starting noise
starting noise
(OP)
Does anyone know what causes electric motor starting noise? The noise to which I am refering is that short "whine" or "chirp" which happens when a motor is accelerating to no load speed from a dead stop. It seems to occur mainly 60 hz line fed 3 phase motors.
Any input would be appreciated.
Any input would be appreciated.





RE: starting noise
Fr start = F
F run = s * F
Were: Fr start = rotor circuit frequency at start.
F= Line frequency ( 50, 60 HZ)
s = Motor slip
F run = Motor steady running frequency ( almost zero at no load condition)
RE: starting noise
Principle of induction
RE: starting noise
Of course various mechanical conditions can contribute to start up noise. These include belt vibration, bearing defects, resonances to VFD modulating frequencies and more.
Is your concern academic, or do you suspect a problem?
RE: starting noise
RE: starting noise
Thanks for your replies. We just recently comlpeted a new design for a new customer. Its a 220V three phase subfractional hp model running at 3600 rpm. no load current is .75A. the stator core is laminated iron. The windings are connected Y. The rotor cores are cast laminated iron. I've noticed what I've always called "starting noise". While this is considered a defect here no one (myself included) can give a definitive answer as to what the cause is. We've tried various things to fix the problem in the past...all with limited success
RE: starting noise
RE: starting noise
It is a good area to study noise therefrom.
A starting Reference for the motor noises is:
M. G. Say "Alternating Current Machines," John Wiley & Sons, 1978, page 293 "Noise":
Mechanical Forces
Magnetic Forces
Aerodynamic Noise
All of the above noises vary during the motor start. However, the Mechanical Forces are heavily dependent on the motor speed implying the biggest noisemaking origin.
RE: starting noise
There are many forces generated at RBPF and RBPF +/-2*LF.
As machine speed increases these frequencies increase through resonances of various parts.
I would think spectral analysis by measuring the sound and attempting fft would be challenging when the frequencies you are trying to measure are changing over time (during a start).
Another thing is the unbalanced magnetic pull is higher during starting for a variety of reasons. If a rub is going to occur it is more likely at start.
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RE: starting noise
You are correct that the frequencies would change as the rotor speed increases.
If the sound lasts long enough for you to notice, than I expect you will be able to capture it in a waterfall plot or perhaps a peak hold plot. The waterfall should do the job. You can trade off spectral resolution vs speed to ensure that you get the data you need.
If you capture a sound file than you can play around with analytical settings without the need to constantly restart the motor.
In addition, you can probably capture the data as vibration using an accelerometer.
After you capture data, you can use sound generating software to recreate the frequencies you have measured and compare them with what you are hearing. This will serve as a useful proof of the data.
RE: starting noise
RE: starting noise
If there is a dramatic reduction in noise, then it seem reasonable to conclude that electromagnetic noise is likely the cause. If not, then it seems reasonable to focus more on mechanical sources: windage, resonances, bearings.
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RE: starting noise
The problem could be the motor design.
The magnetic circuit should be constructed from insulated high permeability laminated steel ( not iron). The yoke cross section is very important for two poles it could saturate if marginal. The relation of stator and rotor slots is important for noise and torque. The air gap, span, coil grouping and rotor skew play a role with smooth operation too.
RE: starting noise
http://www.itee.uq.edu.au/~aupec/aupec02/Final-Papers/N-Hashemi1.pdf
for:
Using a PWM inverter makes it possible to run the machine at different speeds, but this will be noisier than with a purely sinusoidal supply [7, 11-13].