What is full form of DOL? DOL means Direct Online starter which is used to start the induction motor .Different types of techniques are used to start induction motor with safe starting current because these motors utilize more power for starting. During starting when the flow of current through windings is high then there will be a chance to damage the motor winding To overcome this problem, different methods of starter techniques are used. The simple type of starter method is DOL (Direct on Line Starter).
DOL(Full form of DOL is Direct online starter) starter include circuit breaker or MCCB( Molded case circuit breaker), overload relay and contactor for the protection of motor. The operation of an electromagnetic contactor can be done through the thermal overload relay normally closed contact .
Construction of DOL Starter
The DOL starter consists of two switches namely Green and Red & start and stop )where the green switch is used to start the motor and red switch is used to stop the motor.
Full form of DOL is Direct Online starter .The DOL starter include circuit breaker (or) MCCB( Molded case circuit Breaker), thermal overload relay and electromagnetic contactor for protecting the motor. With the help of the two switches we can control the motor. The motor can be started by pressing the green and the full-line voltage are connected to the induction motor.
The contactors are normally 3-poles contactors or 4-pole contactors.Usually a 4-pole type electromagnetic contactor consists of three normally open contacts and one is auxiliary or holds on contact are used to make DOL starter. The 3 pole of the contactor ( NO) are used to connect the induction motor to supply lines whereas the auxiliary contact is used to boost the contactor coil when the start button is opened. If any fault occur then holds on contactor gets deactivated and due to which the DOL starter separates the induction motor from the mains supply by protecting the fault current
Applications of DOL Starter
This type of starter is used where maximum current do not cause any damage such as small compressor ,conveyor belts, water pumps ,fans etc.DOL starter is useful in motor when the 3- phase induction motor is at low rating and the input is very small .
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