The C type miniature circuit breaker is suitable for motor circuit

As we all know, c-type MCB is used for common circuit, such as lighting circuit; D type circuit breaker for motor power circuit, so, C type micro circuit breaker can be used for motor circuit?

Instead of saying yes or no, let’s first look at the difference between type C and TYPE D MCB:

• Type C micro break: contains overload protection and short circuit protection, short circuit protection tripping value is 5~10 times of rated current;

• D type micro break: contains overload protection and short circuit protection, short circuit protection tripping value is 10~20 times of rated current;

Both overload protection is the same, the only difference lies in the short circuit protection tripping range.

Usually, ordinary load has no starting current, that is, the starting current is rated current; The starting current of the motor is about 7-10 times of the rated current. Here’s an example:

4kW three-phase motor, rated current 9A, starting current calculated by 10 times, 90A;Usually choose D-type 16A micro-break as a protection appliance, according to 10 times the action current calculation, short-circuit protection action current is 160A, can avoid the motor starting current;

If you choose C type 16A micro-break as a protection appliance, according to 5 times the action current calculation, short-circuit protection action current is 80A, can not avoid the motor starting current; Does that mean C breakers are definitely not an option?

Of course not, if you choose c-type 25A micro-break as a protection appliance, according to 5 times the action current calculation, short-circuit protection action current is 125A, can avoid the motor starting current; There was no technical problem.

The economy

Take our C63 series MCB as an example.C63 C25A is cheaper than C63 D16A

Thinking: we usually choose the principle of circuit breaker is the circuit breaker rated current is greater than the load current, according to the nature of load type to choose C or D type D is manufacturer specially designed for electric machine load, but it doesn’t mean C type circuit breaker can’t use, just need to adjust the calculation method, the need to explore nature, flexible control.

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