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Circuit BreakerDistribution Of Electricity
Aug 21, 2017

A circuit breaker is a switchgear capable of engaging, carrying and breaking current under normal circuit conditions and capable of engaging and driving current under abnormal circuit conditions (including short circuit conditions) for a specified period of time. Circuit breakers can be used to distribute power, not frequently start the asynchronous motor, the power lines and motors and other protection, when they have a serious overload or short circuit and undervoltage failure can automatically cut off the circuit, its function is equivalent to the fuse switch And a combination of overheat relays and the like. And generally do not need to change the parts after breaking the fault current. At present, has been widely used. Circuit breakers generally by the contact system, arc system, operating mechanism, release, shell and so on. The circuit breaker is divided into miniature circuit breakers, molded case circuit breakers and frame type circuit breakers according to their structure.

The role of the circuit breaker

Cut off and connected to the load circuit, and cut off the fault circuit to prevent the accident to ensure safe operation. And high-voltage circuit breakers to break 1500V, current 1500-2000A of the arc, these arc can be stretched to 2m still continue to burn does not go out. So the arc is a high voltage circuit breaker must solve the problem.

Low-voltage circuit breakers, also known as automatic air switches, can be used to turn on and off the load circuit, can also be used to control the motor is not frequent start. It is equivalent to the knife switch, over current relay, loss of pressure relays, thermal relays and leakage protection devices and other electrical parts of the sum of all the functions of low-voltage distribution network is an important protection of electrical appliances.

Low-voltage circuit breakers with a variety of protection functions (overload, short circuit, undervoltage protection, etc.), adjustable action value, breaking capacity, easy operation, security, etc., so it is widely used. Structure and working principle Low-voltage circuit breaker by the operating mechanism, contacts, protection devices (a variety of release), arc system and other components.

How the circuit breaker works

When the short circuit, the high current (usually 10 to 12 times) to produce the magnetic field to overcome the reaction of the spring, the release device pull the operating mechanism, the switch instantaneous trip.

When the overload, the current becomes larger, heat increased, bimetallic deformation to a certain extent to promote the action of the body (the greater the current, the shorter the action time).

The main contact of the low voltage circuit breaker is by manual operation or by electric closing. When the main contact is closed, the free trip mechanism locks the main contact in the closing position. The coil of the overcurrent release and the thermal element of the thermal release are connected in series with the main circuit, and the coil of the undervoltage release and the power supply are connected in parallel. When the circuit occurs short circuit or serious overload, the over-current release of the armature pull, so that the free trip mechanism, the main contact disconnect the main circuit. When the circuit is overloaded, the thermal element of the thermal release heats the bimetallic sheet to bend and push the free trip mechanism. When the circuit is undervoltage, the armature of the undervoltage release is released. Also let the free trip mechanism move. Shunt release is used as a remote control, in normal operation, the coil is power, in the need for distance control, press the start button, the coil power, armature drive free trip mechanism, so that the main touch Point off. Now there are electronic type, the use of the transformer to collect the current size of each phase, compared with the set value, when the current is abnormal when the microprocessor sends a signal, so that the electronic release device to drive the action.

Circuit breaker parameters

Rated operating voltage (Ue): This is the voltage at which the circuit breaker is operating in normal (uninterrupted) conditions.

Rated current (In): The maximum current value of the circuit breaker with a special overcurrent trip relay at the ambient temperature specified by the manufacturer does not exceed the temperature limit specified by the current receiving part.

Short-circuit relay trip current setting (Im): Short-circuit trip relay (instantaneous or short delay) for high fault current value when the circuit breaker to quickly trip, the trip limit Im.

Rated short-circuit breaking capacity (Icu or Icn): The rated short-circuit breaking current of the circuit breaker is the highest (expected) current value that the circuit breaker can break without damage. The current value provided in the standard is the rms value of the AC component of the fault current. When calculating the standard value, the DC transient component (always occurring in the worst case short circuit) is assumed to be zero. Industrial circuit breaker ratings (Icu) and household circuit breaker ratings (Icn) are usually given in the form of kA rms values.

Short-circuit breaking capacity (Ics): rated breaking capacity of the circuit breaker is divided into rated short-circuit breaking capacity and rated running short-circuit breaking capacity of two.