Quickly and accurately obtaining the internal temperature distribution of a transformer plays a key role in predicting its operating conditions and simplifying the maintenance process.A reasonable equivalent thermal c...Quickly and accurately obtaining the internal temperature distribution of a transformer plays a key role in predicting its operating conditions and simplifying the maintenance process.A reasonable equivalent thermal circuit model is a relatively reliable method of obtaining the internal temperature distribution.However,thermal circuit models without targeted consideration of operating conditions and parameter corrections usually limit the accuracy of the results.This paper proposed a five-node transient thermal circuit model with the introduction of nonlinear thermal resistance,which considered the internal structure and winding layout of the core-type high-frequency transformer.The Nusselt number,a crucial variable in heat convection calculations and directly related to the accuracy of thermal resistance parameters,was calibrated on the basis of the distribution of external cooling air.After parameter calibration,the maximum computational error of the hotspot temperature is reduced by 5.48%compared with that of the uncalibrated model.Finally,an experimental platform for temperature monitoring was established to validate the five-node model and its ability to track the temperature change at each reference point after calibrating the Nusselt number.展开更多
Output voltage is an important performance characteristic of planar insulating core transformer (PICT).In PICT magnetic cores are insulated from their neighboring magnetic cores by solid insulating materials.Solid ins...Output voltage is an important performance characteristic of planar insulating core transformer (PICT).In PICT magnetic cores are insulated from their neighboring magnetic cores by solid insulating materials.Solid insulating materials can increase leakage flux.This results in a low generated voltage in secondary coils,especially on the upper stages.Connecting flux compensation capacitors to secondary coils can compensate the flux loss.Design equations to calculate the flux compensation capacitors value and relevant simulation by CST and Protel software were presented.Simulation results of an actual PICT showed that output voltage increased by 19% after being connected to flux compensation capacitors and the voltage on every stage was equally distributed.Results of simulation were consistent with the following experimental test,which revealed that flux compensation capacitors were effective.展开更多
The design of the insulated core transformer(ICT)needs to consider the flux leakage effects.An equivalent linear circuit model is proposed based on the principle of duality.It is composed by two types of leakage induc...The design of the insulated core transformer(ICT)needs to consider the flux leakage effects.An equivalent linear circuit model is proposed based on the principle of duality.It is composed by two types of leakage inductances:conventional leakage between windings and special leakage introduced mainly by the insulation gaps.The values of leakage inductances depend on the dimensions of the core,gaps,or windings and the property of magnetic materials.The circuit allows for quantitatively evaluating influences of ICT internal parameters on its output properties.The winding self- and mutual inductance matrix is mathematically converted to derive the inductance formula.As an example,the leakage parameters of a sixstage two-dimensional(2D) ICT are calculated and analyzed.展开更多
The paper describes a simulated experiment that focuses on the numeric computation of magnetic loss in the laminated core of a single-phase power transformer. The students’ laboratory work is part of the library of e...The paper describes a simulated experiment that focuses on the numeric computation of magnetic loss in the laminated core of a single-phase power transformer. The students’ laboratory work is part of the library of experiments of the Electrical Machines virtual laboratory and makes use of the two-dimensional open-access electromagnetic field analysis software Finite Element Method Magnetics. The idea of the simulated exercise is to demonstrate how the magnetic loss caused by time-varying excitations affects the magnetic permeability, <em>μ</em>, of the laminated core and the terminal quantities of the energizing winding. A parametric analysis employing different values for the electrical conductivity and maximum hysteresis-induced angle of the laminated material yields five different field problems with increasing magnetic loss. Electric circuits characterized by the (<em>I-V</em>) operating point and reflected impedance of the energizing winding provide the information required to compute the changes in real power Δ<em>P</em>, reactive power Δ<em>Q</em> and magnetically stored energy Δ<em>W</em><sub>m</sub> between successive problems characterized by increasing magnetic loss. The concept of reflected impedance helps to explain the physical meaning of the changes in power dissipation and energy storage in the laminated core.展开更多
To understand the vibration noise behaviors of amorphous metal alloy core distribution transformer(AMACDT), a 10 k VA prototype was tested under no-load and short-circuit conditions, respectively. The vibration charac...To understand the vibration noise behaviors of amorphous metal alloy core distribution transformer(AMACDT), a 10 k VA prototype was tested under no-load and short-circuit conditions, respectively. The vibration characteristics were described when rated voltage was applied to the secondary side, and the primary side was connected with different load resistances. The largest amplitude positions on the upper bracket and tank surfaces were recorded by vibration sensors arranged on the surface. A data-acquisition platform was set up for signal measurement. The vibration amplitude related to frequency was discussed, and experimental results indicated that the position with the largest amplitude accrued in the middle of the upper bracket and tank surface, at phases a and c, respectively. The experimental results suggest that magnetostrictive and electrodynamic forces play a major role in exciting the vibration noise. At the same time, some rib-reinforcements were welded on the upper bracket and tank surfaces to lessen the vibration energy, which reduced the noise.展开更多
An ideal current distribution in the air core transformer coils is obtained using variation principle.Climbing mountain method is utilized for optimizing the dimension and position of the real coils.Not only can the r...An ideal current distribution in the air core transformer coils is obtained using variation principle.Climbing mountain method is utilized for optimizing the dimension and position of the real coils.Not only can the requirement of minimizing the stray field in the plasma region be guaranteed,but also integer turns for the coil can be realized.The latter brings a significant convenience to engineering.展开更多
A novel high-frequency and high power density planar insulated core transformer(PICT) applied to high voltage DC generator is introduced. PICT's operating principle and fundamental configuration are described,and ...A novel high-frequency and high power density planar insulated core transformer(PICT) applied to high voltage DC generator is introduced. PICT's operating principle and fundamental configuration are described,and preliminary experimental results in self-designed PICT apparatus are presented. Emphatically, magnetic leakage flux(MFL) giving rise to the output voltage drop is analyzed in detail both theoretically and by finite element method(FEM). Showing good consistency with experimental result, FEM simulation is considered to be practicable in physical design of PICT. To cancel out leakage inductance and improve the voltage uniformity,compensation capacitor is adopted and experimental verification is also presented. All shows satisfactory results.展开更多
This Paper studies the effect of new suggested ferroresonance limiter on controlling ferroresonance oscillations in the power transformer. It is expected that this limiter generally can control the ferroresonance. For...This Paper studies the effect of new suggested ferroresonance limiter on controlling ferroresonance oscillations in the power transformer. It is expected that this limiter generally can control the ferroresonance. For studying these phenomena, at first ferroresonance is introduced and a general modeling approach is given. A simple case of ferroresonance in a three phase transformer is used to illustrate these phenomena. Then, effect of new suggested ferroresonance limiter on the onset of chaotic ferroresonance and control of these oscillations in a power transformer including linear core losses is studied. Simulation is done on a three phase power transformer while one of its phases is opened, and effect of varying input voltage on occurring ferroresonance overvoltage is studied. Results show that connecting the ferroresonance limiter to the transformer exhibits a great controlling effect on the ferroresonance overvoltage. Phase plane diagram, FFT analysis along with bifurcation diagrams are also presented. Significant effect on occurring chaotic ferroresonance, the range of parameter values that may lead to overvoltage and magnitude of ferroresonance overvoltage is obtained, showed and tabulated.展开更多
基金supported by the National Natural Science Foundation of China(Grant 52207180)Xi'an High Voltage Apparatus Research Institute Co.Ltd.(Grant K222301-01)the Anhui Provincial Natural Science Foundation(Grant 2208085UD18).
文摘Quickly and accurately obtaining the internal temperature distribution of a transformer plays a key role in predicting its operating conditions and simplifying the maintenance process.A reasonable equivalent thermal circuit model is a relatively reliable method of obtaining the internal temperature distribution.However,thermal circuit models without targeted consideration of operating conditions and parameter corrections usually limit the accuracy of the results.This paper proposed a five-node transient thermal circuit model with the introduction of nonlinear thermal resistance,which considered the internal structure and winding layout of the core-type high-frequency transformer.The Nusselt number,a crucial variable in heat convection calculations and directly related to the accuracy of thermal resistance parameters,was calibrated on the basis of the distribution of external cooling air.After parameter calibration,the maximum computational error of the hotspot temperature is reduced by 5.48%compared with that of the uncalibrated model.Finally,an experimental platform for temperature monitoring was established to validate the five-node model and its ability to track the temperature change at each reference point after calibrating the Nusselt number.
文摘Output voltage is an important performance characteristic of planar insulating core transformer (PICT).In PICT magnetic cores are insulated from their neighboring magnetic cores by solid insulating materials.Solid insulating materials can increase leakage flux.This results in a low generated voltage in secondary coils,especially on the upper stages.Connecting flux compensation capacitors to secondary coils can compensate the flux loss.Design equations to calculate the flux compensation capacitors value and relevant simulation by CST and Protel software were presented.Simulation results of an actual PICT showed that output voltage increased by 19% after being connected to flux compensation capacitors and the voltage on every stage was equally distributed.Results of simulation were consistent with the following experimental test,which revealed that flux compensation capacitors were effective.
基金supported by National Natural Science Foundation of China(No.11305068)the‘‘2011 project’’organized by Hubei Collaboration Innovation Center of Non-power Nuclear Technology
文摘The design of the insulated core transformer(ICT)needs to consider the flux leakage effects.An equivalent linear circuit model is proposed based on the principle of duality.It is composed by two types of leakage inductances:conventional leakage between windings and special leakage introduced mainly by the insulation gaps.The values of leakage inductances depend on the dimensions of the core,gaps,or windings and the property of magnetic materials.The circuit allows for quantitatively evaluating influences of ICT internal parameters on its output properties.The winding self- and mutual inductance matrix is mathematically converted to derive the inductance formula.As an example,the leakage parameters of a sixstage two-dimensional(2D) ICT are calculated and analyzed.
文摘The paper describes a simulated experiment that focuses on the numeric computation of magnetic loss in the laminated core of a single-phase power transformer. The students’ laboratory work is part of the library of experiments of the Electrical Machines virtual laboratory and makes use of the two-dimensional open-access electromagnetic field analysis software Finite Element Method Magnetics. The idea of the simulated exercise is to demonstrate how the magnetic loss caused by time-varying excitations affects the magnetic permeability, <em>μ</em>, of the laminated core and the terminal quantities of the energizing winding. A parametric analysis employing different values for the electrical conductivity and maximum hysteresis-induced angle of the laminated material yields five different field problems with increasing magnetic loss. Electric circuits characterized by the (<em>I-V</em>) operating point and reflected impedance of the energizing winding provide the information required to compute the changes in real power Δ<em>P</em>, reactive power Δ<em>Q</em> and magnetically stored energy Δ<em>W</em><sub>m</sub> between successive problems characterized by increasing magnetic loss. The concept of reflected impedance helps to explain the physical meaning of the changes in power dissipation and energy storage in the laminated core.
基金Supported by the National Natural Science Foundation of China(No.51277131)the National Basic Research Program of China("973" Program,No.2014CB239501 and No.2014CB239506)
文摘To understand the vibration noise behaviors of amorphous metal alloy core distribution transformer(AMACDT), a 10 k VA prototype was tested under no-load and short-circuit conditions, respectively. The vibration characteristics were described when rated voltage was applied to the secondary side, and the primary side was connected with different load resistances. The largest amplitude positions on the upper bracket and tank surfaces were recorded by vibration sensors arranged on the surface. A data-acquisition platform was set up for signal measurement. The vibration amplitude related to frequency was discussed, and experimental results indicated that the position with the largest amplitude accrued in the middle of the upper bracket and tank surface, at phases a and c, respectively. The experimental results suggest that magnetostrictive and electrodynamic forces play a major role in exciting the vibration noise. At the same time, some rib-reinforcements were welded on the upper bracket and tank surfaces to lessen the vibration energy, which reduced the noise.
文摘An ideal current distribution in the air core transformer coils is obtained using variation principle.Climbing mountain method is utilized for optimizing the dimension and position of the real coils.Not only can the requirement of minimizing the stray field in the plasma region be guaranteed,but also integer turns for the coil can be realized.The latter brings a significant convenience to engineering.
基金Supported by the Science and Technology Commission of Shanghai Municipality under Grant No.12ZR1436500the Knowledge Innovation Programm of the Chinese Academy of Sciences
文摘A novel high-frequency and high power density planar insulated core transformer(PICT) applied to high voltage DC generator is introduced. PICT's operating principle and fundamental configuration are described,and preliminary experimental results in self-designed PICT apparatus are presented. Emphatically, magnetic leakage flux(MFL) giving rise to the output voltage drop is analyzed in detail both theoretically and by finite element method(FEM). Showing good consistency with experimental result, FEM simulation is considered to be practicable in physical design of PICT. To cancel out leakage inductance and improve the voltage uniformity,compensation capacitor is adopted and experimental verification is also presented. All shows satisfactory results.
文摘This Paper studies the effect of new suggested ferroresonance limiter on controlling ferroresonance oscillations in the power transformer. It is expected that this limiter generally can control the ferroresonance. For studying these phenomena, at first ferroresonance is introduced and a general modeling approach is given. A simple case of ferroresonance in a three phase transformer is used to illustrate these phenomena. Then, effect of new suggested ferroresonance limiter on the onset of chaotic ferroresonance and control of these oscillations in a power transformer including linear core losses is studied. Simulation is done on a three phase power transformer while one of its phases is opened, and effect of varying input voltage on occurring ferroresonance overvoltage is studied. Results show that connecting the ferroresonance limiter to the transformer exhibits a great controlling effect on the ferroresonance overvoltage. Phase plane diagram, FFT analysis along with bifurcation diagrams are also presented. Significant effect on occurring chaotic ferroresonance, the range of parameter values that may lead to overvoltage and magnitude of ferroresonance overvoltage is obtained, showed and tabulated.
