Air-conditioning motor is an important noise source of air-conditioning system, especially the indoor unit of air-conditioning. The electromagnetic noise frequency of the motor is low, and the tone is close to single-frequency pure tone. The working condition of the motor can be judged by identifying the noise of the air-conditioning motor.

There are many ways to identify motor noise. This article introduces a practical load replacement method. There are many reasons for the electromagnetic noise of air conditioner motors, and its characteristic frequency is generally related to the power frequency. Just use a simple load replacement method to distinguish abnormal vibration caused by uneven magnetic field or vibration caused by excessive load. Take the indoor fan of an air conditioner as an example, the noise frequency of the motor has a peak of 600 Hz. Since its frequency does not change with the speed of the motor, and the noise disappears when the power is cut off, it is determined to be the electromagnetic noise of the motor.

Electromagnetic noise is generally caused by poor electromagnetic design and abnormal electromagnetic vibration caused by loose stator and rotor. In order to identify the source of electromagnetic sound, the method of replacing the load is adopted.

The loads affecting the air conditioning fan are:
(1) Wind blade weight;
(2) The position where the center of gravity of the blade is loaded on the motor shaft (for a blade with good static and dynamic balance, its center should fall on the geometric axis), that is, the length of the cantilever. After replacing the blades of the same weight, the 600HZ electromagnetic sound of the motor disappears completely at the same speed. It is found that the original center of gravity is relatively forward, far away from the front bearing of the motor, which lengthens the cantilever of the motor shaft, and when the motor rotates, the rotor eccentricity increases.

Motor failure is an important reason for the noise of the indoor unit of the air conditioner. It is necessary to completely identify the noise source of the motor. In addition to identifying its characteristic frequency according to the conventional method, for some faults with less obvious characteristic frequency, it is necessary to combine acoustic theory and Cooperate with other identification methods. Generally there are the following rules:
(1) For the same motor, the higher the speed, the lower the characteristic frequency;
(2) Excessive motor load (too long cantilever) will cause electromagnetic noise of the motor, and its vibration frequency may exceed 500HZ.