Before choosing the type of plastic case circuit breaker, we should determine how much rated current we need, how to install it, what kind of tripping unit we need, whether we need leakage function, what level and breaking ability.

Here are some common knowledge to be determined and understood before purchasing plastic case circuit breakers.

1. Determine the rated voltage and current of the circuit breaker:

The rated voltage and current of the circuit breaker meet the requirements of the circuit. The rated breaking current is larger than the short circuit current of the circuit, and the thermal stable current is larger than the thermal stable current of the circuit.

2. Determine the rated current of the shell grade of the plastic case circuit breaker:

In the same series, there are many kinds of rated current of shelf grade, and in the same shelf grade, there are many kinds of rated current.

3. Molded case circuit breaker has different volume, shape and breaking capacity.

The volume, shape and breaking capacity of circuit breakers are different, so when choosing the circuit breaker, it is necessary to fill in the model completely, that is, the rated current of the circuit breaker within the rated current of the specific shelf grade.

4. Determining the current setting value of circuit breaker tripper means that the tripper is adjusted to the action current value:

Nowadays, the rated current of some electronic trippers with long overload and delay is adjustable. The regulated current is actually the rated current and the maximum current that can be passed for a long time.

5. Determine the rated working current of plastic case circuit breaker.

6. To determine the rated insulation voltage, the electrical clearance and creepage distance shall be determined by reference to this value:

Some circuit breakers do not specify rated insulation voltage. The maximum rated working voltage should be regarded as rated insulation voltage. In any case, the maximum rated working voltage should not exceed rated insulation voltage.

7. Determine the rated control power supply voltage, i.e. the voltage when the plastic case circuit breaker is equipped with the shunt tripper and the accessories of the motor mechanism:

There are two kinds of rated control power supply voltage: AC and DC. AC or DC should be specified when selecting.

Main Technical Parameters Table of Molded Case Circuit Breaker

8. Appendices for determining the configuration of the selected circuit breaker:

Commonly used circuit breaker accessories are: auxiliary contacts, alarm contacts, shunt trippers, under-voltage trippers, electric operating mechanisms, external rotating operating handles, etc.

Plastic case circuit breaker accessories - auxiliary contacts

9. Matters needing attention in the selection of moulded case circuit breakers:

(1) The purpose of determining the breaking capacity of circuit breakers:

A. Ics can only be interrupted by additional short circuit operation.

B. Extra limit short-circuit breaking is required for Icu.

(2) The selection of plastic case circuit breaker should ensure that it can be used with other components.

10. According to the type of load, it can be divided into distribution system and motor maintenance.

11. According to the capacity of the load, the extra current of the plastic case circuit breaker is larger than the operating current of the load.

12. Selection according to short-circuit current: only when the plastic case circuit breaker operates with short-circuit breaking can it exceed the expected short-circuit current value of the line.

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