Relay and Optocoupler Applications

Safe and flexible: Relays from WAGO are suitable for use in Zone 2 explosive atmospheres and thus cover a wide range of applications.

Hazardous Areas

Potentially explosive areas arise in various applications including the chemical industry, during the production of crude oil or natural gas or in the food industry facilities. These are divided into Zones 0, 1 and 2 according to the frequency and duration of occurrence of potentially explosive atmospheres. Relays from WAGO are suitable for use in Zone 2 explosive atmospheres.

Identifying devices that may be used in hazardous areas is mandatory.

In order to reduce costs but still be able to install the products in the Ex area, facility operators try to use devices with Zone 2 approval.

A type examination certificate or manufacturer’s declaration is required for use in potentially explosive areas. You can download these from the eShop and add them to your system documentation.

Zone 2

Area in which it is not anticipated during normal operation that a potentially explosive atmosphere will occur as a mixture of flammable materials in the form of gas, vapor or mist with air. If one does occur, then it occurs only momentarily.

Reliable switching despite coupling: To switch on, relay modules require nominal voltage U_N. For operation, however, a holding voltage that’s just 15 % of the nominal voltage is sufficient. In standard circuits, all relay modules operate reliably. In circuits with long parallel lines, or those having either active two-wire sensors or digital AC control outputs, however, a low holding voltage often leads to malfunction. The modules no longer switch off.

Brief power spikes, fatal consequences: When equipped with electronic control gears (ECGs) or LED drivers, modern lighting systems offer numerous advantages. They generate flicker-free light with high levels of efficiency. Both in planning new and replacing old lighting systems, the inrush current of the ECGs must be a central focus.

A capacitor in the input circuit of many ECGs and LED drivers causes a substantial current peak when switched they are on that can well exceed ten times the rated current. Even if the current lasts for just a few milliseconds, it can cause the relay contacts to fuse.

What should be considered when planning lighting systems?

In the relay selection process, the inrush current must be considered. Standard relays quickly reach their limits. For such applications, WAGO has developed relay modules with contacts that safely control brief high peak inrush currents. The contact material reliably prevents contacts from catching or fusing.

For maximum inrush currents, relay modules with two contacts working in parallel are available. The first contact, consisting of high-strength tungsten, catches the current peak. The second contact, made of highly conductive silver alloy, conducts the operational current.

As an alternative to relays, the WAGO product portfolio includes optocouplers and solid-state relays for use with capacitive loads. Special designs with zero voltage switches minimize the peaks.

Functional safety: To comply with relevant policies and regulations for functional safety, the use of special components is mandatory. These components must meet strict requirements. For relay modules, force-guided contacts with at least one break contact and make contact are required. They must be connected mechanically so that break contacts and make contacts cannot be closed or opened at the same time. This connection allows errors due to opening failures be clearly identified. Only errors due to opening and isolation failures are important in safety-related matters.

In a circuit, an open break contact can be detected by a closed break contact (error detection). The same applies to a closed make contact when the break contact is open.

Of course, EN 50205 requirements also apply to relays with changeover contacts in safety-related circuits. It stipulates that for each changeover contact, only the break contact or make contact can be used, and the changeover contacts must be force-guided. Therefore, only relays with at least two changeover contacts can be used in safety-related circuits.

The contact material is crucial: In some sectors of industry, like chemical plants and steelworks, as well as in sewage plants, aggressive gasses are common. Higher pollution levels, as well as high humidity and high temperatures, negatively impact electrical components. These are the domains of application for the various contact materials:

AgNi – silver-nickel contact

• Resistance loads

• Weak inductive loads

• For middle to high switching power

AgSnO2 – silver tin oxide contact

• For high switching loads, primarily in supply voltage applications with high inrush currents

• Very low tendency to fuse, good burn-off resistance

• Low material migration when switching from DC

Switching manually and electrically: Switching individual circuits specifically without actuating the controller is incredibly beneficial for a number of applications, e.g., at startup.

For complex building control systems, individual building systems can be checked and commissioned independently of the controller setup. The same applies to commissioning in industrial processes. When troubleshooting, or ensuring limited manual operation, service and maintenance personnel appreciate the option of manual operation.

WAGO offers two alternatives for the relay modules with manual operation. Version one is designed for front panel manual operation, i.e., the contacts are only closed manually. In manual operation, the modules are limited to approximately one hundred switching operations. In automatic mode, these modules complete the usual switching operations of the relay.

In the second version with manual operation, the relay coil is electrically connected. The operating status can be set via a Manual/Off/Auto switch on the front panel. The relay modules complete typical relay switching operations with no limitations.

Versatile: The principle underlying relay modules with a wide input voltage range makes them well-rounded – perfect for virtually any application. Like the WAGO standard relay modules, they comply with all relevant standards and regulations.

Storage and maintenance costs can also be significantly reduced because one single module covers nearly all standard voltage ranges.

All components used in railway applications must operate reliably at voltages between 70 % and 125 % of the nominal voltage. Brief spikes up to 1.4 times the nominal voltage must not be allowed to cause any damage.

Deviations from these rules only apply to components powered by stabilized voltage supplies. Fluctuations of ±10 % of the nominal voltage are permitted – values common for industrial applications.

Durable and wear-free: WAGO has developed a wide range of optocoupler and SSR modules for industrial applications. The optocouplers are directly integrated into the housing for all WAGO optocoupler modules. SSR modules are interchangeable solid-state relays that are PIN compatible with all standard relays.

There is an extensive portfolio with versions for both DC and AC voltages. They are designed for the nominal input voltage range of 5 V to 230 V and nominal output voltage range of 3 V to 280 V.

Socket with a Miniature Switching Relay or Solid-State Relay

Sockets with an Industrial Relay

Rail-Mount Terminal Blocks with Miniature Switching Relay or Optocoupler

Sockets with a Miniature Switching Relay