Can both PC Class and CB Class double power supply change-over switches be equipped with circuit breakers or disconnectors?

The dual power supply change-over switch is also called TSE. If it is automatic, it is called ATSE by adding A (English AUTO, meaning automatic) in front of it.

The national standard related to dual power switch is: GBT14048.11-2008.

Let's take a look at how PC class and CB class are defined in the standard:

Transfer switching devices are classified according to the following methods:

a) Short Circuit Capacity

* PC Class: TSE that can be connected and carried, but not used for sectional short circuit current (note that if the test requirements of PC class can be met, the contactor can be used for PC class)

* CB Class: TSE equipped with over-current release, whose main contact can be connected and used for sectional short-circuit current.

* CC Class: capable of making and carrying, but not used to break the TSE of short-circuit current. The TSE is mainly composed of electrical appliances meeting the requirements of GB 14048.4.

b) Control The Way Of Conversion

* Manual transfer switching equipment (MTSE)

* Remotely operated transfer switching equipment (RTSE)

* Automatic Transfer Switching Equipment (ATSE)

It can be seen that PC Class TSE does not have the ability to break short circuit current, and its front end must be equipped with over-current protector, that is, fuse or circuit breaker. CB Class TSE has the ability to break short circuit current. In fact, CB Class TSE is built with circuit breakers.

The short-time withstand current of ATSE is classified by fuse protection and circuit breaker protection.

See More : CSQ Automatic Transfer Switches

Let's take another look at this topic: "Can both PC Class and CB Class double power supply change-over switches be equipped with circuit breakers or disconnectors?" We can see from it that the questioner is not very clear about the differences and uses of disconnectors, circuit breakers and ATSE.

Let's see what GB14048.4-2008 says:

2.1 (Mechanical) Switch

Under normal circuit conditions (including specified overload working conditions), it is a mechanical switching device that can make, carry and break current, and carry current within a specified time under specified abnormal circuit conditions (such as short circuit).

Note 1: The switch can be connected but cannot break the short-circuit current.

Note 2: (IEV441-14-10).

2.2 Disconnector

Mechanical switching appliances that can meet the specified isolation function requirements in the disconnected state.

Note 1: This definition is different from IEV441-14-05, because the height separation function is not only limited to the requirement of getting rich after separating the south.

Note 2: If the breaking or connecting current is negligible, or the voltage at both ends of the terminal at each pole of the isolator has no obvious change, the isolator can be disconnected and closed.

The circuit and isolator can carry the current under normal circuit conditions, and also can withstand the current under abnormal circuit conditions (short circuit current) within a certain time.

2.3 Switch-Disconnector

A switch that can meet the isolation requirements of the isolator in the off state.

From the above definition, we can see that the switch can turn on and carry the rated current, and can carry the short-circuit current within a certain time; The isolator is a switch with isolation function. The so-called isolation function here refers to a clear visual breakpoint in the open state; The disconnector is a switch with isolator function, which can connect and carry the rated current, and carry the short-circuit current within a certain time. It can be seen that the disconnector does not have the ability to break short circuit current, and it must be used together with over-current protection devices such as fuses and circuit breakers. ATSE, strictly speaking, is a disconnector with two-way mutual switching. Therefore, it must be used together with the over-current protection device. In addition, if the circuit breaker is a draw out type, when it is used in the low-voltage main incoming circuit, because it has a clear breakpoint after being drawn out, there is no need to provide a disconnecting switch in front of the draw out circuit breaker; If the circuit breaker is fixed, it must be equipped with an isolating switch in front of it.