As a ventilation and cooling equipment often used in daily life, Commercial Fan play an important role. Especially in the current humid and sultry environment, Commercial Fan can effectively accelerate air circulation, improve air quality, reduce air humidity, and reduce The role of indoor temperature. Although Commercial Fan have many functions, they also have some minor flaws, such as noise issues. The noise of Commercial Fan mainly comes from the noise generated when the motor is running, which not only affects the working efficiency of the fan, but also affects people's mood. Therefore, reducing the motor noise of Commercial Fan is a very important task.
Electromagnetic noise is caused by magnetic waves acting in the stator, rotor and air gap. When the frequency of this magnetic wave is close to or the same as the natural frequency of the stator core itself, it will excite the resonance of the iron core and generate greater electromagnetic noise. Its performance characteristic is that the electric fan makes a "buzzing" sound with a whistling sound when it is running. The size of electromagnetic noise is related to factors such as the number of stator and rotor slots, rotor skew slots, and winding wiring methods.
1. Reasonable selection of slot number and coordination
To achieve low noise, choosing a suitable slot fit is one of the keys, in order to avoid the generation of synchronous torque.
The greater the difference between the number of stator slots and the number of rotor slots or the greater the number of rotor slots, the higher the harmonic order relative to the rotor teeth and the smaller the harmonic amplitude, which is beneficial to the overload capacity of the motor and noise reduction, but it will Increase the rotor tooth vibration loss. If the number of rotor slots is too large, it will cause certain difficulties in the manufacturing process. At present, the stators of domestic electric fan motors mainly include 8 slots and 16 slots, and the slots matched with the rotor are 8/17, 16/22, etc. The finite element method is used to calculate the natural frequency of the stator, and the machine-assisted analysis shows that with the 16/22 slot fit, the main force wave frequency of the electromagnetic sound produced by the motor is lower than the natural frequency of the motor stator, which can avoid the occurrence of mechanical resonance. .
2. Select the appropriate rotor chute
Appropriate rotor slots can effectively reduce electromagnetic noise caused by rotor tooth harmonics and reduce torque pulsation. Generally, the number of inclined slots in the stator is 1.1 to 1.3 slots. However, it should be noted that if the number of rotor slots is too large, the maximum torque and power factor will be reduced.
3. Reasonable stator winding form
Whether the speed is controlled by the reactor method or the tap method, the closer the magnetic field of the stator winding in the air gap space between the stator and the rotor is to a circular magnetic field, the lower the noise will be. On the contrary, if it is an elliptical magnetic field, the greater the ellipticity, the more obvious the noise will be. For tapped speed-regulating motors, the speed-regulating windings should also be distributed under each pole in a sinusoidal proportion, which can weaken the electromagnetic noise of the motor at medium and low speeds.
