The star connection method is mainly used in high-voltage large or medium-capacity motors, and the stator winding leads out only three wires. The triangle connection method is mainly used in low-voltage medium-sized or small-capacity motors, and the stator winding leads out 6 wires, which are connected into a star or triangle as needed. The Y-type connection is also called the star connection, the voltage of the winding is 220V, and the triangle connection is 380V, which is almost 0.5789 times. On the other hand, the voltage of the triangle connection is 3 times the root number of the voltage of the star connection, of course, the triangle connection can be converted with the Y-line connection, and the W, V, and W are shorted and then the other end is directly connected to convert. In terms of connection, the star connection method is that one end of the three coils is shorted to each other. The other end is connected to the three-phase power supply. The triangle connection method is that the three coils are connected end to end, shaped like a triangle, and the three terminal points are connected to the three-phase power supply. In terms of voltage at both ends, the voltage at both ends of each coil is equal to the phase voltage. The voltage at both ends of each coil is equal to the line voltage. Therefore, the power of the same three sets of coils is less than that of the triangle connection if the connection method is star-shaped.
In addition, when the star-delta step-down start-up is adopted, the phase voltage and phase current of the star-shaped connection are reduced, and the corresponding starting distance is also reduced. There is a limitation to this starting method, that is, the motor must be triangular connection. Today's large and medium-sized motors are all star connections.
All three-phase cage induction motors that are connected to the three-phase stator windings to run in a triangle during normal operation can be started with Y-D step-down. When starting, the stator winding is first connected into a Y connection, connected to the three-phase AC power supply, the starting current drops to 1/3 of the full-voltage start, and the starting current is 5.5~7 times of the rated current IN when the Y series motor is started directly. When the speed is close to the rated speed, the stator winding of the motor is changed to D connection, and the motor enters normal operation. This method is simple and economical, and can be used in the occasion of frequent operation, but its starting torque is only 1/3 of the full voltage start, and the starting torque of Y series motor is 1.4~2.2 times of the rated torque.
1. The same motor can be installed into a Y-type winding, or it can be installed into a △-type winding;
2. When the same motor is installed and wound into a △-type winding, the wire cross-section is small, the number of series turns is large, the working phase voltage is high, and the phase current is low;
3. When the same motor is installed and wound into a Y-shaped winding, the wire cross-section is large, the number of series turns is small, the working phase voltage is low, and the phase current is high;
4. The △ type winding requires good symmetry and high symmetry of the power supply, so that there will be no circulation, otherwise it will heat up and increase the loss;
5. When the Y-type winding is not symmetrical and the symmetry of the power supply is not high, there will be no circulation;
6. In use, the △-type winding can be started by Y-△ starting mode, while the Y-type winding cannot be started by Y-△ starting mode;
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