Compact Certified Industrial Relays: Why Interface Relays Remain Indispensable in the Control Cabinet

Industrial Relays, Plug-in Relays, Interface Relays -

Why They Are Indispensable in Modern Control Cabinets ...

Digitalization and automation are continuously advancing in industrial plants and buildings. Modern PLC controls are taking on more and more tasks, while high demands are placed on availability, ease of maintenance, and electrical safety.

Despite powerful PLC outputs, compact industrial relays and interface relays remain an important component in the control cabinet:

• They provide galvanic isolation.
• They enable potential-free contacts.
• They offer a simple way to expand existing controls.

Especially the relay solutions from the manufacturer SALZ have established themselves in industrial and building automation as a reliable interface between the control and field level. You can find the corresponding products in our Energie-Shop.

Relay or PLC Output – When Is an Interface Relay the Better Choice?

Many modern PLC systems have integrated digital outputs. Therefore, the question often arises whether additional relays are still necessary at all.

In practice, however, PLC outputs often reach their limits. They are primarily designed for signal control and not for directly switching larger loads. If solenoid valves, contactors, signal generators or other consumers need to be controlled, the use of an interface relay is recommended.

The relay takes over the actual switching task and simultaneously protects the sensitive electronics of the control system from loads and disturbances. In addition, different voltage levels can be easily connected with each other. Interface relays serve as an interface between the PLC output and the load circuit. The galvanic isolation between the control and load circuit significantly increases operational safety.

Galvanic Isolation in the Control Cabinet – Protection for Control System and Plant

One of the most important tasks of industrial relays is galvanic isolation.

There is no direct electrical connection between the control circuit and the load circuit. Signals are transmitted while disturbing equalization currents, potential differences, or fault currents are kept away from the PLC.

Especially in industrial plants with long cable runs or different supply systems, this improves immunity to interference and sustainably protects the control electronics.

For control cabinet manufacturers, this means more operational safety and a lower probability of failure for the entire plant.

Potential-Free Contacts – Maximum Flexibility for Automation

Another advantage of interface relays are the potential-free contacts.

These contacts operate independently of the control voltage and allow switching of various loads. For example, a 24-volt PLC can easily control a 230-volt control circuit without both systems having to be electrically connected.

Potential-free contacts are therefore among the most frequently requested functions in building automation, mechanical engineering, and modernization projects of existing plants.

 

Easily Extend Existing PLC Controls

In many projects, additional consumers need to be integrated, even though no free PLC outputs are available or the existing outputs are not sufficiently resilient.

Here, interface relays offer an economical solution. By decoupling the control and load circuit, existing control systems can be easily expanded without having to modify the PLC hardware.

Especially in retrofit projects and modernizations of existing plants, relays enable a quick and cost-effective retrofitting of additional functions.

Interchangeability and Maintenance – a Great Advantage of Plug-in Relays

For maintenance personnel, rapid troubleshooting is paramount.

Plug-in relays offer a decisive advantage here. In case of a fault, the relay can be pulled out of the socket and replaced within a few seconds. Costly wiring work is completely eliminated.

This significantly reduces downtimes and simplifies spare parts management. At the same time, maintenance work can be carried out without changing the entire wiring in the control cabinet.

Especially in production plants with high availability requirements, this is an important economic factor.

 

SALZ Interface Relays as a Practical Solution for Control Cabinet Builders and Building Automators

The relay solutions from the manufacturer SALZ were specially developed for industrial applications. Their compact design enables space-saving installation on the DIN rail and is ideal for modern control cabinets with high packing density.

Typical areas of application include:

• Machine and plant construction
• Building automation
• HVAC systems
• Energy and environmental technology
• Conveyor technology
• Process automation
• Control cabinet manufacturing

In our Energie-Shop, you will find suitable relay solutions for your application area. In addition, we offer the entire product range from the manufacturer SALZ.

Through the combination of galvanic isolation, potential-free contacts, easy interchangeability, and compact design, SALZ industrial relays represent a reliable and economical solution for numerous automation tasks.