Contactor
Contactor
A contactor is an electrically-controlled switch used for switching an electrical power circuit. A contactor is typically controlled by a circuit which has a much lower power level than the switched circuit, such as a 24-volt coil electromagnet controlling a 230-volt motor switch. Unlike a circuit breaker, a contactor is not intended to interrupt a short circuit current.
Design and Operation[edit | edit source]
Contactors come in many forms with varying capacities and features. Unlike relays, contactors are designed to be directly connected to high-current load devices. Contactors range from those having a breaking current of several amperes to thousands of amperes and 24 V DC to many kilovolts. The physical size of contactors ranges from a device small enough to pick up with one hand, to large devices approximately a meter (yard) on a side.
Components[edit | edit source]
A contactor typically consists of:
- An electromagnet (or coil) which provides the force to close the contacts.
- A set of contacts that carry the current and withstand the arc when opening and closing.
- An enclosure to protect the contacts and the electromagnet from dust, oil, and other contaminants.
Types of Contacts[edit | edit source]
Contactors use different types of contacts depending on the application:
- Normally Open (NO) contacts: These contacts close when the contactor is energized.
- Normally Closed (NC) contacts: These contacts open when the contactor is energized.
- Auxiliary contacts: These are used in control circuits and are not designed to carry high currents.
Applications[edit | edit source]
Contactors are used in various applications, including:
- Electric motor control
- Lighting control
- Heating, ventilation, and air conditioning (HVAC) systems
- Capacitor bank switching
- Welding machines
Advantages[edit | edit source]
- High current capacity
- Long operational life
- Reliable performance
- Can be controlled remotely
Disadvantages[edit | edit source]
- Can be bulky
- May require maintenance
- Can generate electrical noise
Related Pages[edit | edit source]
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Contributors: Prab R. Tumpati, MD
