In order to improve the quality of the motor, in recent years, the motor noise has been included in one of the quality assessment indicators, especially for the motor operating environment and close contact with people, the motor noise has become a very important assessment requirements.

In order to control the noise of the asynchronous motor, in addition to choosing a suitable fixed rotor groove in the design, the way of inclined groove can be used to reduce the electromagnetic noise of the motor. However, it is still necessary to further test and verify how much groove inclination is more suitable.

Under normal circumstances, the slope of the rotor slot of the asynchronous motor can be a stator tooth pitch, which can basically meet the requirements. However, in order to further improve motor noise, it is necessary to explore the optimal groove slope, which requires a lot of calculation and verification.

From the perspective of production and manufacturing, the production and processing of straight groove motors is relatively simple, but when necessary, it is necessary to skew the stator slot or rotor slot. It is relatively difficult to skew the stator slot, so in most cases, the rotor slot is tilted. The skew of the rotor slot is generally achieved by machining the skew keyway on the shaft, and the enterprise with more advanced equipment adopts spiral punching to achieve the rotor core manufacturing link.

Motor noise is always a difficult problem to solve, it is mainly caused by electromagnetic, mechanical, ventilation three reasons. Electromagnetic noise in asynchronous motor is caused by the electromagnetic force wave caused by the interaction of harmonic magnetic field established in the air gap between stator and rotor currents, which causes the vibration of the core yoke and forces the surrounding air to vibrate. The main reason is due to improper groove matching, eccentricity of fixed and rotor or too small air gap.

Electromagnetic noise is caused by changes in time and space, and by the magnetic tension between the various parts of the motor. Therefore, for 3 phase asynchronous motors, the causes of electromagnetic noise include:

● The radial force wave of the magnetic field in the air gap space causes radial deformation and periodic vibration of the stator and rotor.

● Radial force waves of higher harmonics in the air gap magnetic field act on the rotor core, causing them to produce radial deformation and periodic vibration.

● The deformation of different order harmonics of the stator core has different natural frequencies, and resonance is caused when the frequency of the radial force wave is close to or equal to a certain natural frequency of the core.

● The stator deformation causes the surrounding air vibration, and the electromagnetic noise is mostly load noise.

When the core is saturated, the component of the third harmonic is increased, so that the electromagnetic noise is increased.

● The rotor slots are open, and there are many "slot opening waves" generated under the action of fundamental wave magnetic potential in the air gap magnetic field. The smaller the air gap, the wider the slot, and the larger their amplitude.

●This avoids the problem, in the design stage of the product through some effective means to improve, such as: select a reasonable magnetic flux density, choose the appropriate winding type and the number of associated ways, increase the number of stator punching slots, reduce the harmonic distribution coefficient of the stator winding, appropriate processing of the stator rotor air gap, select the stator and the rotor slot, the use of rotor slot and other specific measures.