The basics of device circuit breakers | Differences between the technologies
Two examples of characteristic curves for thermal circuit breakers for different nominal currents
Example of a characteristic curve field for thermal miniature circuit breakers
Fig . 9 : Key characteristic curves of thermal circuit breakers at a glance
currents with a delay . The thermal part of this circuit breaker technology also makes it more susceptible to higher ambient temperatures .
The magnetic trip mechanism is designed with a solenoid coil and a plunger or pivoted armature . Currents that exceed the nominal current of the protective device create a magnetic field in the coil . The current strengthens the magnetic field and attracts the armature . When the preset limit value is reached , the armature actuates the trip mechanism and shuts down the protective device . These devices respond to short-circuit currents and excessive overload currents within 3 to 5 milliseconds .
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Trip mechanism |
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Operating lever on / off |
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a ) Bimetal with wrapped , current-carrying heating element > up to 5 A b ) Bimetal , direct with live current > from 6 A
Solenoid coil
Preload setting Coil anchor
Main switching contact
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Functional circuit diagram 1 . Voltage input 2 . Voltage output 11 . Common contact 12 . N / C contact 14 . N / O contact
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Switch rod
Circuit diagram
Fig . 10 : Structure and functional description of thermomagnetic circuit breakers
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