What is Control Relays: Types, Functions and Applications

In today’s electronic devices, a control relay plays an essential part. It is a switch that is controlled by an electrical current. This switch opens or closes to allow current flow through the conducting coil. A control relay makes sure that the flow of current is maintained inside the conducting coil and the electronic device so that it does not travel back to the switch, causing any current surge.

Control relays are used in power supply systems, transistors, motors, power plants and other devices. With electronic devices becoming more intricate, there are various types of control relays to support these devices. If you want a control relay for your electronic device, purchase a thermal overload control relay from Lauritz Knudsen (Formerly L&T Switchgear), as they provide the best-in-class electrical parts for residential and commercial use. Control relays also have a variety of functions and applications, which are to be discussed in this blog.

What is a Control Relay?

Control relays have been an integral part of electrical devices for many years. However, with several advancements in electrical devices, the control relays have also undergone some changes. Nevertheless, a control relay is essentially an electromagnetic switch. Electrical relays or control relays are used to maintain the flow of electrical current through a conducting coil that opens or shuts the switch. A control relay also helps protect the circuit from power spikes. When a control relay has been integrated into the electrical system, there is no need to manually control the switch to change or isolate the state of the electrical current.

What Are The Different Types of Control Relays?

Following are the commonly used types of control relays.

Thermal Overload Relays

Thermal overload relays are crucial protective devices in electrical systems. These devices primarily prevent motors from overheating or potential damage from high currents. A thermal overload relay works on the principle of thermal sensing, which involves measuring the heat created by the motor during its performance. When the motor consumes an excessive amount of current for a prolonged time, notifying a possible overload, the relay trips and disconnects the motor’s power supply. Apart from protecting the motor and detecting potential danger to the electrical system, thermal overload relays also improve operational safety.

Solid State Relays

Solid state relays (SSRs) are made up of relay control systems that do not move. This relay requires a much lower control energy than the output power. It is under this circumstance that the power gained by this relay is much higher compared to other electromagnetic relays. Transformer-coupled SSR and photo-coupled SSR are the two types of solid-state relays that you can put in an electrical system.

Magnetic Latching Relays

Magnetic latching relays utilise permanent magnets or components with high current absorbency to keep the armature in the same position as the coil is electrified after removing the power source. These relays comprise a thin metal strip that rotates between two edges. The switch is either connected or magnetised to one end of the little magnet. The opposite side is hooked to a little wire known as a solenoid.

Lighting Control Relays

A lighting control relay is a protective device that is used to maintain the flow of current in all lighting systems for both commercial and residential uses. It comprises a switch that either opens or closes the current flows through the conducting coil. There can be an occurrence of excessive current passing through the lighting system which can cause potential electrical danger. With the help of lighting control relays, one can detect potential dangers and prevent them from happening while maintaining the performance of the lighting devices.

Reed Relays

Reed relays consist of two magnetic strips (reeds) sealed inside a glass tube. The reed functions as an armature and contact blade. The magnetic field provided to the coil is wrapped around this tube, forcing the reeds to move and, therefore, execute the switching function.

Rectifier Static Relays

These relays have become popular due to the advancements in semiconductor diodes. It includes two rectifier bridges and a movable coil, often known as a polarised movable iron relay. The most common kind is relay substitutes, which are reliant on rectifier bridges and can be organised as phase or amplitude comparators.

What is the Function of Control Relays? How Do They Work?

The core function of control relays is to open or close the switch when the electrical current flows through the conducting coil. The other functions of control relays include preventing electrical devices from a current overload as well as isolating the system from any potential danger involving high voltage. The main principle of the functioning of control relays is electromagnetic induction.

How to wire a control relay? Well, it is simple.

• Based on the principle of electromagnetic induction, the current runs through an electromagnet and forms a magnetic field.
• After that, DC (direct current) is applied to the load through the switch.
• The DC applied to the coil attracts contact. This is how the relay is energised or wired.
• When the current is removed, the control relay returns to its original state. This is called de-energising the relay.

What Are the Applications of Control Relays?

Control relays are used to regulate high-voltage circuits using low-voltage signals in different kinds of use cases. These relay switches are capable of detecting and isolating problems in the distribution system or power transmission. The applications of control relay are:

• Computer interfaces
• Industrial process controllers
• Automotive industry
• Lighting control systems
• Traffic control
• Motor drives control
• Protective mechanism for electrical power systems

Also Read: What Is A Thermal Overload Relay?Types And Use Cases

Conclusion

To help prevent power surges in high-voltage electrical systems like transistors, power supply systems and motors, control relays play an essential part. Control relays shut the entire system down without manually putting the switch on or off when they detect any power hindrance that may cause potential danger. Various control relays are found in the market with advancements in electrical systems, depending on their working principle and applications.

Lauritz Knudsen (Formerly L&T Switchgear) Smartshop comprises various low and medium-voltage switchgear and preventive devices. The wide collection of thermal overload control relays that Lauritz Knudsen (Formerly L&T Switchgear) Smartshop offers immense support to the thermal, and electrical systems with a wide range of products. Not to mention, these control relays come with auto and manual reset modes, which makes it convenient to integrate with the existing electrical systems.