Sudden Braking of Three-Phase Asynchronous Motors Schematic Circuit Diagram
3-phase asynchronous motors consist of two basic components, a stator, and a rotor. The stator is the fixed part of the motor. The stator has a stator core and field windings. In the stators of 3-phase asynchronous motors a separate winding for every 3 phases. The rotor is the rotating part of the motor. There is wind in the rotors of the slip-ring asynchronous motors, and short-circuited bars in the rotor of the squirrel-cage asynchronous motors. The asynchronous motor type generally used in industrial implementations is the squirrel-cage asynchronous motor. The industrial asynchronous motor product range of Volt Motor consists of squirrel-cage asynchronous motors.
When the forward button is pressed in this circuit, the contactor (I) is energized. Normally the closed (I) contact opens, normally open (I) contacts close. The engine starts to rotate in the forward direction. (A) The contact in the forward direction of the instantaneous stop switch closes. The contactor (G) is not energized since the normally-closed contact (I) opens. The current (A) from phase (R) runs the contactor continuously through the contact at the forward direction of the instantaneous stop switch, from the back contact upper contacts and the normally closed (G) contact. The motor thus rotates in the forward direction continuously. The motor rotates in the forward direction until the stop button is pressed.
When the stop button is pressed, the contactor (I) is de-energized. The contacts in the power circuit (I) are switched on and the motor is disconnected from the mains. The contact (I) opened in the control circuit closes. As the rotor is pivoting forward, (A) the contact in the forward direction of the instantaneous stop switch remains closed. It energizes the contactor of the current (G) which passes over the contact and the normally closed (I) contact. The contacts in the power circuit (G) are closed. With the displacement of two phases, the motor is connected to the mains again. When the rotor is rotating in the forward direction, a counter-clockwise torque occurs. The speed drops rapidly and becomes zero. The momentary stop switch returns to its normal position. The (G) contactor is de-energized. The motor is disconnected from the mains. The motor stops abruptly before turning in the opposite direction.