Hi folks I (and I believe, a number of other people) disagree with the last sentence of David's message - in so far as it is NOT merely a question of having a longer grounding pin.
IEC and EN60950 - and I think also the common UL/CSA standard (but not having seen the latest edition) - allow high leakage equipment to be connected by a mains plug ONLY if it can be classified as "Pluggable Type B", and NOT "Pluggable Type A". If you then refer to the definitions of these two types of equipment (in those standards) you will see that Pluggable Type A" uses a domestic grounding plug, whilst "Pluggable Type B" uses an industrial plug , e.g. IEC/EN60309 (but I would also personally class many of the North American NEMA 6P-XX "Twistlock" plugs as being in this category). The significant point about the latter types of plugs is that they have some mechanism to positively lock the plug into the socket and thus ensure the grounding continuity - whereas domestic plugs generally do not and can "rock" badly in the socket - thus compromising the grounding of the equipment. There are also minimum conductor size requirements for the grounding conductor, and an overall 5% limit on the leakage current (although I doubt that this will affect much pluggable equipment!!) John Allen THALES Defence Ltd, Bracknell, UK -----Original Message----- From: David Gelfand [ mailto:[email protected] <mailto:[email protected]> ] Sent: 18 January 2001 21:30 To: EMC-PSTC (E-mail) Subject: Re: Looking at leakage current specs Gary, The measurement is made with all power supplies in parallel, but you can exceed the 3.5 mA limit if you provide a warning to ground equipment before connecting. With standard power cords this is done by having the ground pin slightly longer than the line and neutral. David David Gelfand Regulatory Approvals Memotec Communications Inc. Montreal Canada ----- Original Message ----- From: "Gary McInturff" <[email protected]> To: "EMC-PSTC (E-mail)" <[email protected]> Sent: Thursday, January 18, 2001 10:44 AM Subject: Looking at leakage current specs Was reviewing a number of power supply specifications and would like to parallel a couple, but the leakage/touch current on them is in the 2 mA range. Isn't most of the leakage current produced (produced might not be the word I want) in the upfront filter caps - W and Y capacitors and such? If I parallel these aren't I likely to see a significant increase in the leakage current, and probably blow by the 3.5 mm requirement for ITE? Would the measurement be made twice, once for each supply or would I have to provide a common input to both supplies and then measure between chassis and this common point's protective earth terminal? Gary ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: [email protected] Michael Garretson: [email protected] For policy questions, send mail to: Richard Nute: [email protected] ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: [email protected] Michael Garretson: [email protected] For policy questions, send mail to: Richard Nute: [email protected] ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: [email protected] Michael Garretson: [email protected] For policy questions, send mail to: Richard Nute: [email protected]
