When choosing a circuit breaker to protect the motor, we should pay attention to two characteristics of the motor. One is that it has a certain overload capacity. The other is that its starting current is usually several to ten times the rated current. Therefore, circuit breakers for motor protection can be classified into two categories: one is for protection only and does not bear normal operation; the other is for protection and not frequent operation. In the latter case, operational conditions and electrical life should be considered.

(1) selection principles of circuit breakers for motor protection
① Long delay current setting value = motor rated current.
② Instantaneous setting current. For the circuit breaker of protective cage motor, the instantaneous setting current is 8-15 times the rated current of the motor. The value of the instantaneous setting current depends on the type, capacity and starting conditions of the motor to be protected. For the circuit breaker of the winding rotor motor, the instantaneous setting current is 3-6 times the rated current of the motor. The value depends on the type, capacity and starting conditions of the winding rotor motor.
③ The return time of the 6 times long delay current setting value > the actual starting time of the motor. According to the weight of the load at startup, you can choose a stopover of 1, 3, 5, 8, 15 (s).

(2) The selection of conductor protection circuit breakers for lighting and life use conductor protection circuit breakers refer to the circuit breakers used to protect distribution systems in living buildings. Because the capacity of protected lines is not large, plastic case circuit breakers are often used.
① Long delay setting value < line load current.
② The instantaneous action setting value =6~20 times the circuit load current.

DC mini circuit breaker has super current limiting performance, can accurately protect relay protection, automatic device from overload, short circuit and other fault hazards. DC mcb has the advantages of current limiting and arc extinguishing. Through a large number of comprehensive scientific tests, it can realize full selective protection between main (sub) screens, protection screens and relay screens in DC system below 3000Ah.

DC mini circuit breaker adopts special arc extinguishing and current limiting system, which can quickly break the fault current of DC distribution system and greatly improve the stage difference coordination. DC mcb is especially aimed at the fault of step tripping between test and protection panel and distributor panel in DC system of electric power engineering. The series of DC circuit breakers have excellent performance and can avoid the above fault. The differential matching characteristics of DC circuit breakers are the best products at home and abroad.

DC mcb are suitable for applications such as communication and photovoltaic systems.

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