A high-frequency transformer temperature rise equivalent test device and test method

Abstract

This invention discloses an equivalent temperature rise testing device and method for high-frequency transformers. The device includes a high-frequency AC power supply, a first DC power supply, and a second DC power supply, which are connected in parallel with the primary and secondary windings of the high-frequency transformer under test through a DC blocking capacitor and an isolation inductor, respectively, to simultaneously simulate core losses and winding losses. The testing method includes determining the target loss, adjusting the power supply output to make the actual loss equal to the target loss, and monitoring the temperature rise to a steady state. This method can accurately reproduce the steady-state temperature rise of the transformer under rated operating conditions, and has low testing costs and is easy to operate.

Description

Technical Field

[0001] This invention relates to the field of high-frequency transformer testing technology, and in particular to a high-frequency transformer temperature rise equivalent testing device and test method. Background Technology

[0002] Solid-state transformers have broad application prospects in fields such as new energy aggregation, rail transportation, and data centers. High-frequency transformers, as the core component of solid-state transformers, play a crucial role in voltage isolation and energy routing. Optimizing the design of high-frequency transformers requires comprehensive consideration of insulation design, loss calculation, temperature rise calculation, and heat dissipation design, making it an extremely challenging task. To ensure that the hot spot temperature of high-frequency transformer products does not exceed the maximum allowable temperature limit, temperature rise tests and assessments must be conducted on the designed high-frequency transformer prototypes under rated operating power. Especially for medium-voltage, high-power high-frequency transformers, temperature rise testing is a vital means of assessing their hot spot temperature and evaluating the reliability of their thermal design.

[0003] The application topologies of high-frequency transformers are mostly DAB converters or LLC converters. Their operating frequency, operating voltage, leakage inductance, turns ratio, and other parameters lack unified standards, exhibiting a customized nature. Using single-stage or multi-stage DAB converters or LLC converters as test power supplies for temperature rise tests on medium-voltage, high-power high-frequency transformer prototypes has the disadvantages of complex equipment and high cost. Furthermore, due to the large parameter variations and customized nature of high-frequency transformers, it is difficult to establish a unified standard for test power supplies based on actual operating conditions. Different test power supplies need to be customized for different high-frequency transformer prototype parameters, further increasing the cost of test power supplies. The method of superimposing the temperature rise from no-load tests and short-circuit tests fails to reflect the true operating conditions of high-frequency transformers and cannot consider the impact of temperature on core and winding losses, resulting in significant deviations between the temperature rise test results and actual values.

[0004] The existing technology has the following drawbacks:

[0005] 1. Using actual DAB converters or LLC converters as test power supplies for temperature rise testing of high-frequency transformers has the disadvantages of complex equipment and high cost. In addition, due to the large parameter differences and customization characteristics of high-frequency transformers, it is difficult to form a unified standard for test power supplies based on actual operating conditions. Different test power supplies need to be customized for different high-frequency transformer prototype parameters, which further increases the cost of test power supplies.

[0006] 2. The no-load and load tests are used to measure the no-load temperature rise and load temperature rise of the high-frequency transformer respectively, and the two are superimposed to obtain the total temperature rise of the transformer. This method is difficult to reflect the actual operating conditions of the high-frequency transformer. In addition, this method cannot take into account the influence of temperature on core loss and winding loss, and cannot take into account the bidirectional coupling and mutual influence between temperature and loss.

[0007] Therefore, there is a need for a low-cost equivalent temperature rise testing device for high-frequency transformers and a simple equivalent temperature rise testing method. Summary of the Invention

[0008] To solve the above-mentioned technical problems, the present invention adopts the following solution.

[0009] A high-frequency transformer temperature rise equivalent testing device, the device comprising:

[0010] A high-frequency AC power supply, the output of which is connected to the primary winding via a DC blocking capacitor, is used to provide excitation for the high-frequency transformer under test to generate core losses.

[0011] The first DC power supply has its output terminal connected to the primary winding through a first isolation inductor, and is used to provide DC current to the primary winding to generate primary winding losses.

[0012] And a second DC power supply, the output of which is connected to the secondary winding through a second isolation inductor, for providing DC current to the secondary winding to generate secondary winding losses.

[0013] Optionally, the branch of the first DC power supply may further include a first resistor connected in series with the first DC power supply, and a first filter capacitor connected in parallel with the series branch of the first DC power supply and the first resistor.

[0014] Optionally, the branch of the second DC power supply may further include a second resistor connected in series with the second DC power supply, and a second filter capacitor connected in parallel with the series branch of the second DC power supply and the second resistor.

[0015] Optionally, when the turns ratio of the high-frequency transformer under test is 1:1, the device does not include a second DC power supply and a second isolation inductor. The primary and secondary windings of the high-frequency transformer under test are short-circuited at the same terminals. The first DC power supply and the first isolation inductor are used to simultaneously provide DC current to the primary and secondary windings.

[0016] Optionally, the first DC power supply and the first isolation inductor are connected in series and then connected between the non-same-name terminals of the primary winding and the secondary winding.

[0017] Optionally, the inductance of the first isolation inductor and / or the second isolation inductor is greater than the magnetizing inductance of the high-frequency transformer under test.

[0018] A method for equivalent temperature rise testing of a high-frequency transformer, the method comprising the following steps:

[0019] Determine the target core loss and target winding loss of the high-frequency transformer under rated operating conditions;

[0020] Adjust the output of the high-frequency AC power supply so that the actual core loss generated by the high-frequency transformer under test is equal to the target core loss;

[0021] Adjust the output of the first DC power supply and / or the second DC power supply so that the actual winding loss generated in the winding of the high-frequency transformer under test is equal to the target winding loss.

[0022] The temperature rise of the high-frequency transformer under test when it reaches thermal steady state is measured under the combined effect of the actual core loss and the actual winding loss.

[0023] Optionally, determining the target core loss and target winding loss includes: calculating the target core loss and target winding loss using analytical formulas or finite element methods.

[0024] Optionally, determining the target core loss and target winding loss includes: measuring the core loss characteristics of the high-frequency transformer under test through a no-load test, and measuring the winding resistance characteristics through a short-circuit test.

[0025] Optionally, determining the target core loss and target winding loss further includes: calculating the target core loss and target winding loss based on the characteristics and rated operating parameters.

[0026] Optionally, the steps of adjusting the high-frequency AC power output and adjusting the DC power output are performed simultaneously.

[0027] Compared with the prior art, the present invention has the following beneficial technical effects:

[0028] 1. Temperature Rise Equivalent Testing Device: A temperature rise equivalent testing device for high-frequency transformers is proposed. Using this device, the core loss and winding loss of the high-frequency transformer prototype under test can be applied to the prototype under actual operating conditions, thus replacing the actual DAB or LLC circuit for temperature rise testing. The device can be applied to high-frequency transformer prototypes with arbitrary parameters, and is low in cost and simple to operate.

[0029] 2. Temperature rise equivalent test method: A temperature rise equivalent test method for high-frequency transformers is proposed. This method does not require applying rated load excitation to the transformer prototype under test using a DAB converter or LLC converter. It only requires applying equivalent excitation to the transformer prototype using the proposed equivalent test device to assess the steady-state temperature rise. The steady-state temperature rise depends on the application scenario. In most cases, the steady-state hot spot temperature is required to not exceed 125 degrees Celsius. Attached Figure Description

[0030] The accompanying drawings illustrate exemplary embodiments of the invention and, together with the description thereof, serve to explain the principles of the invention. These drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification.

[0031] Figure 1 This is a schematic diagram of an equivalent temperature rise testing device for high-frequency transformers with arbitrary turns ratios, as described in one embodiment of the present invention.

[0032] Figure 2 This is a schematic diagram of an improved equivalent temperature rise testing device for high-frequency transformers with arbitrary turns ratios, as described in one embodiment of the present invention.

[0033] Figure 3 This is a flowchart of an equivalent temperature rise test method for high-frequency transformers with arbitrary turns ratios, as described in one embodiment of the present invention.

[0034] Figure 4 This is a simplified schematic diagram of a high-frequency transformer temperature rise equivalent test device suitable for a 1:1 turns ratio, according to one embodiment of the present invention.

[0035] Figure 5 This is a schematic diagram of an improved temperature rise equivalent testing device for high-frequency transformers with a 1:1 turns ratio, according to one embodiment of the present invention. Detailed Implementation

[0036] The following is in conjunction with the appendix Figures 1 to 5 The present invention will be further described in detail below with reference to the embodiments. It is to be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be noted that, for ease of description, only the parts relevant to the present invention are shown in the accompanying drawings.

[0037] It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined with each other. The technical solution of this invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0038] Unless otherwise stated, the exemplary embodiments / exemplifications shown are to be understood as providing exemplary features of various details that provide ways in which the technical concept of the invention can be implemented in practice. Therefore, unless otherwise stated, the features of the various embodiments / exemplifications may be additionally combined, separated, interchanged and / or rearranged without departing from the technical concept of the invention.

[0039] The use of crosshairs and / or shading in the accompanying drawings is generally used to clarify the boundaries between adjacent components. Thus, unless otherwise stated, the presence or absence of crosshairs or shading does not convey or indicate any preference or requirement for the specific material, material properties, dimensions, proportions, commonalities between the illustrated components, or any other characteristics, properties, etc., of the components. Furthermore, in the accompanying drawings, the dimensions and relative dimensions of components may be exaggerated for clarity and / or descriptive purposes. When exemplary embodiments can be implemented differently, a specific process sequence may be performed in a different order than that described. For example, two consecutively described processes may be performed substantially simultaneously or in the reverse order of their description. Furthermore, the same reference numerals denote the same components.

[0040] When a component is referred to as being "on" or "above" another component, "connected to," or "joined to" another component, the component may be directly on, directly connected to, or directly joined to the other component, or there may be intermediate components. However, when a component is referred to as being "directly on" another component, "directly connected to," or "directly joined to" another component, there are no intermediate components. Therefore, the term "connection" can refer to a physical connection, an electrical connection, etc., and may or may not have intermediate components.

[0041] For descriptive purposes, the present invention may use spatial relative terms such as “below,” “under,” “below,” “down,” “above,” “above,” “higher,” and “side (e.g., in a “sidewall”)” to describe the relationship between one component and another component as shown in the accompanying drawings. In addition to the orientations depicted in the drawings, the spatial relative terms are also intended to encompass different orientations of the device during use, operation, and / or manufacture. For example, if the device in the drawings is flipped, a component described as “below” or “under” another component or feature would subsequently be positioned “above” said other component or feature. Thus, the exemplary term “below” can encompass both “above” and “below” orientations. Furthermore, the device may be otherwise positioned (e.g., rotated 90 degrees or in other orientations), thus interpreting the spatial relative descriptive terms used herein accordingly.

[0042] The terminology used herein is for the purpose of describing particular embodiments and is not intended to be limiting. As used herein, unless the context clearly indicates otherwise, the singular forms “a” and “the” are intended to include the plural forms as well. Furthermore, when the terms “comprising” and / or “including” and variations thereof are used in this specification, it indicates the presence of the stated features, integrals, steps, operations, parts, components, and / or groups thereof, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, parts, components, and / or groups thereof. It should also be noted that, as used herein, the terms “substantially,” “about,” and other similar terms are used as approximate terms rather than as terms of degree, thus explaining the inherent biases in measurements, calculated values, and / or provided values ​​that would be recognized by one of ordinary skill in the art.

[0043] In one embodiment, the present invention provides a high-frequency transformer temperature rise equivalent testing device, the device comprising:

[0044] A high-frequency AC power supply, the output of which is connected to the primary winding via a DC blocking capacitor, is used to provide excitation for the high-frequency transformer under test to generate core losses.

[0045] The first DC power supply has its output terminal connected to the primary winding through a first isolation inductor, and is used to provide DC current to the primary winding to generate primary winding losses.

[0046] And a second DC power supply, the output of which is connected to the secondary winding through a second isolation inductor, for providing DC current to the secondary winding to generate secondary winding losses.

[0047] This equivalent testing device can apply the same core loss and winding loss as the actual operating conditions to the high-frequency transformer prototype under test, thereby replacing the actual DAB circuit or LLC circuit to conduct temperature rise tests on the high-frequency transformer prototype. The equivalent testing device needs to be able to simulate the loss of the high-frequency transformer under actual operating conditions and be applicable to all high-frequency transformer parameters. Equivalent tests based on this equivalent testing device can simulate the temperature rise of the high-frequency transformer under actual operating conditions.

[0048] Furthermore, the branch of the first DC power supply also includes a first resistor connected in series with the first DC power supply, and a first filter capacitor connected in parallel with the series branch of the first DC power supply and the first resistor.

[0049] Furthermore, the branch of the second DC power supply also includes a second resistor connected in series with the second DC power supply, and a second filter capacitor connected in parallel with the series branch of the second DC power supply and the second resistor.

[0050] Furthermore, when the turns ratio of the high-frequency transformer under test is 1:1, the device does not include a second DC power supply and a second isolation inductor. The primary and secondary windings of the high-frequency transformer under test are short-circuited at the same terminals. The first DC power supply and the first isolation inductor are used to simultaneously provide DC current to the primary and secondary windings.

[0051] Furthermore, the first DC power supply and the first isolation inductor are connected in series and then connected between the non-same-name terminals of the primary winding and the secondary winding.

[0052] Furthermore, the inductance of the first isolation inductor and / or the second isolation inductor is greater than the magnetizing inductance of the high-frequency transformer under test.

[0053] In another embodiment, the present invention provides a high-frequency transformer temperature rise equivalent testing device, the device comprising:

[0054] A high-frequency AC power supply, the output of which is connected to the primary winding of the high-frequency transformer under test through a DC blocking capacitor, is used to provide high-frequency excitation to the high-frequency transformer under test to generate core losses; the high-frequency AC power supply can be a high-frequency sinusoidal power supply or a high-frequency square wave power supply.

[0055] The first DC power supply has its output terminal connected to the primary winding through a first isolation inductor, and is used to provide DC current to the primary winding to generate primary winding losses.

[0056] The second DC power supply has its output terminal connected to the secondary winding through a second isolation inductor, and is used to provide DC current to the secondary winding to generate secondary winding losses.

[0057] The DC blocking capacitor is used to isolate the DC current generated by the first DC power supply and the second DC power supply, so as to avoid the influence of the DC current on the high-frequency AC power supply; the first isolation inductor and the second isolation inductor are used to isolate the AC current generated by the high-frequency AC power supply, so as to avoid the influence of the AC current on the first DC power supply and the second DC power supply; and the inductance of the first isolation inductor and / or the second isolation inductor should be greater than the magnetizing inductance of the high-frequency transformer under test.

[0058] This equivalent testing device can apply the same core and winding losses as under actual operating conditions to the high-frequency transformer prototype through independently controllable high-frequency AC power supplies and the first and second DC power supplies, thereby replacing the actual DAB or LLC circuits to conduct temperature rise tests on the high-frequency transformer prototype. This equivalent testing device can simulate the losses of a high-frequency transformer under actual operating conditions and is applicable to high-frequency transformers with different parameters. Equivalent tests based on this device can accurately simulate the steady-state temperature rise of a high-frequency transformer under actual operating conditions.

[0059] Furthermore, in order to improve the voltage regulation accuracy of the DC power supply and suppress the influence of AC current on the DC power supply, the branch of the first DC power supply also includes a first resistor connected in series with the first DC power supply, and a first filter capacitor connected in parallel with the series branch of the first DC power supply and the first resistor; the branch of the second DC power supply also includes a second resistor connected in series with the second DC power supply, and a second filter capacitor connected in parallel with the series branch of the second DC power supply and the second resistor.

[0060] Furthermore, when the turns ratio of the high-frequency transformer under test is 1:1, the device does not include a second DC power supply and a second isolation inductor; the primary and secondary windings of the high-frequency transformer under test are short-circuited at the same terminals; the first DC power supply and the first isolation inductor are used to simultaneously provide DC current to the primary and secondary windings, thereby combining the losses of the primary and secondary windings.

[0061] Furthermore, in a simplified implementation with a 1:1 turns ratio, the first DC power supply and the first isolation inductor can be connected in series and then directly connected in parallel between the node of the high-frequency AC power supply and the DC blocking capacitor and the other end of the winding of the high-frequency transformer under test. In this case, it is necessary to ensure that the inductance of the first isolation inductor is large enough to achieve effective isolation. Alternatively, an improved connection method can be used: the first DC power supply and the first isolation inductor are connected in series between the non-corresponding terminals of the primary winding and the secondary winding. In this connection method, the voltage across the DC power supply branch is very small, therefore the required inductance of the first isolation inductor can be reduced, making it easier to implement and reducing device costs.

[0062] In another embodiment, the present invention also provides a method for equivalent temperature rise testing of high-frequency transformers, the method comprising the following steps:

[0063] Determine the target core loss and target winding loss of the high-frequency transformer under rated operating conditions;

[0064] Adjust the output of the high-frequency AC power supply so that the actual core loss generated by the high-frequency transformer under test is equal to the target core loss;

[0065] Adjust the output of the first DC power supply and / or the second DC power supply so that the actual winding loss generated in the winding of the high-frequency transformer under test is equal to the target winding loss.

[0066] The temperature rise of the high-frequency transformer under test when it reaches thermal steady state is measured under the combined effect of the actual core loss and the actual winding loss.

[0067] Furthermore, the steps for determining the target core loss and the target winding loss include: calculating the target core loss and the target winding loss using analytical formulas or finite element methods.

[0068] Furthermore, the steps for determining the target core loss and target winding loss include: measuring the core loss characteristics of the high-frequency transformer under test through a no-load test, measuring the winding resistance characteristics through a short-circuit test, and calculating the target core loss and target winding loss based on the characteristics and rated operating condition parameters.

[0069] Furthermore, the steps of adjusting the high-frequency AC power output and adjusting the DC power output are performed simultaneously.

[0070] In another embodiment, the present invention provides an equivalent temperature rise testing device for high-frequency transformers with arbitrary turns ratios, the circuit diagram of which is shown below. Figure 1 As shown. Where T represents the high-frequency transformer prototype to be tested, and U... AC This is a high-frequency AC power supply used to excite the transformer, generating core losses, U AC It can be a high-frequency sine wave power supply or a high-frequency square wave power supply, U DC1 and U DC2 This is a DC power supply, used to provide current to the primary and secondary windings of the transformer, generating primary winding losses and secondary winding losses respectively. C is a DC blocking capacitor, used to isolate the DC power supply U. DC1 and U DC2 The generated DC current should be avoided from affecting the AC power supply U. AC The influence of L1 and L2, which are isolation inductors, is used to isolate the AC power supply U. AC The generated alternating current avoids the alternating current affecting the DC power supply U. DC1 and U DC2 The impact of AC power supply branch and DC power supply branch. Since the AC power supply branch is connected in parallel, to avoid the AC current affecting the DC power supply U... DC1 and U DC2 Due to the influence of the transformer, the inductance values ​​of L1 and L2 should be much greater than the magnetizing inductance of the transformer.

[0071] To further improve the voltage regulation accuracy of the DC power supply and suppress the influence of AC current on the DC power supply, a small-value resistor can be connected in series at the output terminal of the DC power supply, and a filter capacitor can be connected in parallel across the DC power supply and the resistor in series branch. The schematic diagram of the improved temperature rise equivalent test device is shown below. Figure 2 As shown in the diagram. R1 and R2 are the series resistors of the DC power supply, and C1 and C2 are the filter capacitors.

[0072] The core idea of ​​the temperature rise equivalent test method is to apply a certain voltage and current excitation to the transformer core and windings through a high-frequency AC power supply and a DC power supply, so that the losses of the transformer core and windings are the same as those under rated operating conditions. After the temperature of the high-frequency transformer stabilizes, the temperature rise of the high-frequency transformer under this condition is measured and considered to be the same as the temperature rise under the rated operating conditions of the transformer.

[0073] In another embodiment, as follows: Figure 3 As shown, the present invention also provides a method for equivalent temperature rise testing of high-frequency transformers, the method comprising the following steps:

[0074] Step 1: Measure the core loss of the high-frequency transformer under no-load conditions and fit the empirical formula; measure the AC resistance and DC resistance of the high-frequency transformer winding under short-circuit conditions.

[0075] Step 2: Calculate the core loss P of the high-frequency transformer under rated operating conditions using analytical formulas or the finite element method. c1 Primary winding loss P wp1 and secondary winding loss P ws1 ;

[0076] Step 3: Calculate the high-frequency transformer in the high-frequency AC power supply U AC Core loss P under excitation c2 Calculate the high-frequency transformer in DC power supply U DC1 and U DC2 Primary winding loss P under excitation wp2 and secondary winding loss P ws2 ;

[0077] Step 4: Select appropriate AC power supply voltage, frequency, and DC power supply voltage so that P c1 =P c2 P wp1 =P wp2 P ws1 =P ws2 Measuring the steady-state temperature rise of the transformer under this excitation condition can be considered as the steady-state temperature rise of the transformer under rated load conditions.

[0078] In another embodiment, the present invention provides a simplified equivalent temperature rise testing device suitable for high-frequency transformers with a turns ratio of 1:1. Figure 1 The temperature rise equivalent test device shown can be simplified to Figure 4 The apparatus shown is such that the corresponding terminals of the primary and secondary sides of the transformer are short-circuited, and the DC power supply and isolation inductor branch of the secondary side of the transformer can be eliminated. The temperature rise equivalent test method is the same as... Figure 3 The method described is similar, except that the losses of the primary and secondary windings can be calculated together, and only one DC power supply voltage needs to be calculated. To improve the voltage regulation accuracy of the DC power supply and suppress the influence of AC current on the DC power supply, a similar approach can also be used. Figure 2 A similar method involves connecting a small resistor in series at the output of the DC power supply, and connecting a filter capacitor in parallel across the DC power supply and the resistor in series branch.

[0079] exist Figure 4 In the temperature rise equivalent test device introduced, the AC power supply branch and the DC power supply branch are connected in parallel. In order to isolate the influence of the AC power supply on the DC power supply, an inductor with a large inductance needs to be connected in series in the DC power supply branch. Figure 5 The temperature rise equivalent test device shown has improved the location of the DC power supply branch connected to the transformer. Figure 5 In the circuit shown, the voltage across the DC power supply branch is very small; therefore, the inductance of the isolation inductor connected in series with the DC power supply branch can be reduced. When the turns ratio of the prototype high-frequency transformer under test is 1:1, Figure 5 The equivalent test apparatus shown is compared to Figure 4 The equivalent test setup shown is more advantageous and should be used preferentially. Figure 5 The equivalent test apparatus shown, the transformer temperature rise equivalent test method and Figure 3 The methods described are similar, but the difference is that the losses of the primary and secondary windings can be calculated together, and only one DC voltage needs to be calculated.

[0080] In another embodiment, the present invention also provides an equivalent test method for temperature rise of high-frequency transformers with a turns ratio of 1:1, the method comprising the following steps:

[0081] The target core loss and total target winding loss of the high-frequency transformer under rated operating conditions are determined, wherein the total target winding loss is the sum of the primary winding loss and the secondary winding loss.

[0082] Short-circuit the primary winding and the secondary winding of the high-frequency transformer under test.

[0083] The output of the high-frequency AC power supply is adjusted so that the actual core loss generated by the high-frequency transformer under test is equal to the target core loss. The high-frequency AC power supply is connected to the primary winding through a DC blocking capacitor.

[0084] Adjust the output of the first DC power supply so that the total actual winding loss generated in the primary and secondary windings of the high-frequency transformer under test is equal to the total target winding loss.

[0085] The temperature rise of the high-frequency transformer under test when it reaches thermal steady state is measured under the combined effect of the actual core loss and the total actual winding loss.

[0086] The first DC power supply is connected to the high-frequency transformer under test through a first isolation inductor, and is connected between the non-same-name terminal of the primary winding and the non-same-name terminal of the secondary winding.

[0087] In another embodiment, the present invention also provides a temperature rise equivalent test method applicable to high-frequency transformers with arbitrary turns ratio;

[0088] This embodiment uses a medium-voltage high-frequency transformer prototype with a rated power of 50kW, operating frequency of 20kHz, leakage inductance of 10uH, and a turns ratio of 1000V / 500V (2:1) as the test object. Figure 2 The improved temperature rise equivalent test device shown was used for testing.

[0089] 1. Determination of Target Loss: First, the target loss of the prototype under rated operating conditions was determined through experiments and calculations. Through no-load tests, the core loss of the transformer was measured at different frequencies and sinusoidal excitation voltages. An empirical formula for core loss, Pc = k * f^α * B^β, was obtained by fitting the data, where f is the frequency, B is the magnetic flux density, and k, α, and β are Steinmetz coefficients. Through short-circuit tests, the DC resistance of the windings and the AC resistance of the windings at 20kHz, 60kHz, 100kHz…380kHz were measured. Based on the operating parameters of the prototype under rated conditions (50kW, 20kHz, 1000V / 500V), the target core loss Pc1 = 60W was calculated using the empirical formula. The target primary winding loss Pwp1 = 40W and the target secondary winding loss Pws1 = 50W were calculated using the Fourier decomposition method.

[0090] 2. Device setup and parameter settings: Setup as follows Figure 2 The test circuit is shown. The high-frequency AC power supply UAC is a programmable AC source; the DC power supplies UDC1 and UDC2 are programmable DC sources. The DC blocking capacitor C is a 10μF / 1500V film capacitor. The prototype's magnetizing inductance is approximately 2mH, therefore, isolation inductors L1 and L2 with an inductance of 20mH are selected. To improve DC stability, series resistors R1 and R2 are both 0.1Ω, and parallel filter capacitors C1 and C2 are both 1000μF.

[0091] 3. Equivalent Tests and Measurements:

[0092] (1) Adjust the output frequency of the high-frequency AC power supply UAC to 20kHz, adjust its output voltage, and monitor the core loss with a power analyzer until it stabilizes at the target value Pc2 = 60W.

[0093] (2) Calculate the required DC current based on the target winding loss: Primary DC current IDC1 = sqrt(Pwp1 / Rwp_dc) = sqrt(40W / 0.0045Ω) ≈ 94.3A; Secondary DC current IDC2 = sqrt(Pws1 / Rws_dc) = sqrt(50W / 0.005Ω) ≈ 100.0A. Simultaneously adjust the output of DC power supplies UDC1 and UDC2 to stabilize their output currents at 94.3A and 100.0A respectively.

[0094] (3) Under the combined action of the AC and DC excitations described above, multiple thermocouples pre-arranged on the core and windings are used to monitor temperature changes. When the temperature at each measuring point does not change by more than 1°C within 30 minutes, it is considered to have reached thermal steady state. The temperature rise of the core hot spot at this time is recorded as 68°C, and the temperature rise of the winding hot spot is recorded as 75°C. This is the equivalent temperature rise of the prototype under the 50kW rated operating condition.

[0095] This embodiment requires only about 150W (60W + 40W + 50W) of test power to complete the temperature rise assessment of a 50kW rated power transformer. The test cost and equipment requirements are far lower than building a full-power DAB converter. At the same time, because the loss sources are accurately simulated and applied simultaneously, the test results accurately reflect the thermal characteristics under actual operating conditions.

[0096] In another embodiment, the present invention also provides a temperature rise equivalent test method applicable to high-frequency transformers with arbitrary turns ratio;

[0097] This embodiment uses a medium-voltage high-frequency transformer prototype with a rated power of 100kW, operating frequency of 20kHz, leakage inductance of 20uH, and a turns ratio of 800V / 400V (2:1) as the test object. Figure 2 The improved temperature rise equivalent test device shown was used for testing.

[0098] 1. Determination of Target Loss: First, the target loss of the prototype under rated operating conditions was determined through experiments and calculations. Through no-load tests, the core loss of the transformer was measured at different frequencies and sinusoidal excitation voltages. An empirical formula for core loss, Pc = k * f^α * B^β, was obtained by fitting the data, where f is the frequency, B is the magnetic flux density, and k, α, and β are Steinmetz coefficients. Through short-circuit tests, the DC resistance of the windings and the AC resistance of the windings at 20kHz, 60kHz, 100kHz…380kHz were measured. Based on the operating parameters of the prototype under rated conditions (100kW, 20kHz, 800V / 400V), the target core loss Pc1 = 100W was calculated using the empirical formula. The target primary winding loss Pwp1 = 80W and the target secondary winding loss Pws1 = 100W were calculated using the Fourier decomposition method.

[0099] 2. Device setup and parameter settings: Setup as follows Figure 2 The test circuit is shown. The high-frequency AC power supply UAC is a programmable AC source; the DC power supplies UDC1 and UDC2 are programmable DC sources. The DC blocking capacitor C is a 10μF / 1500V film capacitor. The prototype's magnetizing inductance is approximately 1.5mH, therefore, isolation inductors L1 and L2 with an inductance of 15mH are selected. To improve DC stability, series resistors R1 and R2 are both 0.1Ω, and parallel filter capacitors C1 and C2 are both 1000μF.

[0100] 3. Equivalent Tests and Measurements:

[0101] (1) Adjust the output frequency of the high-frequency AC power supply UAC to 20kHz, adjust its output voltage, and monitor the core loss with a power analyzer until it stabilizes at the target value Pc2 = 100W.

[0102] (2) Calculate the required DC current based on the target winding loss: Primary DC current IDC1 = sqrt(Pwp1 / Rwp_dc) = sqrt(80W / 0.005Ω) ≈ 126.5A; Secondary DC current IDC2 = sqrt(Pws1 / Rws_dc) = sqrt(100W / 0.0055Ω) ≈ 134.8A. Simultaneously adjust the output of DC power supplies UDC1 and UDC2 to stabilize their output currents at 126.5A and 134.8A respectively.

[0103] (3) Under the combined action of the AC and DC excitations described above, multiple thermocouples pre-arranged on the core and windings are used to monitor temperature changes. When the temperature at each measuring point does not change by more than 1°C within 30 minutes, it is considered to have reached thermal steady state. The temperature rise of the core hot spot at this time is recorded as 85°C, and the temperature rise of the winding hot spot is recorded as 70°C. This is the equivalent temperature rise of the prototype under 100kW rated operating conditions.

[0104] This embodiment requires only approximately 280W (100W + 80W + 100W) of test power to complete the temperature rise assessment of a 100kW rated power transformer. The test cost and equipment requirements are far lower than building a full-power DAB converter. Furthermore, because the loss sources are precisely simulated and applied simultaneously, the test results accurately reflect the thermal characteristics under actual operating conditions.

[0105] In another embodiment, the present invention also provides an improved temperature rise testing method suitable for 1:1 turns ratio high-frequency transformers; this embodiment uses a high-frequency transformer prototype with a rated power of 80kW, an operating frequency of 20kHz, and a turns ratio of 750V / 750V (1:1) as the test object, employing... Figure 5 The improved testing device is shown. First, the target loss of the prototype under rated operating conditions was determined through experiments and calculations. The DC resistances of the primary and secondary windings of the prototype are 3.8 mΩ and 4.2 mΩ, respectively. The target core loss under rated operating conditions is Pc1 = 120W, and the total winding loss is Pw1 = 115W (50W for the primary winding and 65W for the secondary winding).

[0106] Setup: Short-circuit the same-name terminals of the primary and secondary windings of the prototype. Connect the high-frequency AC power supply UAC across the primary winding via a DC blocking capacitor C. Connect the DC branch, consisting of the DC power supply UDC, isolation inductor L, series resistor R, and filter capacitor, between the non-same-name terminals of the primary and secondary windings. A programmable AC source is used for the high-frequency AC power supply UAC; a programmable DC source is used for the DC power supply UDC; and a 10μF / 1500V film capacitor is used for the DC blocking capacitor C. The prototype's magnetizing inductance is approximately 2.5mH, therefore a 25mH isolation inductor is selected.

[0107] Experimental procedure:

[0108] (1) Adjust the output frequency of the high-frequency AC power supply UAC to 20kHz, adjust its output voltage, and monitor the core loss with a power analyzer until it stabilizes at the target value Pc2 = 120W.

[0109] (2) Calculate the required DC current based on the target winding loss: IDC = sqrt(Pw1 / (Rwp_dc +Rws_dc)) = sqrt(115W / (0.0038Ω + 0.0042Ω)) = 119.9A. Adjust the DC power supply UDC so that the DC current through the winding is 119.9A.

[0110] (3) Under the combined action of the AC and DC excitations described above, multiple thermocouples pre-arranged on the core and windings are used to monitor temperature changes. When the temperature at each measuring point does not change by more than 1°C within 30 minutes, it is considered to have reached thermal steady state. The temperature rise of the core hot spot at this time is recorded as 92°C, and the temperature rise of the winding hot spot is recorded as 82°C. This is the equivalent temperature rise of the prototype under the rated operating condition of 80kW.

[0111] This embodiment employs an optimized circuit topology for the 1:1 transformer, reducing one DC power supply and DC inductor, further lowering the cost and physical size of the test setup while maintaining test accuracy.

[0112] In another embodiment, the present invention also provides an improved temperature rise test method suitable for 1:1 turns ratio high-frequency transformers; this embodiment uses a high-frequency transformer prototype with a rated power of 100kW, an operating frequency of 50kHz, and a turns ratio of 800V / 800V (1:1) as the test object, and employs... Figure 5 The improved testing device is shown. First, the target loss of the prototype under rated operating conditions is determined through experiments and calculations. The DC resistance of both the primary and secondary windings of the prototype is 5mΩ. Under rated operating conditions, the target core loss Pc1 = 200W and the total winding loss Pw1 = 160W (primary winding loss 70W and secondary winding loss 90W).

[0113] Device Setup: Short-circuit the same-name terminals of the primary and secondary windings of the prototype. The high-frequency AC power supply UAC is connected to both ends of the primary winding via a DC blocking capacitor C. A DC branch consisting of a DC power supply UDC, an isolation inductor L, a series resistor R, and a filter capacitor is connected between the non-same-name terminals of the primary and secondary windings. A programmable AC source is used for the high-frequency AC power supply UAC; a programmable DC source is used for the DC power supply UDC; and a 10μF / 1500V film capacitor is used for the DC blocking capacitor C. The prototype's magnetizing inductance is approximately 3mH, therefore a 30mH isolation inductor is selected.

[0114] Experimental procedure:

[0115] (1) Adjust the output frequency of the high-frequency AC power supply UAC to 50kHz, adjust its output voltage, and monitor the core loss with a power analyzer until it stabilizes at the target value Pc2 = 200W.

[0116] (2) Calculate the required DC current based on the target winding loss: IDC = sqrt(Pw1 / (Rwp_dc +Rws_dc)) = sqrt(160W / (0.0045Ω + 0.0055Ω)) = 126.5A. Adjust the DC power supply UDC so that the DC current through the winding is 126.5A.

[0117] (3) Under the combined action of the AC and DC excitations described above, multiple thermocouples pre-arranged on the core and windings are used to monitor temperature changes. When the temperature at each measuring point does not change by more than 1°C within 30 minutes, it is considered to have reached thermal steady state. The temperature rise of the core hot spot at this point is recorded as 90°C, and the temperature rise of the winding hot spot is recorded as 70°C. This is the equivalent temperature rise of the prototype under the 100kW rated operating condition.

[0118] This embodiment employs an optimized circuit topology for the 1:1 transformer, reducing one DC power supply and DC inductor, further lowering the cost and physical size of the test setup while maintaining test accuracy.

[0119] In the description of this specification, the references to terms such as "one embodiment / mode," "some embodiments / modes," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment / mode or example is included in at least one embodiment / mode or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment / mode or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments / modes or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments / modes or examples described in this specification, as well as the features of different embodiments / modes or examples.

[0120] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0121] Those skilled in the art should understand that the above embodiments are merely for illustrating the present invention and are not intended to limit the scope of the invention. Those skilled in the art can make other changes or modifications based on the above disclosure, and these changes or modifications still fall within the scope of the present invention.

Claims

1. A high-frequency transformer temperature rise equivalent testing device, characterized in that, The device includes: A high-frequency AC power supply, the output of which is connected to the primary winding via a DC blocking capacitor, is used to provide excitation for the high-frequency transformer under test to generate core losses. The first DC power supply has its output terminal connected to the primary winding through a first isolation inductor, and is used to provide DC current to the primary winding to generate primary winding losses. And a second DC power supply, the output of which is connected to the secondary winding through a second isolation inductor, for providing DC current to the secondary winding to generate secondary winding losses.

2. The apparatus according to claim 1, characterized in that, Preferably, the branch of the first DC power supply further includes a first resistor connected in series with the first DC power supply, and a first filter capacitor connected in parallel with the series branch of the first DC power supply and the first resistor.

3. The apparatus according to claim 1, characterized in that, When the turns ratio of the high-frequency transformer under test is 1:1, the device does not include a second DC power supply and a second isolation inductor. The primary and secondary windings of the high-frequency transformer under test are short-circuited at the same terminals. The first DC power supply and the first isolation inductor are used to simultaneously provide DC current to the primary and secondary windings.

4. The apparatus according to claim 3, characterized in that, The first DC power supply and the first isolation inductor are connected in series and then connected between the non-same-name terminals of the primary winding and the secondary winding.

5. The apparatus according to claim 1, characterized in that, The inductance of the first isolation inductor and / or the second isolation inductor is greater than the magnetizing inductance of the high-frequency transformer under test.

6. A method for equivalent temperature rise testing of a high-frequency transformer, characterized in that, The method includes the following steps: Determine the target core loss and target winding loss of the high-frequency transformer under rated operating conditions; Adjust the output of the high-frequency AC power supply so that the actual core loss generated by the high-frequency transformer under test is equal to the target core loss; Adjust the output of the first DC power supply and / or the second DC power supply so that the actual winding loss generated in the winding of the high-frequency transformer under test is equal to the target winding loss. The temperature rise of the high-frequency transformer under test when it reaches thermal steady state is measured under the combined effect of the actual core loss and the actual winding loss.

7. The method according to claim 6, characterized in that, The determination of the target core loss and target winding loss includes: calculating the target core loss and target winding loss using analytical formulas or finite element methods.

8. The method according to claim 6, characterized in that, The determination of the target core loss and target winding loss includes: obtaining the core loss characteristics of the high-frequency transformer under test through no-load testing, and obtaining the winding resistance characteristics through short-circuit testing.

9. The method according to claim 8, characterized in that, The determination of target core loss and target winding loss also includes: calculating the target core loss and target winding loss based on the characteristics and rated operating condition parameters.

10. The method according to claim 6, characterized in that, The steps of adjusting the high-frequency AC power output and adjusting the DC power output are performed simultaneously.

Images