Switch Disconnector: Function, Applications, Advantages

A switch disconnector is an electrical component that is used to control and isolate electrical power. It serves as a switch that can be used to turn on or off the flow of electricity as well as a disconnector that can be used to separate different parts of an electrical system. These versatile devices have a wide range of applications and offer numerous benefits including increased safety and improved system efficiency. In this article, we will explore the function, applications and benefits of switch disconnectors in more detail.

What is a Switch Disconnector?

Switch-disconnector combines the functions of a switch with the establishment of a disconnector and is used for breaking load currents up to their rated normal current. It makes and breaks under load conditions and provides safety isolation for any low-voltage circuit, particularly for machine control circuits.

It is normally operated manually and cannot interrupt the current on its own. It is only suitable for all-pole switching on and off and has no protective function. However, it is a condition that a separate protective device should be connected upstream of the systems.

The switch disconnector ensures the safety of the people and the equipment. It supports the users in creating a safe working environment reducing the risk of electrical and mechanical accidents, especially during maintenance and repair work. It is suitable for diverse applications such as machinery, power distribution, switchboards, motor control centers or photovoltaic installations. It is capable of closing
onto an existing short-circuit within the limits of its rated capacity with no risk to the operator or the equipment.

The switch-disconnector can be used as an emergency-off device. Therefore, it must be easily visible, accessible and identifiable for easy identification. It uses special colors stipulated by the standards.

The switch disconnector must be chosen according to

The characteristics of the network on which it is installed.
The location and the application.
Coordination with the upstream protection devices. (in particular overload and short-circuit)

Switch disconnectors are suitable for isolation. By using the handle on the front, the load and power can be disconnected. The mechanical design of switch disconnectors ensures the position of the handle always reflects the position of the main contacts:

The isolation position corresponds to the O (OFF) position.
The operating handle cannot indicate the OFF position unless the contacts are actually open.
Padlocking in the OFF position is not possible unless the contacts are actually open.

Why Switch Disconnector is Used?

The switch disconnector is used for maintenance and switching purposes as:

Local isolation switch
Main switch
Control switch
Fireman switch

It is used in many smaller machines and systems as well as portable devices but also in larger rated current ranges. A switch disconnector is a device comprising movable contacts capable of being mechanically closed to form an electrical circuit to other equipment or of being mechanically opened to physically disconnect one part of the electrical network from an adjacent part and at the same time provide an isolating distance. This provides circuit segregation for operational purposes or with appropriate earthing equipment and application of safety procedures, providing facilities to allow work to be safely undertaken on disconnected and earthed primary electrical equipment.

How Does a Switch Disconnector Work?

A switch disconnector operates by opening the electrical circuit which prevents the flow of electrical current. The switch disconnector is typically composed of two metal contacts or blades that are separated when the switch is opened. When the switch is closed, the contacts come together, allowing electrical current to flow.

When the switch disconnector is opened, the contacts are separated and the circuit is disconnected. This can be done manually by manually turning a knob or lever, or it can be done automatically by a switch or relay. In some switch disconnectors, the contacts may be opened by a spring-loaded mechanism that opens the contacts as soon as the electrical load is removed from the switch.

Advantages of Switch Disconnectors

The followings are the advantages of switch disconnectors:

High safety and reliability.
Top performance.
Minimal maintenance.
Easy installation and commissioning.
Rotary, front and lateral, direct and extended handle options.
Durability to electromagnetic or mechanical vibrations.
A high degree of protection.
Cheap price.
High breaking and making capacity.
Suitable for diverse applications.
Can also be mounted in positions other than the vertical (standard) position.
Multiple accessories suiting application requirements enhance the flexibility of operation and safety level of installation.
Disconnectors are generally hand-operated but may have power operating mechanisms if remote operational facilities
are required.