RE: Thermal breakers vs magnetic breakers 8/7/02 David, One of the reasons they may have been rejected previously is their change in trip point due to temperature changes. The higher the ambient temperature gets the lower the trip point of the thermal device becomes. If they are used side by side in a PDU in a telecom rack they may even generate enough heat to trip with 80% or less of rated current flowing. The trip point of a hydraulic magnetic breaker does not change with temperature. Typically they have a must trip value at 125% of rated current and will hold 100% of rated current. The one thing about magnetic hydraulic breakers at an increased ambient temperature is that the amount of time required to trip at 125% of rated current will be less. In most cases this is not considered a bad attribute. I hope this helps John
David Heald wrote: > >Greetings all, > In the spirit of the continual quest for cost reduction, I have been asked >to look into the use of thermal circuit breakers instead of magnetic ones. >It seems like we rejected thermal breakers before for some reason, but now >no one can remember why. > >Does anyone know of any telecom (or general) reasons why thermal circuit >breakers may be unacceptable for telecom products? > >Thanks and Best Regards, >Dave Heald > >------------------------------------------- >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] > >All emc-pstc postings are archived and searchable on the web at: > http://ieeepstc.mindcruiser.com/ > Click on "browse" and then "emc-pstc mailing list" John Lach Manager Standards and Test [email protected] Carling Technologies 60 Johnson Ave. Plainville, CT 06062 860-793-7167 www.carlingtech.com
