While we're on the subject of PD3, I have some 950-based questions regarding optocouplers and creepage distances. Suppose we have a power supply with a 230Vac supply and a user-accessible secondary somewhere. If you put an optocoupler across the Pri-Sec isolation boundary, it seems to me that the required creepage can easily exceed that offered by standard DIP packages. - The standard DIP gives you 7.4mm while the "wide-body" types can give you up to 10mm. - I haven't looked today, but I recall determining once that the packages of opto's and other IC's are Material Group III - We're discussing Pollution Degree 3 - Reinforced insulation is required in the above scenario A little reverse engineering of the creepage table tells us that only 300V RMS or DC working voltage is needed before the requirement exceeds the 10mm provided on a wide-body package. Standard DIP's with 7.4mm creepage fail at 231Vrms! Q1: Right so far? Q2: Anyone have any differing info re the material group for opto packages? Determination of the working voltage can be confusing. Suppose the primary side of the opto is in a 5V logic circuit but that circuit's reference ground is the same as the rest of the primary = the negative side of the rectified line voltage bus (ie one diode away from the AC neutral). The rectified line voltage bus operates at around 300Vdc (ignore ripple for now). I think we need to consider the working voltage on the primary side of the opto to be 300Vdc. Q3: Is 300Vdc right? Now suppose on the secondary side of the product we have a floating 5V control circuit isolated from the primary by a housekeeping supply, but referenced to the same (floating) secondary ground as the secondary power circuits which include a 45Vdc bus. I think we need to consider the working voltage on the primary side of the opto to be 45Vdc. Q4: Is 45Vdc right? The opto is connected between these two 5V control circuits: one referenced to primary ground and one to a floating secondary ground. Q5: What is the working voltage across the opto, and how do you arrive at it? Q6: If I'm right, the working voltage is 345Vdc and no opto I know of meets the required creepage (interpolates to 11.2mm). Can I apply the easement of par. 2.9.8 by using a conformal coating on the opto, therefore allowing the Table 7 creepage of 2mm? In other words, are opto's considered to be "components conforming to 2.9.7"? Q7: If yes, do I need to do the tests of 2.9.7 to the opto (testing my 2nd and 3rd sources too) or have the opto manufacturers been kind enough to do this for me during the opto's approval process? OK, enough already. I'll stop now and see what replies I get. Thanks in advance for your help. Regards,
Jim Eichner, P.Eng. Group Leader, Engineering Services Xantrex Technology Inc. Mobile Markets web: www.xantrex.com <http://www.xantrex.com> Any opinions expressed are those of my invisible friend, who really exists. Honest. -----Original Message----- From: Massey, Doug C. [mailto:[email protected]] Sent: Tuesday, April 03, 2001 2:10 PM To: 'IEEE Forum' Subject: RE: 950 Pollution degree detirmination The UL interpretation is: Pollution Degree 2, based on the IP66 rating. I think EN60950 3rd Ed., clause 2.10.1 is very open to interpretation - I can make a great case that my power supply inside the enclosure is a subassembly (what else could it be?). Also, that subassembly is sealed against moisture or dust, as evidenced by the type test performed to a harmonized standard. I do understand the intent of PD 1, though, as others have responded in so many words, "that's for things that are potted". We're designing to PD 3 spacings - I've already played devil's advocate as you did. I just wanted to hear a few opinions. Doug -----Original Message----- From: John Juhasz [mailto:[email protected]] Sent: Monday, April 02, 2001 1:35 PM To: Massey, Doug C.; 'IEEE Forum' Subject: RE: 950 Pollution degree detirmination Doug, While I would tend to agree that this may be acceptable, and I would too like to see some sort of 'official' determination on this (I may have a similar situation arise in the next couple of months), I would like to play devil's advocate for a moment to further this discussion . . . As you quoted " . . . EN60950 3rd Ed., clause 2.10.1 defines Pollution Degree 1 " for components and subassemblies which are sealed so as to exclude dust and moisture (see 2.10.7)." It clearly states "for components and subassemblies". Your Pollution 1 argument requires the use of the IP66 enclosure. But is the product/enclosure pairing still considered a 'component' or subassembly'? The way I see it is that the product without the enclosure is the component or subassembly, and that installing the product in the IP66 enclosure make the product a 'top-level'. If for some reason the gasketing on the enclosure fails, or it is not closed properly, the product would not comply. Seems risky to me? (This is my opinion only, not that of my employer). John Juhasz Fiber Options Bohemia, NY -----Original Message----- From: Massey, Doug C. [ mailto:[email protected] <mailto:[email protected]> ] Sent: Monday, April 02, 2001 11:47 AM To: 'IEEE Forum' Subject: 950 Pollution degree detirmination Hello group - In the -950 series standards, three Pollution Degrees are defined for detirming insulation coordination. For instance, in EN60950 3rd Ed., clause 2.10.1 defines Pollution Degree 1 " for components and subassemblies which are sealed so as to exclude dust and moisture (see 2.10.7)." Clause 2.10.7 gives test requirements for temp cycling, humidity, and electric strength tests, although compliance to the clause is given as "...inspection from the outside, measurement, and, if necessary, by test." I would like to use Pollution Degree 1 when evaluating a product that has a dust and water ingress rating of IP66 per IEC - 60529, Degrees of protection provided by enclosures (IP Code) . The product itself is intended for use in a Pollution Degree 3 environment, but the creepages and clearances inside the unit are subject to Pollution Degree 1, thanks to the protection provided by the enclosure. Is the IEC-60529 report, showing a IP rating of IP66, adequate to satisfy the requirements of 2.10.1 & 2.10.7 for using Pollution Degree 1 when assessing clearance and creepage ? Thanks in advance. Doug Massey Safety Approvals Engineer LXE, Inc. Norcross, GA., USA Ph. (770) 447-4224 x3607 FAX (770) 447-6928 e-mail: [email protected] Cruise our website at: http:\\www.lxe.com <http:\\www.lxe.com> ------------------------------------------- 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/ <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: http://www.rcic.com/ <http://www.rcic.com/> click on "Virtual Conference Hall," ------------------------------------------- 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: http://www.rcic.com/ click on "Virtual Conference Hall,"
