# How to Perform NVH Modeling & Simulation using JMAG

This guest contribution on Innovation Intelligence is written by Yusaku Suzuki, Marketing Manager at JSOL Corporation, developers of JMAG. JSOL is a member of the Altair Partner Alliance.

This blog post presents the vibration noise analysis where electromagnetic force obtained from JMAG acts as the vibratory source. I’d like to focus on motors and transformer for the first entry to describe modeling methods to get a grasp on an analysis of resonance from electromagnetic force and Eigenfrequency modes. It would be wonderful if electromechanical designers not involved in electromagnetic vibration took it on or joined with machinery designers to devise methods to counteract vibration noise.

### Flow of the NVH analysis using JMAG software

JMAG is not merely a software with electromagnetic field analysis functions that performs highly accurate calculations, it also has structural analysis functions, and so is capable of carrying out all calculations related to vibration noise in electrical equipment. The flow of the NVH analysis into JMAG is showed below:

Figure 1: Flow of NVH analysis using JMAG.

### Electromagnetic force calculation for the vibration noise analysis

One of the sources of the vibration and noise produced by electrical machines is the Electromagnetic source (electromagnetic forces, magnetostriction forces, etc.). In JMAG, you will create an electromagnetic field analysis to obtain accurate electromagnetic force at the frequency of the vibration or noise. So, confirming the electromagnetic force mode is extremely important in terms of accurately discerning the vibratory force.

Figure 2: Electromagnetic forces on PM motor.

Excitation noise is caused by magnetostriction and magnetic attractive forces near the joints of the cores. In the particular case, when defining the magnetostriction properties of the core, we were also able to obtain the magnetostriction distribution.

Figure 3: Electromagnetic forces (a) and Magnetostriction forces (b) on Transformer.

### Eigenmode calculation for the vibration noise analysis

With JMAG you will build an eigenmode analysis model to obtain an eigenfrequency and eigenmode values. Electromechanical systems are made up of many different parts, so decide on the modeling method from the aspect of individual parts. Assembling individual parts and comparing the actually measured eigenfrequency and eigenmode with the analysis results to always confirm the suitability of the modeling method.

Figure 4: Eigenmode Analysis on Motor and Transformer.

### Vibration Noise/Sound Pressure Analysis

In a vibration/sound calculation, use electromagnetic force and eigenmode obtained respectively from magnetic field and eigenmode analysis model to calculate the vibration and the sound pressure on the specific face. Using electromagnetic force conditions from JMAG’s structural model analysis function can be applied for mapping electromagnetic force in a vibration analysis where modeling methods are different. In the results, we can also check how the parts is deformed in a particular frequency mode

Figure 5: sound pressure distributions: (a) PM Motor at 3600Hz; (b) Transformer at 10KHz.

Coupling with Other CAE Software

We have described coupling using only JMAG’s structural analysis Modules, but note that if you already used other structural analysis software, it is possible to import the electromagnetic force analysis results obtained from JMAG to your software in order to perform a vibration noise analysis. When using another structural analysis software like OptiStruct, Nastran, Abaqus or LMS Virtual.Lab, output an electromagnetic force distribution file using JMAG’s Multi-Purpose File Export tool. Using this tool will output the electromagnetic force distribution in a Nastran, CSV or Universal(.unv) file format.

Figure 6: Mapping Electromagnetic Force and Results from Altair’s OptiStruct.

### Conclusion

This blog post refers only to a Motor and transformer single cases, but it was a description of modeling methods to gain an idea of how an electromagnetic force and eigenfrequency in electric machines create a resonance phenomenon. Electromagnetic force naturally needs countermeasures, being the vibratory force, but steps also need to be taken mechanically against vibration and these can be examined using JMAG. JMAG’s structural analysis function enables geometry creation or condition specification using the same operations as for a magnetic field analysis. When examining a structural analysis as an extension of a magnetic field analysis, there is no need to learn any new operational procedures. Of course it’s also possible to couple with other software formats that specialize in structural analyses and we plan to make it even more powerful moving forward.

Watch the below video for a short introduction on JMAG-Designer: