General Purpose Relays: Purpose, Types & Controls

The electrical processes that take place in most industrial applications are vast. There is a need to control and monitor these processes effectively to ensure that operations run smoothly and effectively. Various components are available to ensure such purposes are fulfilled with a high level of reliability and quality. One such type of component is relays. 

In simple terms, a relay is a device that enables circuit control by opening and closing a switch within the circuit. These relays are controlled via an input signal, a voltage, or a current applied across the relay contacts. In this way, it is possible to control the flow of current within the machinery or control panel. However, this is just a general description and does not give us much. This is why looking at the specific types of relays is much more beneficial. One such type is general purpose relays. This article will examine their purpose, types, and controls. Let’s dive in.

What are general purpose relays?

General-purpose relays are relays used in circuits where a low-power signal is used to control them. Similarly, they are also helpful for situations where a few circuits are limited by one signal. In essence, they can control large loads in the devices they are housed in via low-power signals supplied to their control circuits. Relay switches consist of a control circuit with an electromagnetic coil and a load circuit with a lever and contacts. When a current flows into the switch, the lever in the load circuit moves courtesy of the magnetic field created within the coil. This mechanism turns the device on or off. General purpose relays come in two configurations: Normally Closed (NC) and Normally Open (NO). These configurations refer to the state where the circuit will be in its de-energized case. So, when a low-power signal is passed to an NC relay, it will open, and when it is passed to an NO relay, it will open. 

General purpose relays are sometimes also referred to as ‘plug-in relays.’

What is the purpose of a general purpose relay?

General purpose relays are used in various industrial applications, and how they can be used will depend on their measures. These measures include contact type, voltage rating, curl voltage, current, etc. General purpose relays are often used as control signals in automated machinery, processes, and engine control for various industrial and production sites. Similarly, they are also essential for control systems like air conditioning and lighting, as well as power system networks. In essence, they are used for applications involving high voltages and power loads.

What are the types of general purpose relays?

General purpose relays come in various types, each with unique features that make them ideal for specific purposes. The main ones are the following:

Control Panel Relays

These types of general purpose relays come equipped with 1 to 4 poles. This makes them suitable for I/O applications and relay sequences. Some relays that fall in this category are control, IO, and latching relays.

Built-In Relays

These types of relays come built-in to devices which is where they get their name from. They are used to turn on load supplies inside and so come with a carry current that can go up to 40A. High-capacity relays are a type of built-in relay.

Work saving Relays

These types of relays are used in programmable controllers for I/O applications. Typically, these are used for downsizing and saving work, which is where they get their name from. Some types of work saving relays are terminal relays and relay terminals.

Special Operations Relays

Certain applications require specific operations and features. This is where special operations relays are used which have the unique qualities required for these applications. Some applications where these relays are used are pump-stepping operations and alternative operations. Ratchet relays are a type of special operation relay.

PCB Relays

These are specialized relays that are mounted on the top of PCBs.

What are the advantages of general purpose relays?

General purpose relays offer various benefits over their counterparts. The main advantage of these relays is that they are cost-effective and do not increase the cost of the device, like control panels and PCBs, to which they are added. They also provide extra savings by preventing electrical faults and system failures that can be extremely costly. 

Another great thing about general purpose relays is that they provide ease of use. They are compact, ensuring that the devices they are housed in can also be smaller and lightweight. General purpose relays come with DIN rail mounting and screw mounting options, and users can use whichever option suits their needs. This versatility also makes the wiring and installation process more straightforward. 

Furthermore, general purpose relays come with color codes that represent the specific purpose they are suitable for. This makes them quite helpful in troubleshooting control circuits due to quick and easy testing. General purpose relays also provide convenience by removing the need for high-capacity and complex wiring. As a result, this saves space within the device, ensuring it isn’t bulky and heavy. Since the wiring is more efficient, these relays also lead to savings in cost.

The Bottom line

Relays provide circuit control via low-power signals that can close or open the circuits of high-power load devices. There are various types of relays, one of them being general purpose relays. General purpose relays are used in different industrial processes and production sites, such as engine control, lighting, water treatment, and automated machinery. They can be classified into further types, each having unique features which make them suitable for different applications. General purpose relays provide the following advantages:

• Cost savings
• Flexibility. This is courtesy of the different mounting options and color codes they provide.

We hope this article has been informative and helps you understand general purpose relays. Thank you for reading!