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Contactor is an electromechanical device designed to control high-power electrical circuits by switching them on or off. Widely used in industrial, commercial, and residential applications, contactors ensure reliable operation of motors, lighting systems, HVAC equipment, and more.
What is a Contactor?
A contactor functions as a high-capacity switch controlled by a low-power electrical signal. Using an electromagnetic coil, it actuates contacts to manage high-current circuits. Contactors are specifically built to handle frequent switching cycles and high electrical loads.
Key Features of Contactors
- High Current & Voltage Handling: Handles loads up to hundreds of amperes and voltages up to 1,000V.
- Durability: Built for frequent operations in industrial/commercial environments.
- Safety: Electrically isolates the control circuit from the power circuit.
Classification of Contactors (AC Duty)
Defined by IEC 60947-4-1:
AC-1: Non-Inductive or Slightly Inductive Loads
- Resistive loads like heaters and lighting
- Low contact erosion
AC-2: Starting & Stopping Squirrel-Cage Motors
- Low starting torque motors
AC-3: Starting Motors & Disconnection During Running
- Industrial motor control, conveyors
AC-4: Plugging & Reversing Motors
- Hoists, cranes, elevators
Typical Ratings
- Rated Current (Ie): e.g., 9A, 25A, 50A, 95A
- Rated Voltage (Ue): e.g., 230V, 400V, 690V AC
- Power Ratings (kW): e.g., 7.5kW, 15kW, 22kW
- Coil Voltage: e.g., 24V DC, 110V AC
Popular Contactor Makes
- Siemens: 3RT1025-1AP00
- Schneider: LC1D25M7
- ABB: A26-30-10
- Telemecanique: LC1D09B7
Wiring Diagrams
Contactor vs Relay
| Feature | Contactor | Relay |
|---|---|---|
| Load Capacity | Up to 1000A+ | Up to 20A |
| Use | Industrial / High Power | Control Circuits |
FAQs
How to choose the right contactor?
Identify load type, check voltage/current ratings, and consider environment.
What causes contactor failure?
Overloading, wear & tear, dust/moisture.
Lifespan of a contactor?
Several hundred thousand switching cycles.
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