96 results about "Three phase transformer" patented technology

The invention relates to a flexible loop closing device and a flexible loop closing method. The flexible loop closing device is arranged between a first power distribution network and a second power distribution network, and comprises a three-phase full-bridge inverter and a three-phase transformer, the three-phase output end of the three-phase full-bridge inverter is connected with the primary side of the three-phase transformer. The secondary side of the three-phase transformer is connected with a control switch, and each control switch is connected in series between the first power distribution network and the second power distribution network; and the flexible loop closing device controls the control switch to be closed under the condition that the actual output voltage of the flexible loop closing device meets a preset condition, so that flexible loop closing of the first power distribution network and the second power distribution network is realized. By adopting the device, the switch can be controlled to be switched on under the condition that the actual output voltage of the flexible loop closing device meets the preset condition, at the moment, flexible loop closing of the first power distribution network and the second power distribution network is achieved, and large impact current generated by direct loop closing is restrained.

The invention discloses a power transformer optimization design method considering iron core service magnetic characteristics. The power transformer optimization design method comprises the following steps: carrying out magnetic characteristic measurement on silicon steel sheets at different temperatures by adopting an advanced magnetic characteristic measurement device; through high-precision experimental measurement, a silicon steel material loss characteristic database covering a wide temperature range, multiple frequency bands and different magnetic densities is established; compiling a calculation program of the three-phase transformer considering the service characteristics of the iron core by adopting a C language and integrating an electromagnetic calculation process; and an improved genetic algorithm is adopted, and according to the single-target optimization mathematical model, the silicon steel material loss characteristic database is combined, and the improved genetic algorithm is utilized twice to obtain an optimal design scheme with the minimum power transformer cost and the minimum total loss as targets. The influence of actual working conditions on loss factors is considered, an advanced heuristic algorithm is adopted to replace a traditional optimization mode, and the problems that a traditional design method cannot consider the actual working conditions, and a traditional optimization algorithm is low in calculation efficiency are solved.

The invention discloses high-power three-phase transformer air duct manufacturing equipment, and relates to the field of transformer equipment manufacturing, the high-power three-phase transformer air duct manufacturing equipment comprises a coil and an adjusting piece, the coil is provided with an adjusting device, the adjusting device linearly moves on the coil, a lifting groove is formed in the position, corresponding to the adjusting device, of the coil, and the adjusting piece is arranged in the lifting groove. The adjusting device is located in the lifting groove, an adjusting channel is formed in the side edge of the lifting groove, and the adjusting channel communicates with the lifting groove; the adjusting piece is assembled with the adjusting device through the adjusting channel, and the adjusting piece drives the adjusting device to ascend and descend in the lifting groove; the adjusting device adjusts the perimeter of the coil through the lifting effect so that the wire can be wound into the air duct through the coil, and the inner diameter of the air duct can be adjusted through adjustment of the adjusting piece.

The invention discloses a three-phase transformer single-phase grounding short circuit leakage magnetic field simulation analysis method based on a combination of three single-phase transformers, and aims to solve the problem that leakage magnetic field distribution and electromagnetic force conditions of a three-phase transformer formed by the combination of the three single-phase transformers cannot be accurately simulated when a single-phase grounding short circuit fault occurs in the prior art. Constructing a three-dimensional finite element geometric model of the single-phase transformer according to parameters such as the actual size of the transformer; then importing ansys Maxwell software, and adjusting the position to generate a three-dimensional calculation model; setting material attributes of each field domain, creating a winding, and constructing an external circuit matched with different working conditions; then setting a solution domain and boundary conditions, carrying out reasonable mesh generation, and selecting a transient field for simulation solution; and finally, checking simulation results such as short-circuit current and magnetic flux leakage nephograms. The method can accurately analyze the single-phase grounding short circuit fault of the transformer, accurately simulate the fault condition, find hidden dangers in advance, and provide reliable support for fault prevention and scientific design.

The application discloses a three-phase resonant converter, which comprises a three-phase transformer, a three-phase inverter circuit and a two-phase resonant branch, wherein the three-phase transformer comprises first to third primary windings and first to third secondary windings; the three-phase inverter circuit comprises first to third bridge arms, and each bridge arm is connected between a first input end and a second input end; the connection point of two switch tubes of the second bridge arm is connected with one end of the second primary winding; the two-phase resonant branch comprises first and second resonant branches, and each resonant branch is connected between the connection point of two switch tubes of the first bridge arm and one end of the first primary winding or between the connection point of two switch tubes of the third bridge arm and one end of the third primary winding; and the three-phase resonant converter further comprises a secondary rectifier circuit; wherein one end of the first, second and third primary windings and one end of the first, second and third secondary windings are homonymous ends; and the other end of the first, second and third primary windings and the other end of the first, second and third secondary windings are heteronymous ends. The three-phase resonant converter adopts the two-phase resonant branch, thereby reducing the complexity of the topology, reducing resonant components and lowering the design cost.

A bidirectional DC-DC conversion apparatus and a charging pile. The bidirectional DC-DC conversion apparatus includes a first power conversion circuit, a second power conversion circuit, a three-phase transformer, three phase resonant circuits, a resonant switching switch circuit, and an inductor circuit. Each phase of resonant circuit includes a first capacitor and a first inductor that are connected in series. One end of each phase of resonant circuit is connected to the first power conversion circuit, and the other end of each phase of resonant circuit is connected to the second power conversion circuit via the three-phase transformer. The resonant switching switch circuit is configured to connect a circuit between either of two ends of each phase of resonant circuit and the inductor circuit to enable each phase of resonant circuit and the inductor circuit to form an LLC resonant circuit.

The application provides a residual magnetism estimation method and device for a three-phase transformer and electronic equipment. The estimation method comprises: for any single-phase transformer in the three-phase transformer, obtaining the voltage amplitude U m , the angular frequency ω of the power supply and the primary-side coil turn number N1; calculating the residual magnetism amplitude Φ m according to the voltage amplitude U m and the angular frequency ω of the power supply in combination with formula (1); obtaining the voltage closing angle α, the opening-starting time t open and the opening-ending time t open + Δt of the single-phase transformer at no-load opening; and calculating the residual magnetism Φ r of the single-phase transformer after opening according to the residual magnetism amplitude Φ m , the voltage closing angle α, the opening-starting time t open and the opening-ending time t open + Δt in combination with formula (2). The application calculates the residual magnetism Φ r of the single-phase transformer after opening in combination with formula (2), thereby replacing the complex integral term containing U C , reducing the calculation difficulty, and optimizing the accuracy of the residual magnetism estimation method for the transformer.

The application discloses a kind of traction network impedance simulation system and control method based on voltage source converter, and main substation is simulated by three-phase transformer, and traction substation is simulated by single-phase transformer.Three-phase transformer steps down power supply voltage, and the voltage on the high-voltage side of the single-phase transformer of the traction substation group comes from the same two-phase voltage of the three-phase transformer, which supplies the traction network after stepping down the voltage. Among them, for the impedance simulation of the traction network, the movement of the train is equivalent to the change of the line impedance, and the VSC is used to simulate the impedance of the traction network. The VSC is used to realize the change of the impedance of the traction network on both sides of the train during the train operation. The VSC device is used to simulate the impedance of the traction network on both sides of the train during the train operation, and relevant researchers can use the invention to carry out experimental verification of the related theory of the new type of substation group bilateral traction power supply system, and promote the development of the new type of substation group bilateral traction power supply technology.

A three-phase transformer configured to transform a three-phase voltage. The transformer includes first, second, and third toroidal transformers. The first toroidal transformer is configured to transform a first phase of the three-phase voltage. The second toroidal transformer is electrically connected to the first toroidal transformer. The second toroidal transformer is configured to transform a second phase of the three-phase voltage. The third toroidal transformer is electrically connected to the first toroidal transformer and the second toroidal transformer. The third toroidal transformer is configured to transform a third phase of the three-phase voltage.

The utility model discloses a transformer winding and three-phase transformer relates to transformer technical field, the transformer winding includes the two coil that distributes along the vertical direction, the opposite end face of two coil is both the meshing surface, each meshing surface protrudes towards the other meshing surface to form a plurality of protrusions, the multiple protrusions are distributed in the circumferential direction of the corresponding meshing face at intervals, a groove is formed between any two adjacent protrusions on each meshing face, the multiple protrusions of any meshing face and the multiple grooves of the other meshing face are consistent in number and correspond to each other in a one-to-one mode, and the correspondingly-arranged protrusions and the grooves are matched in shape. And the bulges on one meshing surface are inserted into the corresponding grooves on the other meshing surface, so that the two coils are meshed. According to the transformer winding, when the upper coil and the lower coil are in butt joint, the protrusions of the upper coil are inserted into the grooves of the lower coil, so that the upper coil and the lower coil are tightly attached, the upper coil and the lower coil can be effectively prevented from shaking relatively in the transportation process, and reliability is better.

The application provides a short-circuit protection method and device for a transformer. The short-circuit protection method comprises: obtaining output voltages of a plurality of output lines of at least one winding on a low-voltage side of the transformer; performing real-time calculation and short-circuit judgment according to the output voltages, and sending a protection signal when the short-circuit is judged. The short-circuit protection device comprises: a voltage obtaining unit for obtaining output voltages of a plurality of output lines of at least one winding on a low-voltage side of the transformer; a short-circuit judgment unit for performing real-time calculation and short-circuit judgment according to the output voltages, and sending a protection signal when the short-circuit is judged; and a controllable circuit breaker arranged on a high-voltage side of the transformer and connected with the short-circuit judgment unit, for cutting off the connection between the transformer and a power grid after receiving the protection signal. The application provides a short-circuit protection method and device based on voltage characteristics, realizes short-circuit protection of a three-phase transformer through line voltage detection, greatly reduces the protection cost, and improves the protection reliability.

The application discloses a high-power synchronous motor test system, which comprises a test motor M1, a test motor M2, an auxiliary test motor M3, a three-phase transformer, a first variable-frequency power supply, a second variable-frequency power supply and a voltage sensor. The test motor M1 is coaxially connected with the test motor M2, and the auxiliary test motor M3 is coaxially connected with the test motor M1. The first variable-frequency power supply is circuit-connected with the auxiliary test motor M3, so that the auxiliary test motor M3 drives the test motor M1 and the test motor M2 to synchronously rotate. The output end of the second variable-frequency power supply is circuit-connected with the primary side of the three-phase transformer. The alternating current end of the test motor M1 is circuit-connected with one end of the three open windings of the secondary side of the three-phase transformer. The other ends of the three open windings of the secondary side of the three-phase transformer are circuit-connected with the alternating current end of the test motor M2. The second variable-frequency power supply acquires the three-phase voltage signal of the alternating current end of the test motor M1 through the voltage sensor. The application reduces the test cost and reduces the harmonic influence.

The application discloses a high-voltage direct-current converter topology and a control method thereof, and belongs to the technical field of power generation, power transformation or power distribution. The topology is composed of a high-voltage side filter inductor, a three-phase MMC inverter circuit, a three-phase leakage inductor, a three-phase transformer, a three-phase diode rectifier circuit, a medium-voltage side filter inductor and a medium-voltage side filter capacitor. The topology structure of the application can realize higher reliability, lower cost and smaller size by the relatively mature high-voltage side modular structure and the medium-voltage side diode series connection technology. By precisely controlling the three-phase current to be a positive-negative half-cycle symmetrical trapezoidal current, reliable commutation of the three-phase rectifier diode is realized, and meanwhile, smooth direct-current is synthesized on the high-voltage side and the medium-voltage side, so that the operation efficiency of the converter and the port power quality are significantly improved, and the filter size is reduced.

The utility model discloses a fault detection system, relates to the transformer field, including transformer, detection box and power supply unit, transformer is electrically connected with detection box, the detection box is electrically connected with power supply unit, the detection box includes conveying unit and processing unit, the conveying unit is electrically connected with the power supply unit, and the processing unit is electrically connected with the transformer. And the conveying unit is electrically connected with the processing unit. According to the utility model, through cooperation between the conveying unit and the processing unit, a worker can simultaneously carry out a synchronous experiment on three phases of the transformer when carrying out a characteristic test on the three-phase transformer, so that the experiment time of the three-phase transformer is shortened, and volt-ampere characteristic curve and withstand voltage test can be carried out on the three-phase transformer; extra equipment is not needed to carry out experiment operation on the three-phase transformer, so that a worker can carry out operation better.

To provide a power supply switching device.SOLUTION: A first power supply and a second power supply having three phase alternating current power, a first power switch group, a second power switch group, and a three phase transformer, wherein the three phase transformer comprises a first winding, a second winding, and a third winding arranged in a delta connection configuration to form a first common node, a second common node, and a third common node, the first common node is connected to the first switch and the fourth switch, and the second common node is connected to the second switch and the fifth switch; The third common node is connected to the third switch and the sixth switch.SELECTED DRAWING: Figure 1

The invention provides a pulse bus voltage architecture of a high-energy-consumption production line optical storage power supply system, and relates to the technical field of optical storage power supplies. In the pulsating bus voltage architecture, a power grid supplies power to a high-energy-consumption production line load through a three-phase transformer and a multi-pulse thyristor, and a bus with pulsating voltage is led out from the output end of the multi-pulse thyristor; the photovoltaic array is connected to the bus through the first DC / DC converter; the first DC / DC converter injects pulsating current opposite to the voltage pulsating direction of the bus; the energy storage battery is connected to the bus through a second DC / DC converter, and the second DC / DC converter injects pulsating current opposite to the voltage pulsating direction of the bus. According to the invention, when a power supply system of a high-energy-consumption production line load is connected to the optical storage, a reverse pulsation current is injected, so that an original alternating current bus is changed into a bus of which an access point is voltage pulsation, and the optical storage power supply is effectively connected to an industrial and commercial power supply power supply system.

The invention relates to the technical field of power equipment state evaluation, and discloses a three-phase transformer state evaluation method, system, equipment and medium, and the method comprises the steps: collecting the frequency-amplitude response data of each phase winding of a three-phase transformer; dividing at least two characteristic sensitive frequency bands, wherein the frequency bands respectively correspond to core components of the transformer; extracting difference characterization characteristic parameters of each phase and each frequency band, and calculating a three-phase imbalance coefficient; and generating a dynamic threshold value based on the operation condition of the transformer and historical data, performing multi-level state evaluation in combination with the deviation degree of the unbalance coefficient and the threshold value, and positioning an abnormal phase. The method breaks through the limitation of a traditional fixed threshold value and a single feature, adapts to different operation scenes through the dynamic threshold value, expands feature parameter types and frequency band configuration flexibility, achieves state accurate grading and anomaly tracing, solves the problems that a traditional method is poor in adaptability and narrow in protection range, and remarkably improves the evaluation universality and the intelligent level.

The invention relates to the technical field of transformers, in particular to an energy-saving type three-phase transformer which comprises a three-phase transformer body, a C-shaped connecting frame is fixedly installed at the bottom of the three-phase transformer body, a first plane and a second plane are arranged on the C-shaped connecting frame and are perpendicular to each other, an I-shaped frame is arranged at the bottom of the C-shaped connecting frame, and the I-shaped frame is arranged on the bottom of the C-shaped connecting frame. The three-phase transformer further comprises a positioning mechanism and a locking mechanism, the positioning mechanism is used for rapidly positioning the three-phase transformer body, through the matched design of the special-shaped groove and the sliding block, the transformer body can be rapidly positioned through clamping of the sliding block in the groove, and the installation time and the labor cost are reduced; and the locking mechanism is used for quickly locking the C-shaped connecting frame and the I-shaped frame, so that the three-phase transformer body is fixed in a multi-dimensional manner, the three-phase transformer body is conveniently and quickly mounted and dismounted, traditional bolts are prevented from loosening during equipment operation, and equipment faults caused by loosening are further reduced.

The present invention belongs to the field of magnetizing inrush current suppression and discloses a transformer magnetizing inrush current suppression method based on comprehensive criteria. The method is used in a transformer closing circuit including a power supply side, a main circuit breaker, and a three-phase transformer. The method comprises: installing a phase-controlled closing control device on the transformer closing circuit; recording the voltage of each phase during the closing process of the three-phase transformer using a voltage transformer; calculating the residual magnetism of each phase of the three-phase transformer based on the voltage; calculating the closing angle interval of each phase of the circuit breaker based on the residual magnetism; and closing the main circuit breaker based on the closing angle interval of each phase. The present invention supplements two special cases that exist in the phase-controlled closing strategy based on the voltage integration algorithm. The two cases include: 1. No suitable closing angle interval exists; 2. A suitable closing angle interval exists, but the interval angle is too small, so that closing can be performed more accurately and efficiently.

The present application relates to the technical field of large current generator, disclose a kind of tap winding configuration method of large current generator.The present application method determines the winding division of the secondary side of three-phase transformer by the output level number threshold of output current, and installs tap on the two sides of the independent winding divided, and then adjusts the connection mode of each tap according to the required output current;The present application realizes the shunt of multiple windings, can reduce the design line diameter of winding to reduce the weight of winding, the configuration of tap enables to adjust the output current of large current generator by adjusting the connection mode of tap, solves the technical problem that the adaptability and flexibility of existing large current generator is poor.

A power switching system, comprising a first power source and a second power source each having three-phase AC power. The power switching system comprises a first power switch group, a second power switch group, and a three-phase transformer. The three-phase transformer comprises a first winding, a second winding, and a third winding, the first winding, the second winding, and the third winding being connected in a delta configuration to form three common connection points. The first common connection point is connected to a first switch and a fourth switch, the second common connection point is connected to a second switch and a fifth switch, and the third common connection point is connected to a third switch and a sixth switch.

The present invention discloses a voltage regulating device and its control and protection system, as well as a control and protection method. The voltage regulating device includes: a first transformer, a second transformer, a switching device, an AC contactor, an input circuit breaker, an output circuit breaker, a bypass circuit breaker, and a controller. The first transformer is composed of three single-phase isolation transformers, and the second transformer is a three-phase transformer with multiple voltage levels on the secondary side. The number of switching devices selected depends on the number n of voltage levels on the secondary side of the second transformer. The controller is used to perform current and voltage acquisition on the power grid system side, current and voltage acquisition on the secondary side circuits of the two transformers, and contactor disconnection of each phase circuit, conduction and disconnection of the switching device, and disconnection of the circuit breaker. The present invention solves the problem that existing voltage regulating devices have unreasonable transformer design parameters for different load conditions, resulting in low economic efficiency for large-scale application and an inability to ensure reliable operation.

The invention discloses a capacitance equivalent modeling method for lightning stroke response of a triangular connection side of a three-phase transformer, and the method comprises the steps: forming a triangular topology for a three-phase coupling network model based on the ground capacitance and turn-to-turn capacitance of a winding at the triangular connection side through node connection, precisely simulating the inter-phase coupling in a lightning stroke transient state, and obtaining the lightning stroke response of the triangular connection side; the method can effectively reflect the high-frequency capacitance characteristics of the triangular connection side of the three-phase transformer, determines the capacitance parameters of the three-phase coupling network model through the frequency domain impedance measurement and capacitance calculation mathematical model, improves the accuracy of the capacitance parameters, provides a more reliable basis for lightning stroke protection design, and improves the reliability of lightning stroke protection design. The technical problem that the prediction precision is insufficient in a high-frequency transient state due to the fact that existing transformer lightning stroke modeling neglects the inter-phase coupling effect in triangular connection of a three-phase transformer and does not fully consider the complex influence of a winding series-parallel connection structure on capacitance parameters is solved.

1 Designation Railway power supply system 27.5 kV, 50 or 60 Hz for long-distance rail traffic, measures to improve load symmetry in the feeding high-voltage network. 2 Summary 2.1 Technical Problem Conventional electrical substations for the power supply of long-distance railways at 27.5 kV / 50 Hz or 60 Hz cause a non-negligible negative feedback effect in the feeding high-voltage system 21 due to unbalanced loads. 2.2 Solution to the Problem Instead of the conventional V-connection of two single-phase transformers in a railway power system 2 x 27.5 kV, 50 Hz or 60 Hz, the use of two three-phase transformers T21 and T22 with connection groups Dz0 and Dz4 or Zd0 and Zd8 is proposed as a solution. See the attached drawing Figure 5 2 for an example.3. Application Areas The primary application area is the 2 x 27.5 kV / 50 Hz or 60 Hz power supply for electric railways in long-distance operation, relevant IPC classifications: B60L 3 / 00, B60M 3 / 00, H02J 3 / 26, H02M 5 / 10. Furthermore, it is applicable in electrometallurgy, relevant IPC classifications: H05B 7 / 00, H02J 3 / 26, H02M 5 / 10. Other larger single-phase or unbalanced electrical loads supplied from three-phase networks. Figure 5 shows, as one of the solution approaches, the structure of a typical substation in a simplified representation, with transformers T21 or T22, Zd8 or Zd0 connected.

The invention relates to the technical field of protection equipment in a three-phase alternating-current power distribution or transmission system, in particular to a series-connection type hybrid circuit breaker applied to a three-phase alternating-current power system and a using method, and the series-connection type hybrid circuit breaker comprises a main alternating-current circuit and a circuit breaker unit connected with the main alternating-current circuit in series; the circuit breaker unit comprises a three-phase transformer, a power electron injection branch and a mechanical switch module; the power electron injection branch is connected with the three-phase transformer, and the mechanical switch module is arranged between the three-phase transformer and the main alternating current circuit. The beneficial effects of the invention are that the transformer is coupled in the main loop to induce the voltage with the polarity opposite to that of the power supply, and reverse voltage injection is realized, so that the fault current is rapidly suppressed in a microsecond level; the fault current is modulated into the high-frequency alternating-current ripple current close to zero by using the rapid mode switching of the power electronic branch, so that the action window of the mechanical switch is expanded, and the arc-free interruption is realized.

The invention relates to a three-phase transformer simulation model, a modeling method thereof and electronic equipment, and the method comprises the steps: building a capacitance equivalent circuit of a three-phase transformer, and enabling the capacitance equivalent circuit to comprise the ground capacitance and turn-to-turn capacitance of each phase winding of the three-phase transformer; all phase windings of the three-phase transformer are connected in a triangular mode to form a triangular topology; the impedance value of the winding is measured based on the triangular topology, and frequency domain analysis is carried out based on the impedance value to determine the ground capacitance and turn-to-turn capacitance of each phase of winding, so that the accuracy of model parameters is ensured. By accurately establishing the high-frequency simulation model of the transformer, the inter-phase coupling effect in the lightning stroke transient state can be accurately simulated, the high-frequency capacitance characteristic of the triangular connection side of the three-phase transformer is effectively reflected, the voltage distribution prediction precision is remarkably improved, and a more reliable basis is provided for lightning stroke protection design.

A method of manufacturing a first toroid 214, comprising: unspooling a strip 210 from a first spool 202 which has a longitudinal axis; during unspooling, cutting the strip (cutters 206, e.g laser / mechanical) into a first oval (ellipse) 212 having one axis of symmetry parallel to longitudinal axis of strip; and winding the first oval onto a second spool 204 (mandrel, reel) to form the first toroid 214, all actions occurring preferably contemporaneously. During unspooling, the strip may be cut into a second oval 212 having one axis of symmetry, which is also parallel to the longitudinal axis of the strip; and winding the second oval onto a third spool. This may directly form a second toroid or a second toroid may be formed by spooling from the third to a fourth spool. The first and second ovals may be parallel to one another and form a tessellated shape when viewing the strip in plan view. The strip may be a strip of material having a high magnetic permeability such as bond coated electrical steel. One embodiment also describes a toroid manufactured using the method. The one or more toroids may be used as magnetic core formers for electrical devices (e.g transformers, inductors, motors). May be used to form three phase transformers by joining toroids cut into equal parts (see figures 6A-C). Figures 3A and 4

The application discloses a kind of low-voltage towed cable insulation on-line monitoring device, and towed cable is respectively connected with the low-voltage output end of three-phase transformer and equipment, comprising: signal generation module, neutral point module, current detection module and controller, wherein, the first output end of signal generation module is electrically connected with the neutral point end of neutral point module, and the second output end of signal generation module is electrically connected with ground end by grounding resistance;The output end of neutral point module is electrically connected with the first end of towed cable;Current detection module is connected with first cable, and the output end of current detection module is electrically connected with the input end of controller, wherein, the first cable is the cable connected between the first output end of signal generation module and the neutral point end of neutral point module.This application generates signal and existing signal frequency isolation in cable, there is no interference signal, measurement signal value is relatively larger, easy to measure, and acquisition value is more accurate, so it can accurately detect the insulation condition of towed cable.

A method of performing a circuit opening and closing operation in a power system including three phases, a three-phase transformer, and a circuit breaker system, the method including a) opening all three phases simultaneously such that a reference current of a reference phase is interrupted first at a first current zero crossing after the opening; and b) closing all three phases simultaneously at a phase to ground voltage of the phase lagging the reference phase by 120°, in a time range of ±90° from a negative peak of said phase to ground voltage if the current zero crossing is a positive current zero crossing, or in a time range of ±90° from a positive peak of said phase to ground voltage if the current zero crossing is a negative current zero crossing.

The invention discloses a three-phase transformer connection group number judgment and winding wiring method based on a table look-up method, and belongs to the technical field of transformers. An existing three-phase transformer connection group number judgment and winding wiring method is poor in accuracy and low in efficiency. Three factors influencing the connection group number of the three-phase transformer are made into a head and tail end mark, connection shape, connection phase sequence and inverted sequence digital look-up table, and on this basis, an odd number and even number digital look-up table of the connection group number of the three-phase transformer is made. When the connection group number of the three-phase transformer is judged, the connection group number of the three-phase transformer can be obtained by summing the head end mark, the tail end mark, the connection shape, the connection phase sequence or the inverted sequence look-up table result; when the three-phase transformer winding wiring diagram is drawn, the three-phase transformer connection group number odd number or even number digital query table is queried firstly, and then the three-phase transformer winding wiring diagram can be drawn by querying the head and tail end marks, the connection shapes, the connection phase sequence and the inverted sequence query table. The method is used for judging a three-phase transformer connection group number and drawing a winding wiring diagram.