A magnetic contactor is a relay-controlled switch used to turn a power control circuit on and off. It is electrically controlled and uses less power than other circuits. A magnetic contactor comes in different forms and capacities.
A magnetic contactor has three parts: power contacts, contact springs and auxiliary contacts. The power contact creates, carries and breaks the current in a magnectic contactor. The contact springs create a sufficient amount of pressure on the contacts. Auxiliary contacts perform signaling and interlocking maneuvers. Contactors vary in size and capacity. A contactor may be small enough to fit in your hand or it may be several feet on one side.
In heavy duty magnetic conductors, blowout coils perform magnetic blowouts so the current can go further with more power. Economizer circuits decrease the power needed to keep the contactor closed; these are usually found in direct-circuit contactor coils working to keep the contactor cooler. Vacuum or inert gases, on the other hand, are applied on the contacts, especially for high voltage contactors.
A basic magnetic conductor has a coil input that is driven by either a DC or AC supply, and it can be energized at the same voltage as the motor. It can also be controlled separately using programmable controllers and low voltage pilot devices. Most contactors handle lighting, heating, electric motors and capacitor banks.
Contactors are usually fitted on open contacts, and are designed to suppress and control electric arcs which are produced by interrupting heavy motor currents. They work on the principle of electromagnetism, and the electricity runs through the coil from the core of the contactor. While the core is moving, a force is developed that allows the electromagnet to carry charge and hold the contacts together. Once the contactor coil is de-energized, the spring of the electromagnet returns to its original position.
Magnetic conductors are rated by their load current per contact, duty cycle, voltage and maximum fault to withstand current and coil voltage. Different countries also gauge the strength and power of magnetic conductors differently; European contactors focus on the design and life cycle of the contactor, while North American ratings focus on the contactor’s simplicity of application.