Manual control Y-△ step-down starting circuit

Star-delta step-down start is often called Y-△ step-down start. It is characterized by convenience, simplicity and economy. Its starting current is 1/3 of direct start, so it is only suitable for three-phase motors under no load or light load. case start. There are many types of Y-△ step-down starting circuits, as shown in the figure is the manual control circuit. QX1 is a manual Y-△ starter. When the handle is moved to the "0" position, all eight pairs of contacts are disconnected, and the motor does not run when the power is turned off; when the handle is moved to the "Y" position, contacts 1, 2, 5, 6, and 8 are closed, and contacts 3, 4 , 7 contacts are disconnected, and the stator winding of the motor M is connected into Y (star shape) for step-down start; when the operator sees that the motor speed rises to about 70% of the rated speed, he quickly pulls the handle to the "△" position, and then 1 , contacts 2, 3, 4, 7, and 8 are connected, contacts 5 and 6 are disconnected, and the stator winding of the motor is connected into a △ (triangle) for normal operation. Since the manually controlled Y-△ step-down starter does not have an overcurrent protection device, a rubber-covered knife switch QS is usually installed before the QX1 starter, and is equipped with a fuse matching the M capacity of the motor.