The phase of a motor refers to the direction and number of magnetic poles contained on the motor rotor. Generally speaking, the number of phases of a motor determines its output power and excitation mode. In a three-phase electric system, the three phases are interspersed with each other, so that the motor can generate efficient rotating power. Therefore, when selecting the motor, it is necessary to consider the required power and speed and select the corresponding phase number.
In addition to affecting the power and speed, the phase number of the motor will also affect the running stability and load capacity. Because the number of phases of the motor determines the number of coils on each pole, and the change of the number of coils may affect the efficiency and reliability of the motor when it bears the load. Generally speaking, multiphase motors can bear higher loads, but they are also more complicated and expensive.
For some applications that need low power but high precision control, such as robots and medical equipment, two-phase or four-phase motors are the most common choice. This is because these motors can not only produce high-efficiency rotating power, but also provide relatively high accuracy and reliability at critical moments. In addition, two-phase or four-phase motors are small in size, light in weight and easy to install and operate.