Design method and device of underground small transformer
Patent Information
- Application Number
- CN202310863049.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-07-13
- Publication Date
- 2025-01-14
AI Technical Summary
In the downhole environment, the core saturation flux density and loss density of the transformer are affected by high temperature, resulting in a reduced energy transmission efficiency and a small deep well bore, making it difficult to design a traditional transformer.
By determining the appropriate core material and margin coefficient, calculating the window utilization coefficient, adjusting the number of cores and winding turns, and optimizing the transformer design to adapt to high temperature environments.
It realizes the effective design of small and medium-sized transformers in special underground environments, improves energy transmission efficiency, and meets the needs of underground use.
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Figure CN119312752A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of transformers, and in particular relates to a design method for a small underground transformer. Background Art
[0002] The transformer is the core component in the charging process of the liquid-electric pulse shock wave device, which can realize the functions of voltage boosting and energy transmission.
[0003] In certain special environments such as oil drilling, for example, underground environments, due to the high ambient temperature underground, parameters such as the saturation flux density and loss density of the transformer core will be affected, making it impossible for the transformer to operate in the optimal state, and the energy transmission efficiency of the transformer will be significantly reduced; moreover, the borehole size of deep wells is small, and the volume and shape of the transformer are greatly restricted, making it difficult to design the transformer using traditional methods. Summary of the invention
[0004] The object of the present invention is to provide a design method for a small underground transformer to solve the problem of using the existing transformer in an underground environment mentioned in the above background technology.
[0005] To achieve the above object, the present invention provides the following technical solution: a design method for an underground small transformer, comprising:
[0006] Determine the material of the magnetic core, and obtain the saturation magnetic flux density of the magnetic core under a first temperature condition and the saturation magnetic flux density under a second temperature condition, wherein the first temperature is greater than the second temperature;
[0007] Setting a margin coefficient and the number of magnetic cores, wherein an initial value of the margin coefficient is a ratio of a saturation magnetic flux density of the magnetic core material under a first temperature condition to a saturation magnetic flux density under a second temperature condition, and an initial value of the initial setting of the number of magnetic cores is 1;
[0008] Calculate the window utilization factor based on the margin factor and the initial value of the number of magnetic cores, and compare it with the set value of the window utilization factor;
[0009] When the window utilization coefficient is not less than the set value of the window utilization coefficient, at least one of the margin coefficient and the number of magnetic cores is updated, and the window utilization coefficient is recalculated based on the updated margin coefficient and the number of magnetic cores until the window utilization coefficient is less than the set value.
[0010] Preferably, the method further comprises:
[0011] When the window utilization factor is less than the set value, the transformer design is terminated.
[0012] Preferably, the determining of the magnetic core material comprises:
[0013] Based on the hysteresis loops of the magnetic core under the first temperature and the second temperature conditions, a saturation magnetic flux density of the magnetic core at the first temperature and a saturation magnetic flux density of the magnetic core at the second temperature are obtained;
[0014] The loss density of the magnetic core under the first temperature condition and the loss density under the second temperature condition are calculated respectively;
[0015] Respectively comparing the saturation magnetic flux density of the magnetic core at the first temperature, the ratio of the saturation magnetic flux density of the magnetic core at the first temperature to the saturation magnetic flux density of the magnetic core at the second temperature, and the ratio of the loss density of the magnetic core at the first temperature to the loss density of the magnetic core at the second temperature with their respective set values;
[0016] When the saturation magnetic flux density of the magnetic core at the first temperature and the ratio of the saturation magnetic flux density of the magnetic core at the first temperature to the saturation magnetic flux density of the magnetic core at the second temperature are greater than their respective set values, and the ratio of the loss density of the magnetic core under the first temperature condition to the loss density under the second temperature condition is less than its set value, the magnetic core material is used as the final magnetic core material.
[0017] Preferably, the first temperature is between 120°C and 200°C, and the second temperature is between 20°C and 30°C.
[0018] Preferably, before calculating the window utilization coefficient based on the margin coefficient and the number of magnetic cores, the method further includes:
[0019] Determine the preset parameters of the transformer, wherein the preset parameters include transformation ratio, cross-sectional area of the primary winding wire, cross-sectional area of the secondary winding wire and dimension parameters of the magnetic core.
[0020] Preferably, the method further comprises:
[0021] Based on the size parameters of the magnetic core, the effective cross-sectional area of the transformer magnetic core is obtained.
[0022] Preferably, the calculation of the window utilization coefficient based on the margin coefficient and the number of magnetic cores includes:
[0023] The number of turns of the primary winding is calculated based on the margin coefficient and the effective cross-sectional area of the transformer core;
[0024] The number of turns of the secondary winding is calculated based on the number of turns of the primary winding and the transformation ratio;
[0025] The window utilization factor is calculated based on the number of primary winding turns, the number of secondary winding turns and the size parameters of the magnetic core.
[0026] Preferably, updating at least one of the margin coefficient and the number of magnetic cores comprises:
[0027] Increase the number of magnetic cores;
[0028] Compare the updated number of magnetic cores with the maximum number of magnetic cores;
[0029] When the updated number of magnetic cores is less than the maximum number of magnetic cores, the window utilization factor is recalculated based on the updated number of magnetic cores.
[0030] Preferably, the updating of at least one of the margin coefficient and the number of magnetic cores further comprises:
[0031] When the updated number of magnetic cores is greater than or equal to the maximum number of magnetic cores, the value of the margin coefficient is reduced and the number of magnetic cores is initialized.
[0032] Preferably, the number of magnetic cores increases by 1 each time.
[0033] The present application also discloses a design device for an underground small transformer, the device comprising:
[0034] An oven component, wherein the oven component is configured to construct a test space with a temperature varying between 0°C and 200°C and capable of being maintained at any temperature;
[0035] a signal generator configured to generate an electrical signal;
[0036] A digital oscilloscope has a voltage probe and a current probe connected to it through wires, and generates an image based on voltage or current signals collected by the voltage probe and the current probe.
[0037] Preferably, the device further comprises:
[0038] A power amplifier is used to amplify the electrical signal generated by the signal generator and then output to the primary winding.
[0039] Compared with the prior art, the present invention has the following beneficial effects:
[0040] The present application selects suitable magnetic core materials, measures the saturation magnetic flux density of the magnetic core under a first temperature condition and the saturation magnetic flux density under a second temperature condition, sets a margin coefficient based on the saturation magnetic flux density of the magnetic core under the first temperature condition and the saturation magnetic flux density under the second temperature condition, and verifies the window utilization coefficient of the transformer based on the number of magnetic cores set by the margin coefficient, so as to realize the design of a small underground transformer that can meet the use requirements in special underground environments. BRIEF DESCRIPTION OF THE DRAWINGS
[0041] Figure 1 Application Method Process Figure 1 ;
[0042] Figure 2 Application Method Process Figure 2 ;
[0043] Figure 3 Application Method Process Figure 3 ;
[0044] Figure 4 Application Method Process Figure 4 ;
[0045] Figure 5 This is a schematic diagram of the device of this application. DETAILED DESCRIPTION
[0046] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0047] Reference Figure 5 ,A device for designing a small underground transformer (hereinafter referred to as transformer) (hereinafter referred to as design device), comprising:
[0048] An oven component, the oven component is configured to construct a test space with a temperature varying between 0°C and 200°C and capable of being maintained at any temperature;
[0049] a signal generator configured to generate an electrical signal;
[0050] A digital oscilloscope has a voltage probe and a current probe connected to it through wires, and generates an image based on voltage or current signals collected by the voltage probe and the current probe.
[0051] In some embodiments, the above-mentioned device also includes a power amplifier, which is configured to amplify and output the electrical signal generated by the above-mentioned signal generator.
[0052] In some embodiments, a magnetic core wound with a primary winding and a secondary winding is placed in a test area, the lead wire of the primary winding is connected to the above-mentioned signal generator, and the above-mentioned cable probe is connected to one of the lead wires of the primary winding, and the lead wire of the secondary winding is connected to the above-mentioned voltage probe. When in use, the temperature of the test area in the oven component is adjusted to construct different test environments and realize the design of the transformer.
[0053] In some embodiments, a power amplifier is provided between the primary winding and the signal generator, and the electrical signal generated by the signal generator is amplified by the power amplifier and then output to the primary winding.
[0054] Reference Figure 1-Figure 4 , a design method for a small underground transformer, comprising:
[0055] S100: Determine the core material and obtain the saturation magnetic flux density (B h ) and the saturation flux density (B) under the second temperature condition r ), the first temperature is greater than the second temperature;
[0056] S200: Setting a margin coefficient and the number of magnetic cores, wherein an initial value of the margin coefficient is a ratio of a saturation magnetic flux density of the magnetic core material under a first temperature condition to a saturation magnetic flux density under a second temperature condition, and an initial value of the number of magnetic cores is 1;
[0057] S300: Calculating the window utilization coefficient based on the margin coefficient and the initial value of the number of magnetic cores, and comparing it with the set value of the window utilization coefficient;
[0058] S400: When the window utilization coefficient is not less than a set value of the window utilization coefficient, updating at least one of the margin coefficient and the number of magnetic cores, and recalculating the window utilization coefficient based on the updated margin coefficient and the number of magnetic cores until the window utilization coefficient is less than the set value;
[0059] Furthermore, the above method also includes:
[0060] S401: When the window utilization coefficient is less than the set value, the transformer design is terminated.
[0061] The first temperature is between 120°C and 200°C (including 120°C and 200°C), and the second temperature is room temperature (for example, 25°C);
[0062] Specifically, determining the core material includes:
[0063] S101: Based on the hysteresis loop of the magnetic core at the first temperature and the second temperature, the saturation magnetic flux density (B) of the magnetic core at the first temperature is obtained. h ) and the saturation flux density of the core at the second temperature (B r );
[0064] S102: Calculate the loss density (P) of the magnetic core under the first temperature condition. h ) and the loss density under the second temperature condition (P r );
[0065] S103: respectively calculate the saturation magnetic flux density (B h ), the saturation flux density of the core at the first temperature (B h ) and the saturation flux density of the core at the second temperature (B r ) and the loss density of the core under the first temperature condition (P h) and the loss density under the second temperature condition (P r ) are compared with their respective set values;
[0066] Furthermore, the confirmation of the core material also includes:
[0067] S104: When the saturation flux density (B h ) and the saturation flux density of the core at the first temperature (B h ) and the saturation flux density of the core at the second temperature (B r ) is greater than their respective set values, the loss density (P h ) and the loss density under the second temperature condition (P r ) is less than its set value, the magnetic core material is used as the final magnetic core material;
[0068] In some embodiments, the confirmation of the magnetic material is based on the design process of the magnetic core material implemented by the design device, that is, the selected test magnetic core wound with the primary winding and the secondary winding is placed in the test area in the oven component for testing;
[0069] Specifically, the above determination process is described by selecting a ring-shaped iron-based amorphous alloy magnetic core (hereinafter referred to as magnetic core) as the experimental material, wherein the specifications of the magnetic core include an outer diameter d0, an inner diameter d i The height is h, and the number of turns of the primary winding is N. t1 , the number of turns of the secondary winding is N t2 ,At the same time, the signal generator in the design device is configured to output a sinusoidal voltage with a frequency of 1500HZ;
[0070] During the test, the temperature of the test area in the oven component is set to a normal temperature of 25°C (the second temperature) and a high temperature of 150°C (the first temperature), and the amplification factor of the power amplifier is adjusted so that the peak current in the primary winding reaches D, so that the magnetic core reaches saturation, and the secondary voltage and primary current of the magnetic core are measured by a voltage probe connected to the secondary winding and a current probe connected to the primary winding, respectively, and an image is generated by a digital oscilloscope;
[0071] Based on the voltage and current data measured by the voltage probe and the current probe, combined with basic parameters (such as the size data of the magnetic core), the magnetic field strength is calculated. Specifically, the magnetic field strength is calculated based on the following formula (1):
[0072] H=N t1 i / L c (1)
[0073] In formula (1), H represents the magnetic field strength, N t1Indicates the number of turns of the primary winding of the test, i represents the primary current of the magnetic core, L c Indicates the magnetic path length of the core. Further, L c (Magnetic path length) calculation formula (2) is as follows:
[0074] Lc=π(d0+d i ) / twenty two)
[0075] In formula (2), d0 is the outer diameter of the magnetic core, d i is the inner diameter of the core;
[0076] Based on the voltage and current data measured by the voltage probe and the current probe, combined with basic parameters (such as the size data of the magnetic core), the magnetic flux density is calculated. Specifically, the magnetic flux density is calculated based on the following formula (3):
[0077] B = ∫udt / (N t2 S0) (3)
[0078] In formula (3), B is the magnetic flux density, u is the secondary voltage of the magnetic core, t is the time, N t2 To test the number of turns of the secondary winding, S0 is the cross-sectional area of a single magnetic core, and its calculation formula (4) is as follows:
[0079] S0=h(d0-d i ) / twenty four)
[0080] In formula (4), d0 is the outer diameter of the core, d i is the inner diameter of the core, h is the height of the core;
[0081] After the magnetic field intensity and magnetic flux density data are calculated based on the above formulas (1) and (3), the hysteresis loops of the magnetic core at 25°C and 150°C are drawn based on the magnetic field intensity and magnetic flux density data, and the saturation magnetic flux density B of the magnetic core at 25°C and 150°C is obtained based on the drawn hysteresis loops. r and B h ;
[0082] Furthermore, based on formula (5), the loss density of the magnetic core at 25°C and 150°C is calculated. Specifically, formula (5) is as follows:
[0083] P=fN t2 ∮HdB / N t1 (5)
[0084] In formula (5), P is the loss density, N t1 To test the number of turns of the primary winding, N t2 To test the turns of the secondary winding;
[0085] Based on the above formula (5), the loss density P of the magnetic core at 25℃ and 150℃ is obtained respectively. r and P h ;
[0086] In some embodiments, the saturation flux density B of the magnetic core at 25°C and 150°C calculated based on the above formula is r and B h And the loss density P r and P h , and then judge the quality of the selected magnetic core material. Specifically, the judgment process is as follows:
[0087] Setting a first standard value (e.g., 1 T) for the saturation magnetic flux density of the magnetic core at a first temperature;
[0088] Setting a second marked value for the ratio of the saturation magnetic flux density of the magnetic core at the first temperature to the saturation magnetic flux density of the magnetic core at the second temperature;
[0089] Setting a third standard value for the ratio of the loss density of the magnetic core under the first temperature condition to the loss density under the second temperature condition;
[0090] The calculated saturation flux density (B h ) is the same as the first standard value, the saturation flux density (B) of the magnetic core at the first temperature (150°C) h ) and the saturation flux density (B) of the core at the second temperature (25°C) r ) with the second standard value and the loss density (P h ) and the loss density (P r ) is compared with the third standard value;
[0091] When the saturation flux density (B h ) is greater than the first standard value, the saturation flux density (B h ) and the saturation flux density of the core at the second temperature (B r ) is greater than the second standard value, the loss density of the magnetic core under the first temperature condition (P h ) and the loss density under the second temperature condition (P r ) is less than the third standard value, it means that the selected magnetic core material meets the design standard. Correspondingly, this type of magnetic core is selected as the magnetic core of the downhole transformer. When the comparison result does not meet the above settings, it is necessary to reselect the magnetic core material and repeat the above experiment until the comparison result of the selected magnetic core material meets the above settings.
[0092] In some embodiments, based on the determined magnetic core material, the subsequent transformer design is completed. Specifically, in the early stage of design, some parameters of the transformer need to be preset (hereinafter referred to as preset parameters, step S110). Specifically, the preset parameters include the transformer ratio K (such as voltage ratio), the primary winding wire cross-sectional area (A1) and the secondary winding wire cross-sectional area (A2). At the same time, the size parameters of the magnetic core (such as the inner diameter of the magnetic core, the outer diameter of the magnetic core and the height of the magnetic core) are also determined accordingly, that is, the size parameters of the magnetic core constitute a part of the preset parameters. Correspondingly, based on the size parameters of the magnetic core component, the window area of the magnetic core is calculated by formula (6), and formula (6) is as follows:
[0093] A w =πd i 2 / 4 (6)
[0094] In formula (6), A w represents the window area, d i is the inner diameter of the core;
[0095] In some embodiments, the margin coefficient and the number of magnetic cores are set values (steps S201 and S202), and can be adjusted accordingly based on subsequent calculation results (the adjustment process will be described later), and the initial setting of the margin coefficient is the saturation flux density (B) of the magnetic core under the first temperature (150°C). h ) and the saturation magnetic flux density (B) under the second temperature (25°C) r ), and the initial setting value of the number of magnetic cores is 1;
[0096] Further, after the number of magnetic cores is set, the effective cross-sectional area of the transformer magnetic core is calculated accordingly (step S203). Specifically, the effective cross-sectional area calculation formula (7) of the transformer magnetic core is as follows:
[0097] S=nS0 (7)
[0098] In formula (7), n represents the number of magnetic cores, S0 represents the effective cross-sectional area of a single magnetic core, and its calculation formula refers to formula (4);
[0099] In some embodiments, based on the margin factor (K m ) and the number of magnetic cores (n) to calculate the window utilization coefficient (step S205), specifically including:
[0100] S204a: Calculate the number of turns of the primary winding based on the margin coefficient and the effective cross-sectional area of the transformer core;
[0101] S204b: Calculate the number of turns of the secondary winding based on the number of turns of the primary winding and the transformation ratio;
[0102] S205a: Calculate the window utilization coefficient based on the number of turns of the primary winding, the number of turns of the secondary winding and the size parameters of the magnetic core;
[0103] The formula (8) for calculating the number of primary winding turns based on the margin coefficient, the number of magnetic cores and preset parameters is as follows:
[0104] N1=λ m / k m B r S (8)
[0105] In formula (8), N1 represents the number of turns of the primary winding, K m is the margin factor, B r is the saturation flux density of the core material under the second temperature condition (e.g. 25°C), S is the effective cross-sectional area of the transformer core, and λ m is the maximum value of the primary volt-seconds. Correspondingly, the calculation formula (9) of the primary volt-seconds λ is as follows:
[0106] λ=∫u c dt (9)
[0107] Calculating the number of turns of the secondary winding based on the number of turns of the primary winding and the preset parameters specifically includes obtaining the number of turns of the secondary winding based on the number of turns of the primary winding and the transformation ratio (step S204). Correspondingly, the calculation formula (10) is as follows:
[0108] N2=kN1 (10)
[0109] In formula (10), N2 represents the number of turns of the secondary winding, N1 represents the number of turns of the primary winding, and K represents the transformer ratio;
[0110] The calculation formula (11) for the window utilization coefficient is calculated based on the number of turns of the primary winding, the number of turns of the secondary winding and the preset parameters as follows:
[0111] k u =(N1A1+N2A2) / A w (11)
[0112] In formula (11), K u It represents the window utilization coefficient, A1 is the cross-sectional area of the primary winding wire, A2 is the cross-sectional area of the secondary winding wire, and A w is the window area of the core;
[0113] When the window utilization coefficient (K u ) and then the window utilization coefficient (K u) satisfies the working conditions for judgment (step S301). Specifically, there is a set value for the window utilization coefficient. When the calculated window utilization coefficient is less than the set value, it means that the window utilization coefficient meets the working conditions (that is, step S301 is yes), and the design process of the transformer can be ended. Correspondingly, the above preset parameters and the number of cores are the design parameters of the final transformer. When the calculated window utilization coefficient is greater than or equal to the set value, it means that the window utilization coefficient does not meet the working conditions (that is, step S301 is no). Correspondingly, the above calculation method enters the subsequent correction process, that is, it is necessary to update the number of cores (n) and the margin coefficient (K) correspondingly. m ), specifically, the correction process includes:
[0114] S302: increasing the number of magnetic cores. Specifically, the number of magnetic cores is increased by 1 each time.
[0115] S303: Compare the updated number of magnetic cores with the maximum number of magnetic cores;
[0116] When the updated number of magnetic cores is less than the maximum number of magnetic cores, the window utilization coefficient is recalculated based on the updated number of magnetic cores, that is, steps S203, S204 and S205 are performed;
[0117] Specifically, the window utilization factor is recalculated based on the updated number of magnetic cores including:
[0118] Based on the updated number of magnetic elements, the effective cross-sectional area of the transformer core is recalculated (step S203);
[0119] Repeat the above steps S203 (i.e., calculating the number of turns of the primary winding and the number of turns of the secondary winding), S204 (calculating the updated window utilization coefficient), and S205 (judging whether the window utilization coefficient meets the working conditions);
[0120] When the window utilization factor meets the working conditions, the design process ends;
[0121] When the window utilization coefficient does not meet the working conditions, re-enter the above correction process;
[0122] When the updated number of cores is greater than or equal to the maximum number of cores, reduce the margin factor (K m ) and initialize the number of cores mentioned above. Finally, based on the updated margin coefficient (K m ) and the number of initialized magnetic cores are recalculated. Specifically, the recalculation process includes:
[0123] Recalculate the number of turns of the primary winding and the number of turns of the secondary winding (step S204),
[0124] Recalculating the window utilization coefficient based on the recalculated primary winding turns and secondary winding turns (step S205);
[0125] It is judged whether the recalculated window utilization coefficient meets the working conditions (step S301);
[0126] When the window utilization factor meets the working conditions, the design process ends;
[0127] When the window utilization factor does not meet the working conditions, repeat the above correction process.
[0128] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.
Claims
1. A design method for an underground small transformer, characterized in that: Determine the material of the magnetic core, and obtain the saturation magnetic flux density of the magnetic core under a first temperature condition and the saturation magnetic flux density under a second temperature condition, wherein the first temperature is greater than the second temperature; Setting a margin coefficient and the number of magnetic cores, wherein an initial value of the margin coefficient is a ratio of a saturation magnetic flux density of the magnetic core material under a first temperature condition to a saturation magnetic flux density under a second temperature condition, and an initial value of the number of magnetic cores is 1; Determine the window utilization factor based on the margin factor and the initial value of the number of magnetic cores, and compare with the set value of the window utilization factor; When the window utilization coefficient is not less than the set value of the window utilization coefficient, at least one of the margin coefficient and the number of magnetic cores is updated, and the window utilization coefficient is re-determined based on the updated margin coefficient and the number of magnetic cores until the window utilization coefficient is less than the set value.
2. The design method of a small underground transformer according to claim 1 is characterized in that: The method further comprises: When the window utilization factor is less than the set value, the transformer design is terminated.
3. The design method of a small underground transformer according to claim 1 or 2, characterized in that: Determining the magnetic core material comprises: Based on the hysteresis loops of the magnetic core under the first temperature and the second temperature conditions, a saturation magnetic flux density of the magnetic core at the first temperature and a saturation magnetic flux density of the magnetic core at the second temperature are obtained; The loss density of the magnetic core under the first temperature condition and the loss density under the second temperature condition are calculated respectively; Respectively comparing the saturation magnetic flux density of the magnetic core at the first temperature, the ratio of the saturation magnetic flux density of the magnetic core at the first temperature to the saturation magnetic flux density of the magnetic core at the second temperature, and the ratio of the loss density of the magnetic core at the first temperature to the loss density of the magnetic core at the second temperature with their respective set values; When the saturation magnetic flux density of the magnetic core at the first temperature and the ratio of the saturation magnetic flux density of the magnetic core at the first temperature to the saturation magnetic flux density of the magnetic core at the second temperature are greater than their respective set values, and the ratio of the loss density of the magnetic core under the first temperature condition to the loss density under the second temperature condition is less than its set value, the magnetic core material is used as the final magnetic core material.
4. The design method of a small underground transformer according to claim 1 is characterized in that: The first temperature is between 120°C and 200°C, and the second temperature is between 20°C and 30°C.
5. The design method of a small underground transformer according to claim 1 is characterized in that: Before calculating the window utilization coefficient based on the margin coefficient and the number of magnetic cores, the method further includes: Determine preset parameters of the transformer, the preset parameters including transformation ratio, cross-sectional area of primary winding wire, cross-sectional area of secondary winding wire and dimension parameters of the magnetic core, the transformation ratio being the voltage ratio of the transformer.
6. The design method of a small underground transformer according to claim 5, characterized in that: The method further comprises: Based on the size parameters of the magnetic core, the effective cross-sectional area of the transformer magnetic core is obtained.
7. The design method of a small underground transformer according to claim 6, characterized in that: The determining of the window utilization coefficient based on the initial values of the margin coefficient and the number of magnetic cores or the re-determining of the calculation of the window utilization coefficient based on the updated margin coefficient and the number of magnetic cores includes: The number of turns of the primary winding is calculated based on the margin coefficient and the effective cross-sectional area of the transformer core; The number of turns of the secondary winding is calculated based on the number of turns of the primary winding and the transformation ratio; The window utilization factor is calculated based on the number of primary winding turns, the number of secondary winding turns and the size parameters of the magnetic core.
8. The design method of a small underground transformer according to claim 7, characterized in that: The updating of at least one of the margin coefficient and the number of magnetic cores comprises: Increase the number of magnetic cores; Compare the updated number of magnetic cores with the maximum number of magnetic cores; When the updated number of magnetic cores is less than the maximum number of magnetic cores, the window utilization factor is recalculated based on the updated number of magnetic cores.
9. The design method of a small underground transformer according to claim 8, characterized in that: The updating of at least one of the margin coefficient and the number of magnetic cores further comprises: When the updated number of magnetic cores is greater than or equal to the maximum number of magnetic cores, the value of the margin coefficient is reduced and the number of magnetic cores is initialized.
10. The design method of a small underground transformer according to claim 8, characterized in that: The number of magnetic cores increases by 1 each time.
11. A design device for a small underground transformer, characterized in that: The device is used to implement the method according to any one of claims 1 to 10, and the device includes: An oven component, wherein the oven component is configured to construct a test space with a temperature varying between 0°C and 200°C and capable of being maintained at any temperature; a signal generator configured to generate an electrical signal; A digital oscilloscope has a voltage probe and a current probe connected to it through wires, and generates an image based on voltage or current signals collected by the voltage probe and the current probe.
12. The design device for a small underground transformer according to claim 11, characterized in that: The device also includes: A power amplifier is used to amplify the electrical signal generated by the signal generator and then output to the primary winding.