Miniature circuit breaker product selection and engineering design elements

In the civil design is mainly used for low-voltage circuit breaker overload, short circuit, over current, loss of voltage, grounding, leakage, dual power automatic switching and infrequent start motor protection, operation and other purposes, the choice of In addition to compliance with the principle of low-voltage electrical equipment with ring

Environmental characteristics of the basic principles (see distribution of industrial and civil design manual) still  electric transformer  considered in addition the following conditions:
A) not less than the rated voltage of the circuit breaker rated voltage lines;
2) Rated current breaker with overcurrent tripping device is not less than the rated current of the line to calculate the current;
3) circuit breakers rated short-circuit breaking capacity not less than the maximum short-circuit current;
4) Select the type of distribution to be considered a short delay circuit breaker breaking capacity and delay Voltage stabilizer interstage match;
5) breaker undervoltage release voltage rating equal to the rated line voltage;
6) When used for motor protection, then select the circuit breaker motor starting current to be considered at the starting time and make no action; design calculations see "industrial and civil Distribution Design Handbook";
7) breaker selection should also consider the breaker and circuit breakers, circuit breakers and fuses selective cooperation.
⑴ tie breaker and breaker breaker should be considered superior instantaneous release action value should be greater than the lower end of the circuit breaker outlet maximum expected short circuit current at the circuit breaker if the two loop element impedance value when the difference is small, make little difference in the short-circuit current value, then

Optional superiors breaker trip unit with a short delay.
⑵ In the short-circuit current limiting circuit breaker is greater than or equal to its instantaneous release setting value, it will trip within a few milliseconds, so the lower protection of electrical circuit breakers should not be used to achieve selective protection requirements.
⑶ circuit breaker with a short time delay, when it is at the maximum delay time setting, its ability to drop-off, therefore, the selective protection circuit, consider choosing a short delay circuit breaker breaking capacity should meet the requirements.
⑷ circuit breaker should be considered superior properties and lower latency to return to the circuit breaker operating characteristic time curve should not intersect, short delay characteristic curve between the instantaneous characteristic curve should not intersect.
⑸ use fuses with the circuit breaker should be considered on the lower level with, should the safety second characteristic curve of the circuit breaker and fuse safety second characteristic curve to the short-circuit current in the case of a selective protection.
⑹ breaker for protection of distribution lines, the action should be chosen with a long delay overcurrent trip circuit breaker, when the end of the line single-phase ground short circuit, short-circuit current is not less than the circuit breaker instantaneous overcurrent or short delay tripping setting current of 1.5 times.