# Article: JMAG A to Z

2013-07-02

## Issue 11 Electric Field Analysis from A to Z

JMAG continues to evolve with each passing day. There may be functions in JMAG that even those who have already been using it will learn for the first time. There are also some useful procedures that are not well known yet. Why don't we aim at making operations more efficient by becoming familiar with new functions that we don't know about?
In this series, I would like to give a description of "Things we should know" about JMAG, as well as some advantageous applications.

### Overview

If you asked many JMAG users how to go about conducting an electric field analysis in JMAG, it's fair to say they wouldn't be able to offer a precise answer immediately. People use JMAG for evaluation of magnetic phenomena, but there are only limited numbers of products that need to make allowances for electric field analyses to it's rare for those involved in magnetic field analyses to reach out to electric field analysis, too. Although the names of electric field analysis and magnetic field analysis have a close resemblance, they're handling different phenomena and are evaluated in a divergent manner.
This issue of A to Z will focus on how to handle particular types of phenomena using JMAG's electric field analysis, as well as introduce material properties and various types of conditions so we can get you acquainted with electric field analysis.

### Analysis model and type of analysis

Only 3D geometries can be handled. JMAG's electric field analysis handles three types of analyses: static, frequency response and current distribution. Right click the JMAG-Designer Project Manager, select the type of analysis for the electric field analysis and create the applicable study.
In a static analysis, by giving an input electric potential/electric charge to a static unchanging over time, it enables obtaining the surrounding electric potential/electric charge distribution (Fig. 1).
In a frequency response analysis, the analysis subject is given an electric potential difference with sinusoidal variations, which enables obtaining the electric potential distribution, electric field distribution and current density distribution generated inside the target.
In a current distribution analysis, giving the subject -- a steady state current field with no gushing or absorption -- electric potential/electric charge enables obtaining the current distribution from the subject. Only conductor areas where current flows (or areas in liquids with conductivity) are modeled in current distribution analyses and modeling insulators like air is unnecessary. Allowance is not made for magnetic flux generated by the current flow.

Fig. 1 Positive and Negative Poles and Electric Potential Contour Plot Settings (Static Electric Field Analysis)

### Material Properties

Material properties used in the electric field analysis are electrical properties only. Specify the two types of electrical properties, electric conductivity [S/m] and relative permittivity. Static analyses handle relative permittivity only. Frequency response analyses use both electric conductivity and relative permittivity. Current distribution analyses handle electric conductivity only and calculates current flow when an electric field generates.

### Boundary Conditions

Regardless of the analysis type in an electromagnetic field analysis, the electric potential forming the standard must be set. For boundary conditions other than for electric potential, decide on selections depending on the type of analysis.

#### Electric Potential Boundary

Can be used with all analysis types. Sets the electric potential for the place that is specified. Electric potential that will become a standard is necessary in electric field analyses, so specify at least one place. Settings are possible for all parts, part surfaces, edges and vertex.

#### Current Boundary/Current Density Boundary

Can only be used in a current distribution analysis. Specify the inflow and outflow from a specified place. Part faces can be specified. This report describes two divergent examples of current paths. It is possible to confirm that as the current flows from the left the upper current path is long and that most of the current flows on the lower current path (Fig. 2).

Fig. 2 Divergent Current Path Model (left) and Current Density Vector Diagram (Right)

#### Electric Field Boundary

Useable in static and frequency response analyses. Allows specifying of the electric field in a specified face. In a frequency response analysis, you can also set the phase of an electric field. Part faces can be specified. It is possible to obtain the electric potential distribution to satisfy the specified electric field.

#### Natural Boundary

Can be used with all analysis types. The specified face will be the face in the direction the current flows in. The part face can be specified. This is used frequently in partial models (Fig. 3).

Fig. 3 The Central Line Forming the Natural Boundary and Electric Potential Contour Settings (Left) and Enlargement of Center Vicinity Electric Field Vector Settings (Right)

#### Symmetry Boundary

Can be used with all analysis types. The specified face will be the one in which the current can be expelled vertically. A uniform electric potential is set for the boundary. An electric potential phase can also be specified together with its amplitude in a frequency response analysis. The part face can be specified. Usable when creating a partial model. Here is a one-quarter model with a central boundary between electrodes fixed at 50 (V) (Fig. 4). Note the electric field distribution is different from that of an example of a natural boundary with upper and lower symmetry (Fig. 3). When there is distribution of electric potential on the boundary surface, avoid using a partial model with a symmetrical boundary.

Fig. 4 Natural Boundary, Symmetrical Boundary and Electric Potential Contour Settings (left) and Enlargement of Center Vicinity Electric Field Vector Settings (Right)

#### Periodic Boundary (Rotation) and Periodic Boundary (Translation)

Can be used with all analysis types. Specify the model cross-section and periodic angle when the analysis target is a partial model. Narrowing the analysis scope cuts calculation time and the memory needed for calculation.

### Charge conditions

Giving a charge to a particular part or surface can generate an electric field.

#### Surface Charge

Can only be used in a static analysis. Setting a charge for a specified face generates an electrical field.

#### Volume Charge

Can only be used in a static analysis. Setting a charge for a specified part generates a surrounding electrical field.

### Output

This function calculates the physical amount of a particular scope from an electric field distribution obtained from the results of an electric field analysis.

#### Surface Charge

Can be used with all analysis types. Obtains an electromagnetic force generated in a specified face.

#### Electromagnetic Force

Can be used with all analysis types. Obtains a charge generated in a specified part.

#### Current

Can only be used in a current distribution analysis. Calculates the current amount passed through a specified face.

### Modeling

It's possible to allocate special attributes to certain parts and conduct an analysis of these.

#### Perfect Conductor

Useable in static and frequency response analyses. Calculation occurs on the assumption that specified parts will have the same electric potential as the entire object. This shows an example of a perfect conductor, the long, thin object in the center of the item giving 100(v) to the right end and 0(V) to the left end (Fig. 5). It's possible to confirm the electric potential is uniform inside the conductor (Fig. 6).

Fig. 5 Analysis Model (left) and Electric Potential Contour Settings (right)

Fig. 6 Section Graph Positioning (left) and Electric Potential Graph Cross-section (right)

#### Insulation

Can only be used in a current distribution analysis. A specified face becomes an insulator and current no longer passes through it.

### In Closing

In this edition I have talked about the conditions used in an electric field analysis and described the meaning of its functions and how to use them. We hope you will have a look.

(Hiroshi Hashimoto)