I am just commenting on your last question (d) although it has been answered by Mr. Horst Dierich, you mentioned reinforced insulation from pri to earth, the requirements calkl out for Basic and not reinforced insulation. Thanks sgour
-----Original Message----- From: Juan Pedro Peña [SMTP:[email protected]] Sent: Thursday, October 23, 1997 12:28 PM To: EMC-PSTC; E-SAFETY Subject: Questions about IEC/EN 60950 I have some questions about IEC/EN 60950: a) Last version of the standard doesn't show explicitly the required insulation between conductive parts of different polarity in primary circuit. It looks like obvious that operational insulation is the minimum, but other standards requires basic insulation, at least until the other side of the fuse where operational insulation may be enough. Moreover, X capacitors between phase and neutral conductor has higher requirements (# 1.5.6) than only operational insulation. What's the right interpretation? b) Insulation between both sides of a transformer shall be calculate according to the maximum voltage that can be found between them. If we have a primary circuit with 230 V AC and a secondary circuit with 100 V AC, what voltage should we consider? 230 + 100?, 325-141 V peak if both circuits have the same phase? 325+141 V peak if both circuits have a phase of 180º? Does it depend on the real phase? c) It looks like if the old 4th method of protecting a SELV circuit (never admitted in Europe), has been substituted by # 2.3.5 Isn't it? d) If somebody uses a SELV circuit not earthed, there is no insulation requirement of that circuit from earth. The earth conductor has a reinforce insulation from primary circuit, but no insulation requirement from the SELV circuit. Primary to SELV insulation may be reinforce, but it isn't because it has a way through earth with only basic insulation. What's the right interpretation? Finally, a comment. Thank you very much to the colleague of this forum that have scanned it for all of us. I have visited the Web site http://www.varju.bc.ca/standards/cenelec.txt, where you can find an internal document of CENELEC with several "interpretations" to EN 60950, used by the friends labs that have access to that information. Most of us had never known that document if somebody didn't scan it for us. Those "interpretations" actually is a private amendment to the standard, required but unknown. I disagree with that system. ------------------------------------------------------------------------ --- The above opinions are personal, not from the company Juan P. Pena / Electrical Safety Area Company: CETECOM, S.A. (http://www.cetecom.es) e-mail: [email protected]
