The starting point is the manufacturers data sheet where you will find the rated current, voltage and typical operating life under certain conditions.
A lot depends on the energy level of the in-rush in question. When the application has a high in-rush current in proportion to the steady state condition then you may want to contact the manufacturer for guidance because there are a number of different ways to make a switch mechanism, each with particular advantages. Each manufacturer usually publishes data for current rating which is based on two operating conditions: continuous AC or DC; start-stop cycles assuming inductance in the load. The later is usually the limiting case for in-rush and the switch maker had an application in mind when designing the switch package for example AC power control of 50/60Hz relays and motors; or, low voltage low current signal switching; or, incandescent lamp switching. The in-rush capability has two limiting factors: tendency of the transition to create conditions which encourage arcing; the frequency of operation and the required number of on off cycles in the life of the switch. Because uncontrolled in-rush can be so destructive to the switching elements there are techniques for in-rush control which relieve the primary switch from some of the stress. Examples are a starting circuit that inserts resistance in series with the source for a short period; starting circuit that divides the load into segments that are connected sequentially......etc For many low to medium power applications there are simple two terminal temperature sensitive resistors, packaged under names like Surge Guard and In-rush limiter, which can be selected to handle the continuous load current and which have a 'cold' resistance appropriate to the transient condition. We make power amplifiers and linear power supplies that always need AC turn-on in-rush to be considered. Our primary tool is the magnetic circuit breaker for which carefully defined integral delays have been developed to suit most applications. Can provide names and numbers directly on request. ------------------------------------------- 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: No longer online until our new server is brought online and the old messages are imported into the new server.
