In message
<[email protected]>,
dated Thu, 9 May 2013, "Wiseman, Joshua E"
<[email protected]> writes:
With this type of machine I have been referring to A.14 of IEC
61000-3-3 for the test criteria. There are a couple of items in A.14
that don?t seem to be very clear. First, the 3rd dashed item under a)
says to measure dmax 24 times in accordance with Annex B, but if the
1st measurement is > +/- 10% of the dmax referenced in Clause 5 then
only 1 measurement is required. If the result is higher than that of
Clause 5 isn?t it a failure?
The standard actually says something subtly different. If the first
result is NOT within +/-10% of the limit, only that result is needed.
The point is that some switch-on events cause a very high inrush but
this is rare, so averaging over 24 operations is needed only if such
high values occur.
Second, the last note in A.14 says that Pst and Plt are to be
determined analytically. As I have done the calculations don?t seem to
be very different from the measured values (as long as the source is
stiff enough to handle the inrush.) It does not seem to adjust the
limits at all. Am I seeing this correctly?
I agree that is a bit obscure and I will ask the person 'in charge' of
the standard. Don't hold your breath.
>Third, the equation (5) in Clause 4.2.3.1 calls for the dmax value.
>Since dmax is a percentage should the value be entered as 4 or 0.04 if
>the dmax value is 4%?
It says 'expressed as a percentage', so 4 would be correct.
--
OOO - Own Opinions Only. See www.jmwa.demon.co.uk
They took me to a specialist burns unit - and made me learn 'To a haggis'.
John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK
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