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What are the differences among Disconnector, Circuit Breaker and Load Switch?

Publish Time: 2022-06-02 09:04:07     Author: DELIXI


Disconnector refers to the device that can isolate the circuit. The isolation here includes two aspects. One is that the isolator has the ability to isolate the voltage.  To do this, the fracture must have enough distance to withstand the impact voltage specified by the product;  The second isolator must have a definite breakpoint, which in this case refers to the contact, not the handle.

A disconnector is a switch that functions as an isolator.  In order to make its contacts visible, the contacts of disconnecting switches are generally not covered with arc extinguisher, or simply covered with arc extinguisher.  Therefore, the disconnecting switch does not allow load pulling.

Because the disconnecting switch does not have the breaking ability, when short-circuit occurs, it can only passively bear the impact of short-circuit current, so it must have the following short-circuit parameters:  

Rated short-time withstand current ICW, also known as thermal stability of the disconnector.  It is the maximum short-circuit current the disconnecting switch can withstand in 1 second.  

Rated short circuit on capability ICM, also known as the dynamic stability of the disconnecting switch.  It is the maximum short-circuit current peak that the disconnecting switch can withstand.  


The so-called load switch is to install the fuse on the tool arm of the moving contact of the isolation switch, and the combination of the isolation switch and fuse constructed from this is called the load switch.  

Because the fuse is installed, the load switch has short circuit breaking capability.  Because the short-circuit breaking capacity here is provided by the fuse, it is also called the cut-off current.  

We assume that the load switch controls a motor. Now, due to some reason, one phase of the motor shorts, the corresponding fuse is blown off, and the current of the other two phases surges.  If the load switch is automatically disengaged, the contacts of the load switch (not the fuses, mind you) will experience a large current that may burn the contacts of the load switch. This current is called transfer current.  Therefore, low-voltage load switches are not allowed to automatically break.  


A circuit breaker is also a switch, but it can break the overcurrent, that is, the overload current and the short-circuit current.  Therefore, the circuit breaker must have several parameters of the switch, must also have the parameters of the open short-circuit current.  The circuit breaker has the same parameters as the switch including:  

Rated voltage and rated current  

Short time current tolerance and short circuit switching ability  

These two values are called the thermal stability of the switch and the dynamic stability of the switch.  

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