Which motors are suitable for both star connection and delta connection?

In my country, smaller motors below 3-4KW (kilowatts) are generally required to be connected in a star configuration, and larger motors above are required to be connected in a delta configuration. The star connection method is mainly used in high-voltage large or medium-capacity motors, and only three wires are drawn out of the stator winding. For star connection, the load of each phase is balanced, and the vector sum of the currents flowing through the three phases at any time is equal to zero.

The operating environment of this tutorial: Windows 7 system, Dell G3 computer.

1. Star connection and delta connection both refer to the winding connection of the motor itself. Star connection refers to connecting the three-phase ends of the motor windings together, and the first end of the three phases is the power end. Delta connection refers to connecting the three-phase windings from beginning to end, and the three endpoints are the power terminals. The difference between star connection and delta connection is that the connection methods are different.

2. For three-phase power in star connection, the line voltage is three times the root of the phase voltage, and the line current is equal to the phase current. When the three-phase load is balanced, no current flows through the neutral wire even if it is connected. When the three-phase load is unbalanced, the neutral line should be connected, otherwise the voltage of each phase load will be unequal.

Because there is no neutral point when the motor is connected in triangle, the specific method is to connect the heads and tails of the three-phase windings of the motor respectively. At this time, there is only one voltage level, the line voltage is equal to the phase voltage, and the line current is equal to the phase voltage. The current is about 1.73 times. The difference between star connection and delta connection is that the load is different.

3. In delta connection, each winding of the three-phase motor bears line voltage (380V), while in star connection, each winding of the motor bears phase voltage (220V). When the motor power is the same, the winding current of the angle-wire motor is smaller than that of the star-connected motor. The difference between star connection and delta connection is that they withstand different voltages.

4. When the motor is connected in Y-shape operation, the starting torque is only half of that of delta connection, but the current is only about one-third of that of delta starting. During delta starting, the current is 4-7 times the rated current, but the torque is large. The speed is the same, but the torque is different. The difference between star connection and delta connection is that the current is different.

5, Star-type step-down starting principle, if a three-phase asynchronous motor is directly connected to a three-phase 380 volt full voltage and started directly with a load, the starting current will reach the rated current 5-7 times. If the transformer capacity is insufficient, the 380-volt power supply will fluctuate greatly. Therefore, the essence is to reduce the current at startup by reducing the voltage at startup to avoid impact on the power grid and electrical equipment.

6. The motor with delta connection adopts Y-△ start when starting at light load to reduce the starting current. Light load is the condition, because the torque of Y connection will become smaller, and the purpose is to reduce the starting current. The starting current is reduced by using the Y connection method! Delta connection has high power and starting current, while star connection has low power and starting current.

7. For three-phase asynchronous motors whose stator windings are connected in a triangle during normal operation, Y-△ decompression start can be used. When starting, first connect the stator winding in star shape, so that the voltage of each phase winding is 1/√3 of the phase voltage during normal operation. After starting, the stator winding is restored to delta connection, and the motor enters normal operation under full voltage.

Application; Generally, motors below 3KW have star connection, and motors above 3kW generally have angle connection. According to regulations, motors larger than 15kw need star starting angle operation to reduce starting current. There are also small motors with angle start. If they are to be connected to a three-phase 220V power supply, they must be connected in a star configuration.

In my country, smaller motors below 3-4KW (kilowatts) are generally required to be connected in a star configuration, and larger motors above are required to be connected in a delta configuration. The star connection method is mainly used in high-voltage large or medium-capacity motors, and only three wires are drawn out of the stator winding. For star connection, the load of each phase is balanced, and the vector sum of the currents flowing through the three phases at any time is equal to zero.

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