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7 guidelines for choosing a properly rated circuit breaker

The general procedure for selecting the correctly rated circuit breaker follows the following outline of seven main questions that you must answer.<br><br>7 tips for choosing a properly rated circuit breaker (pictured: COMPACT NSX 100H type low voltage molded case circuit breaker; credit: Edvard Csanyi)

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7 guidelines for choosing a properly rated circuit breaker

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  1. 7 guidelines for choosing a properly rated circuit breaker Selection of nominal circuit breaker The general procedure for selecting the correctly rated circuit breaker follows the following outline of seven main questions that you must answer. 7 tips for choosing a properly rated circuit breaker (pictured: COMPACT NSX 100H type low voltage molded case circuit breaker; credit: Edvard Csanyi) Let’s see the big questions: 1. What is the task of the branch circuit or the supply circuit? 2. What nominal current/setting range? 3. Breaking capacity / production capacity / nominal operating voltage? 4. Special requirements? 5. What kind of coordination? 6. What is the assembly method? 7. Cross section of connecting wire / cable?

  2. circuit breaker 1. What is the task of the branch circuit or the supply circuit? Will it be used for connection cable protection, plant protection, group protection or motor protection? Select the appropriate circuit breaker type , with or without thermal overload protection. Decide what kind of protection feature (cable or motor protection). 2. What nominal current / setting range? Do the thermal and magnetic release adjustment ranges cover the requirements of the particular application (transformer or generator protection)? The setting ranges of the different sizes of circuit breakers overlap. The same current settings may be partially covered by more than one breaker size (For example, an 80A setting may be covered by two or more breaker sizes, 100A or 125A). The following characteristics depend on the size of the circuit breakers:

  3. Accessories (type and number of auxiliary contacts, for example), Operating mode (rotary or rocker handle), Mounting method (snap-in or screw mounting) or The electrical characteristics (breaking capacity, selectivity, etc.). 3. Breaking capacity / production capacity / rated operational voltage? Where is the installation point of the circuit breaker? What is the expected magnitude of the prospective short-circuit current at this location? Is a lower breaking / breaking capacity acceptable (significant reduction in short- circuit current due to the length of the connection cables or other short-circuit protection devices connected upstream)? Is the breaking capacity reduced due to the higher rated operating voltage ( eg> 400 V )? Does it indicate a selection based on i cu (rated ultimate short-circuit breaking capacity, reduced functional capacity after a short-circuit interruption) or based on i cs (rated short-circuit breaking capacity? service circuit, full functional capacity after interrupting the short circuit)? With the help of effective group protection, can smaller and less expensive circuit breakers be used? Don’t know what the cutting and manufacturing capacities are?Learn here 4. Any special requirements? Should reduction factors for the rated current be taken into account due to: ambient air temperature ( > 40… 60 ° ), altitude of the installation site ( > 2000 m above msl ), frequency of higher power supply ( > 400 Hz )? 5. What type of coordination? Selection of the downstream contactor according to the type of contactor coordination type “1” or type 2 “ ? 6. What is the assembly method? Decisive factor for the support / adapter plates of the modular mounting system (suitable for the selected circuit breaker type). 7. Cross section of connection wire / cable? The section of the connection leads to the Motors should be selected according to the current setting of the thermal release of the circuit breaker. Finally, the maximum permissible length of the connection must be taken into account (risk of shock due to the contact potential in the event of a short circuit). Circuit breaker nameplate.

  4. Standardized characteristics indicated on the nameplate of the Compact NSX circuit breaker: 1. Device type– frame size and breaking capacity class 2. U i– rated insulation voltage. 3. U sprite-rated impulse withstands voltage. 4. I cs– service breaking capacity. 5. I cu– ultimate breaking capacity for different values of the rated operational voltage Ue 6. U e– operating voltage. 7. Color label– indicating the breaking capacity class. 8. Circuit breaker-disconnector symbol. 9. Reference standard. 10. Main standards to which the device conforms. Burraq Engineering Solutions is the best training institute in Lahore which is providing practical training of Electrical Automation and Short Electrical Courses including PLC course, SOLAR SYSTEM Installation and DESIGN COURSE, ETAP course, DIALUX course, Panel FABRICATION course, VFD course, ADVANCED Control Panel, SWITCHERGEAR design course, Building Electrical design course, and all electrical diploma courses. Both online and physical classes available. We introduce a platform Lyskills from where you can get lifetime access to your desire courses at a very reasonable price.

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