In UK, because of the ring-main wiring, the effective conductors to a
wall-socket are 5 mm^2.
John Woodgate OOO-Own Opinions Only
J M Woodgate and Associates www.woodjohn.uk
Rayleigh, Essex UK
On 2017-11-20 20:21, Richard Nute wrote:
In the USA, at the load end of a 2-meter #18 power cord, you can expect 100-200
amps short-circuit current, but not more, due to the resistance of the power
cord, the connectors, and the wiring to the breaker box.
If you assume that the source resistance is almost 1 ohm, the short-circuit
current would be 120 amps, maybe down to 0.6 ohms and up to 200 amps (for a
120-volt system). The resistance of the 230-volt system will be more because
the building wiring is smaller than North America, so the short-circuit current
would be about the same.
Rich
-----Original Message-----
From: Brian O'Connell [mailto:[email protected]]
Sent: Monday, November 20, 2017 10:26 AM
To: [email protected]
Subject: Re: [PSES] Regulatory requirements for MOVs placed line-to-ground on
AC mains ports?
Mr. Woodgate,
Is there a recently published spec for a 'typical' 230V mains impedance for the
EU? Have also noted that the source Zs in 61000-4-5 for the instrument seem
rather high. So what is the basis for 1500A interrupt rating?
For U.S., even for an artificially low-Z electronic AC source, seldom see fault
currents exceed 200A peak for 120V mains. Conversely, have noted that at over
100A fault current, any fuse not rated for the 'high' interrupt value will
probably explode.
So either our ratings are suspect, or perhaps the physics behind the standards
are not complete?
Brian
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