Differences between Chinese made low-voltage fixed partition cabinets and UL891 switchgear

Both domestic low-voltage switchgear MLS and foreign brands MNS, B cabinets, etc. have fixed partition cabinet types, that is, circuit breakers are fixedly installed.

UL891 is also a North American low-voltage switchgear mainly used for fixed installation of frame and molded case circuit breakers.

Some domestic manufacturers believe that fixed partition cabinets in China can be equivalent to UL891 low-voltage switchgear, but this is not the case.

The similarities are that both are fixed circuit breaker low-voltage switchgear, and both the plastic shell and frame are generally installed in a fixed manner.

All are safe, economical, reasonable, and reliable switchgear.

differences

Different types of molded case circuit breakers

UL891 adopts a fixed installation of the molded case circuit breaker body, with copper bars and outgoing cables connected at both ends.

Domestic fixed partition cabinets generally use plug-in molded case circuit breakers, which are installed on plug-in bases and connected to copper bars behind the board.

UL891 generally uses fixed frame circuit breakers, while domestically produced fixed partition cabinets generally use withdrawable frame circuit breakers.

Different installation methods

UL891 low-voltage cabinet plastic shell circuit breakers are installed in groups, connected to vertical busbars through branch busbars. The plastic shell circuit breakers are installed horizontally, and the outgoing lines are connected to cables through the LUG head provided by the circuit breaker. Generally, CT and multifunctional meters are not installed.

UL891 molded case circuit breaker modular installation, no separate compartment, high installation density. One switchgear can install 32 100A molded case circuit breakers.

Domestic fixed partition cabinets are installed separately, with separate compartments and compartment doors. The installation modulus varies among different models, and the installation quantity is not large.

Different operating methods

The operating handle of UL891 molded case circuit breaker is directly exposed to the outside of the cover plate, and can be manually moved left and right to achieve opening and closing.

The domestically produced fixed partition cabinet adopts a rotating operating handle installed on the compartment door for opening and closing circuit breakers.

Different outgoing connections

UL891 cable is directly connected to the outlet cable connector at the bottom of the circuit breaker. The circuit breaker is installed horizontally, that is, the cable is directly connected to the front side of the cabinet. The output lines of two horizontally installed plastic case circuit breakers are located on both sides in front of the cabinet.

Domestic fixed partition cabinets are connected to the cabinet using copper bars, and cables are connected to the ends of the copper bars.

The front department cover is different

UL891 adopts a front cover plate bolt fastening design, namely DEAD FRONT. The cover plate requires special tools to open, so ordinary people cannot access the charged body.

However, domestic fixed partition cabinets use separate compartments and door panels. Opening the door panel to enter the circuit breaker compartment, for plug-in molded case circuit breakers, they generally do not touch the live parts, and instead of plug-in type, the side may cause the live parts to be exposed.

Based on the above differences, the structural form of the switchgear is also different and cannot be directly modified with domestically produced fixed partition cabinets. For the position of the busbar, UL891 is generally installed behind the cabinet, and the busbar is located in the upper, middle, and lower positions behind the cabinet, which can be flexibly arranged according to the system scheme.

The busbar of domestic fixed partition cabinets is generally located at the top of the cabinet. For the requirement of cable entry at the top, the busbar at the top of the cabinet prevents the cable from entering, and it is necessary to increase the cabinet depth or deepen the top to connect the cable.

For scenarios such as data centers that require multiple sets of busbars, cabinet top busbars cannot meet the requirements.

UL891 low-voltage switchgear box structure, horizontal busbars and vertical busbars do not require separate compartments or partitions.