: Fusing the mains
Z
RE: Fusing the mains
Interesting, because in some South American countries there system is delta 240vac. Where each phase is fused, and there is no neutral (good thing as many people there seem to be confused about electricity).
RE: Fusing the mains
A neutral can be switched using a ganged two-pole switch or circuit breaker, but not two single pole switches or breakers.
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If we learn from our mistakes I'm getting a great education!
RE: Fusing the mains
This is done to accomodate delta connected power inputs which reduce the power cable count to 3 + ground.
RE: Fusing the mains
There's a thing I didn't know. Thanks.
A.
RE: Fusing the mains
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If we learn from our mistakes I'm getting a great education!