Is to know the rated current, starting current of the motor, how to choose the circuit breaker of the motor

Each type of low voltage circuit breaker has its own overload curve and is inverse time. When the current is larger, the time limit is shorter.

I have to give an example.
Take the DZ47-63 miniature circuit breaker as an example. According to the tripping type, it is mainly divided into D type and C type. It is mainly used for AC 50Hz, rated voltage 380V, and the rated short-circuit current does not exceed 6000A. And short circuit protection, can also be used for infrequent on-off operation and conversion. Type C is used for lighting and civil power distribution, and Type D is used for industrial power distribution. The main technical performance parameters of the DZ47-63(D) miniature circuit breaker are as follows:

(1) Protection function: overload long delay and instantaneous short circuit protection.

(2) Overcurrent tripping characteristics
(3) Rated breaking capacity: 4000A at 380V and 6000A at 220V.

(4) Mechanical and electrical life: 4000 times.

The DZ47-63 type C and D type tripping type miniature circuit breakers differ in that the former requires 5 times of rated current and does not trip within 0.1 seconds, while the latter requires 7 times of rated current without tripping within 0.1 second. The ability to withstand instantaneous peak currents is stronger, and the reliability of avoiding motor starting current is higher.

Therefore, when selecting a low-voltage circuit breaker, it is necessary to select a switch with a strong overload capability for the motor type load. If your protection uses electronic protection, then it's better. For motors with heavy-duty starting, (starting wire and squirrel cage) starting current is 2~4 times of rated current, 4~8 times, starting time is 8~15 seconds, 15~20 seconds. You can use the inverse time setting switch setting.

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May 04, 2023