AMNYTT amnytt.no 1/2021 | Page 82

The basics of device circuit breakers | Differences between the technologies
system controller . If an event occurs , it is detected immediately and reported .
This approach reduces the period of any voltage dip to a minimum . Despite the event , the system voltage remains stable . In the event of overload current or a short circuit , the devices are promptly switched off .
Electronic circuit breakers are in some cases equipped with active current limiting . This function limits the short circuit and overload currents , depending on the product range , to a value of 1.25 to 2 times the nominal current . This protects the power supply against currents that are too high and prevents the output voltage from dropping at the switched-mode power supply unit .
Another benefit of this electronic technology is the ability to virtually completely plan out the connected load of any DC power supply . In addition , longer cable paths between the power supply and load are possible without negatively impacting the shutdown behavior .
Tripping characteristics and dynamics Thanks to intelligent current analysis , modern electronic circuit breakers can differentiate between many different operating and failure scenarios . The result is a dynamic in the characteristic curve . This means that any fault-related shutdown is not dependent solely on current and time . The load and power supply are detected , optimizing the startup process . In this way , the operation of the electronic protection is illustrated in a dynamic characteristic curve . Similar to traditional fuses , this is also done by defining an overload and short-circuit range . Some electronic circuit breakers have different characteristic curves . The purpose of these differences is first and foremost to offer the user familiar selection options . However , it is not necessary to differentiate t , s
100
10
1
0,1
0,01
0,001 1 2 4 8 16 32 64
Fig . 16 : Short-circuit behavior and dynamic overload detection range
among different characteristic curves . As opposed to thermal or thermomagnetic fuses , the electronics in modern electronic circuit breakers react dynamically . Figure 16 shows the various ranges : 1 . Short circuit behavior ( green line ): If a short circuit is detected , the fault is immediately shut down . To prevent any negative impact on the loads , this has to happen without a time delay . Particularly with a PLC , a shutdown must occur within 10 ms ( see also controller standard , p . 5 ).
2 . Dynamic overload detection range ( blue area ): Depending on the height and course of the flowing current , the intelligent detection also ensures a shutdown in the case of an overload . This process permits the overcurrent to persist for different lengths of time , depending on its progression and the stability of the supply voltage . The overload is shut down before a dangerous condition arises . Here also , the dynamics associated with electronic circuit breakers provide a critical advantage . If a fault is detected , it is shut down promptly , keeping the remaining supply in mind . Loads can be detected in this way and can be started even when high starting currents are present . x I n
When it comes to burn-through fuses and thermomagnetic circuit breakers , the different characteristic curves are known , such as fast-acting , medium blow , or slow blow . A modern electronic protective device with intelligent short-circuit detection and dynamic overload behavior is replacing the wide range of characteristics mentioned above .
14 PhoENix CoNtACt