IEEE Std 1458-2017 pdf download – IEEE Recommended Practice for the Selection, Field Testing, and Life Expectancy of Molded-Case Circuit Breakers for Industrial Applications.
1.2 Purpose Molded-case circuit breakers are one of the most widely used circuit protection devices in low- voltage (less than 1000 volt V [ac], 1500 V [dc]) applications. In spite of their wide use in industry, the average person specifying, installing, operating, and maintaining these devices has less than a complete understanding of them. The purpose of this document is to provide people who purchase or maintain molded-case circuit breakers with a single document that includes the following information: —How molded-case circuit breakers operate —How to correctly size and select molded-case circuit breakers —How to safely maintain molded-case circuit breakers —How to determine when a molded-case circuit breaker must be replaced
The circuit breaker might be applied as an individual item in its own enclosure or utilized in conjunction with a wide variety of other equipment in a common enclosure. Depending upon such things as system voltage, type of circuit breaker, and specific application, circuit breakers in common enclosures with other devices might be called panelboards, or switchboards, switchgear, which are is each specifically defined by a set of standards. They might even be referred to as just an assembly. An assembly could include some or all of the following: circuit breakers, control devices, metering devices, regulating devices, equipment interconnections, and supporting structures.
3.6.2 Opening and closing contacts Let’s Consider a three-phase circuit breaker of any kind. Designs are such that three sets of contacts open or close simultaneously. This means that all the contacts are linked together in some manner. This part of the mechanism might be connected mechanically in some fashion to a common handle. The handle, when operated, puts the mechanism into motion, and opens or closes the circuit breaker by opening or closing the contacts. Circuit breakers, by virtue of their size and/or one or more standards requirements, need additional assistance to set the mechanism in motion and open or close the contacts as required. This additional assistance takes the form of opening or closing springs. Springs play a big role in the precise functioning of circuit breaker mechanisms. Springs are stretched or compressed to provide the energy necessary to assist with the proper opening or closing of the contacts.