Introduction to the working principle of LS electric molded case circuit breaker

Molded case circuit breakers are also known as equipment circuit breakers, all parts are sealed in plastic housings, auxiliary contacts, undervoltage trippers and shunt trippers are modular. Because of the very compact structure, the molded case circuit breaker is basically impossible to maintain. It is mostly operated manually, and electric opening and closing can be selected for large capacity. Because of the application of electronic overcurrent trippers, molded case circuit breakers can also be divided into class A and class B, class B has good three-stage maintenance characteristics, but because of the price factor, the market share of class A products with thermomagnetic trippers is higher. Molded case circuit breaker is the contact, arc extinguisher, tripper and operation organization are installed in a plastic shell, generally not considered repair, suitable for branch maintenance switch, overcurrent tripper has two kinds of thermomagnetic and electronic, the general thermomagnetic molded case circuit breaker is a non-selective circuit breaker, only overload long delay and short circuit instantaneous two maintenance methods, electronic molded case circuit breaker has four maintenance functions of overload long delay, short circuit short delay, short circuit instantaneous and grounding fault. Some of the new products of electronic molded case circuit breakers also have a region-selective interlocking function. Most MCCBs are manually operated, and some are operated with motors.

Introduction to the working principle of LS electric molded case circuit breaker

Introduction to the working principle of LS electric molded case circuit breaker

Working conditions:

● Ambient Air Temperature:

○ Upper limit of ambient air temperature +40°C;

○ The lower limit of ambient air temperature is -5°C;

○ The mean value of the surrounding air temperature 24h does not exceed +35 degrees Celsius.

● Altitude: The altitude of the device address does not exceed 2000m.

● Atmospheric conditions:

The relative humidity of the atmosphere does not exceed 50% at the ambient air temperature of +40°C; High relative humidity at lower temperatures; The wet moon has a monthly average high relative humidity of 90% and a monthly average low temperature of +25°C, taking into account condensation on the product surface due to temperature changes.

● Pollution level: The pollution level is 3.

How it works:

The main contact of the low-voltage circuit breaker is either manually operated or electrically closed. When the main contact is closed, the free trip organization locks the main contact in the closing position. The coil of the overcurrent tripper and the thermal element of the thermal tripper are connected in series with the main circuit, and the coil of the undervoltage tripper and the power supply are connected in parallel.

When the circuit produces a short circuit or serious overload, the armature of the overcurrent tripper is engaged, so that the free tripping organization acts, and the main contact disconnects the main circuit.

When the circuit is overloaded, the heat of the thermal element of the thermal tripper causes the bimetal sheet to bend up, propelling the free trip tissue to act, and the main contact disconnects the main circuit.

When the circuit is undervoltage, the armature of the undervoltage tripper is released, which also makes the free tripping organization act, and the main contact disconnects the main circuit.

When the shunt tripping button is pressed, the armature of the shunt tripper is engaged, so that the free tripping organization acts, and the main contact disconnects the main circuit

Classify:

Low-voltage circuit breakers are classified according to different extinguishing mediums, and circuit breakers that use air as the arc extinguishing medium are called air circuit breakers (air switches); Circuit breakers that use inert gas as the arc extinguishing medium are called inert gas circuit breakers (inert gas switches); Circuit breakers that use oil as the arc extinguishing medium are called oil circuit breakers (oil switches).

Introduction to the working principle of LS electric molded case circuit breaker

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