How well do you understand the intermediate relay? We wrote this article to shed more light. Learn how it works, its versions, and when or where to use it. We will also guide you on selecting one using your application requirements.
What is an Intermediate Relay?
The intermediate relay is a low-power device for activating higher-power circuits. It usually sends a control signal to a contactor, which, in turn, operates the load. In some cases, it directly connects to output.
We can also call it an interposing relay. That’s because it buffers control and load circuits. This action facilitates safe switching. Additionally, you can use it to multiply control outputs and loads.
The relay is helpful in many applications. For instance, you need it to turn a high-amp motor on/off using electronic controls. Another example is when operating a lighting circuit from an electronic control panel.
Resource: https://www.youtube.com/watch?v=BSfoIkxqiec
Types of Intermediate Relays
The relay is available in two main types: electromechanical and solid state. One has moving switching components, while the other doesn’t. Here’s what to know about each, including their working and benefits.
Electromagnetic Relays
The electromagnetic relay has moving parts. It primarily comprises a coil around a magnetic core, a movable armature, and contacts. When energized, the core and coil generate a magnetic flux, pulling the armature and closing a circuit.
Being mechanical, it has a simple construction, making it less costly. It also has a higher contact capacity and can control higher voltages. However, it has a low switching speed that may not suit high-frequency circuits.
Solid State Relays
The solid-state relay is semiconductor-based. It relies on electronic components and circuits to work. It generates control pulses when needed, closing circuits and operating more than one switch.
Although more costly, the static type achieves higher switching speeds. Additionally, it experiences less wear over its lifetime. On the downside, it can only handle lower amps and volt levels, limiting its use.
Intermediate Relay Working Principle
The relay uses a small voltage to move a massive electrical load. Here’s what happens when using the mechanical/magnetic type with a power-switching contactor.
- The logic circuit generates a control signal
- This signal goes to the coil windings, generating a magnetic field and force
- The magnetic core amplifies the field, making it strong enough to pull the spring-loaded armature
- This action closes contact to activate a DC or AC contactor
- The contactor uses a similar mechanism to complete the high-power circuit
- The electrical device either starts or stops depending on the control signal type and contactor state
- The armature returns to the original position when the coil is de-energized
- Again, the load and control circuits  experience an opposite reaction
The above operation requires components to move. Electronic relays work differently, switching power using semiconductor devices like transistors. However, the result is similar for both devices.
Resource: https://www.youtube.com/watch?v=mLS_HJ8fORg
What is an Intermediate Relay Used For?
We use it to turn high-power circuits on/off. These are mismatching systems, such as high and low current circuits or AC and DC power. The following are its applications in various systems and settings.
Electrical Control Panel
It increases the current capacity of a PLC controller. The load in this setting is often a magnetic contactor for a high-current device like an industrial motor.
Take, for instance, a case where you need to control a 220V device or power supply. The controller can only take 12V. The relay will use this low voltage to close the 220V circuit, protecting the PLC.
Industrial Automation
It controls industrial loads, switching them on and off. The loads range from low-current to high-voltage motors and other equipment. Industrial applications usually involve using one control source to operate more than one load.
Electrical Protection Circuits
It provides galvanic isolation between a load and control output circuit. That prevents the higher load current and voltage level from causing damage. This function also helps protect input components against electrical noise or EMI.
Resource: https://www.youtube.com/watch?v=BSfoIkxqiec
Advantages of Intermediate Relay
Using this relay offers various benefits. Unlike other types, it has a few unique functions. The following are its key advantages when used in an electrical system.
Reliable Signal Control
It makes the logic signal more reliable by matching it with the load. That, in turn, ensures proper response, making electrical circuits under its control more effective.
Electrical Isolation
It makes control circuits safe by segregating them from load circuits. That way, it helps prevent surges from causing shocks and arcing. It also protects delicate logic control circuits from damage by high currents.
Control System Flexibility
The device can switch more than load using a single control output. In other words, it allows you to expand its functionality without modifying your electrical system. This adaptability is invaluable in automation control operations.
Intermediate vs. Power Relay
The intermediate relay is an electrical device for control and protection circuits. It isolates sensitive controllers, allowing tiny logic signals to switch large amounts of volts and amperes.
A power relay defines the high-current circuits it works with. In other words, it specifies the increased application power levels. Therefore, the immediate type is a power control device if it controls massive loads.
The loads can be lighting systems, industrial machines, or household appliances. In such instances, either relay plays the role of a switching device. It often requires coupling with a contactor to handle the higher switching needs.
Resource: https://www.youtube.com/watch?v=rRgcE_MYBWA
How to Choose an Intermediate Relay
Whether choosing the relay for a simple electric pump or a power system, knowing what to look for is essential. Use these factors to find a product that matches your needs.
Voltage and Current Rating
Your electrical device or system has a rated voltage and current. The relay must, therefore, fit in regarding its specified ratings. Ensure its input/output voltage and current levels are within limits. It will help you avoid incompatibility and possible damage.
Switching Speed
How fast do you want it to switch your load? The product comes with varying speeds for different applications. Carefully select yours based on the system’s needs. This requirement is even more critical in automation for proper system timing.
Application Conditions
Base your choice on the application condition. For example, using a solid state type around flammable materials is necessary. It prevents hazardous situations when operating remote circuits.
It must withstand heat, high humidity, and excessive vibrations. Consider the installation style mounting, such as if it’s a socket or DIN rail. In most cases, you will need a device you can install in the electrical panel or cabinet.
Conclusion
The intermediate relay is standard in many electrical applications. It replaces a switching contactor in some settings and works with one in others. The information in this guide should help you understand the device better. You’ll also find it helpful when selecting it for your electrical needs.
