Load switch

What are load switches and what are the switches used for? What switching properties do the different load switches have and how can you use them for your system? There are many different types of load switches on the market. And safety is the top priority when switching electrical devices. It is therefore important to choose a load switch that is suitable for your application. The following article should help you to make the right purchase decision.

What are switching devices?

Switching processes are omnipresent in electrical engineering. However, it is often not clear to laypersons which switch is the right one for the respective application. We give a brief overview of the various switching devices and take a closer look at the load switch.

TIP:

Working on electrical systems is dangerous for laypersons. Leave installations, repairs and maintenance to an experienced electrician.

Switching devices are electrical devices that are used to control, switch or regulate electrical currents and voltages. These include, for example, switches, relays, current transformers, rectifiers and transformers. Their task is currentless switching, switching operating currents and/or switching short-circuit currents. The devices are differentiated according to their rated data, the switching task and the switching frequency. Commonly used switches are, for example:

circuit breaker

Circuit breakers are used for currentless switching on and off. Their task is to switch off downstream equipment in order to be able to work on it safely.

load switch

Load switches switch currents up to their rated operational current. These switches are also used to switch on currents on an existing short-circuit up to the rated short-circuit inrush current.

switch disconnector

Load-break switches are a combination of load switch and disconnector. These are load switches with a safe isolating distance.

circuit breaker

In the event of faults within the scope of the rated values, circuit breakers can switch on and hold high overload currents and switch off without damage.

contactor

A contactor is similar to a relay and is designed as a switch for high power with a high switching frequency. This is a device with a limited short-circuit making capacity and short-circuit breaking capacity.

For safety:

Isolating equipment serves to ensure safety when working on electrical systems. There must be an all-round separation from non-earthed lines. The fact that there is no voltage is no guarantee for activation.

When selecting a switching device, please note not only its switching characteristics, but also the key figures with regard to:

rated voltage
Rated operational current
rated surge current
Rated short-circuit making current
Rated short-circuit breaking current
Rated breaking current
Rated Insulation Level
Type of arc quenching

Load switches, load-break switches and the circuit breakers that are also often used are among the classic basic items in the eibabo® online shop. Convince yourself of our fair prices and look forward to fast delivery.

What is a load switch?

A load switch is a switching device for low and medium voltage ranges. This safely switches operating currents and short-circuit currents on and off under normal operating conditions. In contrast to a circuit breaker, this is usually not provided with secondary protective devices. In other words: A load switch is a switch for switching loads without a safe isolating distance. A classic example of this is the normal switch to turn the light on and off.

What types of load switches are there?

In the eibabo® shop you can get a large number of different load switches. These include reversing switches, star-delta switches, emergency stop switches, changeover switches, Dahlander switches, step switches and undervoltage releases. Depending on the design, the load switches can be surface-mounted, used in switch consoles or mounted as a series installation device on the DIN rail.

What do I need a reversing switch for?

The reversing switch is also known as a cam switch and usually has a zero position as well as a position 1 and position 2. No contact is closed in the zero position. The contacts of positions 1 and 2 are switched in such a way that a three-phase motor runs either clockwise or counterclockwise. The direction is switched over via the zero position.

What is a star-delta switch?

In three-phase systems, star connection and delta connection are most commonly used. Three-phase current, or three-phase alternating current, is generated in three coils, each offset by 120°, in a homogeneous magnetic field. With the star connection, one coil connection from each of the three coils is connected to a common star point. This star point serves as a connection for the neutral conductor. The other connections of the three coils form the three outer conductors. In a delta connection, the two terminals of one coil are each connected to one terminal of the other two coils. There are three connection points for connecting the three outer conductors. There is no neutral wire. The star-delta switch combines these circuits or allows switching between the circuits. This is necessary, for example, when starting a three-phase motor. In the star connection, the motor only requires about a third of the starting current. When the engine has started, it switches to delta connection. The motor draws more current in the delta connection and therefore has a higher output.

You can also get combined reversing star-delta switches in the eibabo® shop.

Source: eibabo®, Eaton T0-4-8410/I1 star delta switch Picture: Eaton T0-4-8410/I1 star delta switch

What do I use a Dahlander switch for?

The Dahlander switch is used in so-called asynchronous machines (motors with switchable poles). The switch alternates between a delta connection and a double star connection. This changes the number of poles in a ratio of 1:2. This results in a change in engine speed of approximately 2:1. The classic application is, for example, lathes, which have a fast and a slow run.

What are step switches?

Electrical switches with several switching positions are called tap changers. Usually tap changers are constructed as rotary switches. The individual stages are used, for example, to change the voltage step by step or to switch the signal.

What do I use undervoltage releases for?

Undervoltage releases are electromagnetic or electronic components that trigger a switch-off process when the control voltage drops or fails. On the one hand, this protects sensitive devices, assemblies and drives from operation outside the required nominal voltage. On the other hand, it prevents, for example, rotating machines from starting to move uncontrollably when the voltage returns.