Measures to Reduce The Motor Noise

Date: 2022-01-12     From: Longding     Author: admin

Motor noise involves many aspects such as mechanical vibration, physical acoustics, mathematics, electromagnetism, and electronics. Motor noise is not only affected by a moving part of the motor, but also the overall effect of the motor. According to the cause of the noise, motor noise is usually divided into electromagnetic noise, mechanical noise, and ventilation noise.

Types of Motor Noise

1. Electromagnetic noise

Electromagnetic noise is the multiplied frequency sound caused by the vibration of the motor structure caused by the magnetic field pulsation in the motor gap, the alternating electromagnetic attraction between the stator and the rotor, and the magnetostriction. The magnitude of electromagnetic noise is related to the power and series of the motor. For small motors, the power is not large, and the electromagnetic noise is not prominent.

2. Mechanical noise

Mechanical noise is formed by friction, impact, imbalance, and structural resonance of the moving parts of the motor. Its effect on motor noise is second only to ventilation noise.

3. Ventilation noise

When the motor rotates, some protruding parts on the fan and rotor make the air impact and rub to form ventilation noise, which increases with the increase of the peripheral speed of the fan and the rotor. The strength is related to the design of the fan and the ventilation duct.

Measures to reduce motor noise

1. Reduction of electromagnetic noise

A. Matching of the number of stator and rotor slots. The main effect on the vibration and noise of the motor is the force wave with lower vibration order and larger amplitude.

B. Adopt inclined chute. The electromagnetic noise of the inclined stator slot is significantly lower than that of the straight slot, no matter under no-load or loaded state. The stator or rotor with inclined slots can effectively reduce the additional torque and electromagnetic noise caused by the harmonic magnetic field.

C. Increase the motor air gap. The length of the air gap between the stator and the rotor is increased, and the magnetic track of the air gap is reduced, which can reduce the harmonic magnetic flux density of the air gap and reduce the electromagnetic noise.

2. Mechanical noise reduction

A. According to the nature, specification, and use environment of the motor, the balance accuracy of the motor rotor is strictly selected to reduce the noise caused by the eccentricity of the rotor core.

B. Improve the quality of bearings and other components, including the roundness and finish of bearings, slip rings, and commutators.

C. Before assembling the bearing, the bearing should be cleaned and demagnetized, and the corresponding type of lubricating oil should be applied.

3. Reduction of ventilation noise

A. Fans are designed with an odd number of blades, preferably with unequal blade pitches. The fan blades are backward inclined and transitioned with rounded corners.

B. Reasonable design of air duct system to reduce air damping. When changing the direction of the air duct, use a large radius.

C. Add mufflers or sound shields and increase the dynamic stiffness of end caps and covers.