Horst: thank you very much for your answer. I'd like to comment it a little. 1) From figure 5A on page 79c, I deduced I need an operational insulation between two primary circuits, if they exist. But your interpretation is possible. So, you have a operational insulation between phase and neutral conductors, but bridging components between them, like X capacitors, shall comply with stronger requirements than those one for operational insulation. Well, I can accept it, although I don't understand it very well. Moreover, I believe you also think that no weaker requirement is accepted after the fuse. 2) I know the mentioned paragraphs of the standard, but I believe it is not so clear the answer to my question. It seems like you agree that working voltage in a transformer is depending on the phase. But that may have a very expensive consequences. And I'm afraid nobody thought in it while they wrote the standard. 3) I can read that # 2.3.5 deals with connection of SELV to other circuits but please, try to think what it means and compare it with the old fourth method for SELV circuits. Anyway that is only a comment, no problem is in it. 4) I completely agree with you. "Earth is safe to touch. SELV is safe to touch. Why shall there be any need for an insulation to protect against electric shock?" But I'm afraid it is not written in the standard. In fact, if a SELV circuit doesn't use the third method in a class 1 equipment, I think that double or reinforce insulation is necessary between primary and secondary through any way not including the Protection Earth. But it is impossible to measure the electric strength in those ways if you don't cut the Protection Earth way. In my opinion, if I don't miss something, here we have a dark point in the standard.
Best regards 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] ---------- De: Horst Dierich[SMTP:[email protected]] Enviado el: domingo 26 de octubre de 1997 20:29 Para: [email protected] Cc: EMC & Product Safety Forum Asunto: Re: Questions about IEC/EN 60950 ................
