Noise evaluation facility and noise evaluation method

Abstract

A noise evaluation facility (100) is provided with a winding unit (12), a noise measurement device (20), and a vibration measurement device (30). The winding unit (12) is attached to a magnetic core (11) as a target to be evaluated. The noise measurement device (20) includes a microphone (21). The microphone (21) is disposed at a position facing a measurement surface (13) of a measurement object (10) including the magnetic core (11) and the winding unit (12). The noise measurement device (20) is configured to measure noise generated from the object (10) to be measured. The vibration measurement device (30) is configured to measure the vibration of the measurement surface (13) in a direction intersecting the measurement surface (13).

Description

Noise evaluation equipment and noise evaluation method

[0001] The present disclosure relates to a noise evaluation facility and a noise evaluation method.

[0002] For example, devices such as transformers and reactors include a magnetic core and a winding attached to the magnetic core. When such devices are in use, various excitation forces act on the magnetic core, causing it to vibrate and generate noise. For example, Lorentz forces are generated in the winding, causing the winding to vibrate, which can cause the magnetic core to vibrate and generate noise. Furthermore, in the case of a magnetic core made of multiple laminated electromagnetic steel sheets, an attractive force can be generated between the electromagnetic steel sheets, causing the magnetic core to vibrate and generate noise. Furthermore, expansion and contraction due to magnetostriction can occur in the magnetic core, causing the magnetic core to vibrate and generate noise. The vibration of the magnetic core caused by these excitation forces is affected by resonance phenomena, which are determined by the structure of the device, particularly the structure and mechanical characteristics of the magnetic core.

[0003] Patent Document 1 discloses a method for evaluating magnetostriction and noise of an electromagnetic steel sheet used in a transformer core. In the evaluation method of Patent Document 1, a magnetic flux density waveform is generated in an electromagnetic steel sheet sample by controlling an excitation voltage waveform, and the magnetostriction of the electromagnetic steel sheet sample is measured. The magnetic flux density waveform is obtained by measuring or estimating by calculation the magnetic flux density waveform of a local area within the transformer core. In other words, the magnetic flux density waveform is not necessarily a sine wave, but is actually generated locally in the magnetic core. In Patent Document 1, for example, a correlation between the magnetostriction due to the magnetic flux density waveform and actual transformer noise data is obtained in advance, and the noise is estimated from the magnetostriction of the electromagnetic steel sheet sample based on this correlation.

[0004] JP 2009-236904 A

[0005] For example, when developing magnetic core materials such as electromagnetic steel sheets, it is important to evaluate the level of noise caused by magnetostriction after eliminating the effects of resonance phenomena as much as possible. However, as mentioned above, noise from magnetic cores is caused by a variety of factors. In the past, it was difficult to evaluate the level of noise caused by magnetostriction in situations where noise is caused by multiple factors.

[0006] An object of the present disclosure is to provide a noise evaluation facility that can evaluate noise caused by magnetostriction of a magnetic core, among noises generated in a measured object.

[0007] The noise evaluation equipment according to the present disclosure includes a winding section, a noise measuring device, and a vibration measuring device. The winding section is attached to a magnetic core as an evaluation target. The noise measuring device includes a microphone. The microphone is positioned opposite a measurement surface of an object to be measured that includes the magnetic core and the winding section. The noise measuring device is configured to measure noise generated from the object to be measured. The vibration measuring device is configured to measure vibrations of the measurement surface in a direction intersecting the measurement surface.

[0008] According to the noise evaluation equipment of the present disclosure, it is possible to evaluate noise caused by magnetostriction of the magnetic core, among noises generated in the object to be measured.

[0009] Fig. 1 is a perspective view schematically showing a noise evaluation facility according to the first and second embodiments. Fig. 2 is a block diagram showing an example of the configuration of the noise evaluation facility according to the first and second embodiments. Fig. 3 is a hardware configuration diagram of a calculation device included in the noise evaluation facility shown in Fig. 2. Fig. 4 is a flowchart showing a noise evaluation method according to the first embodiment. Fig. 5 is a flowchart showing a noise evaluation method according to the second embodiment.

[0010] A noise evaluation facility according to an embodiment includes a winding, a noise measuring device, and a vibration measuring device. The winding is attached to a magnetic core to be evaluated. The noise measuring device includes a microphone. The microphone is positioned opposite a measurement surface of an object to be measured that includes the magnetic core and the winding. The noise measuring device is configured to measure noise generated from the object to be measured. The vibration measuring device is configured to measure vibrations of the measurement surface in a direction intersecting the measurement surface (first configuration).

[0011] In the noise evaluation equipment according to the first configuration, the microphone of the noise measuring device is positioned opposite a predetermined measurement surface of the object to be measured, and the vibration measuring device is configured to measure vibrations of the measurement surface in a direction intersecting the measurement surface. In other words, the direction in which noise arrives from the object to be measured to the microphone corresponds to the direction in which vibrations are measured by the vibration measuring device. By arranging the microphone of the noise measuring device and the vibration measuring device in this layout, it becomes easier to evaluate noise generated by the object to be measured that is caused by magnetostriction of the magnetic core.

[0012] Specifically, the noise measured by the noise measuring device while the object under test is magnetized includes noise caused by magnetostriction and noise caused by factors other than magnetostriction. Regarding noise caused by factors other than magnetostriction, for example, a mechanical vibration test can be performed in advance to simulate vibrations (vibrations in a direction intersecting the measurement surface) that occur in a magnetized state for the object under test in a non-magnetized state, and a correlation between the magnitude of the vibrations and the noise can be obtained. Based on this correlation, the magnitude of the noise caused by factors other than magnetostriction can be estimated from the magnitude of the vibrations measured by the vibration measuring device while the object under test is magnetized. The magnitude of the noise caused by magnetostriction can be estimated by subtracting the estimated magnitude of the noise caused by factors other than magnetostriction from the magnitude of the noise measured by the noise measuring device.

[0013] In the noise evaluation facility according to the first configuration, the noise measuring device may be configured to measure sound intensity (second configuration).

[0014] In the noise evaluation equipment according to the second configuration, the noise measuring device measures the acoustic intensity of the measurement surface of the object under test. In this case, the noise measuring device can measure the magnitude and direction of the noise generated by the object under test. Therefore, the magnitude of the noise caused by magnetostriction can be more accurately estimated.

[0015] The noise evaluation facility according to the first or second configuration may be configured so that the excitation waveform for exciting the object to be measured can be switched between a plurality of waveforms (third configuration).

[0016] The noise evaluation equipment according to the third configuration can switch the excitation waveform of the test object between multiple waveforms. In this case, the noise and vibration generated by the test object can be dynamically measured. For example, the magnitude of noise caused by magnetostriction can be evaluated for each excitation waveform while switching the excitation waveform of the test object, thereby enabling a variety of evaluations of magnetic core materials. Possible excitation waveforms that can be switched include a waveform simulating DC bias magnetization by superimposing a DC voltage on a sine wave, a waveform containing multiple frequency components, and combinations thereof. Using these waveforms as excitation waveforms makes it possible to evaluate the effects of DC bias magnetization and noise characteristics when a distorted waveform is input. Each waveform can be designed to simulate the changes in the excitation waveform that occur in the practical environment of a device such as a transformer, thereby enabling noise estimation appropriate for the practical environment.

[0017] In the noise evaluation equipment according to any one of the first to third configurations, the winding section may include three primary winding sections and three secondary winding sections. In this case, the primary winding sections and the secondary winding sections may each be configured to have a switchable connection method (fourth configuration).

[0018] In the noise evaluation equipment according to the fourth configuration, the three-phase connection of the primary winding and the three-phase connection of the secondary winding can be switched. The connection of the primary winding and the secondary winding can be switched, for example, between delta connection and star connection. In this case, the noise and vibration generated in the object under test can be measured for each connection, and the magnitude of the noise caused by magnetostriction can be evaluated for each connection. This allows for material development of magnetic cores according to their actual usage. Note that the switchable connection can be other than delta connection and star connection, and can be, for example, a V connection or other connection used in known transformers.

[0019] The noise evaluation equipment according to any one of the first to fourth configurations may further include a vibration generator. The vibration generator may be configured to mechanically apply vibrations to the object to be measured in a direction intersecting the measurement surface (fifth configuration).

[0020] In the noise evaluation facility according to the fifth configuration, the vibration generator can mechanically vibrate the object under test without exciting it. By measuring the noise and vibration of the object under test at this time using a noise measuring device and a vibration measuring device, a correlation can be obtained between the magnitude of the noise and vibration not caused by magnetostriction of the magnetic core. Because the vibration generator is installed in the noise evaluation facility, the noise and vibration of the object under test caused by the vibration generator alone can be measured under the same environment as when the noise and vibration of the object under test are measured in an excited state, and the above correlation can be obtained. This correlation can then be used to accurately estimate the magnitude of the noise generated by the object under magnetostriction.

[0021] The noise evaluation facility according to any one of the first to fifth configurations may further include a calculation device, in which information about the noise measured by the noise measuring device and information about the vibration measured by the vibration measuring device are input to the calculation device (sixth configuration).

[0022] In the noise evaluation facility according to the sixth configuration, noise information measured by the noise measuring device and vibration information measured by the vibration measuring device are input into a common calculation device, making it easier to perform calculations using this information.

[0023] In the noise evaluation equipment according to the sixth configuration, the calculation device may be configured to execute a first process and a second process. In the first process, actual noise information, which is information about noise measured by a noise measuring device while the object to be measured is excited, and actual vibration information, which is information about vibrations measured by a vibration measuring device while the object is excited, are acquired. In the second process, information corresponding to non-magnetostrictive noise obtained based on the actual vibration information is subtracted from the actual noise information. The non-magnetostrictive noise information is information corresponding to noise generated from the object to be measured due to causes other than magnetostriction of the magnetic core (seventh configuration).

[0024] In the noise evaluation equipment according to the seventh configuration, information equivalent to non-magnetostrictive noise can be obtained, for example, by using actual vibration information and the correlation between noise and vibrations generated due to causes other than magnetostriction of the magnetic core (eighth configuration).

[0025] In the noise evaluation equipment according to the eighth configuration, the information equivalent to non-magnetostrictive noise may be obtained by multiplying the actual vibration information by a coefficient indicating the correlation (ninth configuration).

[0026] In the noise evaluation facility according to any one of the first to ninth configurations, the vibration measuring device may include an acceleration pickup or a laser Doppler vibrometer (tenth configuration).

[0027] A noise evaluation method according to an embodiment comprises the following steps: 1) exciting a measurement object including a magnetic core and a winding attached to the magnetic core; 2) while the measurement object is excited, measuring noise generated from the measurement object using the noise measuring device with a microphone of the noise measuring device positioned opposite the measurement surface of the measurement object, and measuring vibration of the measurement surface in a direction intersecting the measurement surface using a vibration measuring device; 3) subtracting non-magnetostrictive noise-equivalent information obtained based on actual vibration information, which is information about vibration measured in the measurement step, from actual noise information, which is information about noise measured in the measurement step. The non-magnetostrictive noise-equivalent information is information corresponding to noise generated from the measurement object due to factors other than the magnetostriction of the magnetic core (eleventh configuration).

[0028] In a noise evaluation method according to an eleventh aspect, a microphone is placed opposite a predetermined measurement surface of the object to be measured, and the noise of the object to be measured is measured by a noise measuring device. At the same time, the vibration of the measurement surface in a direction intersecting the measurement surface is measured by a vibration measuring device. That is, when measuring the noise and vibration of the object to be measured during excitation, the direction of arrival of the noise from the object to the microphone corresponds to the direction of measurement of the vibration by the vibration measuring device. In the noise evaluation method according to the eleventh aspect, the noise caused by magnetostriction is estimated using information on the noise and vibration. Specifically, information equivalent to non-magnetostrictive noise obtained based on information on the measured vibration is subtracted from the measured noise information. This allows information equivalent to the noise caused by magnetostriction to be obtained, excluding factors other than magnetostriction. Therefore, it is possible to evaluate the noise generated by the object to be measured that is caused by the magnetostriction of the magnetic core.

[0029] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In these drawings, the same or equivalent components are designated by the same reference numerals, and the same description will not be repeated.

[0030] 1 is a perspective view that schematically shows a noise evaluation facility 100 according to this embodiment. As shown in FIG. 1, the noise evaluation facility 100 includes a winding portion 12, a noise measuring device 20, and a vibration measuring device 30.

[0031] When using the noise evaluation equipment 100, a measurement object 10 is prepared. The measurement object 10 includes a magnetic core 11 and a winding portion 12 as an evaluation target.

[0032] The magnetic core 11 includes at least one leg 111. The magnetic core 11 may include multiple legs 111. When the magnetic core 11 includes multiple legs 111, these legs 111 are connected by a yoke 112. In this example embodiment, the magnetic core 11 includes three legs 111.

[0033] The magnetic core 11 is made of a magnetic material. The magnetic core 11 is, for example, a stacked core formed by laminating a plurality of steel plates. More specifically, in each layer, the steel plates for the legs 111 and the steel plates for the yoke 112 are separate, and the steel plates are laminated so that the joints between the steel plates for the legs 111 and the steel plates for the yoke 112 are different for each layer or for each plurality of layers. The magnetic core 11 may be fastened from both sides in the lamination direction of the steel plates by, for example, wooden boards or the like (not shown).

[0034] A grain-oriented electromagnetic steel sheet is typically used for the magnetic core 11. However, a non-oriented electromagnetic steel sheet or an amorphous alloy sheet may also be used for the magnetic core 11. Furthermore, the magnetic core 11 is not limited to a stacked core and may be, for example, a wound core. Alternatively, the magnetic core 11 may be a powder core.

[0035] The winding portion 12 is made of a conductive material. When evaluating the magnetic core 11, the winding portion 12 is attached to the magnetic core 11. More specifically, the winding portion 12 is wound around the legs 111 of the magnetic core 11. When the magnetic core 11 is sandwiched between plates (not shown) as described above, the winding portion 12 may be attached to the magnetic core 11 from above the plates.

[0036] The winding section 12 may include at least one primary winding section 121 and at least one secondary winding section 122. The primary winding section 121 and the secondary winding section 122 are wound around any one of the legs 111 of the magnetic core 11. The primary winding section 121 and the secondary winding section 122 may be wound concentrically with the leg 111 or may be aligned in the axial direction of the leg 111.

[0037] 1 , the winding section 12 may include three primary winding sections 121. The winding section 12 may include three secondary winding sections 122 corresponding to the three primary winding sections 121. In the example of the present embodiment, three legs 111 are provided on the magnetic core 11. In this case, the primary winding section 121 and the secondary winding section 122 may be attached to each of the legs 111. However, two or more primary winding sections 121 and / or two or more secondary winding sections 122 may be attached to a common leg 111.

[0038] The three primary winding sections 121 and the three secondary winding sections 122 may each be configured to have a switchable connection method. For example, the connection method of the primary winding section 121 can be switched between a delta connection and a star connection by an operator's action. Furthermore, the connection method of the secondary winding section 122 can be switched between a delta connection and a star connection by an operator's action. The connection methods of the primary winding section 121 and the secondary winding section 122 may be switched between a delta connection or a star connection and a V connection.

[0039] The device under test 10 may be, for example, a transformer model that simulates a transformer. In the example shown in FIG. 1, the device under test 10 is a three-phase, three-legged transformer model. However, the device under test 10 may also be a single-phase transformer model. Alternatively, the device under test 10 may be a model that simulates a device other than a transformer, such as a reactor.

[0040] The noise evaluation equipment 100 is provided with at least one noise measuring device 20. The noise measuring device 20 includes at least one microphone 21. The microphone 21 is positioned opposite the measurement surface 13 of the object to be measured 10. That is, the microphone 21 is positioned on the measurement surface 13 side of the object to be measured 10. In the example of FIG. 1 , the noise measuring device 20 itself is positioned opposite the measurement surface 13 of the object to be measured 10. The measurement surface 13 is one of multiple surfaces of the object to be measured 10. It is preferable that the measurement surface 13 is a surface of the object to be measured 10 that is substantially perpendicular to the thickness direction of the object to be measured 10. However, the measurement surface 13 may also be a surface of the object to be measured 10 that is substantially parallel to the thickness direction of the object to be measured 10. For example, if the magnetic core 11 is a stacked core, the thickness direction of the object to be measured 10 is the lamination direction of the steel sheets used in the magnetic core 11.

[0041] The noise measuring device 20 may include, for example, a preamplifier and a signal processor in addition to the microphone 21. A known or commercially available sound level meter can be used as the noise measuring device 20. The noise measuring device 20 can include one or more sound level meters.

[0042] The noise measuring device 20 may be configured to measure sound intensity. In this case, the noise measuring device 20 includes a plurality of microphones 21. For example, the noise measuring device 20 may include a sound intensity probe including the plurality of microphones 21 and a sound intensity processor. A publicly known or commercially available sound intensity measuring device may be used as the noise measuring device 20. The noise measuring device 20 may include one or more sound intensity measuring devices.

[0043] The vibration measuring device 30 measures the vibration of the measurement target 10. More specifically, the vibration measuring device 30 is configured to measure the vibration of the measurement target 10 in a direction intersecting the measurement target 13. For example, if the measurement target 13 is a surface that is substantially perpendicular to the thickness direction of the measurement target 10, the vibration measuring device 30 may measure the vibration of the measurement target 10 in the thickness direction of the measurement target 10. For example, if the magnetic core 11 is a stacked iron core, the vibration measuring device 30 can measure the vibration of the measurement target 10 in the out-of-plane direction of the steel plate. The vibration measuring device 30 is typically placed on the same side of the measurement target 10 as the noise measuring device 20.

[0044] A known vibrometer can be used as the vibration measuring device 30. The vibration measuring device 30 may include one or more vibrometers. The vibration measuring device 30 includes, for example, an acceleration pickup or a laser Doppler vibrometer. The acceleration pickup can be attached to the measurement surface 13 of the measurement object 10. Examples of acceleration pickups that can be used include a general-purpose sensor such as the VM-83 piezoelectric acceleration pickup manufactured by Riontec, or a sensor such as the PV-91C, a small, lightweight, and highly sensitive piezoelectric acceleration pickup. The laser Doppler vibrometer is positioned facing the measurement surface 13 of the measurement object 10. In this case, for example, a reflector is installed on the measurement surface 13, and the laser Doppler vibrometer irradiates a laser onto the reflector from a position facing the measurement surface 13. Examples of laser Doppler vibrometers that can be used include the LSV-2100 laser surface velocimeter manufactured by Polytec. However, the vibration measuring device 30 can also include other contact or non-contact vibrometers. The vibration measuring device 30 may be, for example, a white light interferometer displacement meter, a capacitance displacement meter, or a laser displacement meter.

[0045] 2 is a block diagram showing an example of the configuration of the noise evaluation facility 100. Referring to FIG. 2, the noise evaluation facility 100 may further include a calculation device 40 and a vibration generating device 50.

[0046] The calculation device 40 is connected to the noise measuring device 20 and the vibration measuring device 30 via a network. The calculation device 40 may be configured to control the noise measurement by the noise measuring device 20 and the vibration measurement by the vibration measuring device 30. Information about the noise measured by the noise measuring device 20 and information about the vibration measured by the vibration measuring device 30 are input to the calculation device 40.

[0047] The computing device 40 is a computer. For example, a terminal device such as a personal computer is used as the computing device 40. Fig. 3 is a hardware configuration diagram of the computing device 40. As shown in Fig. 3, the computing device 40 may include a central processing unit (CPU) 41, a main memory device 42, an auxiliary memory device 43, an input device 44, an output device 45, and the like.

[0048] The CPU 41 executes various programs loaded from the auxiliary storage device 43 to the main storage device 42 and performs information calculations. The main storage device 42 is, for example, a RAM, and is used as a work area for temporarily storing various programs executed by the CPU 41, information used by the CPU 41, calculation results by the CPU 41, etc. The auxiliary storage device 43 is, for example, a HDD or ROM. Some functions of the computing device 40 may be realized, for example, by loading a program pre-stored in the auxiliary storage device 43 into the main storage device 42 and having the CPU 41 execute this program. The input device 44 is a device for an operator to perform input operations, and includes, for example, a pointing device such as a mouse or a touch panel, a keyboard, etc. The output device 45 is a device for outputting processing results, etc., of the CPU 41. The output device 45 may include a display.

[0049] Returning to Fig. 2, the calculation device 40 may be connected to an excitation power supply 60 via a network. The excitation power supply 60 is a power supply that supplies an excitation current to the winding portion 12 (Fig. 1) of the device under test 10 to excite the device under test 10. For example, when an AC voltage is applied from the excitation power supply 60 to the primary winding portion 121 (Fig. 1), an excitation current flows through the primary winding portion 121, and the device under test 10 is excited. The calculation device 40 may be configured to control the excitation of the device under test 10 by the excitation power supply 60.

[0050] 2 , the noise measuring device 20 and the vibration measuring device 30 are also connected to the excitation power supply 60 via a network. In this case, the noise measuring device 20 can acquire information about the noise generated from the measurement target 10 while recording information about the excitation voltage from the excitation power supply 60. Similarly, the vibration measuring device 30 can acquire information about the vibration generated from the measurement target 10 while recording information about the excitation voltage from the excitation power supply 60. For example, the noise measuring device 20 and the vibration measuring device 30 may be connected to the excitation power supply 60 via a common recorder (not shown). In this case, the recorder can collect information about the noise measured by the noise measuring device 20 and information about the vibration measured by the vibration measuring device 30 while recording information about the excitation voltage from the excitation power supply 60.

[0051] The vibration generator 50 is configured to mechanically apply vibrations in a direction intersecting the measurement surface 13 ( FIG. 1 ) to the object to be measured 10. For example, when the measurement surface 13 is a surface that is substantially perpendicular to the thickness direction of the object to be measured 10, the vibration generator 50 can apply vibrations to the object to be measured 10 in the thickness direction (out-of-plane direction of the steel plate).

[0052] A known or commercially available actuator can be used as the vibration generator 50. The vibration generator 50 may be, for example, a device using electromagnetic force such as a motor, or a piezoelectric element. For example, a chip-type piezoelectric actuator PA4FEH3 manufactured by Thorlabs can be used as the actuator. When the vibration to be applied to the measured object 10 is large, an actuator with a high vibration displacement, such as a chip-type piezoelectric actuator PA4FL manufactured by Thorlabs, may be used. As shown in FIG. 1 , one or more vibration generators 50 are installed on the measured object 10. The vibration generators 50 may be attached to the measurement surface 13 of the measured object 10.

[0053] [Noise Evaluation Method] A method for evaluating noise using the noise evaluation equipment 100 will now be described with reference to Fig. 4. Fig. 4 is a flowchart showing the noise evaluation method according to this embodiment. The noise evaluation method includes steps S1, S2, S3, and S4.

[0054] 1 and 2, when a noise evaluation method using noise evaluation equipment 100 is performed, a device under test 10 including a magnetic core 11 and a winding 12 is placed in the noise evaluation equipment 100. In step S1, the device under test 10 is excited. A computing device 40 can output a command to an excitation power supply 60 to excite the device under test 10. The command from the computing device 40 includes information on excitation conditions such as frequency and magnetic flux density.

[0055] The noise evaluation equipment 100 is preferably configured to be able to switch between a plurality of excitation waveforms for exciting the object under test 10. In this case, the calculation device 40 may output a command to the excitation power supply 60 to excite the object under test 10 using an excitation waveform selected from a plurality of waveforms based on an operation by an operator. The calculation device 40 outputs a command to excite the object under test 10 with an excitation voltage waveform selected by the operator from a plurality of excitation voltage waveforms prepared in advance, for example. The excitation power supply 60 excites the object under test 10 based on the command from the calculation device 40.

[0056] In step S2, the noise and vibration generated from the measurement target 10 are measured. More specifically, as shown in Figures 1 and 2, while the measurement target 10 is excited, a microphone 21 is placed at a position facing the measurement surface 13 of the measurement target 10, and the noise generated from the measurement target 10 is measured by a noise measuring device 20. At the same time, a vibration measuring device 30 measures the vibration of the measurement surface 13 in a direction intersecting the measurement surface 13.

[0057] Measurement of noise generated from the object under test 10 can be performed in accordance with standard JEC-2200-2014 of the Electrotechnical Committee of the Institute of Electrical Engineers of Japan. Specifically, noise measurement conditions such as the position of the microphone 21 and the number of noise measurement points can be determined in accordance with this standard. In the example of FIG. 1, multiple microphones 21 are provided in the noise evaluation equipment 100. The microphones 21 are positioned so as to correspond to the center of the object under test 10 in the height direction. As an example, in FIG. 1, the height of the object under test 10 is h, and each microphone 21 is positioned at a height of h / 2.

[0058] The noise measuring device 20 receives noise generated by the excited object 10 using a microphone 21, converts it into an electrical signal, performs necessary signal processing, and outputs noise information. The vibration measuring device 30 detects vibrations of the excited object 10 in a direction intersecting the measurement surface 13, converts them into an electrical signal, performs necessary signal processing, and outputs vibration information.

[0059] The noise information measured by the noise measuring device 20 and the vibration information measured by the vibration measuring device 30 are input to the calculation device 40. In steps S3 and S4, calculations are performed based on the noise information and vibration information of the measurement target 10. This calculation process may be performed by a function of the calculation device 40.

[0060] For example, the computing device 40 may be configured to execute a first process and a second process. In this case, the first process and the second process are performed by the CPU 41 of the computing device 40 executing a program that has been prepared in advance.

[0061] In the first process, the calculation device 40 acquires actual noise information and actual vibration information (step S3). The actual noise information is information about vibrations measured by the noise measuring device 20 while the measurement target 10 is excited. The actual vibration information is information about vibrations measured by the vibration measuring device 30 while the measurement target 10 is excited.

[0062] The actual noise information is primarily information indicating the noise level N generated by the measurement target 10 due to the excitation in step S1. The noise level N is, for example, sound pressure or sound intensity, or sound pressure level or sound intensity level. The information indicating the noise level N may also be time-series noise data collected by the noise measuring device 20. For example, the noise level N can be expressed as a function N(t) of only time t when there is a single excitation magnetic flux density condition, or as a function N(t, B) of time t for each excitation magnetic flux density B when there are multiple excitation magnetic flux density conditions. Alternatively, the noise level N may be expressed as a function N(f, θ) or N(f, θ, B) in the frequency domain (f: frequency, θ: phase). The function N(f, θ) is a function when there is a single excitation magnetic flux density condition, and the function N(f, θ, B) is a function for each excitation magnetic flux density B when there are multiple excitation magnetic flux density conditions. The function N(f, θ) or the function N(f, θ, B) can be obtained by performing frequency analysis such as a Fourier transform on the time-series data collected by the noise measurement device 20, and converting it from the time domain to the frequency domain. The noise level N may be expressed in either a linear scale or a logarithmic scale.

[0063] The actual vibration information may include information indicating the magnitude V of vibration generated in the measurement object 10 due to the excitation in step S1. The information indicating the magnitude V of vibration may be time-series vibration data collected by the vibration measuring device 30. For example, the magnitude V of vibration can be expressed as a function V(t) of time t when there is a single excitation magnetic flux density condition, or as a function V(t, B) of time t for each excitation magnetic flux density B when there are multiple excitation magnetic flux density conditions. Alternatively, the magnitude V of vibration may be expressed as a function V(f, θ) or V(f, θ, B) in the frequency domain (f: frequency, θ: phase). The function V(f, θ) is a function when there is a single excitation magnetic flux density condition, and the function V(f, θ, B) is a function for each excitation magnetic flux density B when there are multiple excitation magnetic flux density conditions. The function V(f, θ) or the function V(f, θ, B) can be obtained by performing frequency analysis such as a Fourier transform on the time-series data collected by the vibration measuring device 30, thereby converting the data from the time domain to the frequency domain. The magnitude V of the vibration may be expressed in a linear scale or a logarithmic scale.

[0064] In the second process, the calculation device 40 subtracts information equivalent to non-magnetostrictive noise, which is obtained based on the actual vibration information, from the actual noise information (step S4). The non-magnetostrictive noise is noise generated from the measured body 10 due to factors other than the magnetostriction of the magnetic core 11. The information equivalent to non-magnetostrictive noise is information equivalent to non-magnetostrictive noise, and includes information indicating the volume of sound equivalent to the non-magnetostrictive noise.

[0065] The non-magnetostrictive noise equivalent information can be obtained using actual noise information and the correlation between the magnitude of the non-magnetostrictive noise and the magnitude of the vibration. The correlation between the magnitude of the non-magnetostrictive noise and the magnitude of the vibration is expressed, for example, by a predetermined coefficient K. The calculation device 40 can store the coefficient K in advance. The coefficient K may also be obtained by conducting a preliminary test before implementing the noise evaluation method according to this embodiment. Note that when there are multiple excitation magnetic flux density conditions, it is desirable to obtain a coefficient K corresponding to each excitation magnetic flux density.

[0066] For example, the non-excited object 10 is mechanically vibrated in a direction intersecting the measurement surface 13 by the vibration generator 50, and the resulting noise is measured by the noise measuring device 20. This makes it possible to obtain information on noise generated when the object 10 vibrates without magnetostriction, i.e., non-magnetostrictive noise. Furthermore, based on the vibration conditions of the vibration generator 50 or the vibration measurement by the vibration measuring device 30, it is possible to obtain information on vibrations corresponding to non-magnetostrictive noise. This information may be obtained for each vibration mode or for each excitation magnetic flux density condition.

[0067] The magnitude NO of the non-magnetostrictive noise may be time-series noise data. When the excitation magnetic flux density condition is uniform, the magnitude NO of the non-magnetostrictive noise is expressed, for example, as a function NO(t,M) of time t for each vibration mode M. On the other hand, the magnitude V0 of the vibration corresponding to the non-magnetostrictive noise can be expressed as a function V0(t,M) of time t for each vibration mode M. In this case, the coefficient K indicating the correlation between the magnitude NO of the non-magnetostrictive noise and the magnitude V0 of the vibration is expressed as K = K(t,M) = NO(t,M) / VO(t,M).

[0068] When there are multiple excitation magnetic flux density conditions, the magnitude NO of the non-magnetostrictive noise can be expressed, for example, as a function NO(t, B) of time t for each excitation magnetic flux density B. On the other hand, the magnitude V of the vibration corresponding to the non-magnetostrictive noise can be expressed as a function V(t, B) of time t for each excitation magnetic flux density B. In this case, the coefficient K indicating the correlation between the magnitude NO of the non-magnetostrictive noise and the magnitude V of the vibration is expressed as K = K(t, B) = NO(t, B) / VO(t, B).

[0069] Alternatively, the coefficient K may be expressed in the form of a transfer function in the frequency domain. In this case, a different transfer function may be prepared as the coefficient K for each vibration measurement result, such as the vibration magnitude. For example, by performing frequency analysis such as a Fourier transform on the noise time-series data and converting from the time domain to the frequency domain, the magnitude N0 of the non-magnetostrictive noise can be expressed as a frequency-domain function N0(f,θ), where f is frequency and θ is phase. Similarly, by performing frequency analysis such as a Fourier transform on the vibration time-series data and converting from the time domain to the frequency domain, the vibration magnitude V0 corresponding to the non-magnetostrictive noise can be expressed as a frequency-domain function V0(f,θ). The coefficient K is expressed as K = K(f,θ) = N0(f,θ) / V0(f,θ). K(f,θ) is a function of the coefficient K when the excitation magnetic flux density condition is single.

[0070] When there are multiple excitation magnetic flux density conditions, the coefficient K may be obtained for each excitation magnetic flux density condition. That is, the magnitude N of the non-magnetostrictive noise can be expressed as a function N(f, θ, B) in the frequency domain, and the magnitude V of the vibration corresponding to the non-magnetostrictive noise can be expressed as a function V(f, θ, B) in the frequency domain. In this case, the coefficient K is expressed as K = K(f, θ, B) = N(f, θ, B) / V(f, θ, B).

[0071] The coefficient K is the constant K Ｃ The constant K Ｃ is preferably determined for each vibration mode M or each excitation magnetic flux density B. When the magnitude N0 of the non-magnetostrictive noise is expressed by a scalar quantity N0 and the magnitude V0 of the vibration corresponding to the non-magnetostrictive noise is expressed by a scalar quantity V0, K=K Ｃ = N0 / V0.

[0072] The information equivalent to non-magnetostrictive noise can be obtained by multiplying the actual vibration information by a coefficient K. More specifically, by multiplying the vibration magnitude V actually measured by the vibration measuring device 30 in step S2 by a coefficient K, the sound magnitude NO corresponding to non-magnetostrictive noise can be obtained. Ｅ can be obtained.

[0073] For example, the coefficient K may be a function K(t,M) in the time domain or a constant K ＣIf so, K(t, M) or K Ｃ By multiplying the vibration magnitude V(t) in the actual vibration information by Ｅ Alternatively, when the coefficient K is a function K(t, B), K(t, B) or K(t, B) corresponding to the excitation magnetic flux density B of the actual vibration information is obtained. Ｃ By multiplying the vibration magnitude V(t, B) in the actual vibration information by Ｅ When the coefficient K is a function K(f, θ) in the frequency domain, the magnitude of vibration V(f, θ) in the frequency domain is multiplied by K(f, θ) to obtain the sound magnitude N0 corresponding to the non-magnetostrictive noise. Ｅ When the coefficient K is a function K(f, θ, B) in the frequency domain, the magnitude of vibration V(f, θ, B) corresponding to the excitation magnetic flux density B can be multiplied by K(f, θ, B) to obtain the sound magnitude N0 corresponding to the non-magnetostrictive noise. Ｅ (f, θ, B) can be obtained.

[0074] In the second process, the calculation device 40 subtracts the non-magnetostrictive noise equivalent information from the actual noise information (step S4). More specifically, the calculation device 40 subtracts the noise level N0 in the non-magnetostrictive noise equivalent information from the noise level N in the actual noise information. Ｅ = Subtract K x V.

[0075] For example, if the noise level N in the actual noise information is a function N(t) of time t, the calculation device 40 calculates N(t)-N0 Ｅ (t)=N(t)-K(t,M)×V(t), or N(t)-K Ｃ When the noise level N in the actual noise information is a function N(t, B) of time t for each excitation magnetic flux density B, the calculation device 40 calculates N(t, B) - N0 Ｅ (t,B)=N(t,B)-K(t,B)×V(t,B), or N(t,B)-K Ｃ ×V(t, B). For example, if the noise level N in the actual noise information is a function N(f, θ) in the frequency domain, the calculation device 40 calculates N(f, θ)−N0 Ｅ(f, θ) = N(f, θ) - K(f, θ) × V(f, θ). When the noise level N in the actual noise information is a function N(f, θ, B) in the frequency domain for each excitation magnetic flux density B, the calculation device 40 calculates N(f, θ, B) - N0 Ｅ Calculate (f, θ, B) = N(f, θ, B) - K(f, θ, B) × V(f, θ, B).

[0076] The noise level in the actual noise information, in other words, the total noise level N generated from the test object 10 during excitation, is subtracted from the sound level N0 corresponding to the non-magnetostrictive noise. Ｅ It is possible to obtain the magnitude of the noise generated by the object 10 due to the magnetostriction of the magnetic core 11 by subtracting . The calculation device 40 may display the result obtained by the calculation in step S4 on the output device 45.

[0077] [Effect] In this embodiment, the noise measuring device 20 measures the noise generated by the object to be measured 10 with the microphone 21 positioned opposite the measurement surface 13, and the vibration measuring device 30 measures the vibration of the measurement surface 13 in a direction intersecting the measurement surface 13. By arranging the object to be measured 10, the microphone 21, and the vibration measuring device 30 in this layout and measuring the vibration and noise, it becomes easier to evaluate the noise generated by the object to be measured 10 that is caused by magnetostriction of the magnetic core 11.

[0078] In this embodiment, when the noise is measured by the noise measuring device 20 while the object 10 is excited, the noise includes noise caused by magnetostriction and noise caused by factors other than magnetostriction. In this embodiment, the noise level N0 corresponding to the non-magnetostrictive noise caused by factors other than magnetostriction is subtracted from the overall noise level N measured by the noise measuring device 20. Ｅ This makes it possible to estimate the noise generated by the object 10 due to magnetostriction.

[0079] In this embodiment, the sound volume NO corresponding to the non-magnetostrictive noise is Ｅcan be calculated using the correlation between the magnitude of non-magnetostrictive noise NO and the magnitude of vibration VO. More specifically, the magnitude of vibration V measured by the vibration measuring device 30 is multiplied by a coefficient K indicating the correlation to obtain the magnitude of sound NO corresponding to the non-magnetostrictive noise. Ｅ Therefore, it is possible to obtain and evaluate the noise caused by magnetostriction through simple calculations.

[0080] In this embodiment, the noise measuring device 20 is preferably configured to measure acoustic intensity. That is, the noise measuring device 20 can measure the acoustic intensity of the object under test 10. In this case, information on the magnitude and direction of the noise generated by the object under test 10 can be obtained. Therefore, the magnitude of the noise generated by the object under test 10 due to magnetostriction can be more accurately estimated.

[0081] The noise evaluation equipment 100 according to this embodiment is preferably configured to be able to switch between multiple excitation waveforms for exciting the object under test 10. For example, an operator can perform noise evaluation of the object under test 10 using a desired excitation waveform (excitation voltage waveform) through input operations into the calculation device 40. This allows the operator to switch between excitation waveforms for the object under test 10 and evaluate the level of noise caused by magnetostriction for each excitation waveform. This allows for a variety of evaluations of the material of the magnetic core 11. More specifically, noise evaluation can be performed using waveforms that simulate excitation waveforms generated in the practical environment of equipment such as transformers, such as waveforms that simulate DC bias magnetization by superimposing a DC voltage on a sine wave, waveforms containing multiple frequency components, and combinations of these. This allows for estimation of noise that corresponds to the practical environment, such as the effects of DC bias magnetization and noise characteristics when a distorted waveform is input.

[0082] In the noise evaluation equipment 100 according to this embodiment, the winding section 12 of the device under test 10 can include a three-phase primary winding section 121 and a three-phase secondary winding section 122. In this case, the primary winding section 121 and the secondary winding section 122 may each be configured to have a switchable connection system. This allows, for example, the noise and vibration generated in the device under test 10 to be measured for each connection system, and the magnitude of noise caused by magnetostriction to be evaluated for each connection system. This allows material development for the magnetic core 11 to be carried out according to the actual usage pattern.

[0083] The noise evaluation facility 100 according to this embodiment can include a vibration generator 50. The vibration generator 50 can mechanically vibrate the object to be measured 10 in a non-excited state. In this case, the vibration generator 50 can be used to perform a preliminary test to obtain, for example, a coefficient K in the same environment as when the noise evaluation of the noise evaluation facility 100 is performed (steps S1 to S4). The obtained coefficient K can be used to accurately estimate the magnitude of the noise generated from the object to be measured 10 due to magnetostriction.

[0084] However, the noise evaluation facility 100 does not necessarily have to include the vibration generator 50. The coefficient K, which indicates the correlation between the magnitude N0 of the non-magnetostrictive noise and the magnitude V0 of the vibration, may be found by a preliminary test carried out at a location spatially separated from the noise evaluation facility 100. It is preferable that this preliminary test be carried out in an environment that is substantially identical to the environment of the noise evaluation facility 100.

[0085] In the noise evaluation equipment 100 according to this embodiment, noise information measured by the noise measurement device 20 and vibration information measured by the vibration measurement device 30 are input to the calculation device 40. This makes it easier to perform calculations using this information.

[0086] In this embodiment, the calculation process of step S4 is performed by the function of the calculation device 40. That is, the calculation device 40 executes a program to perform a process of subtracting the information equivalent to non-magnetostrictive noise from the actual noise information obtained by the noise measuring device 20 measuring the noise of the test object 10 during excitation. However, the calculation device 40 does not necessarily have the function of performing the process of subtracting the information equivalent to non-magnetostrictive noise from the actual noise information. As long as the test object 10, the noise measuring device 20, and the vibration measuring device 30 are arranged in the layout described above and vibration and noise are measured to obtain that information, it is possible to perform the calculation of subtracting the information equivalent to non-magnetostrictive noise from the actual noise information, regardless of the function of the calculation device 40.

[0087] Second Embodiment In the noise evaluation method according to the first embodiment, the non-magnetostrictive noise equivalent information is calculated using the correlation between the magnitude N0 of the non-magnetostrictive noise and the magnitude V0 of the vibration. That is, the non-magnetostrictive noise equivalent information is calculated by multiplying the vibration magnitude V of the test object 10 during excitation by a coefficient K. In contrast, in the noise evaluation method according to this embodiment, the non-magnetostrictive noise equivalent information is calculated without using the coefficient K.

[0088] Fig. 5 is a flowchart showing the noise evaluation method according to this embodiment. As shown in Fig. 5, the noise evaluation method includes step S5 in addition to steps S1, S2, S3, and S4. Step S5 is performed between steps S3 and S4.

[0089] 1 and 2 in addition to Fig. 5, in the noise evaluation method according to this embodiment, steps S1, S2, and S3 are first performed in the same manner as in the first embodiment, thereby obtaining actual vibration information of the measured object 10 in an excited state.

[0090] Next, with the excitation of the object to be measured 10 stopped, the object to be measured 10 is mechanically vibrated by the vibration generator 50 in a direction intersecting the measurement surface 13, and the noise generated at this time is measured by the noise measuring device 20 (step S5). The vibration generator 50 applies vibrations to the object to be measured 10 that simulate the vibrations measured in step S2. Because the object to be measured 10 is not excited in step S5, the noise information measured by the vibration generator 50 can be treated as information equivalent to noise generated from the object to be measured 10 due to factors other than the magnetostriction of the magnetic core 11. In other words, the noise information measured in step S5 is information equivalent to non-magnetostrictive noise.

[0091] The non-magnetostrictive noise equivalent information is the sound volume NO corresponding to the non-magnetostrictive noise. Ｅ The information includes the sound level NO corresponding to non-magnetostrictive noise. Ｅ is the noise level measured by the noise measuring device 20 in step S5. Ｅ is, for example, sound pressure or sound intensity, or sound pressure level or sound intensity level. Ｅ The information indicating N0 may be time-series data collected by the noise measurement device 20. Ｅ is, for example, a function N0 of only time t. Ｅ (t) or N0 Ｅ is the function N0 in the frequency domain Ｅ It may be expressed as (f, θ) (f: frequency, θ: phase). Ｅ (f, θ) can be obtained by performing frequency analysis such as Fourier transform on the time series data collected by the noise measurement device 20 and converting from the time domain to the frequency domain.

[0092] In step S4, the information equivalent to non-magnetostrictive noise obtained in step S5 is subtracted from the actual noise information obtained in steps S2 and S3. More specifically, the noise level N in the actual noise information is subtracted from the sound level N0 equivalent to non-magnetostrictive noise. Ｅ. This makes it possible to obtain the magnitude of the noise generated by the object 10 due to magnetostriction. As in the first embodiment, the calculation device 40 may or may not have a function for performing the process of step S4. Step S4 may be performed by, for example, an operator using the calculation device 40 or another calculation device.

[0093] Even in the noise evaluation method according to this embodiment, the sound level N0 corresponding to the non-magnetostrictive noise caused by factors other than magnetostriction is subtracted from the overall noise level N measured by the noise measurement device 20. Ｅ Therefore, it is possible to estimate the magnitude of the noise caused by magnetostriction among the noises generated in the object 10 to be measured.

[0094] In this embodiment, in step S5, the measured object 10 is mechanically vibrated to simulate the vibration in step S2, and noise caused by factors other than magnetostriction is measured. In this case, it is preferable that the vibration measured in step S2 be as unaffected by magnetostriction as possible. The magnetostriction of the magnetic core 11 causes the measured object 10 to vibrate mainly in the axial direction of the legs 111. Therefore, it is preferable that the measurement surface 13 of the measured object 10 is a surface that is substantially parallel to the axial direction of the legs 111, in other words, a surface that is substantially perpendicular to the thickness direction of the measured object 10. This makes it possible to measure the vibration of the measured object 10 in a direction intersecting the axial direction of the legs 111 in step S2. Therefore, in step S2, vibration information that is less affected by magnetostriction can be obtained.

[0095] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments, and various modifications are possible without departing from the spirit of the present disclosure.

[0096] 100: Noise evaluation equipment 10: Object to be measured 11: Magnetic core 12: Winding section 121: Primary winding section 122: Secondary winding section 13: Measurement surface 20: Noise measuring device 21: Microphone 30: Vibration measuring device 40: Calculating device 50: Vibration generating device

Claims

1. A noise evaluation facility comprising: a winding portion attached to a magnetic core to be evaluated; a noise measuring device including a microphone positioned opposite a measurement surface of an object to be measured that includes the magnetic core and the winding portion, and configured to measure noise generated from the object to be measured; and a vibration measuring device configured to measure vibrations of the measurement surface in a direction intersecting the measurement surface.

2. A noise evaluation facility according to claim 1, wherein the noise measurement device is configured to measure sound intensity.

3. A noise evaluation facility according to claim 1, wherein the noise evaluation facility is configured to be able to switch the excitation waveform for exciting the object to be measured between a plurality of waveforms.

4. A noise evaluation facility according to claim 1, wherein the winding section includes three primary winding sections and three secondary winding sections, and the primary winding sections and the secondary winding sections are each configured so that the connection method can be switched.

5. A noise evaluation facility according to claim 1, further comprising a vibration generator configured to mechanically apply vibrations to the object to be measured in a direction intersecting the measurement surface.

6. A noise evaluation facility according to claim 1, further comprising a calculation device to which information on noise measured by said noise measuring device and information on vibration measured by said vibration measuring device are input.

7. A noise evaluation facility as claimed in claim 6, wherein the calculation device is configured to execute a first process of acquiring actual noise information, which is information on noise measured by the noise measuring device while the object to be measured is being excited, and actual vibration information, which is information on vibrations measured by the vibration measuring device while the object is being excited, and a second process of subtracting, from the actual noise information, information equivalent to non-magnetostrictive noise obtained based on the actual vibration information, wherein the non-magnetostrictive noise equivalent information is information equivalent to noise generated from the object to be measured due to causes other than magnetostriction of the magnetic core.

8. A noise evaluation facility according to claim 7, wherein the non-magnetostrictive noise equivalent information is obtained using the actual vibration information and the correlation between noise and vibrations generated due to causes other than magnetostriction of the magnetic core.

9. A noise evaluation facility according to claim 8, wherein the non-magnetostrictive noise equivalent information is obtained by multiplying the actual vibration information by a coefficient indicating the correlation.

10. A noise evaluation facility according to claim 1, wherein the vibration measuring device includes an acceleration pickup or a laser Doppler vibrometer.

11. A noise evaluation method comprising the steps of: exciting a measurement object including a magnetic core and a winding portion attached to the magnetic core; measuring, while the measurement object is being excited, noise generated from the measurement object using a noise measuring device with a microphone of the noise measuring device positioned opposite a measurement surface of the measurement object, and measuring vibrations of the measurement surface in a direction intersecting the measurement surface using a vibration measuring device; and subtracting, from actual noise information, which is information about the noise measured in the measuring step, information equivalent to non-magnetostrictive noise obtained based on actual vibration information, which is information about the vibration measured in the measuring step; wherein the non-magnetostrictive noise equivalent information is information equivalent to noise generated from the measurement object due to causes other than the magnetostriction of the magnetic core.

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