Can a three-phase motor be converted to two-phase? How to connect a three-phase generator to two-phase electricity?

Three-phase 380V motors are widely used. In some cases where there is only a single-phase power supply, three-phase motors can be converted into two-phase motors through some methods. However, there are also some problems. For example: difficult to start, insufficient output power, only about 60%, low torque, easy to heat, and long-term operation affects the life span.

Renovation Prerequisites

First, you must make sure that the three winding ends of the three-phase motor are correct. If the three-phase motor ends are wrong, the motor will burn out after the change.

If the three-phase motor terminal has not been disassembled, or it is connected to three-phase power and operates normally, it means that the terminal is correct. You can also directly look at the terminal number arrangement in the motor terminal box. The correct arrangement is as follows (pay attention to the wire markings):

wiring

There are two connection methods for converting three phase to single phase: Y type and △ type. Let's first look at the Y type connection, as shown below:

Let's look at the △ type wiring again, as shown below:

In the above wiring, the neutral and live wires can be swapped; if you need to reverse it, just swap one of the wires connected to the capacitor to the other end of the capacitor.

Capacitor selection

The capacitor should be an oil-immersed metal film paper dielectric capacitor, and the withstand voltage must be above 450V.

The calculation formula for running capacitance is: C=1950I/Ucosφ, where C is the running capacitance (uf-microfarad), I is the rated current value of the motor (A), U is the rated voltage, and cosφ is the power factor, which is generally marked on the motor.

According to experience: a 1KW motor generally uses a capacitor of about 70uf, which can be adjusted according to your load conditions.

suggestion

In principle, any motor below 3KW can be modified, but after a high-power three-phase motor is converted to a single-phase motor, the power will be greatly reduced, the heat will be more serious, and it cannot carry heavier loads, so it is recommended to change to a motor below 1.5KW.

If you need to change to a motor above 1.5KW, you will also need to add a starting capacitor. The starting capacitor is generally about twice the running capacitor.