Is a contactor the same as a starter?
The mechanical elements of starters and contactors are identical. The contactor applies voltage to a contactor coil to close the contacts and to supply and interrupt power to the circuit. A motor starter is simply a contactor PLUS an overload relay and is rated by motor HP or amperage.
What do contactors do?
A contactor is an electrical device which is used for switching an electrical circuit on or off. These contacts are in most cases normally open and provide operating power to the load when the contactor coil is energized. Contactors are most commonly used for controlling electric motors.
What does a motor starter have that a contactor does not have?
Contactors and motor starters are also distinct components. The difference is that motor starters have one extra system or systems not found in contactors — an overload relay of some type to cut voltage input should that relay sense a motor-overload or thermally compromising condition due prolonged running overcurrent.
Why are contactors better than switches?
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 relays, contactors are designed with features to control and suppress the arc produced when interrupting heavy motor currents.
Why is a contactor used as a starter for motors?
In motor starter, contactor controls the flow of electric current to the connected motor and repeatedly make and break (interrupt) the power circuit from main power supply. The overload protection block in a starter protects the motor from drawing excessive current and overheating and burning out the circuit.
Why use a relay instead of a contactor?
Relays are used to control contacts of an electrical circuit due to a change of parameters or conditions in the same circuit or any other associated circuit. Contactors, on the other hand, are used to interrupt or establish connections in an electrical circuit repeatedly under different conditions.
Why do contactors chatter?
Low voltage to the contactor coil will allow the contactor to chatter. Contactor chatter can also occur due to chattering switches or loose connections in the control circuit. A low voltage situation can also occur due an unbalanced loading of the motor.
How does a motor starter contactor work?
Motor starters consist of two devices—a contactor that completes the circuit to the motor and an overload relay that monitors the current the motor is drawing. When a condition occurs that causes the motor to exceed the maximum load, the device opens the motor starter control circuit and the motor is turned off.