The low-power three-phase motor can be changed to a single-phase motor, but the power should be smaller, the A phase is used as the phase line, the C phase is used as the neutral line, the B phase is connected to the capacitor, and the capacitor return is connected to the A phase line. That's it. ABC is arbitrarily set Capacitor capacity = watt * 0.07 = microfarads.
The 380V motor has 3 heads except for the ground wire (usually the thickest and longest one). Connect any two ends with a 220V live wire and ground wire. Then use the two feet of the capacitor to connect one end to the empty head, and the other end to any head of 220V. If it is found that the motor is reversed, change the head.
Use a three-phase motor as a single-phase motor. That is, short-circuit 123, connect 45 to 220 volts, and connect 6 via capacitors (20-40 microfarads 450 volts electrolytic capacitors) to 4 (reverse connection to 5), but the power is much smaller. If it doesn't transfer, try connecting to 789 in the same way.
Due to the existence of the main coil and the auxiliary coil after the three-phase is changed to the single-phase, the working modes of each coil are different. Using for a long time will lead to different degrees of aging of each coil. After changing from three-phase to single-phase, the output power will be greatly reduced, the load itself will also increase, and the load range during use will be very small.
Formula: Capacitance (microfarads) = rated current / (rated voltage * power factor), the parameters in the formula are those on the motor nameplate, the power after the modification is 50-90% of the original power, mainly depending on the power factor, speed constant.
For low-power three-phase asynchronous motors with only a few hundred watts, the capacitance can be selected according to C=0.06P (when Y is connected) and C=0.1P (when △ is connected), where the unit of C is (uF), and P is Motor power (W). The capacity of C1 and C2 can be the same. If the rotation speed is too fast, the load can be increased or the capacitor capacity can be reduced. If the rotation speed is too slow, the load can be reduced or the capacitor capacity can be increased.
2. Improved method of adding capacitors: In order to improve the output power of the motor, the selection of C1 is the same as that of C1 in "Method 1", and C2, C3, and R are selected as follows: C2=(2～4)C1 C3=2C1 R= 0.25U/I
3. Capacitance and inductance phase-shifting method: use an inductor (pay attention to the current carrying capacity of the inductor L) and a capacitor to obtain a three-phase symmetrical voltage from a single-phase power supply, and connect as shown in the figure below. This method is more adaptable Strong, but to configure the iron core inductance, you can also use a single-phase auto-voltage regulator instead. This method should be used for larger motors. For example, when the motor is 2.2KW and adopts "△ connection", the capacitor C is selected as 254uF, and the inductance L is selected as 78mH. Capacitor C and inductance L can be selected as follows: C=(Ssin(60+φ)×10^6)/(1.5WU^2)L=(1.5U^2)/(WSsin(60-φ)), In the formula, the working capacitance of C is (uF); L: the inductance (H); S: the rated power of the motor (VA); φ: the power factor angle at the rated load of the motor (degrees); W: the angular frequency (W= 2πF=314).
Fourth, with resistance method: the selection of resistance R should be appropriate. The R value can be selected as 5 to 10 times the resistance value of the two-phase winding.
5. Add switch method: Install the start switch K to connect to single-phase operation.
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