In triangle connection: each winding of the three-phase motor bears the line voltage (380V),

In star connection: each phase voltage of the motor bears (220V).

When the motor power is the same, the winding current of the triangle motor is less than the winding current of the star connection motor.

When the motor is Y-type running, the starting torque is only half of the triangle connection, but the current is only about one-third of the triangle connection. When the triangle starts, the current is 4-7 times the rated current, but the torque is larger. The speed is the same, but the torque is different.

Delta connection

The triangle connection method of the motor is to connect the windings of each phase in turn, and lead each connection point as a three-phase line of three-phase electricity. When the triangle connection is used, the phase voltage of the motor is equal to the line voltage; the line current is equal to the square root of 3 times the phase current.

Star connection

The star connection method of the motor is to connect one end of each phase winding at one point, and their other ends are used as leads, which are three-phase lines. When connected in star, the line voltage is three times the square root of the phase voltage, and the line current is equal to the phase current.

When starting a small power, high torque motor or a high power motor, due to the small starting output power, a star connection is often used, which reduces the loss of the machine, and a triangle connection is used after normal operation. This is often called star-triangle entrepreneurship.

The choice of motor connection is a three-phase motor, and single-phase motors do not have the above two connections. Generally, motors below 3kW have many star connections, and motors above 3KW have many delta connections. According to regulations, motors greater than 15kw require star starting angle operation to reduce the starting current.

There are also small motor angle starts. If you want to connect a three-phase 220V power supply voltage, you must connect it in star.

Generally in China, smaller motors below 3-4KW (kW) require star connection, and larger motors above require delta connection.

Motor terminal box connection

From the motor terminal box, it can be seen that if the other end U2, V2, W2 of the three incoming terminals U1, V1, W1 are short-circuited by the same iron sheet, it is a star (Y) connection; the three incoming terminals U1 and W2, V1 and U2, W1 and V2 are short-circuited, it is a triangle connection (three flat irons in the terminal box), and the line voltage is equal to 1.732 of the phase voltage in the star connection.

For example, if the motor has no terminal box, the first phase winding is marked with 1.4 at the head and tail, the second phase winding is marked with 2.5 at the head and tail, and the third phase winding is marked with 3.6 at the head and tail. Star connection: 135 are connected together, 246 are connected to the power supply, and triangle connection: 1 is connected to 6, 2 is connected to 4, and 3 is connected to 5 to make three lead wires of the motor.

1. When the motor is connected in a triangle, since there is no neutral point, the specific method is to connect the three-phase winding of the motor separately at the head and tail. At this time, there is only one voltage level, the line voltage is equal to the phase voltage, and the line current is about 1.73 times the phase current.

2. When the motor is connected in star, because there is a neutral point (the motor is generally a three-phase symmetrical load, so the neutral line is generally not led out). The specific method is to connect the three tails of the motor's three-phase winding together and connect the three heads to the power supply. At this time, there are two voltage levels: line voltage and phase voltage. The line voltage is about 1.73 times the phase voltage, and the line current is equal to the phase current.

3. It should be noted that the original star-connected motor cannot be connected in a triangle (if connected in a triangle, the phase voltage will rise to about 1.73 times, and the motor will burn out if it runs for a long time).

4. Similarly, the motor connected in a triangle cannot be connected in a star (if connected in a star, the phase voltage will drop to about 1.73 times, and the normal power cannot be reached. If the motor carries the rated load, it will be overloaded at this time, and the motor will inevitably burn out over time).

5. In China, small motors below 3-4KW (kW) are usually required.

For star connection, the phase current is equal to the line current, and the line voltage is three times the square root of the phase voltage. For triangle connection, the line voltage is equal to the phase voltage, and the line current is three times the square root of the phase current. For three-phase symmetrical loads, a certain connection can increase the operating voltage and power of each phase.

Delta connection helps to increase motor power. Disadvantages: large starting current, large winding withstand voltage (380V)! Increased insulation level!

Planetary connection helps to reduce the withstand voltage (220V) and insulation level of the winding! Reduce the starting current, disadvantageous, reduce the motor power! Therefore, most small power motors below 4KW use planetary connection! Greater than 4KW use triangle connection! Motors connected in triangle use Y-start when starting with light load to reduce the starting current! Light load is a condition, because the torque of Y connection will become smaller, and reducing the starting current is the purpose. Y-connection is used to reduce the starting current!

The power of triangle connection is large, and the starting current is also large. The power of star connection is small, and the starting current is also small.

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