SQUARE D DEFINITE PURPOSE MAGNETIC MOTOR STARTERS
GENERAL ELECTRIC IEC SOLID STATE MAGNETIC STARTERS
SHIHLIN ELECTRIC IEC SOLID STATE MAGNETIC STARTERS
A magnetic starter is an electrical switching device commonly used as a initiating mechanism for electric motors and other high current equipment. Also known as a contactor, the magnetic starter relies on an electromagnetic field to close a set of contacts which then transfer power to the motor. This electromagnetic field is supplied by a two part laminated steel core and a wire coil connected to the control circuit of the starter. When the start button or pressure switch on button is pressed, the coil energizes, it creates the magnetic field which pulls the contact mechanism closed and starts the motor. Magnetic starters may have from two to four sets of main contact points and will often feature built-in sets of auxiliary contacts and thermal overload cut-outs.  
Most electric motor and heavy equipment installations use a magnetic starter to initiate operation. Often called contactors or relays, magnetic starters allow for remote starting of equipment and, depending on the specific design, also offer overload protection and auxiliary switching. The main contact points in a magnetic starter act like switches to make or break the main supply circuit to the motor. In the case of smaller single phase motors, only two contact points will be required — one each for the live and neutral lines. Three phase motors will naturally require three contacts, one for each phase.
MAGNETIC MOTOR STARTERS