The basics of device circuit breakers | Differences between the technologies
On / off switch
1
Spring-loaded switch rod
2
Function circuit diagram
Main switching contact Bimetal
Preload setting
Fig . 7 : Structure and functional description of thermal circuit breakers
Circuit diagram
Fig . 8 : Typical tripping characteristics for thermal circuit breakers : t Switch time ( in seconds ) xl Multiple of the nominal current / tripping factor 1 Current ranges of the characteristic field 2 Tripping characteristics of the lower temperature range ( blue ) 3 Tripping characteristics group 1 4 Tripping characteristics group 2 5 Tripping characteristics of the upper temperature range ( red )
Tripping characteristics The tripping time of thermal device circuit breakers depends on the overload current that is flowing and the ambient temperature . The characteristic curves show that the tripping time is reached faster as the overload increases . With smaller overload currents , it therefore takes longer for the connected load to be disconnected from the power supply ( Fig . 8 ). For circuit breakers with different nominal currents , but with the same tripping characteristics , the tripping can also be presented in characteristic curve fields ( Fig . 9 ). Of course , thermal device circuit breakers respond to the effects of heat . The ambient temperature can also affect the tripping time . The circuit breaker trips more easily at a high ambient temperature and more slowly at a low ambient temperature . This behavior is indicated by additional characteristic curves with corresponding information .
2.2 Thermomagnetic circuit breakers
Thermomagnetic device circuit breakers are used among other things in information and communication technology as well as process control . Thanks to a variety of versions with different tripping characteristics , circuit breakers are ideally suited for protecting programmable logic controllers , valves , motors , and frequency converters . The reactivation and immediate remote signaling of the operating state ensure high availability . The different characteristic curves for this protection technology can even start critical loads while at the same time providing secure protection in nominal operation .
Function description Thermomagnetic circuit breakers are equipped with two trip mechanisms .
The temperature-dependent part of the mechanism consists of a bimetal with a heating coil ( Fig . 10 ). Currents that exceed the nominal current of the protective device generate heat in the heating coil . This causes the bimetal to bend and act on the switching mechanism . When the limit value is reached , the protective device shuts down . The devices respond to overload
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