Load break switches

Do you want to disconnect circuits safely under load? Then you need a switch disconnector. But what do you have to pay attention to when buying a load-break switch? Switch disconnectors are available in many different versions. We give you an overview of the different models and help you to make the right purchase decision.

What are switch disconnectors?

Under normal conditions, load switches can switch and carry specified currents. Disconnectors, on the other hand, have a higher dielectric strength and lower leakage currents in the isolating distance. The switches must under no circumstances switch themselves back on automatically as a result of environmental influences and must have a clear indication of the off position. In a load-break switch, the functions of a load switch are combined with those of a disconnector. So it is a combination of both. The device protects, switches and separates with a safe isolating distance. This means that a load-break switch can also be used to reliably disconnect or switch a circuit under load up to the respective rated current. In general, we distinguish between three types of switch disconnectors:

The classic switch disconnector

Classic switch disconnectors are designed for easy disconnection of a system and are used, for example, as a main switch, emergency stop switch or as a repair switch / maintenance switch. These devices are suitable for frequent switching. In the eibabo® shop you can get products for standard applications, for high-performance applications and for remote controls. In addition, we offer standard infrastructure devices for mounting on DIN rails. Please note that with all these devices, the supply line must always be fused separately.

Fuse switch-disconnector

The fuse switch disconnector combines disconnection with a fuse in one device. With this device, the fuse is cut out when switching. This means: When disconnecting under load, a visible arc occurs. Fuse switch-disconnectors are intended for infrequent switching and are used in industry as main switches or in main power distribution.

definition

In electrical engineering, the term 'isolation' refers to the all-round disconnection (of a part) of a system from all non-earthed lines.

Load-break switch with fuse

Switch-disconnectors with a fuse also combine the switching function with a fuse in one device. However, the fuse is activated when the device is switched off. This enables you to safely replace the fuse when it is disconnected. The devices are also designed for frequent switching and are therefore also suitable for high-power applications, as main switches and in the main power distribution.

What do I use a switch disconnector for?

Load-break switches protect people and machines and are used for:

Activation of resources
Switching short-circuit currents
power shifting
Protection against overcurrent
Protection against electric shock

These can be used as the main disconnect device in switchgear, interrupting the power supply to one or more electrical circuits. It is possible to switch or disconnect the circuits even under load up to the level of the respective rated current. With a load-break switch, you separate electrical devices, for example for maintenance work and repair purposes. The aim of the switch is to safely stop the flow of current in order to enable authorized specialist personnel to work safely. It does not matter whether it is a simple or a complex installation. Load-break switches offer ideal performance characteristics for industrial use as on/off switches, main switches, motor switches, control switches, repair switches, emergency stop switches and much more. The function as an isolating switch and load switch makes these devices very economical, especially in small systems, because the use of additional isolating switches is not necessary.

Source: eibabo®, Hager HAB406 switch disconnector Image: Hager HAB406 switch-disconnector

What is the difference between a classic switch disconnector and circuit breaker?

Switch disconnectors and circuit breakers perform different tasks. The switch-disconnector works with the simple objective. to disconnect the power supply. This allows electricians to carry out their maintenance work, repairs and inspections safely. A circuit breaker can take on more tasks than a load-break switch. A circuit breaker connects, carries and interrupts current under standard switching conditions. This is well suited to perform the duties of a disconnector or load switch. Like the load-break switch, it offers full disconnection if required. You can use the circuit breaker as a protective device because it can control the flow of current like a fuse. The device breaks the circuit under unfavorable conditions such as overload and short circuit. A load-break switch does not offer these advantages. Depending on the model, you can control a circuit breaker manually or automatically.

Conclusion: A load-break switch serves as a disconnecting device to completely stop the flow of power and is often associated with a circuit breaker or a load switch. The circuit breaker works as a switching device to interrupt the short-circuit current and the rated current. To ensure maximum security, both devices usually complement each other.

How do switch-disconnectors ensure safe disconnection of the current flow?

Shifting under load is a special process. Sparks and arcs can occur when two conductive contacts are separated. These allow the current to continue to flow, although the contacts are no longer touching. With small currents, a sufficiently large distance between the contacts prevents the sparks from 'jumping over'. These go out by themselves without making a new electrical connection. If this distance is too small compared to the applied voltage or if the contacts are insufficiently insulated, arcs can form.

Electric arc

An arc occurs when there is a high electrical charge difference between two poles. To compensate for this imbalance, a channel forms between the poles. Inside, gas (e.g. air) is ionized and a plasma is created. The current can flow through this plasma channel.

These arcs must be extinguished using special protective devices in the switch. Load-break switches and circuit breakers are therefore equipped with specific extinguishing agents in order to stop the energy flow of the arc in good time. Depending on the type of circuit breaker, these are air, oil, insulating gas or vacuum. Special chambers for deionization (arc quenching chambers) are typically used in switch-disconnectors in the low-voltage range. These artificially lengthen the arc until the voltage required to maintain it becomes too great. The arc breaks off and quenching plates prevent it from igniting again.

Which switch-disconnectors are recommended?

Depending on which requirements you want to meet, your eibabo® online shop offers you the right load switch, disconnector or circuit breaker. When it comes to switch disconnectors, you have the choice between all well-known manufacturers. These include ABB, Ceag, Doepke, Eaton, Elektra, Hager, Legrand Bticino, Siemens and many more.

To make your selection easier, the items in this catalog are already sorted by relevance. Enjoy high quality at low prices as well as many secure payment methods and fast worldwide shipping.