How is the electromagnetic noise of three-phase asynchronous motor generated? Dalan Motor comprehensive analysis!

Although the electromagnetic noise of the motor will not have any impact on the use. But now everyone is very concerned about environmental protection, noise is undoubtedly the focus of our attention, naturally can not be tolerated or accepted. Today, the editor of Dalan Motor talks about how the electromagnetic noise of the three-phase asynchronous motor is generated.

1. Electromagnetic noise of three-phase asynchronous motor

Electromagnetic noise is mainly caused by the periodical changing radial electromagnetic force or unbalanced magnetic pulling force causing the magnetostriction and vibration of the iron core. Electromagnetic noise is also related to the vibration characteristics of the stator and rotor. When the excitation force and natural frequency resonate, even a small electromagnetic force will produce a lot of noise.

2. Electromagnetic noise excited by magnetic field force waves

If there are two harmonic magnetic field orders νa and μa, they will cause two rotating force waves, the order is νa + μa and νa-μa. Low-order force waves are the main reason for the electromagnetic noise of the motor, because the lower the number of force waves, the longer the distance between the two adjacent fulcrums caused by the bending deformation of the iron core, the worse the corresponding rigidity of the iron core, the greater the deformation and vibration .

3. Radial force of magnetic field and noise radiation

Any magnetic field in the air gap can be expressed as a sinusoidal distributed rotating magnetic field, and the radial force generated by the interaction of these magnetic fields can be expressed as

fγ = FγCOS (γθ-ωt-φf) .................. (1)

Where Fγ——Amplitude of radial force wave

γ-the number of force waves (that is, the number of force wave poles)

θ——the angle between the propagation direction of the sound wave and the positive normal of the area element of the imaginary closed surface around the sound source

ω——force wave angular frequency φf——spatial phase of force wave

The sine-distributed rotating force wave represented by formula (1) rotates at the angular velocity ω / γ along the air gap circle, and the frequency of the radial force at any point on the air gap circle changes with time is f = ω / 2π.

4. Radial force generated by the fundamental magnetic field

The fundamental wave (p-pole pair) magnetic density amplitude is the air gap magnetic density Bδ, the radial force wave order γ = 2p, that is, the force wave order is 4p, the force wave frequency f = 2f1, and the force wave amplitude Fγ = Bδ2 / 4μ0, the average radial force acting in a “force pole” of the air gap circumference in the unit length of the iron core is

Fγa = 2 / π · Fγ · πDi1 / 4p .................. (2)

Di1 in formula (2) —— inner diameter of stator core

5. Vibration caused by radial force

Alternating radial force waves act on the stator and rotor cores, causing periodic deformation of the core over time, that is, vibration occurs. The vibration frequency is the frequency of the radial force waves. The rotor core has good rigidity and its deformation can be ignored; the stator core has a thin-walled ring and poor rigidity, and its vibration is the main cause of electromagnetic noise.

6. Noise radiation

The vibration generated by the electromagnetic force is transmitted to the surrounding space by the motor, causing the vibration of particles in the air to generate sound waves. When the frequency of the sound wave is between 20 Hz and 20 kHz, it can be felt by the human ear. This is electromagnetic noise.

----- Responsible Editor: Dalan Oil Pump Motor 02-Procurement Consultant

Copyright http: / (Dalan Motor) Reprint, please indicate the source

================================================== ================================================== ======

Stainless Steel Flange

A flange can also be a plate or ring to form a rim at the end of a pipe when fastened to the pipe. A blind flange is a plate for covering or closing the end of a pipe. A flange joint is a connection of pipes, where the connecting pieces have flanges by which the parts are bolted together.

Although the word flange generally refers to the actual raised rim or lip of a fitting, many flanged plumbing fittings are themselves known as 'flanges':

There are many different flange standards to be found worldwide. To allow easy functionality and interchangeability, these are designed to have standardised dimensions. Common world standards include ASA/ASME (USA), PN/DIN (European), BS10 (British/Australian), and JIS/KS (Japanese/Korean). In the USA, ANSI stopped publishing B16.5 in 1996, and the standard is ASME B16.5

Stainless Steel Flange

Stainless Steel Round Tube Flange,Forged Stainless Steel Flange,Stainless Steel Welded Flange,Galvanized Stainless Steel Floor Flange

Yixing Steel Pole International Trading Co., Ltd ,