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 ri...@sdd.hp.com 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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