Working principle and condition of molded case circuit breaker

Datetime: 7/5/2019 1:44:00 PM   Visit: 935

The working principle of molded case circuit breaker

The main contacts of the low voltage circuit breaker are manually operated or electrically closed. After the main contact is closed, the free trip mechanism locks the main contact in the closed position. The coil of the overcurrent release and the thermal element of the thermal trip are connected in series with the main circuit, and the coil of the undervoltage release is connected in parallel with the power supply.

When the circuit is short-circuited or severely overloaded, the armature of the overcurrent release pulls in, causing the free trip mechanism to act and the main contact to open the main circuit.

When the circuit is overloaded, the heat element of the thermal tripper generates heat to bend the bimetal, pushes the free trip mechanism, and the main contact opens the main circuit.

When the circuit is under voltage, the armature of the undervoltage release is released, and the free trip mechanism is also actuated, and the main contact is disconnected from the main circuit.

When the shunt trip button is pressed, the shunt release armature pulls in, causing the free trip mechanism to act, and the main contact opens the main circuit.

Working conditions of molded case circuit breaker

Ambient air temperature:

  • Ambient air temperature upper limit +40 ° C;
  • The lower limit of ambient air temperature is -5 ° C;
  • The average value of ambient air temperature 24h does not exceed +35 °C.

Altitude:

  • The altitude of the installation site does not exceed 2000m.

Atmospheric conditions:

  • The relative humidity of the atmosphere does not exceed 50% when the ambient air temperature is +40 °C; it can have a higher relative humidity at the lower temperature; the monthly average maximum relative humidity of the wettest month is 90%, and the monthly average of the month is the lowest. The temperature is +25 ° C and takes into account the condensation that occurs on the surface of the product due to temperature changes.

Working principle and condition of molded case circuit breaker

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