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 <[email protected]> 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 > > > > > ------------------------------------------- ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson: [email protected] Dave Heald [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
