Differences Between Relays and Contactors

Summary

In this informative video, Josh Bloom discusses the differences between relays and contactors, emphasizing their functions and applications. Both devices rely on an energized coil to close contacts and allow current flow, but they differ mainly in load capacity. Relays are suited for lower current applications (up to 20 amps) and typically found in single-phase systems, while contactors handle much higher currents (up to 12,500 amps) and are commonly used in three-phase applications. The video highlights key features, such as size differences, contact configurations, and safety measures, making it a valuable resource for understanding industrial hardware.

Takeaways

• 🔌 Relays and contactors operate similarly, using a coil to close contacts and allow current to pass through.
• ⚡ Relays are typically used for loads up to 20 amps, with a common use of 15 amps.
• 🔋 Relays are mostly found in single-phase applications and lower voltage situations, such as safety and automation systems.
• 📏 Relays are generally smaller than contactors, making them suitable for compact applications.
• 🚀 Contactors are designed for higher current loads, often used for large motors, fans, and lighting systems.
• 🌐 Most contactors are used in three-phase applications but can accommodate single-phase uses as well.
• 🔍 Many contactors come with auxiliary contacts to monitor their open or closed state.
• 🔥 Higher voltage contactors may include arc suppression features for increased safety.
• ⚠️ Contactors do not provide overload or short-circuit protection; these are sold separately.
• 📊 The maximum current capacity of relays is 20 amps, while contactors can handle up to 12,500 amps.

Q & A

What is the primary function of both relays and contactors?

Both relays and contactors function by using a coil that, when energized, closes contacts to allow current to pass through.

What is the maximum load current rating for relays?

Relays are typically used in applications with a load current rating of no more than 20 amps, with common usage at or below 15 amps.

In what applications are relays most commonly used?

Relays are most commonly used in single-phase applications, especially in lower voltage situations such as safety and automation systems.

What configurations are relays typically sold in?

Most relays are sold with both normally open and normally closed configurations, allowing control of multiple circuits with a single relay.

What types of loads are contactors designed to switch?

Contactors are designed for switching loads that draw much higher current, such as large motors, fans, and lighting systems.

What is the typical application for contactors?

Most contactors are used in three-phase applications, requiring three separate conductors.

What additional feature do most contactors have?

Most contactors come with a set of auxiliary contacts that allow monitoring of the contactor's state, whether open or closed.

Do contactors provide overload or short-circuit protection?

No, contactors do not offer overload or short-circuit protection; these devices are typically sold separately.

What is the maximum current rating that contactors can handle?

Contactors can handle loads up to 12,500 amps.

What safety feature can some contactors provide in higher voltage situations?

Some contactors can offer arc suppression in higher voltage situations, increasing safety levels.