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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    • Application Catalog

    235 – Reactor Core Stray Loss Analysis

    OverviewWhen designing a high-frequency reactor which is a key component in a converter, inductance and loss, which are parameters required for voltage conversion, are important factors. Copper loss …

    24 Oct 2018

    • Application Catalog

    203 – No-Load Test Analysis of Power Transformer

    OverviewLarge-scale power transformers are expected to be highly-reliable as machinery that will support the industry infrastructure, but unfortunately, it is impossible to conduct tests connecting t…

    • Application Catalog

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

    OverviewA choke coil is an electronic component aimed at filtering high frequency current. The current generated inside a choke coil has a distribution in a single wire, and among the wires, due to c…

    • 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 …

    • JMAG White Papers

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

    1. IntroductionIn electrical equipment design, Computer Aided Engineering (CAE) software is used to make the bestpossible products within allowable timelines. In particular, finite element analysis (…

    26 Mar 2018

    • JMAG White Papers

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

    Overview1. IntroductionLead times for the competitive design of automobiles and electric appliances are getting shorter and moreunforgiving each year. One way to reduce design lead time is to incorpo…

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    238 – Hysteresis Loss Analysis in a Reactor with DC Bias

    OverviewWhen designing a high-frequency reactor which is a key component in a converter, inductance and loss, which are parameters required for voltage conversion, are important factors.A reactor are…

    14 Mar 2018

    • Application Catalog

    232 – AC Loss Analysis of a Reactor

    OverviewIn designing a high-frequency reactor that is a key component of the converter, inductance and loss, which are parameters required for voltage conversion, are important factors.An airgap has …

    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…

    • Application Catalog

    185 – Analysis of Stray Loss in a Power Transformer

    OverviewTransformers are made to be used long-term, so it has become an important design policy to control running costs from losses. These losses include copper loss in the coil and iron loss in the…

    8 Mar 2018

    • Application Catalog

    184 – Reactor Sound Pressure Analysis taking Magnetostriction into Account

    OverviewReactors are used in all sorts of systems related to power systems. For example, they fill the role of making the current pulsation between an inverter and a motor smoother. Reactor vibration…

    • JMAG White Papers

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

    Overview1.BackgroundThere is a strong demand in the market for reducing calculation time in electromagnetic field analysis. One of the reasons is that, it is necessary to calculate time steps of many…

    7 Mar 2018

    • JMAG White Papers

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

    Overview1. IntroductionFor power transformers, stray loss generated in the surrounding structures due to leakage flux originating from windings is a common issue. Because people may make direct phys…

    • JMAG Users Conference Proceedings

    3-D Magnetic Field Analysis of Large Power Transformer Using Parallel Calculation

    Yasuhisa Ito, Development Section, Transformer Design & Development Department, T&D Products Factory, T&D Business Unit, MEIDENSHA CORPORATION

    14 Feb 2018

    • JMAG Users Conference Proceedings

    Loss Analysis for a Reactor Using a Hysteresis Model

    Kouhei Ueda, Engineering Development Managing Division, Mechanic Development Department, Tabuchi Electric Co., Ltd.

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