Dear Gary, I am not talking about an earthing trace on a PWB relied upon for BONDING purposes. The power supply in question has an earthing terminal (terminal block) directly mounted to an earthing trace on the PWB. Such a terminal is not used for bonding purposes (in which case what you say is correct, an earthing impedance test is necessary) but is used to terminate the supply earthing conductor. In case of a fault, this trace should reliably withstand the fault current available (hundreds of amperes).
Most North American standards do not explain this in "black and white"; you only experience it when submitting a product for NRTL tets with supply conductors terminating directly to a PWB via a terminal block. In this case, some tests could be conducted to ensure reliability. UL conducts a 1000 A short-circuit test for ITE type products. I was wondering if any of you have experience with a similar test for Industrial Control Equipment? I suspect that higher short-circuit currents can flow through the ground fault in an industrial environment. Any NRTL persons out there? Regards, From: Gary McInturff <[email protected]> To: "'[email protected]'" <[email protected]>, [email protected] Subject: RE: Earthing at PWB for UL508 Power Supply Date sent: Tue, 3 Nov 1998 12:11:00 -0800 Send reply to: Gary McInturff <[email protected]> > Note my area either, but you are going to want to take a look at Europes > 30 Amp ground continuity test. It is really designed to make sure of two > things. The resistance to ground is very small so that ground current > will flow when it has to, and that the ground path can withstand current > long enough to insure that a mains breaker pops. > Gary Mcinturff > > -----Original Message----- > From: [email protected] [SMTP:[email protected]] > Sent: Monday, November 02, 1998 2:56 PM > To: [email protected] > Subject: Earthing at PWB for UL508 Power Supply > > Dear Group, > > Does anyone have experience with an Industrial Equipment ( > UL508) having an earthing terminal (terminal block or the like) > directly on a trace on the PWB. As I understand, this is an > unacceptable construction for UL508 type equipment and there is > no alternative solution other than providing a dedicated > earthing > terminal on the chassis. > > Note: In UL1950, an earthing terminal may terminate to a trace > on > the PWB if the circuit withstands a 1000 A short-circuit test. > > Regards, > PETER S. MERGUERIAN > MANAGING DIRECTOR > PRODUCT TESTING DIVISION > I.T.L. (PRODUCT TESTING) LTD. > HACHAROSHET 26, P.O.B. 211 > OR YEHUDA 60251, ISRAEL > > TEL: 972-3-5339022 > FAX: 972-3-5339019 > E-MAIL: [email protected] > Visit our Website: http://www.itl.co.il > > --------- > This message is coming from the emc-pstc discussion list. > To cancel your subscription, send mail to [email protected] > with the single line: "unsubscribe emc-pstc" (without the > quotes). For help, send mail to [email protected], > [email protected], [email protected], or > [email protected] (the list administrators). > > --------- > This message is coming from the emc-pstc discussion list. > To cancel your subscription, send mail to [email protected] > with the single line: "unsubscribe emc-pstc" (without the > quotes). For help, send mail to [email protected], > [email protected], [email protected], or > [email protected] (the list administrators). > PETER S. MERGUERIAN MANAGING DIRECTOR PRODUCT TESTING DIVISION I.T.L. (PRODUCT TESTING) LTD. HACHAROSHET 26, P.O.B. 211 OR YEHUDA 60251, ISRAEL TEL: 972-3-5339022 FAX: 972-3-5339019 E-MAIL: [email protected] Visit our Website: http://www.itl.co.il --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to [email protected] with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to [email protected], [email protected], [email protected], or [email protected] (the list administrators).
