High-frequency transformer vibration noise test platform and test method

Abstract

The embodiment of the invention discloses a transformer vibration noise test platform and test method, a bidirectional full-bridge DC-DC converter is established to simulate an actual operation scene of a high-frequency transformer, and a vibration noise rule of the high-frequency transformer in the actual operation scene can be obtained. A high-frequency transformer noise measuring point arrangement method and a high-frequency transformer noise evaluation index are provided, and an accurate high-frequency transformer noise measurement and evaluation method is obtained. Besides, in order to reduce the measurement cost, the embodiment of the invention separates the electrically induced noise of the transformer from the background noise through an empirical mode decomposition (EMD) method, so that the measurement precision is improved, an expensive anechoic chamber is avoided, and the measurement cost is greatly reduced.

Description

Technical Field

[0001] The embodiments of the present application relate to the technical field of high-frequency transformers, and in particular to a transformer vibration noise testing platform and testing method. Background Art

[0002] At present, the vibration and noise test of high-frequency transformers is mainly concentrated under no-load conditions. Under no-load conditions, the vibration of transformers mainly comes from the vibration of the iron core. Therefore, most of the current research on the vibration and noise of high-frequency transformers focuses on the iron core. However, the high-frequency transformer actually works in a DC-DC (direct current-to-direct current) converter. The DC-DC converter transmits power through phase shift, resulting in the primary and secondary voltages of the high-frequency transformer being square waves with different phases. In this working condition, the overall vibration law and vibration distribution of the transformer are still unclear. In addition, there is currently no relevant standard for the noise measurement of high-frequency transformers. Most of the existing noise tests refer to the measurement standards of power transformers and arrange the measurement points close to the transformer. However, the size of high-frequency transformers of the same capacity is much smaller than that of power frequency transformers, and the high-frequency noise attenuates greatly with distance. Directly arranging the noise measurement points of the high-frequency transformer according to the distance of the power frequency transformer measurement points may lead to inaccurate noise measurement results. At present, most of the noise evaluation of high-frequency transformers uses a sound level meter to directly obtain the A-weighted sound pressure level. However, large-capacity high-frequency transformers operate at high frequencies, and the A-weighted curve attenuates high-frequency noise (especially above 10kHz), which may cause the noise measurement value of the high-frequency transformer to be lower than the actual situation. Therefore, using only the A-weighted sound pressure level to evaluate the noise level of high-frequency noise and its impact on the environment and equipment may not be comprehensive enough.

[0003] Therefore, the research, development and manufacturing of high-frequency transformers with weak vibration and low noise has become a technical problem that relevant scientific researchers and transformer designers and manufacturers need to face together. Summary of the invention

[0004] To solve the above problems, the embodiment of the present application provides a transformer vibration noise test platform and test method, and builds a bidirectional full-bridge DC-DC converter to simulate the actual operation scenario of the high-frequency transformer, which can obtain the vibration noise law of the high-frequency transformer in the actual operation scenario, and proposes a method for arranging high-frequency transformer noise measurement points and a high-frequency transformer noise evaluation index, so as to obtain an accurate measurement and evaluation method for high-frequency transformer noise. In addition, in order to reduce the measurement cost, in one embodiment of the present application, the transformer's electrically induced noise can be separated from the background noise by the empirical mode decomposition (EMD) method, which not only improves the measurement accuracy, but also avoids the expensive anechoic chamber, greatly reducing the measurement cost.

[0005] In the first aspect, an embodiment of the present application provides a transformer vibration and noise testing platform, which consists of a direct current-to-direct current (DC-DC) converter, a voltage differential probe, a current probe, a multi-channel data acquisition card, a piezoelectric acceleration sensor, a microphone and a host computer. The high-frequency transformer is installed in the DC-DC converter, the voltage differential probe is connected to the primary and secondary sides of the transformer to measure the primary and secondary voltages of the transformer, the current probe is connected to the primary high-voltage line of the high-frequency transformer to measure the excitation current, the piezoelectric acceleration sensor is pasted on the high-frequency transformer to measure the vibration acceleration, and the microphone is arranged around the transformer to detect the noise sound pressure. The voltage differential probe, the current probe, the piezoelectric acceleration sensor, and the microphone are connected to the multi-channel data acquisition card, and the acquisition card transmits the collected voltage, current, vibration, and sound pressure signals to the host computer for data processing and visual display.

[0006] The bidirectional full-bridge DC-DC converter provides excitation for the high-frequency transformer. The high-frequency square wave voltage generated by the full-bridge circuit in the DC-DC converter acts on the winding of the high-frequency transformer. The different operating conditions of the transformer are controlled by adjusting the switching frequency, input voltage and shift angle of the DC-DC converter. The voltage differential probe is used to measure the primary and secondary voltages of the transformer. The current probe is used to measure the transformer excitation current.

[0007] The piezoelectric accelerometer is used to measure the vibration acceleration of the core and winding of the high-frequency transformer; the microphone is used to measure the radiated noise sound pressure of the high-frequency transformer during the operation of the DC-DC converter; the multi-channel data acquisition card is used to convert the collected voltage, current, vibration acceleration and sound pressure signals into high-precision digital signals, and transmit them to the host computer for further analysis; the host computer obtains the working condition of the transformer at this time according to the measured voltage and current signals, including parameters such as working frequency, phase shift angle and working magnetic flux density, and processes the vibration acceleration and sound pressure signals measured at this time to obtain the time-frequency diagram, characteristic parameters, vibration operational deformation analysis (Operational Deflection Shape, ODS) diagram and noise distribution diagram of the vibration noise at each measuring point, so as to realize the comprehensive evaluation of the vibration noise of the high-frequency transformer under actual operating conditions.

[0008] In a second aspect, the embodiment of the present application further provides a testing method for a transformer vibration noise testing platform, the specific steps are as follows:

[0009] 1) Determine the phase shift angle range corresponding to the transformer to be tested;

[0010] 2) Install the transformer in the DC-DC converter;

[0011] 3) Arrange voltage and current probes;

[0012] 4) Arrange transformer vibration measurement points;

[0013] 5) Background noise measurement: Turn on the DC-DC converter in a quiet environment, with the fan working and the transformer not excited, and measure the background noise at this time;

[0014] 6) Select the test frequency, excitation voltage and phase shift angle, and apply the excitation voltage of the selected frequency and magnitude to the transformer. At this time, a square wave voltage with a phase difference is applied across the transformer.

[0015] 7) Determine the distance between the microphone and the transformer;

[0016] 8) Arrange transformer noise measurement points;

[0017] 9) Each measurement data is transmitted to the host computer through the data acquisition card;

[0018] 10) Host computer data processing.

[0019] In step 1), determining the phase shift angle range corresponding to the transformer to be tested includes the following steps S1 to S3.

[0020] S1: Calculate the maximum phase shift angle according to the maximum transmission power of the transformer;

[0021] If the transformer ratio is n:1, power is transferred from the primary side to the secondary side in the forward direction, that is, 0≤D≤1, the maximum power transmission of the transformer is:

[0022]

[0023] Where: n is the ratio of the primary and secondary voltages of the transformer, U1 and U2 are the primary and secondary voltages of the transformer respectively, D is the duty cycle, f is the switching frequency, and L is the leakage inductance of the transformer.

[0024] According to the maximum transmission power of the transformer, the maximum duty cycle D can be obtained max , according to the duty cycle D max , find the maximum shift angle φ max for:

[0025] φ max =D max ·π

[0026] S2: Calculate the minimum phase shift angle of the transformer

[0027] The minimum phase shift angle is usually related to the minimum power output. For no-load or very low-load conditions, the power is almost zero. Theoretically, when = 0, the phase difference between the full bridges on both sides is zero, and the power transfer is zero at this time.

[0028] S3: Obtain the loadable phase shift angle range

[0029] Through the above two steps, the range of the phase shift angle can be determined;

[0030] φ min ≤φ≤φ max

[0031] In step 4), vibration measuring points are arranged near the air gap of the transformer core, on the side and front, on the top and bottom clamps, and in the middle of the winding, and the piezoelectric acceleration sensors are pasted to the corresponding measuring points.

[0032] In step 10), the noise data processing in the host computer data processing includes the following steps S101 to S106.

[0033] S101: Perform empirical mode decomposition (EMD) on the noise signals measured by each microphone after applying excitation to obtain a set of intrinsic mode functions (IMFs):

[0034]

[0035] Where: n is the amount of IMF drawn, IMF i (t) is the eigenmode function at different frequency levels, and r(t) is the residual term.

[0036] S102: Perform EMD decomposition on the background noise to obtain its IMF component:

[0037]

[0038] Where: IMF bg,i (t) is the different frequency components of the background noise, r bg (t) is the residual trend term of the background noise, and m refers to the number of IMFs of the extracted background noise.

[0039] S103: Perform Fourier transform on the IMF components of the total noise signal and the IMF components of the background noise, compare their frequency distributions, find IMF components with similar frequency characteristics, and remove the IMF components with similar characteristics to the background noise in the total noise signal:

[0040] IMF elec,i (t) = IMF i (t)-IMF bg,i (t)

[0041] S104: Reconstruct the retained IMF components to obtain the transformer's electrically induced noise N elec (t):

[0042]

[0043] S105: Performing Fourier decomposition on the obtained electro-induced noise sound pressure at each measuring point to obtain the amplitude and phase of each harmonic in the noise signal;

[0044] S106: According to the A-weighted curve, the sound pressure of each frequency band is corrected, and finally the corrected sound pressure level of each frequency band is obtained by energy addition to obtain the A-weighted sound pressure value.

[0045] In a third aspect, an embodiment of the present application provides a testing device for a transformer vibration and noise testing platform, which can be applied to the transformer vibration and noise testing platform provided in any embodiment of the present application, and the device includes:

[0046] The data processing module is used to perform data processing according to the transformer primary voltage, the transformer secondary voltage, the excitation current, the vibration acceleration and the noise sound pressure to obtain the measurement result of the transformer vibration and noise test platform.

[0047] The beneficial effects of the embodiments of the present application are:

[0048] 1. By building a bidirectional full-bridge DC-DC converter, simulating the actual operating scenario of the high-frequency transformer, and changing the different operating conditions of the transformer by changing different phase shift angles, different frequencies and different magnetic flux densities, measuring the vibration and radiation noise of the core, winding and clamps of the high-frequency transformer in the DC-DC converter, and obtaining the distribution characteristics and transmission paths of the vibration and noise of each component of the transformer under actual working conditions, not only can the vibration and noise data of various parts of the transformer be obtained, the most violent vibration position can be found, and a transformer vibration and noise database containing various working conditions can be established, but it can also help find the location of violent vibration and serious noise, providing a reference for the design and manufacture of low-vibration, low-noise high-frequency transformers.

[0049] 2. A method for arranging noise measurement points for high-frequency transformers is proposed, which solves the problem that the existing distance of measurement points for power transformers is not suitable for high-frequency transformers and ensures the accuracy of noise measurement.

[0050] 3. Use a multi-channel data acquisition card to collect vibration noise, and use the current signal as a reference to perform phase correction on the vibration noise signal, so as to achieve synchronous measurement of the vibration noise at each measuring point, obtain the time-frequency diagram, characteristic parameters, and vibration ODS diagram of the vibration noise at each measuring point; and obtain the frequency domain characteristics of the noise sound pressure at each measuring point, which solves the problem of inaccurate evaluation of high-frequency transformer noise using only A-weighted sound pressure level, provides a more comprehensive high-frequency noise evaluation method, and realizes the comprehensive evaluation of high-frequency transformer vibration noise.

[0051] 4. Tests are conducted under normal conditions, and background noise and electrically induced noise are separated by empirical mode decomposition. There is no need to build an expensive anechoic chamber, and the test cost is greatly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 Transformer vibration and noise test platform structure diagram;

[0053] Figure 2 High frequency transformer vibration noise test flow chart;

[0054] Figure 3 A schematic diagram of the structure of a computer device according to an embodiment of the present application. DETAILED DESCRIPTION

[0055] Next, the scheme of the embodiment of the present application is introduced. In the following description, for the purpose of illustration rather than limitation, specific details such as specific system structures, technologies, etc. are proposed to provide a thorough understanding of the embodiment of the present application. However, it should be clear to those skilled in the art that the present application can also be implemented in other embodiments without these specific details. In other cases, the detailed description of well-known systems, devices, circuits and methods is omitted to prevent unnecessary details from hindering the description of the present application.

[0056] It should be understood that when used in the present specification and the appended claims, the term "comprising" indicates the presence of described features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

[0057] As used in the specification and appended claims of this application, the term "if" can be interpreted as "when" or "uponce" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrase "if it is determined" or "if [described condition or event] is detected" can be interpreted as meaning "uponce it is determined" or "in response to determining" or "uponce [described condition or event] is detected" or "in response to detecting [described condition or event]", depending on the context.

[0058] References to "one embodiment" or "some embodiments" etc. described in the specification of this application mean that one or more embodiments of the present application include specific features, structures or characteristics described in conjunction with the embodiment. Therefore, the statements "in one embodiment", "in some embodiments", "in some other embodiments", "in some other embodiments", etc. that appear in different places in this specification do not necessarily refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized in other ways. The terms "including", "comprising", "having" and their variations all mean "including but not limited to", unless otherwise specifically emphasized in other ways.

[0059] The transformer vibration and noise test platform provided in the embodiment of the present application includes: a bidirectional full-bridge DC-DC converter, a voltage differential probe, a current probe, a piezoelectric acceleration sensor, a microphone and a host computer; the transformer is arranged in the DC-DC converter, the voltage differential probe is connected to the primary side of the transformer, and is used to measure the primary side voltage of the transformer, and the voltage differential probe is also connected to the secondary side of the transformer, and is used to measure the secondary side voltage of the transformer; the current probe is connected to the primary high-voltage line of the transformer, and is used to measure the excitation current; the piezoelectric acceleration sensor is arranged on the transformer, and is used to measure the vibration acceleration at the arranged position; the microphone is arranged around the transformer, and is used to detect the noise sound pressure; the host computer is used to process the data of the primary side voltage of the transformer, the secondary side voltage of the transformer, the excitation current, the vibration acceleration and the noise sound pressure to obtain the measurement result.

[0060] The above-mentioned bidirectional full-bridge DC-DC converter is a highly efficient DC power conversion device, which has the ability to transmit electric energy in both directions, that is, it can realize the forward and reverse flow of energy.

[0061] A voltage differential probe can be used to measure the voltage difference between two signal points, that is, the differential voltage. The voltage differential probe can suppress common-mode noise (the part common to the two signals) and only amplify and display the differential signal, thereby improving the accuracy and reliability of the measurement.

[0062] Piezoelectric acceleration sensors, also known as piezoelectric accelerometers, can refer to sensors that measure acceleration based on the piezoelectric effect. Piezoelectric acceleration sensors can work by using the piezoelectric effect of certain substances (such as quartz crystals or piezoelectric ceramics). When these substances are deformed by force in a certain direction, polarization will occur inside them, and charges of opposite signs will be generated on two surfaces. When the external force is removed, they will return to an uncharged state. This phenomenon is called the "piezoelectric effect." In an acceleration sensor, the force applied by the mass block to the piezoelectric element changes with the acceleration, thereby generating a charge or voltage output that is proportional to the acceleration.

[0063] The primary side of the transformer can refer to the side of the transformer where the input voltage is applied, that is, the coil on the input side. By generating a magnetic field by inputting voltage and current on the primary side of the transformer, voltage and current can be induced on the secondary side (output side). Therefore, when the primary voltage of the transformer is generated, the secondary voltage of the transformer is also generated accordingly.

[0064] In the embodiment of the present application, the transformer may be a high frequency transformer, that is, the frequency of the transformer is higher than the set frequency value. The phase shift angle may also be referred to as the phase shift angle. The DC-DC converter may also be referred to as a DC-DC converter or a bidirectional full-bridge DC-DC converter.

[0065] In one embodiment, the measurement results include: operating condition information, vibration characteristic information and electrically induced noise sound pressure information; the operating condition information is determined based on the primary voltage of the transformer and the secondary voltage of the transformer; the vibration characteristic information is determined based on the excitation current and the vibration acceleration; the electrically induced noise sound pressure information is determined based on the noise sound pressure.

[0066] In one embodiment, the operating condition information includes the frequency of the transformer, the magnetic flux density of the transformer and the phase shift angle of the transformer; the vibration characteristic information includes a vibration time domain and frequency domain signal diagram, a time domain and frequency domain characteristic value, a switching frequency within a preset frequency, an amplitude corresponding to each multiple frequency, a phase corresponding to each multiple frequency, and a working deformation analysis diagram; the electrically induced noise sound pressure information includes a time domain and frequency domain signal diagram of the noise sound pressure, the sound pressure amplitude and phase of each harmonic in the noise signal, and an A-weighted sound pressure value.

[0067] The frequency of the above-mentioned transformer may refer to the frequency of the alternating current when the transformer is working.

[0068] Transformer flux density can refer to the number of magnetic flux lines passing through a unit area, or the ratio of the magnetic flux passing through the transformer core to the cross-sectional area of ​​the core.

[0069] The phase shift angle of a transformer refers to the phase difference between the transformer output voltage and the input voltage, which is of great significance for the stable operation of the power system and the optimization of the voltage waveform.

[0070] A vibration time domain signal graph may be a graph showing the relationship between vibration displacement and time, also known as an amplitude time domain graph. A vibration time domain signal graph may be obtained by measuring the signal output by a vibration sensor and plotting it against a time axis.

[0071] The time domain and frequency domain eigenvalues ​​can include time domain eigenvalues ​​and frequency domain eigenvalues. The time domain eigenvalues ​​can mainly describe the characteristics of vibration acceleration changing with time. The frequency domain eigenvalues ​​and time domain eigenvalues ​​can describe the characteristics of vibration acceleration in frequency.

[0072] The switching frequency may refer to the number of times the switching action is repeated per unit time. In one implementation, the switching frequency may be the speed at which the magnetic flux in the transformer changes, that is, the number of times the magnetic flux changes in the positive and negative directions per second. The switching frequency may be used to indicate the number of times the switching elements (such as transistors, relays, etc.) inside the transformer are turned on and off per unit time, and may be measured in Hertz (Hz).

[0073] The above phase may refer to the phase of the transformer, and further may refer to the phase difference between the voltages on the primary and secondary sides of the transformer. Each multiplied frequency may refer to a plurality of preset multiplied frequencies, and the multiplied frequency may refer to an integer multiple of the input signal frequency.

[0074] Operational Deflection Shape (ODS) can refer to: an analysis image (or chart) that directly uses the response in the time domain or frequency domain to display the deformation vibration shape by measuring the response of the structure in the working state.

[0075] The above-mentioned A-weighted sound pressure value can refer to the sound pressure level measured by the A-weighted network. There are three standard frequency weighting networks in the noise meter: A, B, and C. The A network simulates the response of the human ear to the 40-square pure tone in the equal loudness curve. The shape of its noise meter curve is opposite to the 340-square equal loudness curve, so that the mid- and low-frequency bands of the electrical signal have a greater attenuation.

[0076] In one embodiment, the full-bridge circuit in the bidirectional full-bridge DC-DC converter is used to generate a square wave voltage with a set frequency and adjustable amplitude, and the square wave voltage acts on the winding of the high-frequency transformer to provide different operating conditions for the transformer; the square wave voltage is applied to the primary side of the transformer to generate a primary voltage, and the secondary voltage is generated when the primary voltage is applied.

[0077] In one implementation, the excitation current is used as a reference signal to correct the phase of the vibration acceleration.

[0078] In one implementation, the vibration acceleration measured by the piezoelectric acceleration sensor is the vibration acceleration of the core and windings of the transformer; the noise sound pressure measured by the microphone is the radiation noise sound pressure of the transformer when the DC-DC converter is working.

[0079] In one embodiment, the transformer vibration and noise test platform also includes a multi-channel data acquisition card, which is used to convert the collected voltage, current, vibration acceleration and sound pressure signals into digital signals, and to transmit the digital signals to a host computer for further analysis.

[0080] In one example of this application, the transformer vibration noise test platform refers to Figure 1As shown, the transformer vibration and noise test platform of the embodiment of the present application is composed of a bidirectional full-bridge DC-DC converter, a voltage differential probe, a current probe, a multi-channel data acquisition card, a piezoelectric acceleration sensor, a microphone and a host computer. The high-frequency transformer is installed in the DC-DC converter, and the voltage differential probe is connected to the primary and secondary sides of the high-frequency transformer to measure the primary voltage and secondary voltage of the high-frequency transformer; the current probe is connected to the primary high-voltage line of the high-frequency transformer to measure the excitation current, and the piezoelectric acceleration sensor is pasted on the high-frequency transformer to measure the vibration acceleration; the microphone is arranged around the high-frequency transformer to detect the noise sound pressure; the voltage differential probe, the current probe, the piezoelectric acceleration sensor, and the microphone are connected to the multi-channel data acquisition card; the acquisition card transmits the collected voltage, current, vibration, and sound pressure signals to the host computer for data processing and visual display.

[0081] An embodiment of the present application also provides a testing method for a transformer vibration and noise testing platform, which is applied to the transformer vibration and noise testing platform provided by any embodiment of the present application. The method includes: performing data processing according to the primary voltage of the transformer, the secondary voltage of the transformer, the excitation current, the vibration acceleration and the noise sound pressure to obtain measurement results of the transformer vibration and noise testing platform.

[0082] In the embodiment of the present application, the primary voltage and the secondary voltage may be collectively referred to as the primary-secondary voltage, and the primary side and the secondary side may be collectively referred to as the primary-secondary side.

[0083] In one embodiment, the method further includes: determining a phase shift angle range of the transformer; determining a phase shift angle of the transformer based on the phase shift angle range; and applying a square wave voltage to the primary high voltage line of the transformer based on the phase shift angle to generate the excitation current.

[0084] In one example of the present application, the test method of the transformer vibration noise test platform can refer to Figure 2 As shown, the following steps are included:

[0085] 1) Through the following steps S1 to S3, the phase shift angle range corresponding to the transformer to be tested is determined.

[0086] S1: Calculate the maximum phase shift angle of the transformer based on the maximum transmission power of the transformer.

[0087] In step S1, if the transformer ratio is n:1, power is transferred from the primary side to the secondary side in the forward direction, that is, 0≤D≤1, and the maximum power transmission of the transformer is:

[0088]

[0089] Where: n is the ratio of the primary and secondary voltages of the transformer, U1 and U2 are the primary and secondary voltages of the transformer respectively, D is the duty cycle, f is the switching frequency, and L is the leakage inductance of the transformer.

[0090] Among them, the primary voltage is the voltage applied to the primary side (input side) of the transformer. It is the voltage source that provides power when the transformer is working. The secondary voltage is the voltage generated by the secondary side (output side) of the transformer. It is the voltage that the transformer outputs to the load after converting the primary voltage.

[0091] On the basis of determining the maximum transmission power, the maximum duty cycle D can be obtained according to the maximum transmission power of the transformer. max , according to the duty cycle D max , find the maximum shift angle φ max for:

[0092] φ max =D max ·π.

[0093] S2: Calculate the minimum phase shift angle of the transformer.

[0094] The minimum phase shift angle is usually related to the minimum power output. For no-load or very low-load conditions, the power is almost zero. Theoretically, when = 0, the phase difference between the full bridges on both sides is zero, and the power transfer is zero at this time.

[0095] S3: Obtain the loadable phase shift angle range.

[0096] The range of the phase shift angle can be determined by the maximum phase shift angle and the minimum phase shift angle determined in the above two steps S1 and S2:

[0097] φ min ≤φ≤φ max .

[0098] In the formula, min is the minimum value of the phase shift angle, is the phase shift angle, max is the maximum value of the phase shift angle.

[0099] Before the method provided in the embodiment of the present application is implemented, the transformer may be installed in the DC-DC converter; voltage and current probes may be arranged, and then transformer vibration measurement points may be arranged.

[0100] The voltage differential probe can be set on the primary and secondary sides of the transformer, and the current probe is connected to the primary side of the transformer to measure the excitation current of the transformer.

[0101] The vibration measurement points can be set near the air gap of the transformer core, on the side and front, on the top and bottom clamps, and in the middle of the winding, and the piezoelectric acceleration sensor can be set at the corresponding measurement point.

[0102] 2) Background noise measurement: The background noise is measured in a quiet environment with the DC-DC converter turned on, the fan working, and the transformer not excited.

[0103] 3) Apply excitation voltage to the transformer according to the selected test frequency, excitation voltage magnitude and phase shift angle.

[0104] In step 3), a square wave voltage with a phase difference is present across both ends of the transformer.

[0105] 4) Determine the distance between the microphone and the transformer through the following steps S71 to S73.

[0106] S71: In order to make the measurement closer to the free sound field, it is necessary to avoid the interference of the sound wave by the reflecting surface. The minimum distance between the microphone and the noise source can refer to the far field distance. The empirical formula is:

[0107]

[0108] Among them, d min is the minimum distance between the microphone and the transformer; D is the characteristic size of the transformer; λ is the wavelength of the sound wave, λ = c / f, c is the speed of sound, which is about 340m / s, and f is the main frequency of the noise, which is calculated at twice the frequency of the DC-DC converter.

[0109] S72: Starting from the minimum distance, gradually move away from the transformer and record the change in sound pressure level until the change in sound pressure level becomes stable (i.e., enters the far field region).

[0110] S73: Compare the sound pressure levels at different measuring points: If the sound pressure levels at different measuring points are relatively consistent, it indicates that the measuring distance is sufficient and the sound wave propagation meets the free field conditions. This distance is used as the high-frequency transformer noise test distance.

[0111] 5) When the microphone is set at the transformer noise measurement point, the noise sound pressure is detected by the microphone.

[0112] The microphones may be arranged at a distance from the center point of the four sides and the top (5 faces) of the transformer to the high-frequency transformer noise test distance. The high-frequency transformer noise test distance has been calculated in step 4).

[0113] 6) Each measurement data is transmitted to the host computer through the data acquisition card.

[0114] In one example, the voltage differential probe and the current probe can be connected to the channel without IEPE (Integrated Electronics Piezo-Electric) interface in the multi-channel digital acquisition card, the piezoelectric acceleration sensor and the microphone are connected to the channel with IEPE interface in the digital acquisition card, the sampling rate of the acquisition card is at least N times the switching frequency and the sampling rate is guaranteed to be the same for each measurement, and the data of each channel of the acquisition card is transmitted to the host computer for data processing. N can be 1-100, further, N can be 5-15, further, N can be 10.

[0115] 7) Perform data processing through the host computer.

[0116] Step 7) further includes the following steps (1) to (4).

[0117] (1) Calculate the working magnetic flux density of the transformer.

[0118] In the single-phase control process, the working magnetic flux density of the core is calculated according to the secondary voltage U2(t) of the transformer based on the following formula:

[0119]

[0120] Where: B(t) is the working magnetic flux density of the transformer core; U2(t) is the secondary voltage of the transformer; N2 is the number of turns of the secondary winding; A c is the effective cross-sectional area of ​​the transformer core.

[0121] (2) Vibration data processing through the following steps S21 to S23:

[0122] S21: fix one of the vibration measuring points A as a reference signal, compare the current phase offsets of the remaining measuring points with that of the measuring point A, and translate the vibration signals and current signals of the remaining measuring points along the time axis together to make the phase offset of the current signal zero;

[0123] In step S21 , the vibration signal may refer to vibration acceleration.

[0124] S22: Perform Fourier decomposition on the time domain acceleration signal of each measuring point to obtain the vibration spectrum, and extract time domain characteristic values ​​such as effective value, peak value, peak factor, kurtosis, skewness, and frequency domain characteristic values ​​such as main frequency, spectrum energy, harmonic component, and frequency band energy;

[0125] S23: Extract the amplitude and phase corresponding to each multiple frequency of the switching frequency within the set frequency, define the coordinates of each measuring point, complete the vibration conditions of the remaining measuring points of the measuring surface according to the cubic spline interpolation method, and visualize the frequency domain ODS of the measuring surface through the matrix laboratory (matlab) to obtain the vibration distribution and vibration characteristics of the transformer core winding and the clamp at different frequencies. The set frequency can be 1-100KHz, further, the set frequency can be 10-50KHz, and further, the set frequency can be 20KHz.

[0126] (3) Noise data processing is performed through the following steps S31 to S36:

[0127] S31: Perform empirical mode decomposition (EMD) on the noise signals measured by each microphone after applying the excitation, and obtain a set of intrinsic mode functions (IMFs):

[0128]

[0129] Where: IMF i (t) is the eigenmode function at different frequency levels, and r(t) is the residual term.

[0130] S32: Perform EMD decomposition on the background noise to obtain its IMF component:

[0131]

[0132] Where: IMF bg,i (t) is the different frequency components of the background noise, r bg (t) is the residual trend term of the background noise.

[0133] S33: Perform Fourier transform on the IMF components of the total noise signal and the IMF components of the background noise, compare their frequency distributions, find IMF components with similar frequency characteristics, and remove the IMF components with similar characteristics to the background noise in the total noise signal:

[0134] IMF elec,i (t) = IMF i (t)-IMF bg,i (t)

[0135] S34: Reconstruct the retained IMF components to obtain the transformer's electrically induced noise N elec (t):

[0136]

[0137] S35: performing Fourier decomposition on the obtained electro-induced noise sound pressure at each measuring point to obtain the amplitude and phase of each harmonic in the noise signal;

[0138] S36: According to the A-weighted curve, the sound pressure of each frequency band is corrected, and finally the corrected sound pressure level of each frequency band is obtained by energy summing up to obtain the A-weighted sound pressure value.

[0139] (4) Store the transformer operating frequency, operating magnetic flux density, phase shift angle, and vibration test results of each measuring point under the corresponding working conditions and noise test results in the set folder. The vibration test results include the time-frequency domain signals of each measuring point, the time-frequency domain eigenvalues, the amplitude and phase corresponding to each multiple frequency of the switching frequency within 20kHz, and the frequency domain ODS of the measurement surface; the noise test results include the time-frequency domain signals of the sound pressure of each measuring point, the sound pressure amplitude and phase of each harmonic in the noise signal, and the A-weighted sound pressure value.

[0140] An embodiment of the present application also provides a testing device for a transformer vibration and noise testing platform, which can be applied to the transformer vibration and noise testing platform provided by any embodiment of the present application. The device includes: a data processing module, used to perform data processing according to the primary voltage of the transformer, the secondary voltage of the transformer, the excitation current, the vibration acceleration and the noise sound pressure to obtain the measurement results of the transformer vibration and noise testing platform.

[0141] It should be noted that the information interaction, execution process, etc. between the above-mentioned modules and other modules are based on the same concept as the method embodiment of the present application. Their specific functions and technical effects can be found in the method embodiment part and will not be repeated here.

[0142] Those skilled in the art can clearly understand that, for the convenience and simplicity of description, only the division of the above-mentioned functional modules is used as an example for illustration. In actual applications, the above-mentioned function allocation can be completed by different functional modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional modules in the embodiment can be integrated in a processing unit, or can exist physically alone, or can be integrated in a unit together with other modules. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of software functional units. In addition, the specific names of the modules are only for the convenience of distinguishing each other, and are not used to limit the scope of protection of this application. In other embodiments of the present application, the specific working process of the modules included in the device can refer to the corresponding process in the aforementioned method embodiment, which will not be repeated here.

[0143] Figure 3 This is a schematic diagram of the structure of a computer device provided in one embodiment of the present application. Figure 3 As shown, the computer device of this embodiment includes: at least one processor 20 ( Figure 3Only one is shown in the figure), a memory 21, and a computer program 22 stored in the memory 21 and executable on the at least one processor 20, wherein the processor 20 implements the steps of any of the above-mentioned parking environment analysis method embodiments when executing the computer program 22.

[0144] The computer device may include, but is not limited to, a processor 20 and a memory 21. Those skilled in the art will appreciate that Figure 3 It is only an example of a computer device and does not constitute a limitation of the computer device. It may include more or fewer components than shown in the figure, or a combination of certain components, or different components. For example, it may also include input and output devices, network access devices, etc.

[0145] The processor 20 may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor, etc.

[0146] In some embodiments, the memory 21 may be an internal storage unit of the computer device, such as a hard disk or memory of the computer device. In other embodiments, the memory 21 may also be an external storage device of the computer device, such as a plug-in hard disk, a smart memory card (Smart Media Card, SMC), a secure digital (Secure Digital, SD) card, a flash card (Flash Card), etc. equipped on the computer device. Further, the memory 21 may also include both an internal storage unit of the computer device and an external storage device. The memory 21 is used to store an operating system, an application program, a boot loader (BootLoader), data, and other programs, such as the program code of the computer program. The memory 21 may also be used to temporarily store data that has been output or is to be output.

[0147] An embodiment of the present application also provides a computer device, which includes: at least one processor, a memory, and a computer program stored in the memory and executable on the at least one processor, wherein the processor implements the steps in any of the above-mentioned method embodiments when executing the computer program.

[0148] An embodiment of the present application further provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps in the above-mentioned method embodiments can be implemented.

[0149] An embodiment of the present application provides a computer program product. When the computer program product runs on a mobile terminal, the mobile terminal can implement the steps in the above-mentioned method embodiments when executing the computer program product.

[0150] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the present application implements all or part of the processes in the above-mentioned embodiment method, which can be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium, and the computer program can implement the steps of the above-mentioned various method embodiments when executed by the processor. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. The computer-readable medium can at least include: any entity or device that can carry the computer program code to the camera / terminal device, recording medium, computer memory, read-only memory (ROM, Read-Only Memory), random access memory (RAM, RandomAccess Memory), electric carrier signal, telecommunication signal and software distribution medium. For example, a USB flash drive, a mobile hard disk, a magnetic disk or an optical disk. In some jurisdictions, according to legislation and patent practice, computer-readable media cannot be electric carrier signals and telecommunication signals.

[0151] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0152] Those of ordinary skill in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this application.

[0153] In the embodiments provided in the present application, it should be understood that the disclosed devices / network equipment and methods can be implemented in other ways. For example, the device / network equipment embodiments described above are merely schematic. For example, the division of the modules or units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0154] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0155] The embodiments described above are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A transformer vibration noise test platform, characterized in that: include: DC-DC converter, voltage differential probe, current probe, piezoelectric accelerometer, microphone and host computer; The transformer is arranged in a DC-DC converter, the voltage differential probe is connected to the primary side of the transformer for measuring the primary side voltage of the transformer, and the voltage differential probe is also connected to the secondary side of the transformer for measuring the secondary side voltage of the transformer; The current probe is connected to the primary high-voltage line of the transformer and is used to measure the excitation current; The piezoelectric acceleration sensor is arranged on the transformer and is used to measure the vibration acceleration at the arranged position; The microphone is arranged around the transformer and is used to detect the noise sound pressure; The host computer is used to perform data processing on the transformer primary voltage, the transformer secondary voltage, the excitation current, the vibration acceleration and the noise sound pressure to obtain measurement results.

2. The transformer vibration and noise testing platform according to claim 1, characterized in that: The measurement results include: operating condition information, vibration characteristic information and electrically induced noise sound pressure information; the operating condition information is determined based on the primary voltage of the transformer and the secondary voltage of the transformer; the vibration characteristic information is determined based on the excitation current and the vibration acceleration; the electrically induced noise sound pressure information is determined based on the noise sound pressure.

3. The transformer vibration and noise testing platform according to claim 2, characterized in that: The operating condition information includes at least one of the frequency of the transformer, the magnetic flux density of the transformer and the phase shift angle of the transformer; the vibration characteristic information includes at least one of a vibration time-domain and frequency-domain signal diagram, a time-domain and frequency-domain characteristic value, a switching frequency within a preset frequency, an amplitude corresponding to each multiple frequency, a phase corresponding to each multiple frequency, and a working deformation analysis diagram; the electrically induced noise sound pressure information includes at least one of a time-frequency domain signal diagram of the noise sound pressure, the sound pressure amplitude and phase of each harmonic in the noise signal, and an A-weighted sound pressure value.

4. The transformer vibration and noise testing platform according to claim 1, characterized in that: The full-bridge circuit in the DC-DC converter is used to generate a square wave voltage with adjustable frequency and amplitude, and the square wave voltage acts on the winding of the transformer to provide different operating conditions for the transformer; The square wave voltage is applied to the primary side of the transformer to generate a primary voltage, and the secondary voltage is generated when the primary voltage is applied.

5. The transformer vibration and noise testing platform according to claim 1, characterized in that: The excitation current is used as a reference signal to correct the phase of the vibration acceleration.

6. The transformer vibration and noise testing platform according to claim 1, characterized in that: The vibration acceleration measured by the piezoelectric acceleration sensor is the vibration acceleration of the iron core and windings of the transformer; the noise sound pressure measured by the microphone is the radiation noise sound pressure of the transformer when the DC-DC converter is working.

7. The transformer vibration and noise testing platform according to claim 1, characterized in that: It also includes a multi-channel data acquisition card, which is used to convert the collected voltage, current, vibration acceleration and sound pressure signals into digital signals, and to transmit the digital signals to a host computer for further analysis.

8. A testing method applied to the transformer vibration noise testing platform according to any one of claims 1 to 7, characterized in that: The method comprises: Data processing is performed according to the transformer primary voltage, the transformer secondary voltage, the excitation current, the vibration acceleration and the noise sound pressure to obtain measurement results of the transformer vibration and noise test platform.

9. The method according to claim 8, characterized in that The method further comprises: Determining a phase shift angle range of the transformer; Determining the phase shift angle of the transformer according to the phase shift angle range; A square wave voltage is applied to the primary high voltage line of the transformer according to the phase shift angle to generate the excitation current.

10. The method according to claim 9, characterized in that The determining the phase shift angle range corresponding to the transformer comprises: Calculate the maximum transmission power of the transformer: If the transformation ratio of the transformer is n:1, and power is transferred from the primary side of the transformer to the secondary side of the transformer in a positive direction, the maximum transmission power P of the transformer is: Wherein: n is the ratio of the primary voltage to the secondary voltage of the transformer, U1 is the primary voltage of the transformer, U2 is the primary and secondary voltages of the transformer, D is the duty cycle of the transformer, f is the switching frequency, L is the leakage inductance of the transformer; P is the maximum transmission power of the transformer; Calculate the maximum duty cycle Dmax of the transformer according to the maximum transmission power of the transformer; According to the maximum duty cycle Dmax of the transformer, the maximum shift angle φmax of the transformer is calculated, and the calculation formula is: f max =D max ·p; Determine the minimum phase shift angle of the transformer, wherein when the transformer is unloaded, the phase difference of the full bridges on both sides of the full bridge DC-DC converter is zero, at this time the power transmission is zero, and the minimum phase shift angle is 0; The range of the phase shift angle is determined according to the maximum phase shift angle of the transformer and the minimum phase shift angle of the transformer.

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