Update date:2017-12-09 Source:MAXGE

A magnetic motor starter is an electromagnetically operated device that starts and stops a connected motor load. Magnetic starters consist of an electrical contactor and an overload which provides protection in case of a sudden loss of power.




Contactor vs Relay

The contactor is similar to a relay but is designed to switch a larger amount of electrical power and handle higher voltage loads. Unlike a relay, a contactor does not have an energized common pole which switches between the normally open and normally closed poles. The contactor consists of a contact carrier with electrical contacts to connect the incoming line power contact to the load contact, an electromagnet (commonly referred to as the “coil”) which provides the force to close the contacts to allow current to flow, and the enclosure which is an insulating material to hold the parts together and provide some measure of safety against a person touching the terminals. Contactors are typically made with normally open contacts, meaning the power will not flow to the load until the coil is activated, which closes the contactor. Coil activation is typically done by a control operator, either manual, i.e. a person pushing a button/flipping a switch, or automatically using a sensor, or timer which switches when a particular condition is reached. Contactors can be provided with auxiliary contacts (either normally open or normally closed) to perform additional operations when the contactor is closed.


 When the contactor is closed, this allows current to go to the “coil” (electromagnet).  This can be the same voltage as the power going through the contacts, or often a lower “control” voltage is used only to energize the coil.  When the coil is energized, this creates a magnetic coupling between the contacts & contact carrier, allowing them to stay together and current to flow to the motor or other load until the system is shut off by de-energizing the coil. When de-energized, a spring causes the contacts to separate and halt the flow of power through the contacts, thus turning off the motor or load.


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Copyright© 2017 All Rights Reserved.







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