Power Transformer

Problems associated with power transformers are not only related to design matters such as satisfying basic characteristics, but also includes many issues related to testing and maintenance. For example, magnetic flux leakage accompanying increased capacity causes localized stray loss in the tank. A coil’s dielectric strength needs to be verified by a local maximum electric field. The part arrangement between core and coil or magnetic flux distribution also has an effect on vibration caused by the electromagnetic force.
JMAG enables the visualization of the phenomena and ease in moving forward with analyzing causes. It also makes possible quantitative evaluations of temperature rising inside objects or noise where measurement is difficult.

Evaluation Items

Magnetic saturation, eddy current, induced voltage, stray loss, iron loss, magnetostrictive force, power, efficiency, temperature, electric fields

Case Studies / Functions

Stray Loss in the Iron Core

The following illustration shows the loss distribution of the iron core in a short circuit test. It can be observed that the leakage flux from the coil end enters perpendicularly to the plane of the steel sheet resulting in eddy currents generated on its surface. This leakage flux causes local heat generation during operation. By applying anisotropy to magnetic properties and electric conductivity, the behavior of magnetic flux and eddy currents in the laminated iron core can be correctly captured.

Iron Loss Distribution in the Core

Transformer cores sometimes use anisotropic materials which have different material properties in different directions. In a laminated iron core transformer, material isotropy has an impact on losses. In this example, the transformer has a V-notch to join the different leg and yoke components. The analysis shows that iron losses concentrate at these intersections.

Iron Loss Distribution in the Core

Not only confirms iron loss distribution generated in a core geometry, but also capable of separating hysteresis loss and joule loss making up iron loss to evaluate the contribution of each.

JMAG’s function: Anisotropic Magnetic Properties

Defines magnetic and iron loss characteristics in both easy and hard magnetization directions for directional magnetic steel sheets.

Evaluating Magnetic Flux Leakage and Stray Loss

By getting an accurate grasp of the magnetic flux leakage difficult to evaluate in a magnetic circuit, it becomes possible to evaluate stray loss generated in a tank wall. Examining the loss distribution enables design taking into account the optimal positioning relationship between the tank and transformer.

JMAG’s function: Thin sheet mesh

Automatically generates a layer mesh for thin items like the tank or shield plate.

JMAG’s function: Defeaturing

Simplifies complicated geometries such as those for a step lap core.

Evaluating Insulation Durability

Evaluates insulation durability in the transformer, including the coil, from localized electric field distribution.

JMAG’s function: Electric Field Analysis

Evaluates coil’s dielectric strength based on electric field intensity between coils.

Heat Generation Phenomena

Evaluates temperature distribution in places like the core and tank walls through a thermal analysis using core iron loss, coil copper loss and tank stray loss as a heat source.

JMAG’s function: Coupled magnetic field and thermal analysis

Runs a temperature evaluation using iron, copper and stray loss generated in each part as a heat source generation.


Analyzing both vibrations caused by the electromagnetic force and magnetostrictive force enables the contribution of comparisons.

JMAG’s function: Magnetostriction characteristics

Defines strain in magnetic flux density. Coupled magnetic field and structural analysis, linking with LMS Virtual.Lab. Evaluates vibration and noise using electromagnetic force, Lorentz force and magnetostriction equivalent force working on each part as a source of exciting force

Evaluating Electromagnetic Force in the Coil

Transient current generated when applying power generates significant Lorentz force in the coil. It is possible to give a predicted evaluation of the localized wear in the insulating film.

JMAG’s function: Electromagnetic Force Calculation

Calculates Lorentz force applied to the currentflowing through a coil and electromagnetic force on a core.

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    • JMAG Leaflet

    [L-TR-44] Winding Vibration Analysis of a Power Transformer

    Winding vibration originating from a transformer is a vibration phenomenon that uses Lorentz force as the vibration force, which occurs when flux leakage from the winding works on the current inside …

    5 Apr 2019

    • JMAG White Papers

    [W-TR-15] Loss Evaluation of a Transformer Shield Based on the Homogenization Method

    In this paper, each electromagnetic steel sheet of the shield is not modeled; by applying the homogenization method which replaces magnetically and electrically equivalent materials, a realistic mesh…

    27 Mar 2019

    • JMAG White Papers

    [W-SE-72] Reduction of Time Steps by Using Time Periodic Explicit Error Correction Method

    In electrical equipment design, Computer Aided Engineering (CAE) software is used to make the best possible products within allowable timelines.

    • JMAG White Papers

    [W-SE-53] Transition to Steady State in a Short Time

    In the following, it is shown that the steady state analysis results can be obtained with less number of time steps by using the TP-EEC method.

    • JMAG White Papers

    [W-HU-71] Notes on Performance Evaluation and Hardware Selection of JMAG Parallel Solver

    This document can be thought of as pointers and precautions for hardware selection and software operation.

    26 Mar 2019

    • JMAG Users Conference Proceedings

    Analysis of Winding Losses of Shunt Reactor using “Zooming Analysis”


    7 Mar 2019

    • JMAG Users Conference Proceedings

    3D Magnetic Field Analysis of Large Power Transformer with Parallel Calculation Processing

    Hirokazu Hayashida, Fuji Electric Co.,Ltd.

    • Application Catalog

    254 – Vibration Analysis of Oil-Immersed Large Transformer

    This document introduces a case example of evaluating the vibrations of a large transformer. Parts that are usually the source of vibrations are the core, tank, and windings, but this case example fo…

    12 Feb 2019

    • Application Catalog

    235 – Reactor Core Stray Loss Analysis

    In this example, reactor core stray loss is described.

    24 Oct 2018

    • Application Catalog

    203 – No-Load Test Analysis of Power Transformer

    This example focuses on modeling in the analysis of no-load tests in JMAG and obtains the iron loss distribution, current, excitation conductance, and excitation susceptance that can be acquired from…

    • Application Catalog

    221 – Confirmation of the Influence in the Reduction of High-Frequency Resistance of a Magnetically Plated Wire Choke Coil

    In this example, high frequency resistance values are obtained from choke coil copper loss analysis results using JMAG’s layer coating mesh function, and the effectiveness of reducing the resistance …

    • Application Catalog

    202 – Core Stray Loss Analysis of Power Transformer

    OverviewStray loss is mainly caused by leakage flux from winding, but structures closer to the winding will tend to be affected easier by leakage flux. The ratio of stray loss relative to all losses …

    • Application Catalog

    238 – Hysteresis Loss Analysis in a Reactor with DC Bias

    In this example, we will observe the difference between the hysteresis losses calculation method loop count and the play model for the model that is subjected to a DC bias filed on top of a AC field.

    14 Mar 2018

    • Application Catalog

    232 – Reactor Joule Loss Analysis

    In this example, investigating Joule loss with respect to the positions of air gaps in a reactor is presented.

    13 Mar 2018

    • Application Catalog

    206 – Temperature Analysis of an Oil-Immersed Transformer Using a Coupled Magnetic Field and Thermal Fluid Analysis

    OverviewLarge power transformers are used to transform high voltage power generated at a power station into power that can be transmitted. For the structure of the transformer, oil-immersed transform…

    9 Mar 2018

    • Application Catalog

    204 – Copper Loss Reduction Effect Analysis of Switching Transformers using Litz Wire

    OverviewFlyback converters are used for various applications such as power supply circuits, which is suitable for small electrical power that realizes switching power supply. Since there are not many…

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