Air-conditioning motor is an important noise source of […]
Air-conditioning motor is an important noise source of air-conditioning system, especially the indoor unit of air-conditioning. The frequency of electromagnetic noise 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 air-conditioning motor.There are many ways to identify motor noise. This article introduces a practical load replacement method. There are various reasons for the electromagnetic noise of air-conditioning motors, and their characteristic frequencies are generally related to the power frequency. With a simple load replacement method, you can distinguish between abnormal vibrations caused by uneven magnetic fields or vibrations caused by excessive loads. Taking an air-conditioning indoor fan as an example, the motor noise frequency has a peak value of 600 Hz. Because its frequency does not change with the speed of the motor, and the noise disappears with the power cut off, it is determined as the electromagnetic noise of the motor.
Electromagnetic noise is generally caused by poor electromagnetic design and abnormal electromagnetic vibration caused by loose rotor and rotor. In order to determine the source of electromagnetic sound, the method of changing the load is adopted.The loads that affect air conditioning fans are: (1) the weight of the blades; (2) the position of the center of gravity of the blades on the motor shaft (for static, dynamically balanced blades, the center should fall on the geometric axis), that is, Cantilever length. After replacing the blades with the same weight, the electromagnetic sound of the motor 600HZ completely disappeared at the same speed. The comparison found that the original center of gravity was relatively forward, away from the front bearing of the motor, so that the cantilever of the motor shaft was lengthened, and the eccentricity of the rotor increased when the motor was rotating.
The failure of the motor is an important cause of the noise of the indoor unit of the air conditioner. In order to completely identify the source of the motor noise, in addition to identifying its characteristic frequency in accordance with conventional methods, for some faults with less obvious characteristic frequencies, 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 its characteristic frequency; (2) Excessive motor load (excessive cantilever) will cause electromagnetic noise of the motor, and its vibration frequency may exceed 500HZ.