I also agree with the 4.4mm reinforced and 2.2mm basic/supp. calculation. I will assume that there is a creepage requirement also and would use pollution 1 in this application as long as the enclosure does not have openings.

Ed

>From: vit...@aol.com
>Reply-To: vit...@aol.com
>To: ,
>CC:
>Subject: Re: [Fwd: clearance and working voltage]
>Date: Wed, 28 Nov 2001 21:51:04 EST
>
>
>Rich and Xing,
>
>No arguments from me about the clearance of 4.4 mm for reinforced. The other 6.4 mm clearance requirement is probably a misapplication of the clarance rules using the 840 v peak row of Table 3H.
>
>I think the original question may also need to consider creepage requirements. Then again, maybe not. Can the inside of an ac adapter be considered a pollution degree 1 environment? If so, the creepages are determined using the clearance table. Has anyone taken this approach? I presume no ventillation openings are allowed? How good a seal is needed for the enclosure halves and connectors/output cables?
>
>vgl
>
>In a message dated Wed, 28 Nov 2001 7:50:37 PM Eastern Standard Time, Rich Nute writes:
>
> > Hi Xing Weibing:
> >
> >
> > Here is my answer to the question.
> >
> > > Hi group I have a question regarding clearance and working voltage of
> > > IEC60950. If I HAVE A AC ADAPTER(AC 100-240V 50/60Hz) ,THE WORKING
> > > VOLTAGE MEASURED ARE AS FOLLOWS: Nominal supply voltage: AC240V PRIMARY
> > > AND SECONDARY : 364V(RMS), 540V(PEAK) MEASURED clearance: 5.3mm I HAVE
> > > READ SOME CB TEST REPORT FOR THIS THIS SITUATION: SOME REQUIRE: MINIMUM
> > > CLEARANCE 4.0+0.4mmother require: minimium clearance 6.4mm which is
> > > correct for this situation? regards Xingwbbtiep2001-11-28
> >
> > Since the product is an adapter, I will assume that
> > the question addresses clearance between the mains
> > circuit and a SELV secondary circuit.
> >
> > I will also assume that the applicable standard is
> > IEC 60950, either
> >
> > 2nd Ed (Tables 3 and 4) or
> > 3rd Ed (Tables 2H and 2J).
> >
> > The parameters are:
> >
> > nominal mains voltage: 240 V rms
> > 340 V peak
> > working voltage: 364 V rms
> > 540 V peak
> >
> > The problem is confused because there is
> >
> > a set of requirements for working voltage,
> > in Table 3/H, and
> >
> > a set of requirements for peak working voltage,
> > Table 4/2J.
> >
> > (The 2nd Ed. refers to "repetitive peak voltage;"
> > the 3rd Ed refers to "peak working voltage.")
> >
> > According to the standard, if the peak value of the
> > working voltage exceeds the peak value of the mains
> > voltage, then the working voltage in Table 3/2H is
> > taken as the mains voltage. Then, the peak working
> > voltage (aka repetitive peak voltage) is used in
> > Table 4/2J.
> >
> > In the example, the peak value of the working voltage
> > exceeds the peak value of the mains voltage.
> >
> > The minimum clearance in Table 3/2H for 240 V mains
> > and 240 V working is:
> >
> > 4.0 mm reinforced
> > 2.0 mm basic/supplementary
> >
> > The additional clearance in Table 4/2J for 240 V mains
> > and 540 V peak is:
> >
> > 0.4 mm reinforced (567 V peak)
> > 0.2 mm basic/supplemenatry (567 V peak)
> >
> > So, the total clearance is:
> >
> > 4.4 mm reinforced
> > 2.2 mm basic/supplementary.
> >
> > Arguments? Another view or interpretation?
> >
> >
> > Best regards,
> > Rich
> >
> >
> >
> >
> > -------------------------------------------
>
>
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