Of chattogram polytechnic institute
MOTOR OPERATION USING DOL STARTER
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A Direct On-Line (DOL) starter is a type of motor starter that connects the motor directly to the power source. The DOL starter is the simplest and most economical type of motor starter. However, it also has the highest starting current. To start a motor using a DOL starter, the following steps are performed: Press the start button. This energizes the contactor coil. The contactor closes, connecting the motor to the power source. The motor starts rotating. When the motor reaches its operating speed, the start button can be released. To stop the motor, press the stop button. This de-energizes the contactor coil. The contactor opens, disconnecting the motor from the power source. The DOL starter is a simple and economical way to start a motor. However, it has the highest starting current of all the types of motor starters. This can cause a voltage drop in the power system, which can affect other devices that are connected to the same power system. Here are some of the advantages of using a DOL starter: Simple and economical Easy to install and maintain Reliable Here are some of the disadvantages of using a DOL starter: High starting current Can cause voltage drop in the power system Not suitable for large motors The DOL starter is a good choice for small motors that do not require a high starting current. For larger motors, a different type of motor starter, such as a soft starter, may be a better choice MOTOR OPERATION USING STAR-DELTA STARTER A star-delta starter is a type of motor starter that uses a star-delta connection to reduce the starting current of a three-phase induction motor. The star-delta connection is made by connecting the motor windings in a star configuration at start-up and then switching to a delta configuration once the motor has reached a predetermined speed. The star-delta connection reduces the starting current of the motor by dividing the line voltage by three. This is because in a star connection, each winding is connected to only two of the three line voltages. In a delta connection, each winding is connected to all three line voltages. The star-delta starter is a simple and effective way to reduce the starting current of a three-phase induction motor. It is commonly used in applications where the motor is started infrequently, such as in conveyor systems and pumps. Here are the steps involved in the operation of a star-delta starter: The motor is started in star configuration. This is done by closing the star contactor and opening the delta contactor. Once the motor has reached a predetermined speed, the star contactor is opened and the delta contactor is closed. This switches the motor to delta configuration. The motor continues to run in delta configuration until it is stopped. The star-delta starter has a number of advantages, including: It reduces the starting current of the motor, which can protect the motor and the electrical system from damage. It is simple and easy to use. It is relatively inexpensive. However, the star-delta starter also has some disadvantages, including: It reduces the starting torque of the motor, which can affect the performance of the motor in some applications. It requires additional components, such as the star and delta contactors. It can increase the complexity of the motor control system. Overall, the star-delta starter is a versatile and effective way to start three-phase induction motors. It is a good choice for applications where the motor is started infrequently and where the starting current needs to be reduced. Download 5.21 Mb. Share with your friends:
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