The basics of device circuit breakers | Differences between the technologies
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Differences between the technologies
The demands placed on optimum device protection vary depending on where it is deployed and how it is used . Device circuit breakers therefore work with a wide range of technologies : electronic , thermal , and thermomagnetic .
The differences are in the tripping technology and shutdown behavior . Characteristic curves clearly illustrate the switch-off characteristics of the various device circuit breakers .
2.1 Thermal device circuit breakers
Thermal device circuit breakers provide optimum protection against overload for inductive and resistive loads in power distribution systems , control cabinet engineering , and systems manufacturing . They are resistant to high starting currents such as those that occur when starting a motor or switching on a transformer . They are also used for protecting circuits in battery and onboard systems . Compared to other protection technologies , however , thermal circuit breakers do not offer rapid protection from short circuits .
Main switching contact
Reactivation switch
Bimetal
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Function circuit diagram
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Function description The tripping element of thermal device circuit breakers is bimetallic . It may also be a combination of bimetal and an electrical heating element . The bimetal consists of steel and zinc , which is formed by heat . When a predefined heat level is reached as a result of an excessively high current in the heating element , the thermal bimetal trips the shutdown mechanism . This thermal tripping element makes the thermal protection more susceptible to higher ambient temperatures . Thermal
Fig . 6 : Structure and functional description of thermal circuit breakers
device circuit breakers represent a simple , cost-effective solution for applications which do not necessarily require fast and precise shutdown ( Fig . 6 and 7 ).
Circuit diagram
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