Issue 103: the difference of two wiring methods of Hengyu Guoqiang reducer motor
Time：2018-11-29 | Source：恒宇国强 | Browse：871954
There are two wiring methods for the speed reducing motor, namely, the triangle connection method and the star connection method,
The triangle connection method is that the three-phase windings are connected end to end and connected in turn, so the starting torque is large; The star connection method is to connect the head to head or tail to tail, and the starting torque is small, which can reduce the starting current and voltage. The star triangle starting method is to start the motor whose stator winding is triangle connection.
In delta connection, each winding of three-phase motor bears line voltage (380V), while in star connection, each winding bears phase voltage (220V). When the motor power is the same, the winding current of the angle motor is smaller than that of the star motor.
When the motor is connected to Y-type, the starting torque is only half of the triangle connection, but the current is only about one third of the triangle connection. When starting with triangle, the current is 4-7 times of the rated current, but the torque is large. The speed is the same, but the torque is different.
Triangle connection
The triangle connection method of motor is to connect each phase winding end to end in turn, and lead out each connected point as three phase lines of three-phase electricity. When the motor is connected in triangle, the phase voltage is equal to the line voltage; The line current is equal to three times the phase current of the root.
Star connection
The star connection method of the motor is to connect one end of each phase winding at one point, and the other end of each phase winding is used as the outgoing line, which is three phase lines respectively. When star connected, the line voltage is three times the root of the phase voltage, and the line current is equal to the phase current.
Star connection is often used in small power, high torque motor or high power motor when starting because of its small output power. In this way, the loss of the machine is small, and the triangle connection is used after normal operation. This is often referred to as the star triangle start.
Selection of motor connection method
Is a three-phase motor, single-phase motor does not have the above two kinds of connection.
Generally, there are more star type connections for motors below 3KW, and angle type connections for motors above 3KW. According to the regulation, the motor larger than 15kw needs star starting angle operation to reduce the starting current.
There are small motor angle start, if you want to connect in three-phase 220 V power supply voltage, must be connected into a star.
In our country, generally, the smaller motor below 3-4kw (kw) is required to be connected into a star, and the larger motor above is required to be connected into a triangle.
Triangle connection, help to improve the motor power, the disadvantage is the starting current, winding withstand voltage (380V) big! Increased insulation level!
The star connection method is helpful to reduce the withstand voltage (220 V) of the winding, reduce the insulation level, and reduce the starting current; The disadvantage is that the motor power is reduced!
Therefore, most of the low-power motors below 4kw adopt planetary connection method. The triangle connection method is adopted for those larger than 4kw. When the motor with triangle connection is started under light load, Y - △ is used to reduce the starting current. Light load is the condition, because the torque of Y connection method will be smaller, the purpose is to reduce the starting current, and Y connection method is used to reduce the starting current.
Just a little
1. Because there is no neutral point when the motor is connected in triangle, the specific method is that the head and tail of the three-phase winding of the motor are connected 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 about 1,73 times of the phase current.
2. When the motor is star connected, because there is a neutral point (the motor is generally three-phase symmetrical load, so the neutral line is generally not led out), the specific method is that the three tails of the three-phase winding of the motor are connected together, and the three heads are connected to the power supply. At this time, there are two voltage levels, namely line voltage and phase voltage, and the line voltage is equal to about 1.73 times of the phase voltage, and the line current is equal to the phase current.
3. It should be noted that the original star connected motor can not be connected into a triangle (if it is connected into a triangle, the phase voltage will rise to about 1.73 times, and the motor will be burned if it runs for a long time).
4. Similarly, the motor with the original triangle connection method cannot be connected into a star (if it is connected into a star, the phase voltage will be reduced to about 1.73 times, and the normal power can not be reached. If it has a rated load, then it belongs to the overload state, and the motor will be burned after a long time).
5. In our country, generally, the smaller motors below 3-4kw (kw) are required to be connected into a star, and the larger motors above are required to be connected into a triangle.
6. Why are the high-power motors connected into triangles? The advantage is that when starting under light load, in order to facilitate the step-down starting (when starting, it is connected into a star, when running, it is changed into a triangle, the motor starting time is very short, it doesn't matter to connect into a star, the advantage is that the starting current can be reduced to 1 / 3, etc.).
In star connection, the phase current is equal to the line current, and the line voltage is three times of the root of the phase voltage. In triangle connection, the line voltage is equal to the phase voltage, and the line current is three times of the root of the phase current. For three-phase symmetrical load, a certain connection can improve the working voltage and power of each phase.
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