The basics of device circuit breakers | Why device circuit breakers ?
short circuit occurs , the best approach is to shut off the fault as soon as possible , depending on how high the current is . This is where device circuit breakers come in .
The elements needed to ensure optimum device protection vary depending on the area of application and availability requirements . This is why different types of device circuit breakers that work with different technologies have been developed over time . These types include electronic , thermomagnetic and thermal device circuit breakers . They differ from each other in how they are tripped , their shutdown behavior , and their tripping time . Characteristic curves are used to clearly illustrate the shutdown characteristics of the various device circuit breakers . Furthermore , selection also depends on what precisely is needed in terms of protection and system availability .
Controller standard IEC / EN 61131-2
This standard describes the equipment requirements and testing for programmable logic controllers . There are two important points to note here to ensure system availability :
• A controller in a non-battery-powered system must be able to withstand a voltage dip of up to 10 ms without any effect . This results in a time window within which a shutdown must occur if there is a threat of a longer voltage dip .
• The guaranteed operating voltage range must fall within the range of 19.2 - 30 V DC . The controller may fluctuate above or below the specification , which can lead to malfunctions .
However , controllers are generally able to function with lower voltages . The standard can only be used as a baseline , however , which makes the indicated voltage range significant at a fundamental level .
1.2 Differences between miniature circuit breakers and device circuit breakers
Miniature circuit breakers ( MCBs ) Miniature circuit breakers were designed and developed first and foremost to provide cable protection in a building . They are covered under the standard IEC / EN 60898 ( Electrical accessories – Circuit-breakers for overcurrent protection for household and similar installations ). The current drawn by the load is not known at this point . Therefore , the wiring is designed such that it can continuously carry the nominal current of the protective device . At the same time , a certain amount of inertia is desired , because the cable must be protected and the tripping should not be too fast . For a long time , lower current values were not used , as these are not necessary for the building installation . Furthermore , miniature circuit breakers are characterized by their high short-circuit shutoff capacity , which is necessary for operation on the grid . The electric arc that occurs at shutoff is high in energy and needs to be interrupted during shutoff . This is the only way to ensure a safe shutoff .
Device circuit breakers Device circuit breakers are described in IEC / EN 60934 . They are not just used for cable protection , but first and foremost for device protection . For this reason , their nominal currents start at less than 1 A and they are subdivided into small current increments . This makes it possible to adapt the protection to the corresponding device as precisely as possible . A variety of characteristic curves that have been specially developed and established for DC voltage also assist in this .
Since device circuit breakers do not depend directly on the mains , no quenching plates are required , as is the case with miniature circuit breakers . They are therefore significantly more compact , saving space in the control cabinet .
Problems associated with MCB-based protection MCBs were designed for different applications than device circuit breakers . Therefore , they need a very high tripping current : An MCB shutoff is divided into two parts : a thermal and a magnetic shutoff . Thermal shutoff takes place in the lower seconds to minutes range , whereas
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