Starters and contactors both control electric motors; they may seem to describe the same function, but a closer look reveals their functional and physical differences.
A starter usually refers to a component assembly that includes a housing, a contactor and an additional relay for overload protection and that is used to start an electrical motor. A contactor is an electrical switch similar to a relay used for switching current on and off in a circuit without overload protection.
Both starters and contactors make use of low voltage to pull contacts together. Contactors are rated by their current in amps and operate by sending a control voltage to the contractor coil. Starters are rated by their horsepower capacity and the amount of current they use.
As electrically controlled switches, contactors control electric motors, heating circuits and assorted electrical loads without providing overload protection. The contactor applies voltage to a contactor coil to close the contacts and to supply and interrupt power to the circuit. Starters control electrical power to contacts for control of electric motors. The starter employs overload relays to protect the motor from load surges by shutting it down to prevent overheating. Both components come in various sizes, from hand-held assemblies to a foot long or larger.
