Rectifier transformer with built-in saturable reactor and load test circuit and method thereof

Abstract

The invention provides a rectifier transformer with a built-in saturable reactor and a load test circuit and method.The rectifier transformer comprises a power module, a test sample and an intermediate transformer connected with the power module and the test sample, and a compensation reactor is connected between the power module and the intermediate transformer in parallel; a compensation capacitor is connected in parallel between the intermediate transformer and the test sample, a saturable reactor is arranged in the test sample, the saturable reactor adopts a single-group iron core winding structure, and the single-group iron core winding structure at least comprises two groups of independent windings. And the positive terminal of each group of independent windings is connected with the negative terminal of the adjacent independent winding.

Description

Technical Field

[0001] The present application relates to the technical field of transformers, and in particular to a rectifier transformer with a built-in saturable reactor and a load test circuit and method thereof. Background Art

[0002] When conducting temperature rise tests on existing rectifier transformers, current is usually applied from the high voltage side because the voltage regulator section of the rectifier transformer only has a high voltage winding and a compensation winding. The capacity of the compensation winding is much lower than the rated capacity of the product. Therefore, current can only be applied from the high voltage side. See the attached schematic diagram of the rectifier transformer. Figure 3 .

[0003] Typically, transformers undergoing temperature rise (load) tests are inductive, resulting in an extremely low power factor and requiring a very large power supply. Without parallel compensation capacitors, the test manufacturer would not be able to obtain such a large power supply. When testing with a saturated reactor, due to the unique load characteristics, the load current oscillates, maintaining a high level at the moment of closing. This is typically between 50% and 65% of the rated applied current, representing the equilibrium point. The current at this equilibrium point is determined by the high-voltage side voltage and the reactive power compensation capacity of the capacitors. At the conclusion of the test, the current is reduced. Once it reaches this equilibrium point, it cannot be reduced any further. Therefore, the test will open the circuit breaker between 50% and 60% of the rated current.

[0004] The compensating current is capacitive, which helps magnetize the generator set. If the compensating capacitance is too large, the intermediate transformer's ratio will be poorly matched (slightly too high), the compensating capacitance will be excessive, and the capacitive current will cause the generator to self-excite. This will cause the generator voltage to rise instantaneously, triggering the generator's overcurrent protection device. Furthermore, the test piece will instantly disconnect under high load, making this situation unsafe for the generator, the compensating capacitor, and the test piece. Summary of the Invention

[0005] The embodiments of the present application provide a rectifier transformer with a built-in saturable reactor and a load test circuit and method thereof, so as to at least address the deficiencies in the above-mentioned related technologies.

[0006] In the first aspect, an embodiment of the present application provides a rectifier transformer with a built-in saturated inductor, comprising a power module, a test sample, and an intermediate transformer connecting the power module and the test sample, a compensation inductor is connected in parallel between the power module and the intermediate transformer, a compensation capacitor is connected in parallel between the intermediate transformer and the test sample, a saturated inductor is provided in the test sample, and the saturated inductor adopts a single-group iron core winding structure, and the single-group iron core winding structure includes at least two groups of independent windings, and the positive terminal of each group of independent windings is connected to the negative terminal of its adjacent independent winding.

[0007] Furthermore, the negative terminals of the independent windings are connected in parallel to reduce the impedance difference between phases.

[0008] The present invention further provides a load test method for a rectifier transformer with a built-in saturable reactor, which is applied to the above-mentioned rectifier transformer. The load test method comprises the following steps:

[0009] Step 1: Obtaining the impedance voltage value of the saturated reactor in the test sample in a saturated state;

[0010] Step 2: performing a load test on the rectifier transformer to obtain the transformation ratio value of the saturated reactor in the high-voltage state and the low-voltage state, and determining the impedance voltage conversion value of the saturated reactor using the transformation ratio value;

[0011] Step three: Calculate the compensation capacity of the rectifier transformer according to the impedance voltage conversion value, and adjust the capacity of the compensation reactor according to the compensation capacity to achieve mutual cancellation of currents between capacitors and inductors.

[0012] Furthermore, the calculation formula of the impedance voltage conversion value of the saturated reactor is:

[0013]

[0014] Where, u represents the impedance voltage value of the saturated reactor in the saturated state, Indicates the transformation ratio of the saturated reactor in high voltage state and low voltage state.

[0015] Furthermore, the calculation formula of the compensation capacity of the rectifier transformer is:

[0016]

[0017] Where U B Indicates the high-voltage side impedance voltage value under the rated loss of the main modulating transformer load test, Q c Indicates the total capacitance corresponding to the load test.

[0018] The present invention also provides a load test circuit for a rectifier transformer with a built-in saturable reactor, which is applied to the above-mentioned rectifier transformer.

[0019] Compared with the related art, the embodiment of the present application provides a rectifier transformer with a built-in saturated inductor and its load test circuit and method. By converting the impedance voltage value of the load test, the compensation capacity is determined using the converted value, and the compensation capacity is used to construct a reactive inductance compensation of equal capacity in series with the line. The mutual cancellation characteristic of the capacitor and inductor current is used for suppression, so that the opening and closing current of the test product is very close to zero, eliminating current oscillation.

[0020] The details of one or more embodiments of the present application are set forth in the following drawings and description to make other features, objects, and advantages of the present application more readily apparent. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0022] Figure 1 The impedance ohm value distribution diagram of the same rectifier transformer with and without saturated reactor at the same current in the prior art;

[0023] Figure 2 This is the wiring diagram for the temperature rise test of a product with a built-in saturated reactor in the prior art;

[0024] Figure 3 It is the principle diagram of the rectifier transformer in the prior art;

[0025] Figure 4 This is a wiring diagram for the temperature rise test of the rectifier transformer in the first embodiment of the present invention;

[0026] Figure 5 This is a structural diagram of a saturable reactor included in the first embodiment of the present invention;

[0027] Figure 6 Flowchart of a load test method for a rectifier transformer with a built-in saturable reactor according to a second embodiment of the present invention;

[0028] Figure 7 This is a schematic structural diagram of a built-in saturable reactor according to a second embodiment of the present invention;

[0029] Figure 8 1 is a diagram showing the impedance ohmic value distribution of the rectifier transformer in the prior art and the rectifier transformer in the second embodiment of the present invention under the same current.

[0030] The following specific embodiments will further illustrate the present invention in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of this application more clearly understood, the present application is described and illustrated below in conjunction with the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely used to explain this application and are not intended to limit this application. Based on the embodiments provided in this application, all other embodiments obtained by those of ordinary skill in the art without making any creative efforts are within the scope of protection of this application.

[0032] Obviously, the drawings described below are merely examples or embodiments of the present application. Those skilled in the art can, without inventive effort, apply the present application to other similar scenarios based on these drawings. Furthermore, it is also understood that, although the effort involved in such a development process may be complex and lengthy, for those skilled in the art related to the content disclosed in this application, changes in design, manufacturing, or production based on the technical content disclosed in this application are merely conventional technical means and should not be construed as an insufficiency of the content disclosed in this application.

[0033] References to "embodiments" in this application mean that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it refer to independent or alternative embodiments that are mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described in this application may be combined with other embodiments unless there is a conflict.

[0034] Unless otherwise defined, the technical terms or scientific terms involved in this application should be understood by people with ordinary skills in the technical field to which this application belongs. The words "one", "a", "a", "the" and the like involved in this application do not indicate a quantitative limitation and may represent the singular or plural. The terms "include", "comprise", "have" and any of their variations involved in this application are intended to cover non-exclusive inclusions; for example, a process, method, system, product or device that includes a series of steps or modules (units) is not limited to the listed steps or units, but may also include steps or units that are not listed, or may also include other steps or units inherent to these processes, methods, products or devices. The words "connect", "connected", "coupled" and the like involved in this application are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect.

[0035] In the prior art, the impedance ohm value of the same rectifier transformer with and without saturation reactor at the same current is as follows: Figure 1 As shown, in the coordinate system: the horizontal axis represents the current value on the high-voltage side of the test piece, the vertical axis represents the voltage value on the high-voltage side of the test piece, straight line 1 represents the impedance ohmic value curve of the rectifier transformer without a saturated reactor, straight line 2 represents the impedance ohmic value curve of the rectifier transformer with a built-in saturated reactor, and straight line 3U' represents the high-voltage side voltage value at the moment when the high and low voltage windings are turned on during the temperature rise (load) test of the rectifier transformer with a saturated reactor.

[0036] Line 1 shows the impedance voltage versus applied current curve for the test product with the built-in saturated reactor removed. Line 1 shows that when current is applied to the product, a corresponding voltage value appears at the line end. The two are directly proportional, i.e., U / I = Z, where Z is a constant value.

[0037] Line 2 represents the curve of the impedance voltage value and current change of the transformer with a saturated reactor (hereinafter referred to as saturated reactor) inside the same test product.

[0038] The straight line portion U' represents the impedance voltage value converted to the impedance voltage value on the high-voltage side after saturation.

[0039] The impedance voltage value of the product with saturated impedance is divided into two parts, one is the fixed value U', which is the impedance voltage value of the saturated impedance, and the other is the impedance voltage value of the transformer itself that changes with the current. Figure 1 It can be seen that the slope of the straight line 2, which is the impedance value with saturation resistor of the same product, is greater than the slope of the straight line 1, which is the impedance value without saturation resistor.

[0040] As can be seen from the straight line portion of Line 2, when the test product voltage reaches a very high level, it does not exceed the U' value. Due to the saturation resistor impedance (large inductance), the test product current remains zero, that is, IL is zero. At this point, the test circuit is purely capacitive. This is in stark contrast to a test product without a saturation resistor. Once current flows through the test product, the saturation resistor immediately enters saturation, generating a fixed impedance voltage value, U'. At this point, the line oscillates under the influence of the compensation capacitor and the test product inductance, causing the test product current to surge instantaneously. If the intermediate transformer ratio and compensation capacitance are not properly matched, the power supply overload protection may even be triggered at the moment of closing the circuit. The reasons for this will be explained later.

[0041] It is precisely because of the load characteristics of the product with built-in saturated inductor that the implementation of temperature rise (load) test is difficult.

[0042] The wiring diagram for the temperature rise (or load test) test of the saturated reactor product is attached. Figure 2 As shown, the test sample is pressed Figure 2 After the mode is connected, the corresponding parameters will be set before power is supplied. The parameters are divided into the transformation ratio of the intermediate transformer and the compensation capacitance of the compensation capacitor.

[0043] During the temperature rise test, current is usually applied from the high voltage side because the voltage regulator of the rectifier transformer only has a high voltage winding and a compensation winding. The capacity of the compensation winding is much lower than the rated capacity of the product. Therefore, the rectifier transformer can only be applied from the high voltage side. See the attached schematic diagram of the rectifier transformer. Figure 3 .

[0044] Usually, when the transformer is tested for temperature rise (load), it is inductive and the power factor is extremely low, so the required power capacity is very large. If the compensation capacitor is not connected in parallel, the test manufacturer will not be able to have such a large power supply. Because of this, a large amount of capacitor reactive power compensation is invested in the early stage according to the test parameters. Figure 1 As can be seen from line 2, when the test voltage is applied to a higher value, as shown in U', the current of the test sample with a saturated reactor is zero. However, because the compensation capacitor has been connected to the test line diagram, the entire circuit is a purely capacitive circuit. At this time, the test power supply is connected to a purely capacitive load, that is, the load of the test power supply is the compensation capacitor (see attached). Figure 2 ). In order to match the reactive power at this time, the test power supply container needs to be large enough. This is the first condition that needs to be met. That is, the test power supply capacity must be greater than the compensation capacitor capacity of the U' stage. The calculated value of the compensation capacitor capacity of the U' stage

[0045] from Figure 1 As can be seen from line 3, when the test object voltage exceeds U′, the test object circuit conducts, meaning current only flows through the winding. The key point is that the test object is essentially conducting at a higher voltage. The current from the compensation source is instantly compensated to the test object's internal saturated reactor (simply put, it was previously absorbed from the power source, but now it is released to the test object's internal saturated reactor). This causes the test object's high-voltage terminal voltage to momentarily increase above U′. This superposition of voltages gradually increases the capacitor's reactive compensation current, causing brief oscillations in the test circuit. During this test, the load current remains high at the moment of closing due to oscillations. This equilibrium point is typically between 50% and 65% of the rated applied current. The current at this equilibrium point is determined by the high-voltage side voltage and the capacitor's reactive compensation capacity. At the end of the test, the current is reduced. Once it reaches this equilibrium point, the current cannot be reduced any further. Therefore, this test will open the circuit breaker between 50% and 60% of the rated current.

[0046] The compensating current is capacitive, which helps the generator set's magnetization. If the compensating capacitance is too large, the intermediate transformer's ratio will be poorly matched (slightly too high), the compensating capacitance will be excessive, and the capacitive current will cause the generator to self-excite. This will cause the generator set's voltage to rise instantaneously, triggering the generator's overcurrent protection device. Furthermore, the test unit will experience a momentary disconnection under high load.

[0047] This situation is unsafe for the generator, compensation capacitor and test product.

[0048] Example 1

[0049] See also Figures 4 and 5, shown is a rectifier transformer with a built-in saturable inductor in the first embodiment of the present invention, including a power module, a test sample, and an intermediate transformer connecting the power module and the test sample, a compensation inductor is connected in parallel between the power module and the intermediate transformer, and a compensation capacitor is connected in parallel between the intermediate transformer and the test sample. The test sample is provided with a saturable inductor, and the saturable inductor adopts a single-group iron core winding structure, and the single-group iron core winding structure includes at least two groups of independent windings, and the positive terminal of each group of independent windings is connected to the negative terminal of its adjacent independent winding.

[0050] Furthermore, the negative terminals of the independent windings are connected in parallel to reduce the impedance difference between phases.

[0051] Example 2

[0052] See also Figure 6 The present invention also provides a load test method for a rectifier transformer with a built-in saturable reactor, which is applied to the above-mentioned rectifier transformer. The load test method includes the following steps:

[0053] S101, obtaining an impedance voltage value of a saturated reactor in a saturated state in the test sample;

[0054] S102, performing a load test on the rectifier transformer to obtain a transformation ratio value of the saturated reactor in a high-voltage state and a low-voltage state, and determining an impedance voltage conversion value of the saturated reactor using the transformation ratio value;

[0055] S103, calculating the compensation capacity of the rectifier transformer according to the impedance voltage conversion value, and adjusting the capacity of the compensation reactor according to the compensation capacity to achieve mutual cancellation of currents between capacitors and inductors.

[0056] Furthermore, the calculation formula of the impedance voltage conversion value of the saturated reactor is:

[0057]

[0058] Where, u represents the impedance voltage value of the saturated reactor in the saturated state, Indicates the transformation ratio of the saturated reactor in high voltage state and low voltage state.

[0059] Furthermore, the calculation formula of the compensation capacity of the rectifier transformer is:

[0060]

[0061] Where U B Indicates the high-voltage side impedance voltage value under the rated loss of the main modulating transformer load test, Q cIndicates the total capacitance corresponding to the load test.

[0062] During implementation, understanding the temperature rise (load) test characteristics of products with saturated reactors allows for the development of appropriate test plans and controls, ensuring the test is conducted safely. Typically, when testing linear 1 products, a larger intermediate transformer ratio is selected (to reduce the power supply voltage) for equipment safety. Furthermore, to minimize the use of the test power supply, a larger capacitive compensation capacity is selected based on the test product parameters.

[0063] Specifically, before estimating circuit parameters, three parts of test values must be obtained:

[0064] 1. Impedance and loss of the voltage regulator;

[0065] 2. Impedance and loss of rectifier transformer;

[0066] 3. Impedance and loss of the built-in saturated reactor;

[0067] The above parameters can be obtained in the semi-finished product (before connection). The impedance and loss values of the modulation and rectification transformers can be obtained by conventional load test methods. We will not elaborate on this here. The following focuses on the impedance and loss measurement of the built-in saturated reactor. The structure of the built-in saturated reactor is as follows: Figure 7 As shown;

[0068] The impedance voltage value of the saturated reactor in the saturated state can be obtained after the saturated reactor is manufactured. That is, apply AC current to the secondary side of the saturated reactor (T1T2, Y1Y2, K1K2) and measure the voltage drop of the primary side conductive copper busbar. This value is the impedance voltage value u of the saturated reactor. This value is determined by the designed DC voltage regulation depth of the saturated reactor. Generally, the DC voltage regulation depth of large rectifier transformers is about 50-70V. Under AC conditions, the impedance voltage value u of the saturated reactor is about 35V. Figure 3 It can be seen that the saturation resistor is connected in series on the low-voltage side of the main transformer. During the temperature rise test, the impedance voltage value u of the saturation resistor should be converted to Figure 1 The U′ value of line 3 is

[0069] Specifically, the U′ value is determined by the DC voltage regulation depth of the built-in saturated reactor, the DC voltage regulation depth of the reactor, and the transformation ratio between the high voltage and low voltage of the transformer, and is usually around 5000V-7000V.

[0070] Assume that U′=5000V, Figure 1 It can be seen that before the voltage applied to the test sample is lower than U', no current flows through the test sample winding. However, the compensation capacitor has already taken effect. Compensation capacity (U' value)

[0071] When the Q' value is obtained, you can make a reactive inductor with the same capacity to compensate Q L Connect in series to the circuit, see attached Figure 4 .Q L When it is slightly smaller than Q', the capacitor and inductor currents are suppressed by canceling each other out.

[0072] Q L The capacity should be slightly smaller than the capacity of Q', and the linearity is with Q C Consistent reactive inductance compensator. At this time, effective suppression can be performed so that the current can be applied at a position close to zero (see Figure 8 Straight line 4). At the same time, after the test is completed, the test sample's opening and closing current can also be restored to this position. After the improvement, the test sample's opening and closing current is very close to zero, eliminating current oscillation.

[0073] exist Figure 8 In the figure, straight line 1 represents the impedance ohm value curve of the rectifier transformer without a saturated reactor; straight line 2 represents the impedance ohm value curve of the rectifier transformer with a built-in saturated reactor; straight line 3 represents the impedance ohm value curve of the rectifier transformer with a parallel compensation reactor.

[0074] This embodiment further provides a load test circuit for a rectifier transformer with a built-in saturable reactor, which is applied to the above-mentioned rectifier transformer.

[0075] In summary, the rectifier transformer with a built-in saturated reactor and its load test circuit and method in the above-mentioned embodiments of the present invention convert the impedance voltage value of the load test, use the converted value to determine the compensation capacity, use the compensation capacity to construct a reactive inductance compensation of equal capacity in series to the line, and use the mutual cancellation characteristic of the capacitor and inductor currents to suppress them, so that the test sample's opening and closing current is very close to zero, eliminating current oscillations.

[0076] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0077] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A rectifier transformer with a built-in saturable reactor, characterized in that: It includes a power module, a test sample and an intermediate transformer connecting the power module and the test sample, a compensation inductor is connected in parallel between the power module and the intermediate transformer, a compensation capacitor is connected in parallel between the intermediate transformer and the test sample, and a saturated inductor is provided in the test sample. The saturated inductor adopts a single-group iron core winding structure, and the single-group iron core winding structure includes at least two groups of independent windings, and the positive terminal of each group of independent windings is connected to the negative terminal of its adjacent independent winding.

2. The rectifier transformer according to claim 1, characterized in that The negative terminals of the independent windings are connected in parallel to reduce impedance differences between phases.

3. A load test method for a rectifier transformer with a built-in saturable reactor, applied to the rectifier transformer according to any one of claims 1-2, characterized in that: The load test method comprises the following steps: Step 1: Obtaining the impedance voltage value of the saturated reactor in the test sample in a saturated state; Step 2: performing a load test on the rectifier transformer to obtain the transformation ratio value of the saturated reactor in the high-voltage state and the low-voltage state, and determining the impedance voltage conversion value of the saturated reactor using the transformation ratio value; Step three: Calculate the compensation capacity of the rectifier transformer according to the impedance voltage conversion value, and adjust the capacity of the compensation reactor according to the compensation capacity to achieve mutual cancellation of currents between capacitors and inductors.

4. The load test method according to claim 3, characterized in that: The calculation formula of the impedance voltage conversion value of the saturated reactor is: ； Where, Indicates the impedance voltage value of the saturated reactor in the saturated state. Indicates the transformation ratio of the saturated reactor in high voltage state and low voltage state.

5. The load test method according to claim 4, characterized in that: The calculation formula of the compensation capacity of the rectifier transformer is: ； Where, Indicates the high-voltage side impedance voltage value under the rated loss of the main modulating transformer load test. Indicates the total capacitance corresponding to the load test.

6. A load test circuit for a rectifier transformer with a built-in saturable reactor, applied to the rectifier transformer according to any one of claims 1-2.

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