Analysis on Starting Control Mode of Wound Asynchronous Motor

In addition to cage type, the rotor winding of asynchronous motor also has wound rotor type, also known as wound rotor asynchronous motor.

The winding rotor coil can be connected into a star or a triangle, and the rotor is equipped with a collecting ring, which is connected internally and externally through a brush device. It is characterized by limiting the starting current and increasing the starting torque through several starting resistances connected in series by a collecting ring and a brush in the rotor circuit. There are two starting methods for wound rotor asynchronous motor, one is resistance graded starting, and the other is frequency sensitive rheostat starting. So today, I will briefly introduce the starting control methods of wound rotor asynchronous motor, and I hope it can help you.

1. Starting control of series resistance of rotor circuit

The starting control of rotor series resistance is to connect several stages of resistance in series respectively in the three-phase rotor winding, which is star connected. Before starting, all starting resistors are connected to the current limiting starting circuit. When starting, the starting current decreases with the increase of the speed, and the starting resistance is gradually short circuited. After starting, all resistors are short circuited and the motor operates under normal full voltage. There are two starting modes for resistance short circuit: three-phase resistance unbalanced short circuit and three-phase resistance balanced short circuit. Unbalanced short circuit method is controlled by the controller, and the resistance of each phase is shorted in sequence. The balanced short circuit method is controlled by the contactor, and the three-phase resistance is short circuited at the same time. The control mode of the rotor series resistance starting control circuit is to cut off the starting resistance gradually during the motor starting process, resulting in sudden changes in current and torque, which will cause mechanical impact.

2. Starting control of rotor circuit series frequency sensitive rheostat

When the rotor is started with series resistance, because the resistance is cut off gradually during the starting process, the sudden change of current and torque * * * mechanical impact, and its control circuit is complex, the starting resistance is large, energy consumption is high, and maintenance is troublesome, so other starting methods are often used in actual production. However, series resistance starting has the advantage of large starting torque, and it is still a common starting mode for transmission devices with low speed operation requirements and large initial starting torque.

Another starting method of wound rotor asynchronous motor is to start the rotor circuit in series with a frequency sensitive rheostat. This starting mode has the characteristics of constant torque starting and braking. It is a static contactless electronic component that requires little maintenance. Therefore, it is commonly used in the starting of wound asynchronous motor, and widely used in the starting control of large capacity wound asynchronous motor.