Contactor vs Circuit Breaker: Understanding the Differences

When it comes to electrical systems, several components play a crucial role in ensuring safety and reliability. Two such components are contactors and circuit breakers. Although both serve the purpose of controlling the flow of electrical current, they are different in their functionality and applications. In this article, we will delve into the differences between contactors and circuit breakers, their functions and when to use each of them.

Differences between contactor and circuit breaker

The differences between contactor and circuit breaker are:

1. Definitions and duties

“Contactor” is also a type of switching device that is used for controlling heavy loads like motors, lighting and heating equipment. “Circuit breaker” is a protection device that protects circuits against overloads and short circuits.

The contactor must control electrical loads but the circuit breaker must protect electrical loads. The contactor works under normal conditions but the circuit breaker works under abnormal conditions.

2. Working principle

When control power flows through the magnet coil of a contactor, the resulting magnetic field attracts the mechanical contact carrier. By interruption of the coil control circuit, the mechanical contact carrier returns to the starting position.

A circuit breaker is a switch that has a piece of metal inside. If the current in the circuit is too high, the metal warms up and bends. When the metal bends, it flips the switch and opens the circuit. The flow of current stops before the wires get too hot.

3. Applications

Contactors are mainly used for controlling 3-phase motors and generally for controlling power circuits. The contactors can also be used for many other applications such as bypass, capacitor switching, lighting and DC power circuits. (downstream circuits)

Circuit breakers can be used where circuit protection is needed. (upstream and downstream circuits)

4. The size

Generally, the size of a power contactor is larger than a miniature circuit breaker but smaller than molded case circuit breaker and air circuit breaker.

5. The current carrying capacity

A contactor can have a rating of up to 2000A and for a circuit breaker to have a rating of up to 6300A, but it depends on the specific product and brand. It is important to verify the ratings with the manufacturer or supplier to ensure accuracy.

6. Types

Contactors have various types such as power, mini, modular, bar-type and capacitor-type. Miniature circuit breakers, molded case circuit breakers and air circuit breakers are the types of circuit breakers.

7. The number of poles

Contactors are available in two-pole, three-pole and four-pole configurations. 1, 2, 3 and 4 pole circuit breakers are available in the electrical market.

8. The price

The price of a contactor is cheaper than a circuit breaker but the market size of the circuit breaker is larger than a contactor. You will 100% see a circuit breaker when you open the door of any electrical panel. But you can see contactors in special applications.

9. Lifespan

The lifespan of the contactor is longer than circuit breakers. The average lifetime of a C.B is around 10000 but the average lifetime of a contactor goes up to 1000000.

10. Remote operation

Contactors can operate remotely. Remote operation is the basic principle of the contactor. Circuit breakers are also able to operate remotely but an accessory like shunt release, closing release, undervoltage release or motor operator should be mounted on them.

11. Manual operation

The circuit breaker can be operated manually using its handle. So, a circuit breaker acts as a switch also. You cannot control a contactor manually.

12. Maintenance

Contactors do not require much maintenance. However, in the case of permanent heavy load switching, spare parts are offered by manufacturers. Maintenance of circuit breakers should be done periodically to ensure they are functioning properly and to prevent any potential issues.

13. The history and inventors

The circuit breaker has a longer history compared to the contactor.

An early form of circuit breaker was described by Thomas Edison in an 1879 patent application. Edison’s purpose was to protect lighting circuit wiring from short circuits and overloads. A modern miniature circuit breaker was patented by Brown, Boveri & Cie in 1924. Hugo Stotz.

Hein Moeller developed the first small oil contactor.

In conclusion, contactors and circuit breakers are crucial components in electrical systems. Although they serve the purpose of controlling the flow of electrical current, they differ in their functionality, working principles, applications, sizes, current carrying capacities, types, number of poles, price, lifespan, remote operation, manual operation, maintenance and even their inventors. Understanding the differences between contactors and circuit breakers can help ensure the safety and reliability of electrical systems, and selecting the appropriate component for a specific application can help optimize the efficiency and effectiveness of the system.

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