Motor Noise and Vibration Test Research

Some factors, such as friction, vibration, and so on, can result in the fault and abnormal noise in the motor. Based on the detection and analysis of noise and vibration, we can identify and eliminate the faults of the motor. This is helpful not only to ensure the completion of production tasks, but also to prevent accidents. In this paper, we briefly introduce the motor noise generation principle. A laptop computer and LabVIEW software are used to design the experiment system to detect and analysis the noise and vibration of motor. External microphone and computer with sound card constitute noise detection system hardware. Vibration sensor and the data acquisition card constitute vibration detection system hardware. LabVIEW software combined with FFT analysis is used to realize the noise signal acquisition, recording and spectral analysis. Detecting and analyzing the noise of the permanent magnet DC motor and three-phase asynchronous motor proves that the motor noise and vibration detecting experimental platform is fully meet the requirements of motor test and research. This detection and analysis system has a good man-machine interface and strong operability.


Introduction
At present, the motor is the main power in the industrial and widely used in social production [1][2].When the motor works, it brings noise, the motor vibration and noise problem will cause vibration and noise problem of related products, which may affect product quality.Motor noise and vibration research is very complex, involving the electromagnetic, mechanical vibration, acoustics, mathematics and many other disciplines.In general, the noise of analysis is more difficult than vibration analysis, and the motor of the complexity also increased the difficulty of research.
With the development of the virtual instrument technology, a virtual test system constructed by virtual instrument software has been becoming a trend in recent years [3][4][5][6][7].The permanent magnet DC motor and three-phase asynchronous motor as the object in this paper, using the Lab VIEW software to research the system noise and vibration problems.

Motor Noise Mechanism Analysis
When the motor operates, there are usually multiple noise sources at the same time.They can be divided into three categories [8]: (i) Electromagnetic noise: When power is applied to the motor, there are electromagnetic force in the air gap between the stator and rotor.This will generate rotational torque wave or pulse wave and cause the vibration of the motor and emit noise.This type of noise is called electromagnetic noise.The amplitude and frequency of electromagnetic noise are influenced by the motor air gap within the harmonic magnetic field in the air gap of the motor, the amplitude of the electromagnetic torque, frequency, and the number of poles and the vibration characteristics of the stator.(ii) Mechanical noise: mechanical noise is mainly caused by the bearing and brush of the motor.The mechanical noise is related to the materials, manufacturing quality and the assembly process of the motor.(iii) Air dynamic noise: It is produced by the cooling fan in the motor.The influence factors include the fan type, the import and export structure design of the fan and ventilation.In high speed motor, air dynamic noise is the dominant noise.
Here, noise classification is give out in Table 1 [9].
Table 1.The motor noise and vibration spectrum analysis

Motor Noise and Vibration Test System 3.1. Noise Detection Hardware
The noise test system is constructed by a microphone and a laptop as shown in figure 1.
Figure 1.The hardware of noise testing system

Noise Detection Software
LabVIEW can help users quickly realizing the real time signal acquisition [10], analysis and display.The LabVIEW noise acquisition and analysis procedure consists of (here, list maim module) as shown in Figure 2.After we know the frequency component of the environment, we add the power on the motor.In one minute later, the motor is into its steady state and we test the noise waveform.Then we turn off the power, the motor continues to rotate for a short period.We type the noise wave form this period.

Noise Experiment of Three-Phase Asynchronous Motor
The experimental motor is a Y90S-4 three-phase asynchronous motor.The basic parameters are listed as follow.
Rated  The humidity of the environmental is 20% and the temperature is 22 0 .Figure 7 gives out the electromagnetic noise and mechanical noise of the three-phase asynchronous motor.
(c) Three-phase asynchronous motor mechanical noise time-domain graph (d) Three-phase motor mechanical noise spectrum analysis diagram  The vibration and noise of permanent magnet DC motor is caused by the unbalanced magnetic force of switching coil, and also caused by the electromagnetic vibration of the coil.The coil of the permanent magnet motor is 3 phase in general, most of the switching time is a square wave or PWM wave [18].The magnetic field strength of the switching time will produce large fluctuations, which causes the vibration of the motor and the electromagnetic noise.
The factors of the causing noise and vibration of the thee-phase asynchronous motor includes fundamental magnetic flux, high-order harmonic of the electromagnetic noise, electromagnetic imbalance and mechanical imbalance [19].
The noise and vibration test system can be used to evaluate the condition of different motors.

TELKOMNIKA
ISSN: 1693-6930  Motor Noise and Vibration Test Research (Zhongjie Wang)91This waveform is the mechanical noise and environmental noise[16][17].Because we have known the environmental noise, we can obtain the electromagnetic noise and mechanical noise easily.

Figure 6
Figure 6 gives out the running noise of the permanent motor.Figure (a) gives out the time domain waveform of the electromagnetic noise.Figure (b) gives out the frequency spectrum of the electromagnetic noise.There are plentiful frequency components distributed in the frequency of 50Hz ~2500Hz in electromagnetic noise.The peak frequency is at about 900 Hz and the peak is about 320 dB.Figure (c) gives out the time domain waveform of the mechanical noise.Figure (d) gives out the frequency spectrum of the mechanical noise.The peak frequency components are at about 90 Hz and the peak is about 230 dB.
Figure 6 gives out the running noise of the permanent motor.Figure (a) gives out the time domain waveform of the electromagnetic noise.Figure (b) gives out the frequency spectrum of the electromagnetic noise.There are plentiful frequency components distributed in the frequency of 50Hz ~2500Hz in electromagnetic noise.The peak frequency is at about 900 Hz and the peak is about 320 dB.Figure (c) gives out the time domain waveform of the mechanical noise.Figure (d) gives out the frequency spectrum of the mechanical noise.The peak frequency components are at about 90 Hz and the peak is about 230 dB.

Figure 6 .
Figure 6.The running noise of the permanent magnet motor