Purpose and Selection Guide of AC Contactor

I. Basic Functions of AC Contactor

An AC contactor is an electrical switching device used to control motors, heating equipment or other electrical loads. Its main function is to remotely connect and disconnect circuits through electromagnetic drive. It is widely used in industrial automation, building electrical systems and mechanical equipment.

The core functions of AC contactors include:
 

Remote control: Use low current signals (such as PLC or buttons) to switch high power loads.

Frequent operation: Compared with mechanical switches, contactors are more suitable for high-frequency switching.

Safety protection: Used in conjunction with thermal relays or electronic protectors, it can provide overload and phase loss protection for motors.

II. Common types and applications of AC contactors

1.Standard AC contactor

The CJX2 series is a widely used AC contactor in China, suitable for general motor control, lighting systems and heating equipment. Main features:

Modular design: Compatible with auxiliary contacts and mechanical interlocking devices.

Long mechanical life: Typically more than 1 million operations, suitable for medium frequency use.

Cost-effective: Suitable for standard industrial environments.

Applications: Fans, pumps, conveyors and other loads that are not frequently started/stopped.

2.High-frequency starting contactors

For applications that require frequent switching (e.g., inching control, cranes, machine tools), standard contactors may experience contact wear. High-frequency starting contactors should be used, which have the following features:

Silver alloy contacts: Resistant to arcing and welding.

Enhanced arc suppression: Reduces contact damage
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Higher mechanical durability: More than 3 million operations.

3.Automation control contactors

In automation systems controlled by PLC, inverter or servo, contactors must have fast response, low noise and anti-interference capabilities. Key requirements:

Low power coil: Reduce PLC load.

High sensitivity: Ensure fast action.

EMC design: Prevent false triggering.

III. Key factors in selecting AC contactors
 

Selecting a suitable AC contactor depends on the following parameters:
 

IV. Which contactor is best for frequent start/stop?

For motors that start/stop frequently (e.g., cranes, presses, automated machinery), consider:

1. High-frequency contactors (e.g., CJX2-F or LC1-D).

2. Solid-state relays (SSRs): no contacts, ideal for ultra-high frequency use (but more expensive).

3. Soft starters or inverters: reduce starting shock and extend contactor life.

V. Motor protection solutions

AC contactors are often used in conjunction with the following protection devices:

Thermal relays (e.g., JRS1): provide overload protection, but have a slow response.

Motor protection circuit breakers (e.g., GV2): integrate short-circuit and overload protection.

Intelligent protectors (e.g., EOCR): support phase loss, stall, and current imbalance protection.

VI. Conclusion

AC contactors are essential in automation control, and selection depends on load type, switching frequency, and environmental conditions. For general use, the CJX2 series offers cost efficiency, while high-frequency start contactors are ideal for frequent switching. Combining them with soft starters or smart protection enhances system reliability and longevity.

Proper selection improves equipment stability and reduces maintenance costs, making it a critical aspect of electrical design.