 Transformer / Reactor | 158 - Superimposed Direct Current Characteristic Analysis of a Reactor That Accounts for Minor Hysteresis Loops | Module:FQ,ST | 2012-07-31 | High-frequency reactors used in equipment like DC-DC converters have a high-frequency current accompanying the switching direct current. The reactor's performance requires a stable inductance in a wide direct current region that is superimposed by alternating current components. If there is only a direct current, the magnetic flux is generated against the external magnetic field, following the magnetic steel sheet's DC magnetization curve. However, when there is a current waveform whose high-frequency components are superimposed on the direct current component, the response displays a minor loop against the external magnetic field. The values of the inductance in the reactor can have significant differences depending on the method used to measure them. This can make it difficult to carry out a performance prediction during an actual state of operation.
In order to handle the responsiveness of a magnetic field against a current waveform that is superimposed by a higher harmonic with a small amplitude for the direct current component, a magnetic field analysis that accounts for material modeling needs to be carried out. With a magnetic field analysis, it is possible to analyze the machine characteristics from the magnetic flux density distribution.
This Application Note presents the use of the frozen permeability condition to obtain the superimposed direct current characteristic that includes minor hysteresis loops of a high-frequency reactor.
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 | 152 - Electromagnetic Force Analysis of Short-circuited Power Transformer Windings | Module:FQ | 2011-07-12 | Electromagnetic force is produced by the current on the windings of the transformer. The windings can be deformed or damaged by the powerful electromagnetic force produced when there is a short-circuit current flowing. Therefore, confirming where the various forces are acting on the windings using analyses is vital.
This note presents the use of a magnetic field analysis to obtain the Lorentz force density and electromagnetic force produced in the windings when short-circuited by changing the position of the windings to display the effects of the primary and secondary windings.
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| 151 - Insulation Evaluation Analysis of a Power Transformer | Module:EL | 2012-07-31 | A transformer is an electrical device that uses electromagnetic induction to convert the voltage level of alternating current power. Among transformers, power transformers that are used in power conversion have extremely high electric fields applied to their coils, so insulation technology like the winding structure, insulating materials, and insulation structure are vital in attaining miniaturization and higher capacity. In addition to normal power conversion, a transformer's insulation structure has to be designed to be able to withstand lightning strikes and excess voltage during short circuits.
A transformer's dielectric strength is dependent on the electric field intensity applied to the insulating material, so the electric field intensity needs to be examined before the safety factor for the insulation breakdown can be estimated.
This Application Note shows how to obtain the electric field intensity distribution when a lightning strike or short circuit occurs and the assumed maximum voltage is applied to the winding.
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| 148 - Loss Analysis of a Power Transformer (Flyback Converter) | Module:DP,LS,TR,TS | 2012-08-31 | A flyback converter is a well-known system for small capacity power supplies in the several-dozen W class. They are cheap and have a simple structure, so they are widely used as converters for pressurization in home appliances. In recent years there has been a trend toward making small-scale switching transformers even smaller and higher-frequency, so it is not rare to see converters using the flyback system drive 100 kHz or more.
Because of the higher frequencies and smaller scales of transformers, an important challenge of how to control their heat generation has emerged in the design process. The losses that produce heat can be separated into copper loss in the coil and iron loss in the core. Copper loss is distributed inside of the coils because of the proximity effect, which is caused by influence from the skin effect and leakage flux. This means that local heat generation in the coils becomes a problem.
Iron loss also has a complex distribution because it depends on the magnetic flux density distribution that accounts for the core's magnetic saturation, so the core's local heat generation becomes a problem as well.
A magnetic field analysis simulation based on the finite element method (FEM) can precisely evaluate the complex loss distributions of the coil and core, so it is optimal for an advance study of a switching transformer's thermal design.
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| 146 - Analysis of Stray Loss in a Transformer | Module:FQ,HT,LS | 2012-07-31 | Transformers 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 core. In high-capacity transformers, however, there is also stray loss in the tank from flux leakage from the core. From a safety standpoint, companies want to contain the heat produced from stray losses in the tank to well below the standards required for heat resistant design because they anticipate injuries from people touching the tank itself.
Predicting these losses and the heat that they generate is a vital component of transformer design, but it is difficult to estimate them from desktop calculations, so evaluations and detailed analyses using the finite element method (FEM) are indispensible.
This Application Note explains how to obtain losses in a transformer tank and use them to evaluate the temperature distribution in each part.
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| 143 - Inductance Analysis of an Air Core Coil | Module:ST | 2011-01-17 | Air core coils that have a smaller inductance than a coil with a core are used in high-frequency filters and oscillators.
The inductance needs to be investigated thoroughly because any change to the dimensions can affect the inductance.
This example presents the use of a magnetic field analysis to compare the analyzed inductance of an air core coil with the inductance that is theorized.
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| 133 - Thermal Analysis of a Three-phase Transformer | Module:HT | 2011-02-28 | Recently, the growing demand for energy conservation and highly efficient transformers is raising the importance of reducing losses.
The iron loss of the core and the copper loss of the winding cause a raise in temperature and reduction in the efficiency of a transformer because the energy is released as heat.
Evaluating the heat generated by the iron and copper losses through simulation becomes advantageous when designing a transformer.
This example presents the use of a thermal analysis to obtain the temperature distribution of the heat generated by the iron losses and copper losses of the three-phase transformer.
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| 132 - Loss Analysis of a Three-phase Transformer | Module:FQ,LS | 2011-01-17 | Recently, the growing demand for energy conservation and highly efficient transformers is raising the importance of reducing losses. The iron losses of the core and the copper losses of the coil cause a raise in temperature and reduction in the efficiency of a transformer because the energy is released as heat. Evaluating the ratio and distribution of the iron and copper losses through simulation becomes advantageous when designing a transformer.
This note presents the use of a magnetic field analysis to obtain the iron and copper losses of a three-phase transformer.
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| 123 - Thermal Analysis of a Choke Coil | Module:HT,TS | 2012-07-31 | A choke coil is an electric component that is intended to filter high-frequency current. The current generated in the choke coil has offsets caused by the skin effect, proximity effect, and leakage flux near the gap, so it is distributed both inside of and between the wires. Iron loss generated in the core is also distributed by offsets in the core's magnetic flux density.
Iron loss in the choke coil's core and copper loss in its coil become a heat source in addition to reducing efficiency, so they need to be understood and reduced from a heating design standpoint. An analysis using the finite element method (FEM) is effective in getting more information about the design by quantitatively evaluating the heat generation phenomena with copper and iron losses as the heat sources.
This Application Note shows the use of a thermal analysis to obtain the temperature distribution using the iron losses and copper losses in the choke coil as the heat source.
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| 117 - Iron Loss Analysis of a Transformer | Module:FQ,LS | 2011-01-31 | Recently, the growing demand for energy conservation and highly efficient transformers is raising the importance of reducing the amount of loss. Iron loss, which is one of the major losses for transformers, consumes electric power as heat inside magnetic materials, causing the efficiency of the transformer to decrease, and the temperature to rise.
Evaluating the percentage and distribution of the iron losses through simulation becomes advantageous when designing a transformer.
This example presents the use of a magnetic field analysis to obtain the iron loss of a transformer.
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| 110 - Loss Analysis of a Choke Coil | Module:FQ,LS,TS | 2012-07-31 | A choke coil is an electric component that is intended to filter high-frequency current. Measures to evaluate the heat source as well as the core iron losses that occur within the choke coil and the copper losses of the coil that decrease efficiency need to be used for this analysis.
The current generated in the choke coil has offsets caused by the skin effect, proximity effect, and leakage flux near the gap, so it is distributed both inside of and between the wires. Iron loss generated in the core is also distributed by offsets in the core's magnetic flux density. It is helpful to get tips for the design quantitatively and visually studying these detailed distributions, and an effective way of doing this is a magnetic field analysis that uses the finite element method (FEM).
This Application Note shows how to obtain the iron loss and copper loss in a choke coil.
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| 105 - Leakage Inductance Analysis of a Transformer | Module:FQ,TS | 2012-07-31 | Inductance is an important physical quantity that determines a transformer's response characteristics against electric signals. Inductance is generally categorized into self-inductance and leakage inductance. Self-inductance is an indicator of to what extent the transformer can produce magnetic flux, and leakage inductance is an indicator of how much magnetic flux the transformer can send from the primary coil to the secondary coil without leaking. This is why self-inductance and leakage inductance are important items for transformer design requirements.
The amount of inductance is dependent on the magnetic circuit, but the nonlinear characteristics of the magnetic properties make it so that the magnetic circuit changes when the operating point changes. The leakage inductance has all of the same properties, but it also has a flux path in non-magnetic regions, making it easily affected by the arrangement and geometry of the winding in addition to the core. This is why a magnetic field analysis using the finite element method (FEM) is necessary when evaluating these types of inductance.
This Application Note explains how to obtain self-inductance and leakage inductance for two types of secondary coiling in a transformer: uniform coiling and close coiling.
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| 101 - AL-Value Current Characteristic Analysis of a Choke Coil UP! | Module:ST | 2013-04-26 | A choke coil is an electric component that is intended to filter high-frequency current. The AL-value is a vital parameter in a choke coil design that determines the cutoff frequency of a high-frequency current.
Because the AL-value is often set as a design specification and AL-value is a nonlinear magnetic property of the core, it varies widely according to the making current. Finite element analysis (FEA) enables accurate reflection of magnetic properties, and so can obtain AL-value current properties and provide feedback for design.
This note presents the use of a magnetic field analysis to obtain the AL-value current properties of a choke coil.
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| 99 - Superimposed Direct Current Characteristic Analysis of a High Current Reactor | Module:TR | 2011-01-17 | High current reactors with a high-frequency have a superimposed current composed of a high-frequency ripple and direct current.
The performance of a reactor is evaluated by a stable inductance in a wide direct current region.
The gap that is designed to prevent magnetic saturation from the core largely affects the inductance. The gap is a vital parameter of the reactor's design.
This example analyzes the superimposed direct current characteristics of a high current reactor with a high frequency.
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| 97 - Sound Pressure Analysis of a Transformer | Module:DS,FQ | 2011-07-12 | In recent years, the demand to reduce vibration and noise is growing while the requirements for higher efficiency and smaller and lighter transformers grow with environmental conservation trends. The primary cause of noise for transformers is the electromagnetic vibrations and the resonance phenomena at the eigenfrequency of the structure. A sound pressure analysis can be performed with a coupled magnetic field and structural analysis that uses the electromagnetic force as excitation force.
This example presents the use of a coupled magnetic field and structural analysis to obtain the sound pressure distribution accounting for the electromagnetic force of the core when the transformer is operating on a power supply frequency of 6 kHz.
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| 81 - AL-value Analysis of a Choke Coil | Module:ST | 2013-02-28 | A choke coil is an electric component that is intended to filter high-frequency current. The AL-value is a vital parameter in a choke coil design that determines the cutoff frequency of a high-frequency current.
The AL-value varies greatly depending on gap width, so it is effective for the advance study of a design to accurately obtain the AL-value dependency on the gap width (air gap versus AL characteristics) for the geometry of a choke coil by using a finite element analysis (FEA).
This Application Note explains a case example that obtains the air gap versus AL characteristics of a choke coil.
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| 78 - Loss Analysis of a Sheet Coil Transformer | Module:FQ,LS | 2013-01-28 | Power transformers need to be able to operate over the long term, so they are always required to control running costs from losses. Iron loss is one of the main losses in a transformer, and it can lead to temperature increases and efficiency decreases because it consumes electric power as heat in a magnetic material.
Using a finite element analysis (FEA) to display the iron loss density distribution and obtain the iron loss values in a transformer makes it possible to study the local geometry and get design feedback at the design stage.
This Application Note shows how to obtain the iron loss of a sheet coil transformer.
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| 75 - Iron Loss Analysis of a Reactor | Module:FQ,LS | 2013-01-28 | Reactors are installed on the input or output side of inverter circuits. Because they are required for long-term operation, the ability to control running costs from losses is an important challenge for their design. Iron loss is one of the major types of losses in a reactor. It consumes electric power as heat in a magnetic body, so it causes heat to increase and efficiency to decrease in the reactor.
Using a finite element analysis (FEA) to confirm the distribution of iron loss density makes it possible to study a reactor's local geometry during its design, so it is useful in providing feedback about the design itself.
This Application Note analyzes the iron loss of a reactor.
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| 60 - Superimposed Direct Current Characteristic Analysis of a Reactor UP! | Module:TR | 2013-04-26 | A high-frequency reactor, used in equipment such as DC-DC converters, has a high-frequency current accompanying the switching direct current. The performance of a reactor is evaluated by a stable inductance in a wide direct current region. The gap that is designed to prevent magnetic saturation from the core largely affects the inductance, so it is a vital parameter of the reactor's design.
The magnetic resistance is determined by the gap when there is a large gap width, which is used as a parameter for the superimposed direct current of the inductance. This means that the resistance can be evaluated using the magnetic circuit method, but when the gap width is small, the current is large, and magnetic saturation has a large effect on the inductance, an advance study using a finite element analysis (FEA) is an effective tool.
This Application Note explains a case example that obtains the superimposed direct current characteristics of a high-frequency reactor when the gap width is changed.
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| 60 - Superimposed Direct Current Characteristic Analysis of a Reactor | Module:TR | 2012-08-31 | A high-frequency reactor, used in equipment such as DC-DC converters, has a high-frequency current accompanying the switching direct current. The performance of a reactor is evaluated by a stable inductance in a wide direct current region. The gap that is designed to prevent magnetic saturation from the core largely affects the inductance, so it is a vital parameter of the reactor's design.
The magnetic resistance is determined by the gap when there is a large gap width, which is used as a parameter for the superimposed direct current of the inductance. This means that the resistance can be evaluated using the magnetic circuit method, but when the gap width is small, the current is large, and magnetic saturation has a large effect on the inductance, an advance study using a finite element analysis (FEA) is an effective tool.
This Application Note explains a case example that obtains the superimposed direct current characteristics of a high-frequency reactor when the gap width is changed.
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| 52 - Inductance Analysis of a Sheet Coil Transformer | Module:FQ | 2013-02-28 | Power transformer requires large currents, so their geometry tends to be large. This means that they are particularly hard parts to miniaturize when electrical product designs get smaller. The sheet coil transformer introduced in this Application Note achieves thinner dimensions by winding its coil in a thin sheet.
Self-inductance and leakage inductance are critical items in a transformer's design requirements. The amount of inductance is dependent on the magnetic circuit, but the nonlinear characteristics of the magnetic properties make it so that the magnetic circuit changes when the operating point changes. The leakage inductance has all of the same properties, but it also has a flux path in non-magnetic regions, making it easily affected by the geometry and coil arrangement in addition to the core. This is why a magnetic field analysis using the finite element method (FEM) is necessary when evaluating these types of inductance.
This Application Note explains how to obtain the self-inductance and leakage inductance of a sheet coil transformer.
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| 32 - Analysis of a Transformer | Module:FQ | 2012-07-31 | A transformer is an electrical device that uses electromagnetic induction to convert the voltage level of alternating current power. In an ideal transformer the secondary voltage is constant regardless of the load, but in reality it tends to vary with the size of the load and the power factor. The size of a transformer's voltage variations is a vital output characteristic when considering constant voltage reception. It is also important to maintain a balanced state because an imbalance in the voltage and current in each phase can bring about a rise in the transformer's temperature or a fault in the device using the transformer.
A transformer's output characteristics depend on the leakage flux from the iron core. Leakage flux passes through the air instead of the iron core, so it is hard to predict accurately during the design phase. It is possible to handle magnetic flux passing through the air in a magnetic field analysis, meaning that it is also possible to evaluate a transformer's output characteristics, including the effects of leakage flux.
This Application Note presents the use of a magnetic field analysis to evaluate changes in the secondary voltage caused by load variations in a low frequency transformer.
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| 4 - Sound Pressure Analysis of a Reactor UP! | Module:DS,TR | 2013-04-26 | Reactors are used in a variety of electric power systems. For instance, they fill the role of making the current pulsation between an inverter and a motor more smooth. On the other hand, the sound that originates from a resonance phenomenon between an electromagnetic force and an eigenfrequency can become a problem.
The reactor in this analysis has a gap in the magnetic circuit to prevent magnetic saturation. Due to the magnetic fields that occur with high frequency currents, electromagnetic force generates near the gap, and this electromagnetic excitation force in turn causes noise. Vibration and sound grow larger when the electromagnetic excitation force and the transformer's eigenmode resonate. In order to evaluate this phenomenon with good accuracy, it is necessary to find the electromagnetic force distribution and eigenmode in the high frequencies that become particular problems by using the finite element method (FEM).
This Application Note shows an example of an evaluation of a reactor's sound pressure when a part of a spacer has been removed.
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