Manual automatic Y-△ step-down starting circuit

As shown in the figure, SA is a manual-automatic selection switch. When SA is dialed to the "manual" position (as shown in the figure), press the start button ST. The AC contactor KM pulls in, its normally open contact moves, the KMY coil pulls in, the main contacts KM and KMY move, and the motor M enters the Y connection method to start with reduced voltage. When the motor speed is close to 70% of the full speed, press the run button SN, the KMY coil loses power and releases, the intermediate relay K closes, its normally open contact action turns on the KM△ coil power, the main contact KMY releases, KM and KM △ is connected, the stator coil of the motor M forms a △-shaped connection, and the motor changes from Y-shaped starting to △-shaped operation. Press the stop button STP, the motor M stops; when SA is set to the "automatic" position, press the start button ST, the KM, KT, and KMY coils are energized at the same time, the main contacts KM and KMY act, and the motor M enters the Y shape Pressure reduction starts. At the same time, KT delayed the timing. After KT reaches the setting time, its normally closed contact KT is disconnected, the KMY coil loses power, its normally open contact KT closes instantly, the intermediate relay K is powered and closed, and the normally open contact of K acts, KM△ The coil pulls in. The motor enters △-shaped full-voltage operation. Press the STP stop button and the motor M stops.