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In modern electrical and electronic systems, electromagnetic relays play a crucial role in controlling circuits and switching electrical loads. Whether in industrial automation, automotive systems, or PCB designs, different types of electromagnetic relay are selected based on functionality, space constraints, switching capacity, and durability.
Understanding these relay types is essential for engineers, technicians, and designers who seek reliable and efficient control solutions. In this blog, we will explore six of the most common electromagnetic relay types you should know.
What Are The 6 Common Types of Electromagnetic Relay?
| Relay Type | Key Features |
|---|---|
| General Purpose Power Relay | – Handles up to 600V / 100A – Strong and cost-effective – Used in HVAC and control panels |
| Automotive Relay | – Compact and durable – 12V or 24V coils – Withstands harsh environments |
| PCB Relay | – Mounted on circuit boards – Small size, good isolation – Used in electronics and automation |
| Time Delay Relay | – Delays switching (on/off-delay) – Enhances sequencing – Prevents inrush currents |
| Latching Relay | – Remembers last state – Low power usage – Suitable for lighting and automation |
| Reed Relay | – Fast switching – Sealed contacts resist contamination – Ideal for signal applications |
General Purpose Power Relays
General Purpose Power Relays are the workhorses of the relay world. These electromechanical relays are designed to switch medium to high currents, typically up to 600V and 100A, making them suitable for HVAC systems, industrial machinery, and control panels. They are available in single or multiple pole configurations and are often used in conjunction with contactors in larger systems.
Key advantages include:
- High current-carrying capability
- Robust mechanical structure
- Cost-effective for switching power loads
These relays are often controlled using pulse width modulation (PWM) schemes to improve efficiency and reduce heat buildup in the coil.
Automotive Relays
Automotive relays are specifically designed for vehicle electrical systems. They operate in harsh environments and are used for switching headlights, fuel pumps, horns, and other automotive functions. Automotive relays often conform to ISO mini/micro formats for plug-in compatibility and are built to withstand vibration, temperature extremes, and moisture.
Key features:
- Compact and rugged
- Typically 12V or 24V coil voltage
- High mechanical endurance for millions of cycles
These electronic relays can also support intelligent control systems in electric vehicles (EVs) and ADAS components.
PCB Relays
PCB (Printed Circuit Board) relays are compact electromechanical relays mounted directly onto circuit boards. They are ideal for consumer electronics, appliances, and industrial automation systems. These relays offer precise control in small spaces, often switching both AC and DC currents with high reliability.
Why they’re useful:
- Small footprint, ideal for tight layouts
- Available in power and signal versions
- Excellent electrical isolation
Applications include power supplies, alarm systems, and programmable logic controllers (PLCs).
Time Delay Relays
Time Delay Relays (TDRs) are used when an operation must be delayed for a preset time before switching. These electromagnetic relay types are widely applied in industrial automation, motor control, and sequencing operations.
There are two main categories:
- On-delay: the relay turns on after a delay
- Off-delay: the relay turns off after a delay
Benefits:
- Adjustable timing functions
- Improved system sequencing and logic control
- Can be used to prevent inrush current or stagger motor startups
Latching Relays
Unlike traditional relays that return to a default position when power is removed, latching relays (also called bistable relays) retain their position until a counter-pulse is applied. These electromagnetic relays are ideal for applications that require memory of the last state without continuous power supply, such as lighting controls, building automation, and energy-saving systems.
Advantages:
- Minimal power consumption after switching
- Heat reduction due to no continuous coil energizing
- Stable performance even during power outages
Latching relays are available in both mechanical and magnetic designs.
Reed Relays
Reed relays use a pair of magnetically-actuated reed contacts sealed within a glass tube. When a coil surrounding the tube is energized, the contacts close. These relays are often used in signal switching and low-current applications such as telecommunication devices, testing instruments, and RF circuits.
Main benefits:
- Fast switching speed
- Hermetically sealed contacts resist contamination
- Long electrical life
While they handle smaller loads than other types, their precision and reliability make them indispensable in electronic relay applications.
Conclusion
Understanding the different electromagnetic relay types is vital for designing safe, efficient, and scalable electrical systems. From general purpose relays used in industrial equipment to reed relays suited for delicate signal switching, each type serves a specific need.
