316 results about "Skin effect" patented technology

The invention relates to the technical field of fault diagnosis of power electronic equipment, and particularly discloses a fault analysis and diagnosis method and system for a mining high-voltage frequency converter, and the method comprises the steps: collecting the skin effect depth and parasitic parameter drift distance in real time under a high-frequency working condition through a multi-physics field sensor array; constructing three-dimensional current density distribution of the conductor based on a non-Euclidean space mesh generation technology, and dynamically correcting the equivalent resistivity of the conductor in combination with a metamaterial database to calculate a dynamic eddy current loss characteristic value; optimizing and solving the parasitic parameter time-varying evolution equation by using a quantum annealing algorithm to obtain a voltage peak sensitivity characteristic value; inputting the characteristic value into a pre-trained deep residual shrinkage network diagnosis model for multi-modal fusion analysis, and outputting a fault risk assessment result; according to the method, the problem of parasitic parameter time-varying characteristic modeling in the vibration environment is innovatively solved, and early warning of hidden faults is achieved.

The invention relates to a metal surface defect identification method and device based on artificial intelligence, equipment and a medium. The identification method comprises the following steps: synchronously acquiring an electromagnetic impedance signal and an optical image of a metal surface based on an eddy current sensor and an industrial camera; generating a spatially positioned interference area mask by quantifying cross-physics field interference intensity of the electromagnetic gradient and the optical edge feature; performing skin effect compensation on an electromagnetic signal by using the mask, and simultaneously performing shadow suppression on an optical image to realize physical field decoupling; a double-branch neural network is called to fuse the decoupled electromagnetic impedance features and optical texture features, and cross-modal associated joint feature expression is established; and analyzing the defect probability heat map based on the fused features, and outputting defect types and coordinates in combination with geometric feature matching. According to the method, the problem of defect feature mixing caused by mutual interference of electromagnetic-optical signals is solved, and the recognition precision and the positioning reliability of the micro defects are remarkably improved.

The invention provides a current sensor. The current sensor adopts a magnetic-core-free design, and adopts a diversion row group with a special structure to guide a target current so as to enhance the electrifying capability of the current sensor and reduce the adverse effect of a high-frequency current skin effect on measurement. Based on the structural characteristics of the diversion row group, the magnetic sensitive component for measuring the target current and the corresponding sensing signal processing method are arranged in a matched manner, so that the measurement precision of high-frequency large current is improved, the suppression capability of an interference magnetic field is improved, and the signal-to-noise ratio of an effective measurement signal is increased. The current sensor provided by the invention is compact in structure, simple in manufacturing process, strong in electrifying capability and high in signal-to-noise ratio of a sensing signal, not only widens the measuring range of the current sensor, but also effectively improves the measurement precision of high-frequency large current, and expands the application range of the magnetic-core-free current sensor.

The invention provides an optimized winding method and system for a high-frequency transformer winding. A comprehensive parameter database based on current density distribution data of a high-frequency switching power supply is established, the axial temperature of a winding layer is collected in real time in combination with a self-calibration multi-axis winding device, and tension and interlayer gap compensation parameters are generated through temperature gradient feedback. The tension parameter drives the machine to adjust the winding tightness, and the gap parameter optimizes the heat dissipation channel. And synchronously fusing the current distortion data of the LLC resonant topology and an electromagnetic field simulation result, and generating a resonant frequency adjustment signal to suppress abnormal high-frequency current distribution. And dynamic matching of winding tightness, current distribution and heat dissipation requirements is realized through cooperative control. According to the system, electromagnetic, mechanical and thermal field multi-dimensional linkage is adopted, the skin effect and hot spot concentration are reduced, the temperature rise gradient is balanced, and the high-frequency working condition stability is enhanced. According to the technical scheme, through electromagnetic, mechanical and thermal field cooperative regulation and control, the temperature rise peak value of the high-frequency winding is greatly reduced, and the efficiency is greatly improved.

The invention discloses an amorphous wire stress-electromagnetic coupling effect modeling method based on a micro-magnetism theory, and belongs to the technical field of magnetic materials and electromagnetic property regulation and control. According to the method, an amorphous wire micro-magnetic three-dimensional simulation model is constructed, solving is conducted through a finite element method, cross-scale simulation of magnetic domain structure evolution of the amorphous wire under the action of external stress is achieved, the change of effective magnetic conductivity of the amorphous wire under the action of different stress fields is further calculated, the skin effect and the magneto-impedance theory are fused, and the magnetic conductivity of the amorphous wire is calculated. And establishing an amorphous wire electromagnetic impedance spectrum model. According to the method, a quantitative mapping relation among the effective magnetic conductivity, the electromagnetic impedance characteristic and the external stress is established, a magnetic domain structure under the action of different stress fields can be deduced, and key parameters such as the effective magnetic conductivity and the electromagnetic impedance spectrum are output; theoretical guidance is provided for wide application of the amorphous wire in the fields of high-sensitivity stress sensing device design, broadband adjustable electromagnetic wave absorption / shielding, self-sensing composite material structure health monitoring and the like.

The invention relates to a copper foil and a preparation method and application thereof, the copper foil comprises an electrolytic copper foil layer and secondary long copper layers located on the surfaces of the two sides of the electrolytic copper foil layer, the maximum Feret diameter average value of crystal grains of the secondary long copper layers is 2.5-3 microns, and the maximum Feret diameter average value of crystal grains of the electrolytic copper foil layer is 1-2 microns. The maximum Feret diameter average value of grains of the secondary growing copper layer on the surface of the copper foil is 2.3-3 microns, the maximum Feret diameter average value of grains of the internal electrolytic copper foil layer is 1-2 microns, a structure with the grain size of the surface layer being large and the grain size of the inner layer being small is formed, and when the copper foil is used for transmitting a high-speed high-frequency electric signal, due to the skin effect of current, the high-speed high-frequency electric signal can be transmitted. More electric signals are transmitted along the surface layer of the copper foil, the grain size of the surface layer is large, the grain boundary is correspondingly reduced, and the obstruction to current is reduced, so that the loss of the electric signals is reduced, and the transmission integrity of the electric signals is improved.

The invention relates to the technical field of electromechanical hydraulic systems, and particularly discloses a low-temperature cold start control method based on high-frequency injection, which comprises the following steps: analyzing a motor state, and carrying out observation and feed-forward compensation on disturbance caused by the motor state to a load torque and a viscosity coefficient through a sliding mode observer algorithm; according to the motor state, obtaining a state equation, constructing an extended sliding mode observer equation, deriving to obtain an observer error equation, and observing the load torque; analyzing the obtained load torque, wherein the motor load torque reflects the oil viscosity; high-frequency current injection, injection frequency control, skin effect enhancement and current amplitude control are carried out in a low-temperature state according to an oil viscosity result, copper loss and a high-frequency magnetic field eddy current effect are used for assisting heat generation, and according to a final oil viscosity result, when electromagnetic heat generation viscosity is reduced and a load is reduced, an injection voltage amplitude is gradually reduced. And after a normal starting condition is reached, switching to normal id = 0 control.

The invention discloses a coil structure-based length self-sensing method for high polymer twisted artificial muscle, which comprises the following steps of: firstly, enabling the artificial muscle to be equivalent to N equidistant circular current loops, establishing an inductance calculation formula by combining a Biot-Savart law and a magnetic field superposition principle, and breaking through the limitation of a traditional solenoid model on a helical angle; then through MATLAB numerical simulation and iterative computation, fitting to obtain a power function describing the relation between inductance and length; and finally, proposing a parameter dynamic correction mode based on single-time initial inductance measurement according to complex factors such as actual magnetic flux leakage and skin effect, and realizing rapid adaptive calibration by adjusting a parameter b. In a word, the method creatively combines theoretical modeling with experimental correction, the sensing precision in a dynamic stretching scene is remarkably improved while the inductance-length macroscopic trend prediction capability is ensured, dependence on a large amount of experimental data is not needed, and the method has good engineering applicability and is worthy of popularization.

The invention relates to the technical field of radio frequency integrated circuits and advanced semiconductor packaging, in particular to a radio frequency resistor calibration structure based on an RDL process and a manufacturing method, and the radio frequency resistor calibration structure comprises a main resistor module, a redundant resistor module, a laser fine tuning module, a shielding layer module and a temperature compensation module. The main resistor module is sputtered into a film through a low-temperature coefficient metal alloy, and the high-frequency skin effect is reduced by adopting a snakelike or interdigital geometric layout; and the redundant resistor module drives metal ions to migrate through a narrow-neck structure and an electromigration effect, and compensates photoetching line width deviation and uneven sputtering thickness. The laser fine tuning module adjusts a conductive path through selective ablation or annealing of pulse laser, and forms closed-loop calibration in combination with real-time feedback of the metal induction electrode. And the consistency regulation and control of radio frequency circuit parameters of a packaging level are realized.

The invention relates to the technical field of semiconductors, in particular to a precise circuit board with an ultrahigh-frequency multilayer memory bank, which comprises a functional circuit surface layer, a high-speed signal layer, an upper grounding layer, an upper waveguide insulating layer, a power supply layer, a lower waveguide insulating layer, a lower grounding layer and a functional circuit bottom layer, the functional circuit surface layer, the high-speed signal layer, the upper grounding layer, the upper waveguide insulating layer, the power supply layer, the lower waveguide insulating layer, the lower grounding layer and the functional circuit bottom layer are sequentially stacked from top to bottom, a conductive groove is formed in the high-speed signal layer in a penetrating mode, a conductive column is arranged in the conductive groove in a matched mode, and waveguide grooves are formed in the tops of the upper waveguide insulating layer and the lower waveguide insulating layer. And a waveguide tube is arranged in the waveguide groove. According to the scheme provided by the invention, by arranging the trapezoidal conductive columns and utilizing the function of dispersing high-frequency current distribution by the asymmetric cross sections of the conductive columns, the skin effect is reduced, the signal integrity is improved, and the effect of optimizing the high-speed signal transmission time sequence consistency is achieved through the obliquely arranged waveguide tubes.

The invention discloses a solid-state transformer magnetic core loss calculation method adaptive to electric power system characteristics. The method comprises the following steps: firstly, collecting actually measured ferrite core loss data, and fitting hysteresis and eddy current loss parameters of a classical two-item model; setting 100kHz as a low-frequency and medium-high-frequency demarcation point through an eddy current and magnetic hysteresis loss balance point and a relaxation effect, and dividing three frequency bands by taking a skin effect characterization parameter greater than 2 as a medium-frequency and high-frequency demarcation point; adding a specific compensation item according to the loss characteristics of each frequency band, and constructing a segmented two-item model with compensation items; and fitting the parameters by adopting an L-M algorithm to calculate the total loss. According to the method, through frequency and flux density interval double division and compensation item introduction, the influence of nonlinear factors is effectively considered, and the magnetic core loss calculation precision is remarkably improved.

The utility model relates to a current detection device used for a copper bar, the current detection device is installed on the copper bar, one side or two sides of the copper bar are provided with gaps, the current detection device comprises a current detection chip and a shielding case, the shielding case covers the copper bar, and the current detection chip is parallel to the copper bar and is installed on the surface of the copper bar or above the surface of the copper bar. Compared with the prior art, one side or two sides of the copper bar are provided with the gaps, so that an internal magnetic field of the shielding cover translates in the horizontal direction when the alternating current changes, and the influence of the skin effect on the induction magnetic field intensity of the current detection chip is reduced; the current in the copper bar can be detected without an additional communication wire harness or a shell, so that the size is greatly reduced, and the cost is reduced; current detection can be carried out by arranging the current detection chip on the surface of the copper bar, the installation position can be flexibly adjusted according to the internal space requirement of the product, and the application range is wide.

The invention discloses a low-alternating-current-loss motor stator and a stator winding conductor design method thereof. The method comprises the following steps of S1, determining structural parameters of a stator winding conductor; and S2, on the basis of a preset rapid estimation model of alternating current loss, temperature rise and motor output power based on the structural parameters, searching an optimal solution of a structural parameter combination by taking the minimum overall alternating current loss of the stator winding conductor as a target in a value range of the structural parameters of the stator winding conductor so as to obtain an optimal structural parameter combination of the stator winding conductor. When the optimal structural parameters of the stator winding are applied to the motor, the skin effect and the neighbor effect of the conductor of the stator winding under the high-frequency working condition can be effectively inhibited, so that the alternating-current loss and the temperature rise of the conductor of the stator winding are reduced.

The invention discloses a super-magnetostrictive transducer electromagnetic energy loss optimization method based on SCReg-PGNN, and the method comprises the steps: building a super-magnetostrictive bar magnetic energy loss test platform to test the magnetic energy loss under different working conditions, then carrying out the precise calculation of the electromagnetic loss of an excitation coil through considering the skin effect, proximity effect and fringe effect, and carrying out the optimization of the electromagnetic energy loss of the excitation coil. And finally, establishing an electromagnetic energy loss model of the high-power giant magnetostrictive transducer based on SCReg-PGNN, carrying out rapid calculation on electromagnetic loss characteristics of the giant magnetostrictive transducer, and finally, searching for optimal electromagnetic structure parameters of the high-power giant magnetostrictive transducer by means of a particle swarm optimization algorithm of non-dominated sorting. According to the method, high-precision modeling and response prediction of the electromagnetic loss of the transducer can be realized under the conditions of multiple working conditions and multivariable input, and collaborative optimization of structural parameters under multiple targets is further realized, so that the overall energy efficiency and the working reliability of a transducer system are improved.

The invention discloses a metamaterial RFID (Radio Frequency Identification) anti-interference antenna structure for a severe environment and a manufacturing method of the metamaterial RFID anti-interference antenna structure. The middle layer of a substrate of the antenna structure is made of corrosion-resistant polyether-ether-ketone resin doped carbon nanotubes; the upper-layer metal patch of the electromagnetic band gap unit array and the lower-layer metal layer of the annular gap are respectively attached to the upper surface and the lower surface of the middle layer of the substrate; and a self-adaptive impedance matching module is arranged at the joint of the equipment antenna and the feeder line. And each unit in the electromagnetic band gap unit array vertically penetrates through the substrate through a metalized via hole and is connected with the upper-layer metal patch and the lower-layer metal grounding layer of the substrate to form an LC resonance unit. The skin effect of eddy current on the metal surface can be counteracted through the reverse induction current, the loss of energy on the metal surface is greatly reduced, and the radiation efficiency of the metal surface is remarkably improved. In a complex electromagnetic environment, signals can be radiated and received more efficiently, the communication stability and reliability of an RFID system are effectively enhanced, and the probability of signal loss and error codes is reduced.

The invention belongs to the technical field of non-magnetic material nondestructive testing, and discloses a non-ferromagnetic material thickness and conductivity synchronous measurement method based on eddy current phase characteristics, and the method comprises the specific steps: S1, estimating the conductivity and thickness range of a to-be-tested piece based on data such as a product specification or an industrial standard; s2, determining excitation frequency according to a frequency selection criterion (high frequency enables the skin effect depth to be smaller than 1 / 3 of the thickness, and low frequency enables the skin effect depth to be larger than two times of the thickness of the sample); s3, an eddy current method is adopted to obtain the impedance variable quantity phase of the to-be-measured non-ferromagnetic material; and S4, substituting the phases into corresponding simplified model formulas respectively, and obtaining the conductivity and the thickness at the same time. Aiming at the problems of multiple calibration, blindness in excitation frequency selection, low single-parameter measurement efficiency and the like in conductivity or thickness measurement by an existing eddy current method, double-parameter output of single measurement is realized, multiple calibration and inversion calculation are not needed, the calculation is simple, rapid and accurate, the hardware cost is low, and the applicability is wide.

The invention belongs to the technical field of high-frequency electromagnetic devices, and particularly relates to a circular litz wire alternating current resistance coefficient optimization calculation method based on a winding shape, which comprises the following steps of: 1, fitting a winding external magnetic field analytical expression of a circular litz wire under a rectangular coordinate system according to the winding shape; 2, converting the winding external magnetic field analytical expression under the rectangular coordinate system into a cylindrical coordinate system for expression; 3, deriving an external proximity effect loss analytical expression of the single-turn circular litz wire by adopting a winding external magnetic field analytical expression under a cylindrical coordinate system; 4, deriving a winding alternating-current resistance coefficient analytical expression corresponding to the external proximity effect of the circular litz wire winding by adopting a single-turn circular litz wire external proximity effect loss analytical expression; and 5, superposing the alternating current resistance coefficient analytical expressions corresponding to the external proximity effect of the winding, the skin effect and the internal proximity effect to form an alternating current resistance coefficient analytical calculation improved formula of the circular litz wire winding.

The application provides a hetero-composite wave-absorbing material based on attapulgite, a preparation method and application thereof. The wave-absorbing material is prepared by acid activation and high-frequency ultrasonic stirring to disperse attapulgite in a deionized water system to form an attapulgite emulsion, and the well-dispersed attapulgite fibers are uniformly coated with a carbon layer on the surface through hydrothermal stirring and high-temperature carbonization; then, a flower-like NiCo2O4 is grown in situ on the carbon-coated attapulgite to construct a hetero-interface, the carbon-coated attapulgite is used as a dielectric loss material, the flower-like NiCo2O4 is used as a magnetic loss material, through hetero-structure design, the carbon layer can inhibit the skin effect caused by the cross-linked flower-like NiCo2O4, so as to amplify the magnetic response behavior of the NiCo2O4; the hetero-interface formed between the two can significantly enhance the interface polarization, realize impedance matching, significantly improve the microwave absorption performance, and overcome the defects of impedance mismatch and structure design existing in the prior art magnetic-dielectric synergistic wave-absorbing material.

The present invention relates to the field of offshore wind power technology, and provides a submarine cable comprising: a central pipe, a first electrical unit, a second electrical unit, and a third electrical unit; the central pipe is used to be filled with a cooling medium; the first electrical unit is coated on the outside of the central pipe, the first electrical unit includes a first phase conductor layer, the first phase conductor layer includes a plurality of first phase conductors; the second electrical unit is coated on the outside of the first electrical unit, the second electrical unit includes a second phase conductor layer, the second phase conductor layer includes a plurality of second phase conductors; the third electrical unit is coated on the outside of the second electrical unit, the third electrical unit includes a third phase conductor layer, the third phase conductor layer includes a plurality of third phase conductors, and the first phase conductor, the second phase conductor, and the third phase conductor are spirally wound. The above-mentioned submarine cable reduces the influence of the skin effect, reduces the resistance of the conductor, improves the current carrying capacity, and realizes the use of a smaller conductor cross-section to meet the demand for a larger transmission capacity.

A thermal measurement system includes a temperature-controlled chamber configured to house a Device Under Test (DUT) and a first temperature sensor to measure an external temperature of the DUT inside the temperature-controlled chamber. The thermal measurement system further includes a heating device for heating a test material outside the temperature-controlled chamber and a controller configured to control the heating device to heat the test material to the external temperature measured by the first temperature sensor of the DUT inside the temperature-controlled chamber. In one aspect, a thermethesiometer indicates a skin effect of a surface temperature of the test material outside the temperature-controlled chamber.

The application discloses a kind of conductor operation risk assessment method, system and its terminal equipment, belong to conductor state assessment technical field, this method is: based on real-time operating tension and conductor structure parameter acquisition interlayer comprehensive contact thermal resistance set;Based on real-time line current, conductor structure parameter and preset skin effect coefficient calculation unit length heat generation rate, based on unit length heat generation rate and interlayer comprehensive contact thermal resistance set constructs radial temperature distribution thermal circuit model;Conductor surface layer temperature and ambient temperature are input in radial temperature distribution thermal circuit model to obtain real-time temperature;Based on real-time temperature and temperature-mechanical property degradation model obtains tensile strength, to based on tensile strength and conductor structure parameter calculation limit bearing capacity;Based on real-time operating tension to obtain actual share load and calculate safety margin, to based on safety margin and preset safety threshold value output the risk assessment result of to-be-measured conductor, realize to the precise dynamic evaluation of each layer failure risk in conductor internal.

The present invention provides a modular combined high-frequency switching transformer, which belongs to the technical field of electrical components. The transformer comprises a bracket mechanism, wherein the bracket mechanism comprises a side frame, and a magnetic core mechanism is provided on the side of the side frame. The magnetic core mechanism comprises an E-shaped magnetic core that is snap-connected to the side of the side frame, and a winding group is provided on the inner side of the E-shaped magnetic core. The side of the winding group is snap-connected with a spool and a connecting block. The side of the spool is snap-connected with a circular disk, and a rotating shaft seat is mounted on the side of the circular disk relative to the spool. A support rod is fixedly connected to the outer surface of the circular disk. The spool is combed and squeezed by the snap-connection between the spool and the circular disk, so that the side of the winding group does not bulge during winding. After squeezing, the thickness of the winding group is reduced and the width is increased, so that the cross-section of the winding group becomes strip-shaped, further minimizing the skin effect of the winding group when high-frequency power is applied.

This invention relates to the application of electromagnetic shielding composite materials, specifically to an electromagnetic shielding composite film with a gradient structure and its preparation method. Using a polymer film as the core layer, electromagnetic functional layers are sequentially deposited on both sides of the polymer core layer, and a carbon fiber felt is composited on at least one side, resulting in an electromagnetic shielding composite film with excellent electromagnetic shielding performance. The gradient multilayer structure design of this invention utilizes the principles of impedance mismatch at different interfaces and the skin effect to effectively improve the multiple reflections of electromagnetic waves between different functional layers. Furthermore, the type of polymer core layer can be changed according to different needs; using a polymer-based high-barrier film as the core layer can yield a high-barrier electromagnetic shielding packaging film that combines high barrier properties with high electromagnetic shielding.

The invention relates to the technical field of chip design, in particular to a bare chip and a power supply design method thereof, a chip packaging structure and electronic equipment. The power supply design method of the bare chip comprises the following steps of: 1. The method comprises the following steps: acquiring the highest clock frequency of a bare chip, calculating the skin depth of a current transmission conductor in the bare chip according to the highest clock frequency, setting the width of the current transmission conductor to be twice of the skin depth, and wiring a power supply area of the bare chip according to the set width of the current transmission conductor. According to the power supply design method, the width of the current transmission conductor is reasonably set, so that the resistance and inductance of the power supply network are reduced, the total equivalent resistance and inductance of the power supply network are reduced to the minimum, and meanwhile, by fully considering the skin effect and the width and layout of the current transmission conductor, the power supply network can be ensured to be stable even under high-frequency work. Current transmission is still efficient, and the power supply network can effectively suppress high-frequency noise and maintain good power supply stability.

The utility model discloses a Litz wire, a stator winding and a motor, and relates to the technical field of motors, the Litz wire comprises a plurality of strands of basic wires, the plurality of strands of basic wires are twisted into a whole, and each basic wire comprises a metal inner core, a graphene layer wrapping the metal inner core and an insulating layer wrapping the graphene layer; according to the technical scheme provided by the utility model, the technical effects of improving conductivity, reducing direct current loss, reducing heating, reducing skin effect and proximity effect under a high-frequency working condition, improving uniformity of current distribution, reducing alternating current loss and improving efficiency of the motor can be achieved.

This invention provides a leadframe packaging method and structure, relating to the field of chip packaging technology. First, a leadframe is provided. Then, wire bonding is applied to the front side of each first pseudo-pin to form a first connecting arc, achieving electrical connection between multiple first pseudo-pins and / or multiple connecting pins. Next, an adhesive layer is formed on the back side of the connecting frame, and the chip is mounted on the leadframe. Then, a molding compound is formed on the front side of the connecting frame. The adhesive layer is removed, a stepped groove is formed, and finally, a back gold layer is formed. Compared to existing technologies, this invention improves the adhesive bonding strength of the adhesive layer, effectively reducing the risk of adhesive layer detachment during molding, thereby reducing the risk of back adhesive overflow contamination during molding. Furthermore, it mitigates the skin effect during electroplating, improving electroplating quality and process efficiency, resulting in better electroplating quality and higher process efficiency.

The present application relates to the technical field of magnetron sputtering target recovery, and discloses a method for efficient recovery of a diffusion welding target using an electromagnetic induction heating technology. For the diffusion welding target using pure aluminum or an aluminum alloy as an intermediate layer, an electromagnetic induction alternating current is applied to the aluminum intermediate layer, and on the basis of the skin effect of the alternating current, a target blank and the aluminum intermediate layer are rapidly heated in the form of an eddy current. Due to the relatively low melting point, the aluminum intermediate layer can be rapidly heated above the melting point and melted, such that the target blank is separated from the aluminum intermediate layer. Finally, aluminum residues on the surface of the target blank are removed by means of machining turning, and cleaning and drying are carried out, to obtain a high-purity target blank that can be recycled. By employing rapid electromagnetic induction heating, the present application can effectively improve recovery efficiency and economic benefits while ensuring the purity of the target surface, and is environmentally friendly and pollution-free during the recovery process, and can be widely applied to 8-inch and 12-inch targets containing an aluminum intermediate layer.

To provide a power conversion device capable of suppressing local heat generation even when a skin effect occurs in an AC bus bar.SOLUTION: A power conversion device that converts DC power into AC power includes a plurality of semiconductor modules, and an AC busbar that is commonly connected to output terminals of the plurality of semiconductor modules, in which the AC busbar has a multilayer structure divided into a plurality of parts in a thickness direction, and includes an insulating layer that is partially provided between an upper plate that is an upper side and a lower plate that is a lower side.SELECTED DRAWING: Figure 5

The present application relates to a kind of heat treatment processes for improving H13 mandrel impact energy, comprising the following steps: after forging ultrafine treatment, medium frequency quenching, first tempering, second tempering, after forging heat treatment adopts ultrafine treatment process, eliminates reticular structure, obtains good spheroidizing structure, prepares good organizational condition for subsequent quenching and tempering, performance heat treatment adopts medium frequency quenching and tempering, because medium frequency induction coil heating is carried out by skin effect, heating speed is fast, grain is more fine, product heating and cooling stress is small, product straightness is good, using the heat treatment mode of after forging ultrafine treatment+medium frequency quenching and tempering can make the refining steel diameter≤φ200mm specification mandrel obtain higher strength and good impact energy, better solve the problem of low impact energy of H13 mandrel forgings below specification ≤φ200mm of vacuum refining steel production using conventional heat treatment process, meet product design and use requirement, under the premise of strength satisfying design requirement, room temperature average impact energy KV2≥20J.

The invention provides a method and a system for detecting the conductivity of a metal surface of a nano-silver coating. The method comprises the following steps: acquiring induction signals of a coating metal sample under alternating electromagnetic fields with different test frequencies; selecting a test frequency as a selected test frequency, determining an electric field reflection relation of an interface between a coating and a substrate in the coating metal sample according to the induction signal under the selected test frequency, and identifying electromagnetic attenuation of induced eddy current flowing through different depths of the coating metal sample based on the electric field reflection relation; according to all the electromagnetic attenuation amounts, the accumulated migration amount of the charge skin effect in the coating metal sample under the selected test frequency is recognized; and determining a frequency constraint condition of conductivity detection according to the accumulated migration volume under all the test frequencies, and detecting the surface conductivity of the coating metal sample according to the frequency constraint condition. By adopting the scheme of the invention, the influence of the surface roughness on the eddy current detection can be limited while the interference of the skin effect is avoided.