Inspection device and inspection method

Abstract

To inspect a magnetic core before incorporated into a measuring instrument as a converter, and estimate measurement errors of a sinusoidal half-wave rectification current on the instrument side.SOLUTION: An inspection device 1 comprises: an inspection current supply circuit 10 that supplies an inspection current It to an inspection coil 20 wound around a magnetic core 2 to be inspected; a bias current supply circuit 11 that superimposes a DC bias current Ib on the inspection current It, and supplies it to the coil 20; an estimation unit 15 that estimates a measurement error of the half-wave rectification current measured by a measuring instrument, based on an inductance L measured by an inductance measuring device 12 from the relation between the inductance L of the coil 20 and the measurement error stored in a storage unit 13; and a presentation unit 17 that presents the estimation result by the estimation unit 15.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an inspection apparatus and an inspection method, and particularly relates to an inspection technique for a magnetic core of a current transformer.

Background Art

[0002] Conventionally, a wattmeter has been widely used as an instrument incorporating a current transformer (CT). As a performance requirement for a wattmeter incorporating a current transformer, it is required to keep the measurement accuracy of a sine half-wave rectified current obtained by half-wave rectifying a sine-wave alternating current within a certain range. By making the measurement accuracy of an asymmetric alternating current such as a half-wave rectified waveform constant, accurate power measurement in a wattmeter is ensured.

[0003] For example, Japanese Industrial Standards (JIS) stipulate that the measurement accuracy of a sine half-wave rectified current detected by a current transformer used in a wattmeter should be within a certain error range with respect to the measurement accuracy in the case of a sine-wave alternating current (see JIS C1271-2). In JIS, it is stipulated as "the influence of direct current and even harmonics in the current circuit", and is generally called half-wave error.

[0004] In order to improve the measurement accuracy of a current in which a sine half-wave rectified current or a direct current is superimposed, for example, Patent Document 1 discloses a magnetic core formed of an amorphous alloy having a composition and crystal grain size suitable for detecting a sine half-wave rectified current. However, in the technique disclosed in Patent Document 1, when a current transformer is configured with a magnetic core and the current transformer is incorporated into a wattmeter, the relationship between the measurement accuracy of the sine half-wave rectified current on the wattmeter side and the magnetic characteristics of the magnetic core is unclear.

[0005] Therefore, unless the magnetic core disclosed in Patent Document 1 is in a completed state as a current transformer, it is impossible to conduct a test on the measurement accuracy of the sine half-wave rectified current in a wattmeter. Therefore, as a result of verification by testing, when the measurement accuracy of the sine half-wave rectified current in a wattmeter does not meet the measurement accuracy defined by the standard specification, there is a problem that coils with a turn number of more than a thousand turns used in the magnetic core become wasted.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] Thus, according to the conventional technology, it has been difficult to inspect the magnetic core in the state before being incorporated into the instrument as a current transformer and estimate the measurement error of the sine half-wave rectified current on the instrument side.

[0008] The present invention has been made to solve the above-described problems, and an object thereof is to inspect the magnetic core in the state before being incorporated into the instrument as a current transformer and estimate the measurement error of the sine half-wave rectified current on the instrument side.

Means for Solving the Problems

[0009] In order to solve the above-described problems, an inspection apparatus according to the present invention includes an inspection current supply circuit that supplies an inspection current to an inspection coil wound around a magnetic core to be inspected, a bias current supply circuit that superimposes a DC bias current on the inspection current and supplies the current to the coil, an inductance measuring device that measures the inductance of the coil when the DC bias current is superimposed on the inspection current and supplied to the coil, an inductance of the coil when the DC bias current is superimposed on the inspection current and supplied based on a previous measurement, and a relationship between the inductance and a measurement error of a half-wave rectified current of a sine wave alternating current detected by a current transformer including the magnetic core and further measured by an instrument including the current transformer. A storage unit that stores the relationship, and an estimation unit that estimates the measurement error of the half-wave rectified current measured by the instrument based on the inductance measured by the inductance measuring device from the relationship between the measurement error stored in the storage unit. And a presentation unit that presents the estimation result by the estimation unit.

[0010] Also, in the inspection apparatus according to the present invention, the DC bias current supplied by the bias current supply circuit can be proportional to the peak current value of the half-wave rectified current input to the current transformer.

[0011] Also, in the inspection apparatus according to the present invention, further, based on the estimation result by the estimation unit, a determination unit that determines whether or not the magnetic core satisfies a criterion for setting the measurement error in the instrument within a preset range is provided, and the presentation unit may present the determination result by the determination unit.

[0012] Also, in the inspection apparatus according to the present invention, the inspection current may be a sinusoidal alternating current.

[0013] Also, in the inspection apparatus according to the present invention, the number of turns of the coil may be 10 or more.

[0014] Also, in the inspection apparatus according to the present invention, the magnetic core has a relative permeability μ in a state where the DC bias current is not superimposed on the inspection current. r may be in the range of 1,500 to 5,500.

[0015] In order to solve the above problems, the inspection method according to the present invention includes an inspection current supply step of supplying an inspection current to an inspection coil wound around a magnetic core to be inspected, a bias current supply step of superimposing a DC bias current on the inspection current and supplying it to the coil, an inductance measurement step of measuring the inductance of the coil when the DC bias current is superimposed on the inspection current and supplied to the coil, a storage step of storing in a storage unit the relationship between the inductance of the coil when the DC bias current is superimposed on the inspection current and supplied, obtained by a previous measurement, and the measurement error of the half-wave rectified current of the sinusoidal alternating current detected by a current transformer having the magnetic core and further measured by an instrument having the current transformer, an estimation step of estimating the measurement error of the half-wave rectified current measured by the instrument based on the inductance measured in the inductance measurement step from the relationship with the measurement error stored in the storage unit, and a presentation step of presenting the estimation result in the estimation step.

[0016] Further, in the inspection method according to the present invention, the DC bias current supplied in the bias current supply step can be proportional to the peak current value of the half-wave rectified current input to the current transformer.

[0017] Further, in the inspection method according to the present invention, a determination step is further provided for determining whether or not the magnetic core satisfies a criterion for keeping the measurement error in the instrument within a preset range based on the estimation result in the estimation step, and the presentation step may present the determination result in the determination step.

Advantages of the Invention

[0018] According to the present invention, based on the relationship between the inductance of a coil when a DC bias current is superimposed on and supplied as an inspection current, and the measurement error of the half-wave rectified current of a sinusoidal AC current detected by a current transformer having a magnetic core and further measured by an instrument including the current transformer, the measurement error of the half-wave rectified current measured by the instrument is estimated. Therefore, it is possible to inspect the magnetic core in a state before being incorporated into the instrument, and estimate the measurement error of the sinusoidal half-wave rectified current on the instrument side.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0020] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to FIGS. 1 to 6. [Configuration of Inspection Apparatus] FIG. 1 is a block diagram showing the configuration of an inspection apparatus 1 according to the present embodiment. The inspection apparatus 1 inspects a magnetic core 2. The magnetic core 2 is a core manufactured for a current transformer incorporated in a wattmeter which is an instrument.

[0021] The magnetic core 2 is an annular magnetic material having an inner diameter ID, an outer diameter OD, and a thickness h, and can be formed of a material such as an Fe-based amorphous alloy. A coil 20 for inspection is wound around the magnetic core 2, and the ends t1 and t2 of the coil 20 are connected to an inspection current supply circuit 10, a bias current supply circuit 11, and an inductance measuring device 12 provided in the inspection apparatus 1.

[0022] The number of turns of the coil 20 is set to a number of turns suitable for making the value of the inductance L of the coil 20 measured in the inspection apparatus 1 equal to or greater than a certain value. Specifically, by setting the number of turns of the coil 20 to 10 turns or more, the inspection accuracy can be sufficiently ensured as compared with the case where the number of turns less than 10 turns is adopted. Although the inspection accuracy is improved by increasing the number of turns of the coil 20, considering the ease of manufacturing, it is more preferable to set the number of turns of the coil 20 to 10 turns. Note that, as the coil 20 for inspection, a coil having the same diameter and cross-sectional shape as the coil for the product can be used.

[0023] As shown in FIG. 1, the inspection apparatus 1 includes an inspection current supply circuit 10, a bias current supply circuit 11, an inductance measuring device 12, a storage unit 13, a setting unit 14, an estimation unit 15, a determination unit 16, and a presentation unit 17. The inspection apparatus 1 measures the inductance L of the coil 20 when a DC bias current I b is superimposed on the inspection current I t and supplied to the coil 20, and estimates the measurement error of the sinusoidal half-wave rectified current in the instrument side, that is, the wattmeter, based on the measurement result.

[0024] The inspection current supply circuit 10 supplies the inspection current I t to the coil 20 wound around the magnetic core 2 to be inspected. The inspection current supply circuit 10 includes an AC current source, and generates and supplies the inspection current I t of a preset sinusoidal AC current to the coil 20. As an example, the inspection current supply circuit 10 generates the inspection current I t of a sinusoidal AC current of 1 [kHz] and 1 [V].

[0025] The bias current supply circuit 11 supplies the DC bias current Ib is superimposed on the inspection current I t and supplied to the coil 20. The bias current supply circuit 11 includes a DC current source and a DC bias current I b is superimposed on the inspection current I t of the AC signal. For example, a configuration using a coupling capacitor can be adopted.

[0026] The bias current supply circuit 11 generates a DC bias current I b of a set value. The DC bias current I b is set so that a magnetomotive force of a preset value is generated when flowing through the coil 20 wound around the magnetic core 2. In the following, the magnetomotive force F [A] generated in the coil 20 by the supply of the DC bias current I b will be described as the DC bias F b [A].

[0027] The inductance measuring device 12 measures the inductance L of the coil 20 when the DC bias current I b is superimposed on the inspection current I t and supplied to the coil 20. More specifically, the inductance measuring device 12 measures the inductance L between the ends t1 and t2 of the coil 20 when a DC bias F b is generated in the coil 20 by the DC bias current I b . The inductance measuring device 12 can use an LCR meter or the like.

[0028] The storage unit 13 stores the relationship between the inductance L of the coil 20 when the DC bias current I b obtained by previous measurements is superimposed on the inspection current I t and supplied, and the measurement error related to the half-wave rectified current of the sinusoidal AC current detected by the current transformer including the magnetic core 2 and further measured by the watt-hour meter including the current transformer.

[0029] The relationship with the measurement error stored in the storage unit 13 is data based on previous measurements and evaluations. More specifically, through previous experiments, the DC bias F bwhile generating the inspection current I t Determine the relationship between the value of the inductance L of the coil 20 measured in the sine wave of t and the actual measurement error based on the measurement on the wattmeter side of the current transformer using the magnetic core 2. In the experiment, a coil with the same design and number of turns as the inspection coil 20 can be provided on the secondary side, and a one-turn through wire for applying a DC current can be prepared. Furthermore, by applying a voltage to the coil on the secondary side, an inspection current can be supplied, and the inductance L between both ends of the coil on the secondary side can be measured.

[0030] Here, the relationship between the magnetic characteristics of the magnetic core 2 and the measurement error of the half-wave rectified current on the wattmeter side of the current transformer using the magnetic core 2 will be described. FIG. 2 is a diagram for explaining the inspection current I t and the DC bias F b , as well as the half-wave rectified current. In FIG. 2, the horizontal axis represents the phase angle [degrees (°)], and the vertical axis represents the current [A] (magnetomotive force [A]). The half-wave waveform shown in FIG. 2 is the half-wave rectified current a obtained by half-wave rectifying a sinusoidal alternating current. The half-wave waveform of the half-wave rectified current a is the waveform measured during the measurement of the electric energy by the wattmeter. That is, when a coil with the number of turns for the product is wound around the magnetic core 2 and incorporated into the current transformer, it shows the waveform of the half-wave rectified current a input to the current transformer and measured on the wattmeter side.

[0031] The peak current value a1 of the half-wave rectified current a is the effective value of the rated current of the current transformer used in the half-wave rectified current error test of the wattmeter defined in standard specifications such as JIS standards. For example, when the rated current according to the specifications of the current transformer is 30 [A], a half-wave rectified current a of a 50 [Hz] sine wave with a peak current value of 21.2 [A] is used. Also, according to the JIS standard, it is stipulated that the measurement error of the half-wave rectified current a of the sinusoidal alternating current measured by the wattmeter shall be in the range of ±6 [%] (see JIS C1271-2). Note that the range of the measurement error is conditioned when the power factor pf is 1.0.

[0032] Here, the measurement error of the half-wave rectified current a in the watt-hour meter, i.e., the half-wave error, is the measurement error in watt-hour [Ws]. More specifically, the half-wave error is the error of the watt-hour measured by the watt-hour meter connected to the secondary side based on the half-wave rectified current input to the primary side of the current transformer equipped with the magnetic core 2 with respect to the watt-hour measured based on the reference sinusoidal alternating current. The peak current value in the reference sinusoidal alternating current is set to 1 / 2 of the peak current value of the half-wave rectified current. This is due to the fact that the area of the current waveform in one cycle is theoretically the same. Specifically, when the rated current of the current transformer is 30 [A], the reference alternating current is a sine wave with a peak current value of 10.6 [A], which is 1 / 2 of the peak current value of 21.2 [A] of the half-wave rectified current.

[0033] Returning to FIG. 2, the waveform of the half-wave rectified current a and the inspection current I b with the DC bias F b generated by t superimposed are common at the points where the current value changes in the positive region. Also, as shown in FIG. 3, as the peak current value a1 of the half-wave rectified current a increases, the value of the DC bias F b which is the product of the DC bias current I b and the number of turns of the coil 20 increases and changes to a proportional relationship. That is, as the peak current value a1 of the half-wave rectified current a increases, the value of the DC bias current I b increases and changes to a proportional relationship. Note that the horizontal axis in FIG. 3 represents the rated current [A] of the current transformer, and the left vertical axis represents the current [A]. Also, the right vertical axis represents the relative permeability μ r of the magnetic core 2. Details about the relative permeability μ r of the magnetic core 2 will be described later.

[0034] Next, the relationship between the magnetic characteristics of the magnetic core 2 and the measurement error of the half-wave rectified current in the watt-hour meter will be described. FIG. 4 shows the DC bias F b generated by the DC bias current I bThis is a diagram showing the relationship between the inductance L of the coil 20 that has occurred and the measurement error of the half-wave rectified current a in the wattmeter, that is, the half-wave error. The horizontal axis of FIG. 4 represents the inductance L [uH] of the coil 20, and the vertical axis represents the measurement error [%].

[0035] The measured value of the inductance L [uH] shown in FIG. 4 is under the condition of a DC bias F of 12 [A], b a sinusoidal AC current inspection current I of 1 [kHz] and 1 [V], t and is the value measured under the condition that the number of turns of the coil 20 is 10 turns. Also, in FIG. 4, the values of the measurement errors of the half-wave rectified current a of the actual sinusoidal AC current in the wattmeter corresponding to each inductance L [uH] are plotted. Further, the measurement error [%] of the half-wave rectified current a shown in FIG. 4 is the value of the measurement error in the wattage when the rated current of the current transformer is 30 [A] and the peak current value a1 is 21.2 [A].

[0036] As shown in FIG. 4, by experiment, when the rated current of the current transformer is 30 [A], it can be seen that there is a high correlation between the inductance L of the coil 20 and the measurement error of the half-wave rectified current in the wattmeter when the DC bias F b is 12 [A]. Similarly, by experiment, when the rated current of the current transformer is 60 [A], a high-correlation result between the inductance L of the coil 20 and the measurement error of the half-wave rectified current in the wattmeter is obtained when the DC bias F b is 24 [A]. Furthermore, when the rated current of the current transformer is 120 [A], a high-correlation result between the inductance L of the coil 20 and the measurement error of the half-wave rectified current in the wattmeter is obtained when the DC bias F b is 40 [A].

[0037] This means that, as shown in FIG. 3, as the rated current of the current transformer equipped with the magnetic core 2 increases, the DC bias F b that has a high correlation with the half-wave error, that is, the value of the DC bias current I b increases. Thus, in this embodiment, based on the correlation between the magnetic characteristics in the magnetic core 2 and the measurement error of the half-wave rectified current in the wattmeter, the DC bias current Ib The value of and the DC bias F applied to the coil 20 b are set.

[0038] For example, when the rated current of the current converter is 30 [A] and the peak current value of the half-wave rectified current a is 21.2 [A], the DC bias F b can be set to 12 [A]. In this case, the DC bias current I supplied by the bias current supply circuit 11 to the coil 20 b has a value of 1.2 [A]. Similarly, when the rated current is 60 [A] and the peak current value of the half-wave rectified current a is 42.4 [A], the DC bias F b can be set to 24 [A]. In this case, the DC bias current I supplied by the bias current supply circuit 11 to the coil 20 b has a value of 2.4 [A].

[0039] Furthermore, when the rated current is 120 [A] and the peak current value of the half-wave rectified current a is 84.9 [A], the DC bias F b can be set to 40 [A]. Also, in this case, the DC bias current I supplied by the bias current supply circuit 11 to the coil 20 b has a value of 4.0 [A]. Note that the specific values of the DC bias F b and the DC bias current I b are set according to the circuit configuration of the watt-hour meter.

[0040] Here, the inductance L of the coil 20 has a characteristic of gradually decreasing as the DC bias F b is increased. Regarding the relative permeability μ of the magnetic core 2 r , as shown in FIG. 3, a Fe-based amorphous alloy with a relative permeability μ b such that the inductance L does not decrease rapidly when the DC bias F r is applied is selected.

[0041] The curve c of the relative permeability μ in FIG. 3 r represents the optimal relative permeability μ of the magnetic core 2 for each rated current and the value of the DC bias F b r ​is shown. As shown by the curve c of the relative permeability μ in FIG. 3 r when a DC bias F b is applied, the relative permeability μ of the magnetic core 2 required to obtain the inductance L, that is, to obtain the half-wave performance r is in the range of about 1,500 to 5,500, more preferably in the range of about 2,000 to 5,500. If the relative permeability μ of the magnetic core 2 r greatly deviates from these value ranges, the half-wave error will deteriorate.

[0042] Thus, for the magnetic material of the magnetic core 2, a Fe amorphous alloy or the like adjusted so that the relative permeability μ b is in the range of about 1,500 to 5,500, or about 2,000 to 5,500 without applying the DC bias F r can be selected.

[0043] As described above, the storage unit 13 can store the relationship between the inductance L shown in FIG. 4 and the measurement error of the half-wave rectified current by the wattmeter based on prior measurement and evaluation.

[0044] Returning to FIG. 1, the setting unit 14 sets the value of the DC bias current I b supplied by the bias current supply circuit 11. Further, the setting unit 14 sets the frequency and voltage of the inspection current I t supplied by the inspection current supply circuit 10. Furthermore, a threshold value used by the determination unit 16 described later is set. For example, the setting unit 14 sets the value of the DC bias F b in response to the input of the rated current value of the current transformer received from the outside, and sets the value of the DC bias current I b corresponding to the value of the DC bias F b . The bias current supply circuit 11 generates the DC bias current I b with the value set by the setting unit 14.

[0045] Based on the relationship between the inductance L stored in the storage unit 13 and the measurement error of the half-wave rectified current, the estimation unit 15 estimates the measurement error of the half-wave rectified current measured by the watt-hour meter based on the inductance L of the coil 20 measured by the inductance measuring device 12.

[0046] For example, consider the case of estimating the measurement error of the half-wave rectified current by a watt-hour meter incorporating a current transformer with a rated current of 30 [A]. In this case, the estimation unit 15 refers to the relationship between the inductance L shown in FIG. 4 stored in the storage unit 13 and the measurement error of the half-wave rectified current, and can obtain the measurement error (half-wave error) [%] corresponding to the inductance L on the horizontal axis as the estimation result.

[0047] Based on the estimation result by the estimation unit 15, the determination unit 16 determines whether the magnetic core 2 satisfies the criteria for keeping the measurement error of the half-wave rectified current in the watt-hour meter within a preset range. For example, the determination unit 16 can use a value corresponding to the value within the error range defined in a predetermined standard specification (for example, ±6 [%]) as the determination criterion. The determination unit 16 can determine whether the value of the measurement error indicated by the estimation result is within the set value range (for example, ±6 [%]).

[0048] Alternatively, the determination unit 16 can perform a determination process by setting a threshold value for the inductance L measured by the inductance measuring device 12. According to the example of FIG. 4, in order to manage the measurement error of the watt-hour meter, for example, at -4 [%] or more, a threshold value of 30 [μH] can be set. When the measured inductance L is equal to or greater than the threshold value, the determination unit 16 can issue a determination result that the magnetic core 2 to be inspected is qualified.

[0049] Note that since the threshold value of the inductance L changes due to the winding resistance and the load resistance of the circuit, the determination unit 16 can perform determination using the threshold value of the inductance L when there is no significant change in them. When it is possible to make a determination without a significant change in the winding resistance or the load resistance of the circuit, the determination unit 16 can perform determination processing using a threshold value of the inductance L that becomes a higher value as the winding resistance or the load resistance increases.

[0050] The presentation unit 17 presents the estimation result and the determination result by the estimation unit 15. For example, the presentation unit 17 can display the value of the measurement error obtained as the estimation result on the display screen. Further, the presentation unit 17 can display on the display screen whether the magnetic core 2 to be inspected is acceptable or not as the determination result. Also, the presentation unit 17 can send the estimation result and the determination result to an external server or the like via the communication network NW.

[0051] [Computer Configuration of the Inspection Device] Next, an example of the computer configuration of the inspection device 1 having the above-described configuration will be described with reference to FIG. 5.

[0052] As shown in FIG. 5, the inspection device 1 includes, for example, a computer including a processor 102, a main storage device 103, a communication interface 104, an auxiliary storage device 105, and an input / output I / O 106 connected via a bus 101, and a part of the configuration can be realized by a program that controls these hardware resources. Further, the inspection device 1 can include a display device 107 connected via the bus 101. Note that the inspection device 1 includes an inspection current supply circuit 10, a bias current supply circuit 11, and an inductance measuring device 12 (not shown) connected via the bus 101.

[0053] In the main storage device 103, programs for the processor 102 to perform various controls and calculations are stored in advance. The functions of the inspection device 1, such as the setting unit 14, the estimation unit 15, and the determination unit 16 shown in FIG. 1, are realized by the processor 102 and the main storage device 103.

[0054] The communication interface 104 is an interface circuit for network-connecting the inspection device 1 and various external electronic devices.

[0055] The auxiliary storage device 105 is composed of a readable and writable storage medium and a driving device for reading and writing various information such as programs and data to and from the storage medium. As the storage medium, a semiconductor memory such as a hard disk or a flash memory can be used in the auxiliary storage device 105.

[0056] The auxiliary storage device 105 has a program storage area for storing the inspection program executed by the inspection device 1. The storage unit 13 described in FIG. 1 is realized by the auxiliary storage device 105. Further, the auxiliary storage device 105 has an area for storing the inductance L measured by the inductance measuring device 12 and an area for storing the value of the DC bias F b associated with the rated current value of the current transformer, etc. Furthermore, for example, it may have a backup area for backing up the above-described data, programs, etc.

[0057] The input / output I / O 106 is composed of I / O terminals for inputting signals from external devices and outputting signals to external devices. By connecting the input / output I / O 106 to an input device such as a keyboard or a touch panel, the setting unit 14 described in FIG. 1 is realized.

[0058] The display device 107 is composed of an organic EL display, a liquid crystal display, or the like. The presentation unit 17 described in FIG. 1 can be realized by the display device 107. Further, the display device 107 can be configured as a touch panel display.

[0059] [Operation of the inspection device] Next, the operation of the inspection device 1 having the above-described configuration will be described with reference to the flowchart of FIG. 6.

[0060] Here, it is assumed that the storage unit 13 stores the relationship between the inductance L and the measurement error of the wattmeter obtained by prior measurement. When the magnetic core 2 to be inspected with the inspection coil 20 wound 10 turns is placed on the inspection table of the inspection apparatus 1, the following inspection process is executed.

[0061] First, the setting unit 14 performs initial settings of the inspection apparatus 1, such as setting the frequency and voltage of the inspection current I t and setting the value of the DC bias current I b . Next, the inspection current supply circuit 10 supplies the inspection current I t to the coil 20 wound around the magnetic core 2 to be inspected (step S2). The inspection current supply circuit 10 can supply a sine-wave inspection current I t of 1 [kHz] and 1 [V] to the coil 20 according to the settings by the setting unit 14.

[0062] Next, the bias current supply circuit 11 superimposes the DC bias current I b on the inspection current I t and supplies it to the coil 20 (step S3). The DC bias current I b supplied by the bias current supply circuit 11 is proportional to the peak current value of the half-wave rectified current input to the current transformer including the magnetic core 2. Further, the value of the DC bias current I b increases as the rated current of the current transformer increases.

[0063] Next, the inductance measuring device 12 measures the inductance L of the coil 20 when the DC bias current I b is superimposed on and supplied to the inspection current I t (step S4).

[0064] Subsequently, the estimation unit 15 estimates the measurement error of the half-wave rectified current in the watt-hour meter in which the current transformer including the magnetic core 2 to be inspected is incorporated and detected based on the inductance L of the coil 20 measured in step S4 from the relationship between the inductance L and the measurement error in the watt-hour meter stored in the storage unit 13 (step S5). More specifically, the estimation unit 15 uses the DC bias F b Based on the correlation between the inductance L of the coil 20 and the measurement error of the half-wave rectified current in the watt-hour meter (Fig. 4) when applied, the value of the measurement error corresponding to the measured inductance L can be obtained as an estimated value.

[0065] Next, the determination unit 16 determines whether or not the magnetic core 2 to be inspected satisfies the criteria for keeping the measurement error of the half-wave rectified current in the watt-hour meter within a preset range based on the estimation result of the measurement error obtained in step S5 (step S6). For example, when the estimated value of the measurement error is ±6 [%], the determination unit 16 can determine that the magnetic core 2 satisfies the criteria.

[0066] Alternatively, the determination unit 16 may be configured to determine whether or not the magnetic core 2 to be inspected satisfies the criteria for keeping the measurement error of the half-wave rectified current in the watt-hour meter within a preset range based on the value of the inductance L of the coil 20 measured in step S4 under certain conditions.

[0067] In this case, the determination unit 16 can set the value of the inductance L of the coil 20 corresponding to the predetermined error range as a threshold value in order to set the measurement error range to a predetermined range (for example, ±6 [%]). When the inductance L of the coil 20 measured in step S5 is equal to or greater than the threshold value, the determination unit 16 can determine that when the magnetic core 2 to be inspected is incorporated into the watt-hour meter as a current transformer, the half-wave error in the watt-hour meter is within the set measurement error range.

[0068] Next, the presentation unit 17 presents the estimation result in step S5 and the determination result in step S6 (step S7). More specifically, the presentation unit 17 can display, on the display screen of the display device 107 provided in the inspection device 1, as an inspection result, an estimated value of the measurement error on the wattmeter side obtained for the magnetic core 2 to be inspected. Further, the presentation unit 17 can display, on the display screen of the display device 107, a determination result indicating whether or not the half-wave error of the wattmeter is within the error range defined by a predetermined standard specification when the magnetic core 2 is incorporated into the wattmeter as a current transformer.

[0069] As described above, according to the inspection device 1 according to the present embodiment, the DC bias current I b is set as a value proportional to the peak current value of the half-wave rectified current of the sinusoidal AC current, and the inductance L of the coil 20 when the sinusoidal inspection current I b is biased by the DC bias F b generated by the supply of the DC bias current I t is measured. Further, based on the measured inductance L, the measurement error of the sinusoidal half-wave rectified current on the wattmeter side is estimated. Therefore, it is possible to perform an inspection on the magnetic core 2 alone in a state before being incorporated into the wattmeter as a current transformer, and estimate the measurement error of the sinusoidal half-wave rectified current on the wattmeter, that is, the half-wave error.

[0070] Also, according to the inspection device 1 according to the present embodiment, the magnetic core 2 is inspected by using the correlation between the magnetic characteristics of the magnetic core 2 and the half-wave error on the wattmeter side in which a current transformer including the magnetic core 2 is incorporated. Therefore, it is possible to cover the measurement error related to the half-wave rectified current on the wattmeter side depending on the performance of the current transformer including the magnetic core 2.

[0071] In the above-described embodiment, the case where the inspection target of the inspection device 1 is the magnetic core 2 has been described. However, the inspection device 1 can also use a current transformer including the magnetic core 2 as an inspection target.

[0072] As described above, the embodiments of the inspection apparatus and inspection method of the present invention have been described. However, the present invention is not limited to the described embodiments, and various modifications conceivable by those skilled in the art can be made within the scope of the invention described in the claims.

Explanation of Signs

[0073] 1... Inspection apparatus, 2... Magnetic core, 10... Inspection current supply circuit, 11... Bias current supply circuit, 12... Inductance measuring device, 13... Storage unit, 14... Setting unit, 15... Estimation unit, 16... Judgment unit, 17... Presentation unit, 20... Coil, 101... Bus, 102... Processor, 103... Main storage device, 104... Communication interface, 105... Auxiliary storage device, 106... Input / output I / O, 107... Display device, NW... Network.

Claims

1. An inspection current supply circuit that supplies an inspection current to an inspection coil wound around a magnetic core to be inspected; A bias current supply circuit that superimposes a DC bias current on the inspection current and supplies it to the coil; An inductance measuring device that measures the inductance of the coil when the DC bias current is superimposed on the inspection current and supplied to the coil; A storage unit that stores the relationship between the inductance of the coil when the DC bias current is superimposed on the inspection current and supplied, obtained by previous measurement, and the measurement error of the half-wave rectified current of the sinusoidal AC current detected by a current transformer having the magnetic core and further measured by an instrument having the current transformer; An estimation unit that estimates the measurement error of the half-wave rectified current measured by the instrument based on the inductance measured by the inductance measuring device according to the relationship with the measurement error stored in the storage unit; A presentation unit that presents the estimation result by the estimation unit An inspection device comprising.

2. In the inspection device according to Claim 1, The DC bias current supplied by the bias current supply circuit is proportional to the peak current value of the half-wave rectified current input to the current transformer An inspection device characterized by this.

3. In the inspection device according to Claim 1 or 2, Furthermore, based on the estimation result by the estimation unit, a determination unit that determines whether the magnetic core satisfies a criterion for keeping the measurement error in the instrument within a preset range is provided, The presentation unit presents the determination result by the determination unit An inspection device characterized by this.

4. In the inspection device according to Claim 3, The inspection current is a sinusoidal AC current An inspection device characterized by this.

5. In the inspection device according to Claim 3, The number of turns of the coil is 10 or more An inspection device characterized by this.

6. In the inspection device according to Claim 3, The magnetic core has a relative permeability μ in a state where the DC bias current is not superimposed on the inspection current ｒ in the range of 1,500 to 5,500 An inspection device characterized by this.

7. An inspection current supply step of supplying an inspection current to an inspection coil wound around a magnetic core to be inspected; A bias current supply step of superimposing a DC bias current on the inspection current and supplying it to the coil; An inductance measurement step of measuring the inductance of the coil when the DC bias current is superimposed on the inspection current and supplied to the coil; A storage step of storing in a storage unit the relationship between the inductance of the coil when the DC bias current obtained by a previous measurement is superimposed on and supplied to the inspection current, and the measurement error of the half-wave rectified current of the sinusoidal alternating current detected by a current transformer including the magnetic core and further measured by an instrument including the current transformer; An estimation step of estimating the measurement error of the half-wave rectified current measured by the instrument based on the inductance measured in the inductance measurement step from the relationship with the measurement error stored in the storage unit; A presentation step of presenting the estimation result in the estimation step; An inspection method comprising:

8. In the inspection method according to Claim 7, the DC bias current supplied in the bias current supply step is proportional to the peak current value of the half-wave rectified current input to the current transformer. An inspection method characterized by this.

9. In the inspection method according to Claim 7 or 8, further, a determination step of determining whether or not the magnetic core satisfies a criterion for keeping the measurement error in the instrument within a preset range based on the estimation result in the estimation step; comprising, the presentation step presents the determination result in the determination step. An inspection method characterized by this.

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