I read in !emc-pstc that Peter L. Tarver <[email protected]> wrote (in <[email protected]>) about 'Circuit Breaker Tripping Dring Fault Tests' on Wed, 29 Jan 2003: >In a typical household operating at 120V, it's unlikely >that a fault current available to Pluggable Equipment Type A >will be much above 5kA, even if the outlet supplying the >equipment is within 5 ft. of the service entrance. In a >typical household operating at 240V, the available fault >current will be somewhat higher (approximately doubled +).
H'mm. IEC 60725 gives a 'reference impedance' (a sort of weighted average, omitting extreme values) for a 230 V 50 Hz 100 A service-rating household supply as 0.47 ohms at the service entry. Allowing another 0.5 ohms for the mains wiring and the flexible mains lead, we get 230 V and 0.97 ohms at the appliance, giving a prospective short-circuit current of about 240 A. The appliance fuse should be able to interrupt that without exploding. UK plug-top fuses are tested to break 6000 A safely, though. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk Interested in professional sound reinforcement and distribution? Then go to http://www.isce.org.uk PLEASE do NOT copy news posts to me by E-MAIL! 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: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
