Pole-changing speed regulation is realized by ch […]
Pole-changing speed regulation is realized by changing the series-parallel relationship of the motor winding through external switch switching. Only step adjustment is possible (generally has two speeds). If the motor is switched from two poles to four poles, the speed will be reduced from about 3000 rpm to about 1500 rpm.
Pole-changing speed regulation is generally based on two speeds, supplemented by valve and baffle adjustment, which is better than simply using the valve and baffle, but there is still potential for energy saving. In addition, due to the complex structure, the efficiency of the pole-changing motor is slightly lower than that of the conventional general-purpose motor.
The method of changing the number of poles of an asynchronous motor to change the synchronous speed for speed regulation is called pole-variable speed regulation. Its speed can only be changed in a stepped manner, not continuously. The basic principle of variable pole speed regulation is: if the grid frequency is unchanged, the synchronous speed of the motor is inversely proportional to the number of pole pairs. Therefore, changing the wiring method of the motor winding to make it run under different pole pairs will change the synchronous speed accordingly. The number of pole pairs of an asynchronous motor is determined by the connection mode of the stator winding, so that the number of pole pairs of the asynchronous motor can be changed by changing the connection of the stator winding. The speed regulation method of changing the number of pole pairs is generally only applicable to cage asynchronous motors. Two-speed motors and three-speed motors are the two most commonly used forms of variable pole speed regulation.