Can the C-type micro-break be used for the motor power supply circuit?
We all know that C-type micro-break is used for ordinary circuits, such as lighting circuits; D-type circuit breakers are used for motor circuits, then I would like to ask everyone, can C-type micro-breaks be used for motor circuits?
Let's not say yes, let's take a look at the difference between C-type and D-type micro-break:
C-type micro-break: contains overload protection and short-circuit protection, short-circuit protection trip value is 5~10 times of rated current;
D-type micro-break: contains overload protection and short-circuit protection, short-circuit protection trip value is 10~20 times of rated current;
The overload protection is the same, the only difference is the short-circuit protection trip range.
Generally, the normal load has no starting current, that is, the starting current is the rated current; the starting current of the motor is about 7 to 10 times of the rated current.
For example: 4kW three-phase motor, rated current 9A, starting current is calculated by 10 times, 90A;
Usually choose D type 16A micro-break as a protective device, calculated by 10 times the action current, the short-circuit protection action current is 160A, which can avoid the motor starting current;
If you choose C-type 16A micro-break as a protective device, according to the 5 times action current calculation, the short-circuit protection action current is 80A, can't escape the motor starting current; does that mean absolutely no choice of C-type circuit breaker?
Of course not. If you choose C-type 25A micro-break as a protective device, calculate the operating current of the short-circuit protection by 125 times according to the action current of 5 times, which can avoid the starting current of the motor; there is no technical problem.
Let us look at the economy again:
Take the Schneider C65 series micro-break as an example.
C65N3PC25A price is 130.3 yuan
C65N3PD16A price is 158.9 yuan
It can be seen that from the price point of view, the C series is still slightly lower.
Thinking: Usually the principle of our choice of circuit breaker is that the rated current of the circuit breaker is greater than the load current, and the C or D type is selected according to the nature of the load. The D type is specially designed for the motor type load, but it does not mean that the C type circuit breaker cannot be used, but the calculation method needs to be adjusted. We still need to explore the essence and be flexible in our study.
