Re: [PSES] Inrush Current

```Just curious to why delete the highest and lowest values before taking the
average?```
```
Ralph McDiarmid
Product Compliance
Engineering
Schneider Electric

From: John Woodgate [mailto:jmw1...@btinternet.com]
Sent: Thursday, August 10, 2017 5:00 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] Inrush Current

Look at Annex B of IEC/EN 61000-3-3. I did a lot of work on this for that Annex
and you will often get different results each time, because of differences in
how the current is interrupted at the previous switch-off. You do not select a
point on the voltage waveform for the switching instant; you can't, anyway,
because you must use the product's own mains switch (unless it doesn't have
one). You switch at random points, because that is what happens in practice.

For duration,  you leave the mains voltage applied until the inrush transient
is over (look at the current waveform); this is usually after three or fewer
cycles, but for some products it can be rather longer. Normally, the first
current peak is the highest, but occasionally the second peak is higher.

With best wishes DESIGN IT IN! OOO - Own Opinions Only
http://www.jmwa.demon.co.uk/ J M Woodgate and Associates Rayleigh England

Sylvae in aeternum manent.

From: Kim Boll Jensen [mailto:k...@bolls.dk]
Sent: 10 August 2017 12:30
To: mailto:EMC-PSTC@LISTSERV.IEEE.ORG
Subject: [PSES] Inrush Current

Hi

We have several times been asked to test Inrush Current and have this function
on our Harmonic tester, but it is not defined how it measure and we get very
different measurements each time we switch ON the same EUT.

I can't find an IEC definition on the measurement other than "peak current".

I asume that it is most correctly to measure the current  by switching ON at
the top of the sine (90 deg), but what about duration?

A peak current with a duration of 0.1 ms is not as interresting as the same
current for 1 ms. And what if there are several current peaks after each other
such as ringing wave form?

Best regards,

Kim Boll Jensen
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