A star delta starter is a type of motor starting device that is used to reduce the starting current of an AC motor. It is also known as a wye delta starter or a soft starter. In this article, we will discuss the wiring diagram of a star delta starter and its working principle.
What is a Star Delta Starter?
A star delta starter is a connection between three-phase induction motor terminals. It consists of three contactors, a timer, and overload relays. The contactors are used to switch the motor from star to delta configuration, while the timer is used to delay the switching between the two configurations. The overload relays are used for motor protection against overloading and short-circuit.
The star delta starter is mainly used for high power motors, as it reduces the starting current and torque of the motor. This reduces the voltage drop in the power supply system, which can improve the power quality and efficiency of the motor.
Wiring Diagram
| Contactors | Timer | Overload Relays |
|---|---|---|
| Contactor 1 – Main Contactor | Timer – Star/Delta Timer | Overload Relay 1 – Star Side |
| Contactor 2 – Delta Contactor | Overload Relay 2 – Delta Side | |
| Contactor 3 – Control Contactor |
The wiring diagram of a star delta starter is shown in the table above. The three-phase power supply is connected to the main contactor (contactor 1), which is used to switch the motor between star and delta configuration. The delta contactor (contactor 2) is used to connect the motor windings in delta configuration. The control contactor (contactor 3) is used to control the operation of the star delta starter.
The overload relays (overload relay 1 on the star side, and overload relay 2 on the delta side) are used to protect the motor against overloading and short-circuit. The star/delta timer is used to delay the switching between star and delta configuration, to ensure that the motor has reached a stable speed before switching to delta configuration.
Working Principle
The working principle of a star delta starter is based on the fact that the starting current and torque of an AC motor are higher in star configuration than in delta configuration. In star configuration, the motor windings are connected in series and the voltage across each winding is reduced, resulting in a lower starting current and torque. In delta configuration, the motor windings are connected in parallel, resulting in a higher starting current and torque.
When the motor is started, the main contactor (contactor 1) is closed and the motor windings are connected in star configuration. The motor is then started with reduced current and torque. After a predetermined time delay, the star/delta timer opens the main contactor and closes the delta contactor (contactor 2), switching the motor from star to delta configuration. The motor then runs at full speed with higher current and torque.
The control contactor (contactor 3) is used to control the operation of the star delta starter. When the control contactor is closed, the timer is activated and the motor is started in star configuration. When the control contactor is opened, the timer is reset and the motor is stopped.
FAQ
What is the purpose of a star delta starter?
A star delta starter is used to reduce the starting current and torque of an AC motor. This reduces the voltage drop in the power supply system, which can improve the power quality and efficiency of the motor. It is mainly used for high power motors.
How does a star delta starter work?
A star delta starter works by switching the motor between star and delta configuration. In star configuration, the motor windings are connected in series and the voltage across each winding is reduced, resulting in a lower starting current and torque. In delta configuration, the motor windings are connected in parallel, resulting in a higher starting current and torque. The star delta starter delays the switching between the two configurations to ensure that the motor has reached a stable speed before switching to delta configuration.
What are the components of a star delta starter?
A star delta starter consists of three contactors, a timer, and overload relays. The contactors are used to switch the motor between star and delta configuration, while the timer is used to delay the switching between the two configurations. The overload relays are used for motor protection against overloading and short-circuit.
What is the wiring diagram of a star delta starter?
The wiring diagram of a star delta starter consists of three contactors, a timer, and overload relays. The three-phase power supply is connected to the main contactor, which is used to switch the motor between star and delta configuration. The delta contactor is used to connect the motor windings in delta configuration. The control contactor is used to control the operation of the star delta starter. The overload relays are used to protect the motor against overloading and short-circuit.
When is a star delta starter used?
A star delta starter is mainly used for high power motors, as it reduces the starting current and torque of the motor. This reduces the voltage drop in the power supply system, which can improve the power quality and efficiency of the motor.
