What is the step-down starting of three-phase asynchronous motor? What are the common methods? What are their characteristics?

The commonly used step-down starting methods of three-phase asynchronous motor are: stator series resistance (or reactor) step-down starting, star delta step-down starting, autotransformer step-down starting and Yanbian triangle step-down starting.

When the stator winding of a three-phase asynchronous motor is connected with the starting resistor in series, the starting voltage of the stator winding is reduced due to the partial voltage of the starting resistor. After starting, the resistor is shorted to make the motor run normally at the rated voltage, which can reduce the starting current.

This starting mode is not limited by the wiring form of the motor, and the equipment is simple and economical, which is widely used in small and medium-sized production machinery.

In normal operation, the three-phase asynchronous motor with stator windings connected in triangle can adopt star triangle step-down starting mode. When starting, the winding voltage of each phase drops to normal working voltage, the starting current drops, and the motor starts to rotate. When the speed is close to the rated speed, the stator winding of the motor becomes triangular and the motor enters the normal operation state.