Several simple ways to change three-phase motors to single-phase motors


Dalan Motor Xiaobian introduces several simple and easy methods to change the three-phase motor to single-phase operation without changing the internal winding of the motor:

The low-power three-phase motor can be changed to a single-phase motor, but the power should be smaller. The phase A is used as the phase line, the phase C is the neutral line, the B phase is connected to the capacitor, and the capacitor is connected back to the A phase line. If it is reversed, the AB is reversed. Just fine. ABC is an arbitrary capacitor capacity = watts * 0.07 = micro method.

The 380V motor removes the ground wire (usually the thickest and longest one) and has three heads. Connect any two heads with a 220V live wire. Then use the two legs of the capacitor to connect to the empty head and the other end to any of the 220V heads. If the motor is found to be reversed, change the head.

Use a three-phase motor as a single-phase motor. That is, short 123, 45 to 220 volts, 6 through the capacitor (20 ~ 40 micro-450 volt electrolytic capacitor) connected to 4 (with 5 reverse), but the power is much smaller. If you don't turn, use the same method to pick up 789.

Since the three phases are changed to single phase, there are main coils and auxiliary coils, and the coils work differently. Long-term use will result in different degrees of aging of the coils. After the three-phase is changed to single phase, the output power will be greatly reduced, and its own load will also increase, and the load range during use will be small.

Formula: Capacitance (micro method) = rated current / (rated voltage * power factor), the parameter in the formula is on the motor nameplate, the power after the change is 50-90% of the original power, mainly depends on the power factor, the speed constant.

1. Adding capacitance method: At this time, the output power of the motor is 55% to 90% of the nominal power. C1 is the running capacitor, and C2 is the starting capacitor. Both power capacitors are required, and the withstand voltage must be no less than 450V. The capacity of C1 and C2 can be estimated by the following formula: C1=1950I/U×cosθC2=(1~4) C unit (uF) in the formula C1; I is the rated current of the motor (A); U is the rated voltage of the motor (V) ); cos θ is the power factor, generally taking 0.5 to 0.7. In particular, for a three-phase asynchronous motor having a power of 1 KW or less, C2 may not be used, but the value of C1 is appropriately increased. It can be estimated by C1=13I, where the unit of C1 is (uF) and I is the rated current (A) of the original motor. The capacity of the capacitor should be selected properly, otherwise the motor will not operate normally and the temperature rise will be too high.

For a small-power three-phase asynchronous motor with only a few hundred watts, the capacitance can be selected according to C=0.06P (Y-connected) and C=0.1P (Δ-connected). The unit of C is (uF), P is Motor power (W). The capacity of C1 and C2 can be the same. If the speed is too fast, the load can be increased or the capacity can be reduced. If the speed is too slow, the load can be reduced or the capacity can be increased.

Second, the improved addition capacitance method: In order to improve the output power of the motor, the selection of C1 is the same as C1, C2, C3, and R in "Method 1": C2 = (2 ~ 4) C1 C3 = 2C1 R = 0.25U/I

Third, the capacitance, inductance phase shift method: the use of an inductor (should pay attention to the current carrying capacity of the inductor L) and a capacitor to obtain a three-phase symmetrical voltage from the single-phase power supply, the wiring method as shown below, this method is more adaptable Strong, but to configure the core inductor, you can also use a single-phase auto-transformer instead. This method should be used for larger motors. For example, when the motor is 2.2 KW with "△ connection", the capacitor C selects 254uF, and the inductance L selects 78mH. Capacitor C, inductor L can be selected as follows: C = (Ssin (60 + φ) × 10 ^ 6) / (1.5WU ^ 2) L = (1.5U ^ 2) / (WSsin (60 - φ)), Where the working capacitance of C is (uF); L: inductance (H); S: rated power of motor (VA); φ: power factor angle (degrees) when rated load of motor; W: angular frequency (W = 2πF=314).

Fourth, with the resistance method: the choice of resistor R should be appropriate. The value of R can be selected to be 5 to 10 times the resistance of the two-phase winding.

5. Adding switch method: When the start switch K is installed, it can be connected to single-phase operation.
















----- Editor-in-Chief: Dalan Oil Pump Motor 02-Procurement Consultant

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