Why do high voltage motors use star connection?
For three-phase motors, the stator windings are connected by triangles and stars. The star connection is to connect the tails of the three-phase windings together. The heads of the three-phase windings are connected to the power supply; the star connection has an external connection and an internal connection. In the two cases of star connection, the inner star is connected to the motor to fix the star point of the three-phase winding to the appropriate part of the stator winding, and three outlet ends are led out, while the outer star connects the head and the tail of the three-phase winding. And connect and wire the outside of the motor.
The delta connection is to connect the head of one phase winding to the tail of another phase winding, that is, U1 is connected to W2, V1 is connected to U2, W1 is connected to V2, and the connection point is connected with the power supply.
If each phase winding is treated as a line, the stars are connected like a glowing star, and the triangle connection is like a triangle, so it is called a star connection or a triangle connection. The delta connection motor can also be connected to the inner and outer angles.
If it is a single-voltage motor, both internal and external can be used, but for a dual-voltage motor, only the head and tail of the three-phase winding can be taken out, and then externally connected according to the voltage. The high voltage corresponds to the star connection, and the low voltage corresponds. Corner connection.
Why do high-voltage motors use star connections?
For low-voltage motors, the power will be segmented according to the power. For example, the basic series motor is divided according to 3kW, no more than 3kW is connected by star, and the other is connected by angle. For variable frequency motor, it is divided by 45kW, and no more than 45kW is connected by star. According to the corner connection, for the lifting and metallurgical motors, there are more stars, and the large-size lifting motor will also adopt the corner connection.
High-voltage motors are generally star-shaped connections in order to avoid high voltages on the motor windings. In the star connection method, the line current is equal to the phase current, and the line voltage is 3 times the root of the phase voltage (in the delta connection, the line voltage is equal to the phase voltage and the line current is equal to √3 times the phase current), so the motor winding is subjected to The voltage is relatively low. In high-voltage motors, the current tends to be small, and the insulation level of the motor is relatively high. Therefore, the insulation of the star-connected motor is better and more economical.
