What is the function of the busbar in a switchgear, and how to select an appropriate busbar?

The role of busbars in switchgear：

Busbars are conductors in switchgear that collect, distribute, and transmit electrical energy. They connect the power source (such as the output terminal of a transformer) to various branches (such as the incoming terminals of circuit breakers), acting as a transfer station for electrical energy. This enables electrical energy to be distributed to different electrical equipment or circuits as required.

Methods for selecting appropriate busbars：

Current - carrying capacity

Select busbars according to the rated current of the switchgear to ensure that the busbars will not be damaged by overheating when operating at the rated current. Generally, refer to the busbar current - carrying capacity table and make corrections considering factors such as ambient temperature and installation method. For example, in a high - temperature environment, the current - carrying capacity of the busbar will decrease, and a larger - sized busbar needs to be selected.

Material

Common busbar materials include copper and aluminum. Copper busbars have good electrical conductivity, high mechanical strength, and corrosion resistance, but they are relatively costly. Aluminum busbars are less expensive, but their electrical conductivity and mechanical strength are relatively weaker. For occasions with high reliability requirements and limited space, copper busbars are mostly selected. In some cost - sensitive situations where space allows, aluminum busbars can be chosen.

Shape and size

Busbars come in shapes such as rectangular and circular. Rectangular busbars have good heat dissipation, small skin effect, and are easy to install and connect. Circular busbars have high mechanical strength. Select appropriate shapes and sizes according to the current magnitude and installation space. In high - current situations, multiple rectangular busbars may need to be used in parallel.

There are bare busbars and insulated busbars. Bare busbars are less costly but need to be used when there is sufficient safety distance. Insulated busbars have high safety and can reduce the risk of inter - phase short - circuits. They are suitable for switchgear with compact space and high safety requirements.