Current detector and power conversion device

Abstract

To provide a low-cost, small man-hour current detector for power conversion devices.SOLUTION: This current detector is composed by having a bus bar 11 for voltage detection of a conductive member connected to a computation unit. The bus bar 11 for voltage detection has such an electric characteristic regarding two types of conductors 11a, 11b differing in length and width and equal in thickness, that resistance values R are different and inductance values L are the same. A differential voltage between the first voltage of a bus bar A detected using a voltage detection unit 13a and a reference potential unit 13b at points corresponding to both ends of the conductor 11a and the second voltage of a bus bar B detected using a voltage detection unit 13c and the reference potential unit 13b at points corresponding to both ends of the conductor 11b is divided by a differential resistance between the previously designed first resistance of the bus bar A and second resistance of the bus bar B by the computation unit, and current detection is carried out applying Ohm's law. The inductance component voltage is cancelled out at differential voltage computation time.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a current detector and a power conversion device. [Background technology]

[0002] In recent years, as the output of power conversion devices has increased, the size of the units has increased. To solve this problem, studies have been conducted on miniaturizing current detectors that measure the current flowing in power conversion devices.

[0003] In power conversion devices, current detectors that utilize the Hall effect are generally used, but the sensor sensitivity of the Hall element itself is low, and the element alone cannot obtain sufficient output. For this reason, current detection is made possible by using a magnetic core or an amplifier circuit, but on the other hand, this leads to an increase in the size of the current detector, which is an obstacle to miniaturization of power conversion devices.

[0004] In view of this, a technique for detecting current using a shunt resistor is known as a current detection method that can miniaturize a current detector. Well-known techniques related to such current detection include "Shunt Resistor and Manufacturing Method Thereof" (see Patent Document 1), which improves the current detection accuracy in resistors with a low resistance value of 1 mΩ or less for use in detecting large currents, and "Shunt Resistor and Shunt-Type Current Detection Device" (see Patent Document 2), which detects the current flowing through a resistor. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2011-3694 A [Patent Document 2] JP 2017-208475 A Summary of the Invention [Problem to be solved by the invention]

[0006] In the techniques disclosed in the above-mentioned Patent Documents 1 and 2, a shunt resistor is connected to a path for passing a current to detect the current. However, a shunt resistor is generally made by joining two or more kinds of metal materials. Therefore, there are problems in that the number of steps required for joining the metal materials increases and the cost increases due to the use of multiple metal materials.

[0007] One method to solve these problems is to detect the voltage drop of the parasitic resistance component of the busbar, which is used as the current path of the power conversion device instead of the shunt resistor, and detect the current by Ohm's law. Busbars are usually formed by pressing one type of metal, so they are less expensive and require less labor than shunt resistors that are made by joining two or more types of metal materials. However, busbars usually have an inductance component in addition to the resistance component. Therefore, when measuring a current with an alternating current (AC) component, the voltage generated in the busbar is equal to the sum of the resistance component voltage and the inductance component voltage. In other words, it is impossible to detect the current by simply applying Ohm's law. For these reasons, no attempt has been made to detect AC current using a busbar.

[0008] The present invention has been made to solve such problems. An object of the present invention is to provide a current detector for a power conversion device that is capable of detecting a current having an AC component with a simplified configuration, and a power conversion device using the current detector. [Means for solving the problem]

[0009] In order to solve the above problems, the present invention provides a busbar for voltage detection that is conductively connected to a portion of a power conversion device through which an AC current flows, the busbar for voltage detection having two conductor portions each including a first and a second reference potential portion and a first voltage detection portion and a second voltage detection portion, the two conductor portions being different in a ratio of a first resistance value between the first voltage detection portion and the first reference potential portion and a second resistance value between the second voltage detection portion and the second reference potential portion, and a ratio of a first inductance value between the first voltage detection portion and the first reference potential portion and a second inductance value between the second voltage detection portion and the second reference potential portion. The voltage detection bus bar has one or more types of notches in the base material made of the metal material so that the electrical characteristics of the two conductor portions are different. It is characterized by the above.

[0010] The two conductor portions may each be formed from one or more types of metallic material, and may have a shape obtained by changing at least two or more elements that define the shape of the conductor portions, among length, width, and thickness.

[0011] According to another aspect of the present invention, the busbar of the present invention is a voltage detection busbar that is conductively connected to a portion of a power conversion device through which an alternating current flows, the voltage detection busbar being formed of one type of metal material and including two conductor portions having first and second reference potential portions and a first voltage detection portion and a second voltage detection portion, the two conductor portions being characterized in that a ratio of a first resistance value between the first voltage detection portion and the first reference potential portion to a second resistance value between the second voltage detection portion and the second reference potential portion is different from a ratio of a first inductance value between the first voltage detection portion and the first reference potential portion to a second inductance value between the second voltage detection portion and the second reference potential portion. The voltage detection busbar may have a shape obtained by providing one or more types of notches in a base body made of the metal material.

[0012] The first and second reference potential sections may be at the same potential.

[0013] The power supply includes a voltage detection busbar, and a calculation unit that performs current detection by dividing a differential voltage between a first voltage between a first voltage detection unit and a first reference potential unit and a second voltage between a second voltage detection unit and a second reference potential unit by a differential resistance value between the first resistance value and the second resistance value.

[0014] The current detector of the present invention may be provided at a location where an alternating current flows. Effect of the Invention

[0015] According to the above aspect of the present invention, a voltage detection busbar is used for a current detector for a power conversion device. The two conductor parts of the voltage detection busbar have different resistance values ​​and have electrical characteristics with equal inductance values. Therefore, in a situation where a current having an AC current component flows, it is possible to cancel only the inductance component voltage by calculating the differential voltage of the voltages detected by the two conductor parts. Furthermore, in the calculation unit, the differential voltage related to the voltage detected using the voltage detection units provided at both ends of each conductor part of the voltage detection busbar is divided by the differential resistance related to the resistance of each conductive part designed in advance, and Ohm's law is applied to enable current detection. This allows the current detector to be simplified and miniaturized, so that the configuration of the above other aspect or the configuration of another aspect makes it possible to provide a miniaturized power conversion device. [Brief description of the drawings]

[0016] [Figure 1] 1 is a perspective view showing an external configuration of a voltage detection busbar used in a current detector according to a first embodiment of the present invention, viewed from above on one side surface. [Diagram 2] 1 is a perspective view showing an external configuration of a voltage detection busbar having a voltage detection portion and a reference potential portion provided on a side surface thereof, viewed from above on one side surface. [Diagram 3] 2 is an equivalent circuit diagram of a bus bar of two conductor portions included in the voltage detection bus bar shown in FIG. 1. [Figure 4] 10 is a perspective view showing an external configuration of a voltage detection busbar used in a current detector according to a second embodiment of the present invention, viewed from above on one side surface. FIG. [Diagram 5] 11 is a perspective view showing an external configuration of a voltage detection busbar used in a current detector according to a third embodiment of the present invention, viewed from above on one side surface. FIG. [Figure 6] 2 is a diagram illustrating a basic configuration of a power conversion device in which a current detector using the voltage detection bus bar and a calculation unit shown in FIG. 1 is applied to an output stage of an inverter circuit unit. [Figure 7]8(a) and 8(b) are diagrams showing the relationship between current and time in a current waveform when a current having an AC current component flows to the voltage detection busbar shown in Fig. 1. (a) is a waveform diagram related to the actual output current, and (b) is a waveform diagram related to the detected current calculated by the calculation unit of the current detector based on the differential voltage in Fig. 8(c). [Figure 8] 2 is a diagram showing the relationship between voltage and time for waveforms of detected voltages when a current having an AC current component flows in the busbars of two conductor parts included in the voltage detection busbar shown in Fig. 1. (a) is a waveform diagram relating to a first voltage detected in the busbar of one conductor part, (b) is a waveform diagram relating to a second voltage detected in the busbar of the other conductor part, and (c) is a waveform diagram relating to a differential voltage obtained by subtracting the first voltage of (a) from the second voltage of (b). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The current detector of the present invention is attached to a portion of the power conversion device where AC current flows, as shown in Fig. 6, and is composed of a voltage detection busbar and a calculation unit. Note that current detector 100b in Fig. 6 is the current detector of the present invention, the voltage detection busbar is voltage detection busbar 11, and the calculation unit is calculation unit 110.

[0018] Hereinafter, current detectors according to several embodiments and overall configuration examples of the present invention will be described in detail with reference to the drawings.

[0019] (Embodiment 1) In this embodiment, a method for designing the voltage detection busbar used in the current detector of the present invention and a calculation method of the calculation unit will also be described, but these contents are similar to those of this embodiment in other embodiments, so they will be omitted.

[0020] First, the shape of the voltage detection busbar in this embodiment will be described.

[0021] Fig. 1 shows an example of a voltage detection busbar 11 used in a current detector according to the present invention. The voltage detection busbar 11 has a shape including two types of conductor portions 11a and 11b that are different in length (longitudinal direction in Fig. 1) and width (transverse direction in Fig. 1) but have the same thickness (depth direction in Fig. 1). The length of conductor portion 11a is longer than the length of conductor portion 11b, and the width of conductor portion 11a is wider than the width of conductor portion 11b. Note that conductor portions 11a and 11b in this embodiment are examples of the two conductor portions in the claims.

[0022] The voltage detection busbar 11 has voltage detection parts 13a, 13c and a reference potential part 13b provided at both ends of a part dividing one conductor part 11a and a part dividing the other conductor part 11b. That is, the voltage detection busbar 11 has the voltage detection part 13a and the reference potential part 13b at both ends corresponding to the one conductor part 11a, and the voltage detection part 13c and the reference potential part 13b at both ends corresponding to the other conductor part 11b. In this embodiment, the reference potential part 13b is configured to be shared by the one conductor part 11a and the other conductor part 11b. In addition, the busbar A is between the voltage detection part 13a and the reference potential part 13b, and the busbar B is between the voltage detection part 13c of the other conductor part 11b and the reference potential part 13b, and the busbar A and the busbar B are designed to have the same inductance value L and different resistance values ​​R. The hole part 12 is a hole provided for connection with another conductor. In this embodiment, the first and second reference potential parts in the claims are 13b, that is, in this embodiment, the first and second reference potential parts have the same potential.

[0023] In addition, in the voltage detection busbar 11 in FIG. 1, the voltage detection portions 13a, 13c and the reference potential portion 13b are provided on the surface of the voltage detection busbar 11 (the surface formed by the longitudinal direction in FIG. 1 and the lateral direction in FIG. 1), but this is not limited to the above. As an example, FIG. 2 shows a configuration in which the voltage detection portions 13a, 13c and the reference potential portion 13b are provided on the side surface of the voltage detection busbar 11. By configuring as in FIG. 2, the voltage detection portions and the reference potential portion can be formed simultaneously with the press working that forms the busbar. Therefore, it can be said that the number of man-hours is even smaller than that for the voltage detection busbar 11 in FIG. 1.

[0024] 1, the voltage is measured by connecting lead terminals to the pin-shaped voltage detection parts 13a, 13c and the reference potential part 13b. Instead of the lead terminals, a configuration in which voltage measurement wires are screwed to the voltage detection parts 13a, 13c and the reference potential part 13b may be used.

[0025] The configurations of the voltage detection section and the reference potential section described above can also be applied to other shapes of voltage detection busbars, which will be described later.

[0026] As described above, voltage detection busbar 11 needs to be designed so that the resistance R and inductance L of conductor portions 11a and 11b, i.e., busbar A and busbar B, are equal, but the resistances R are different.

[0027] The design method will be described below. The design method will be described when copper Cu is selected as the conductive material for the resistance value R and inductance value L of the conductor parts 11a and 11b. The resistance value R when the conductive material is copper Cu can be calculated by the relational expression (A). R[mΩ]=(ρ×d) / (t×w)×10 Equation (A) In the relational formula (A), d is the length [mm] of the conductor portions 11a and 11b, w is the width [mm] of the conductor portions 11a and 11b, t is the thickness [mm] of the conductor portions 11a and 11b, and ρ is the resistivity of copper [μΩm]. Furthermore, when the conductor portions 11a and 11b are made of copper Cu, the inductance value L can be determined by the relational expression (B). L[nH]=0.2×d×(ln(2×d) / (w+t)+0.2235×(w+t) / d+0.5) Relation (B) In the relation (B), d is the length [mm] of the conductors 11a and 11b, w is the width [mm] of the conductors 11a and 11b, t is the thickness [mm] of the conductors 11a and 11b, and ln is the natural logarithm.

[0028] In other words, the two conductor parts of the voltage detection busbar can be made into different shapes by changing at least two or more elements that define the shape of the two conductor parts, namely, the length, width, and thickness. The voltage detection busbar in FIG. 1 has a structure in which the two conductor parts are different in length and width and have the same thickness, but instead, the two conductor parts may have the same length but different widths and thicknesses, or the two conductor parts may have the same width but different lengths and thicknesses. In such cases, the same action and effect can be obtained as long as the resistance value R differs depending on the obtained shape and the inductance value L has the same electrical characteristics.

[0029] Although copper (Cu) is exemplified as one type of metal material used for the voltage detection busbar, other metal materials may be used, such as Cu-Mn-Ni, Cu-Ni, and Ni-Cr alloy materials.

[0030] In addition, a method of deriving the resistance value R from the relational expression (A) and the inductance value L from the relational expression (B) has been described, but instead, the derivation may be performed using electromagnetic field analysis software or the like.

[0031] The above-mentioned design method can also be applied to other shapes of voltage detection busbars, which will be described later.

[0032] Next, the calculation method of the calculation unit will be described.

[0033] 3 is an equivalent circuit diagram of busbars A and B of two conductor parts 11a and 11b included in voltage detection busbar 11. As described above, busbars A and B are designed to have the same inductance value L and different resistance values ​​R. Therefore, in the equivalent circuit of busbar A, a resistance value R1 and an inductance value L exist between voltage detection part 13a and reference potential part 13b, and a first voltage VA is detected as a sum of resistance component voltage VR1 and inductance component voltage VL. In addition, in the equivalent circuit of busbar B, a resistance value R2 and an inductance value L exist between voltage detection part 13c and reference potential part 13b, and a second voltage VB is detected as a sum of resistance component voltage VR2 and inductance component voltage VL.

[0034] In light of the above, a current calculation method in the current detector of the present invention will be described.

[0035] When an AC current i flows through the voltage detection busbar 11, the first voltage VA generated across the busbars A and B in FIG. 3 can be expressed by the relational expression (C), and the second voltage VB can be expressed by the relational expression (D). VA=(R1×i)+L(di / dt) Relational expression (C) VB=(R2×i)+L(di / dt) Relational formula (D)

[0036] As described above, busbar A and busbar B are designed to have the same inductance value L but different resistance values ​​R. Therefore, the differential voltage between the first voltage VA and the second voltage VB can be expressed by relational equation (E) based on relational equation (C) and relational equation (D). (VB-VA)=(R2-R1)×i Equation (E) It can be seen from the relational expression (E) that the influence of the inductance component in the detected voltage can be eliminated by calculating the differential voltage between the first voltage VA and the second voltage VB. Furthermore, by solving the relational expression (E) for the AC current i, the current flowing through the voltage detection busbar 11 can be expressed by the relational expression (F). i=(VB-VA) / (R2-R1) Relational formula (F) From relational equation (F), it can be said that by dividing the differential voltage between the first voltage VA and the second voltage VB by the difference between the first resistance R1 and the second resistance R2, Ohm's law can be applied to detect the current without being affected by the inductance component.

[0037] The calculation unit reads the value of the first voltage VA and the value of the second voltage VB from the voltage detection busbar as detection values, and performs calculations of the relational expressions (E) and (F) using a calculator. The computing unit may be a digital computing unit such as a microcomputer, or an analog computing unit may be an operational amplifier or the like.

[0038] Since the calculation unit calculates the current using the relational expression (F), it is desirable that the resistance values ​​R1 and R2 are fixed values, but the resistance value of the voltage detection busbar changes depending on its own temperature. Therefore, in order to improve the current detection accuracy, it is advisable to incorporate an algorithm that corrects the detected current according to temperature into the calculation unit. For example, if the temperature of the voltage detection busbar is estimated based on the ambient temperature and the detected voltage, and the resistivity value of the metal material corresponding to the obtained temperature is used in the current detection calculation, temperature correction is possible. Also, instead of estimating the temperature of the voltage detection busbar, a temperature sensor may be installed near the voltage detection busbar to actually measure the temperature of the voltage detection busbar.

[0039] It is also an effective means to keep the temperature of the voltage detection busbar constant by using a cooler such as a fan.

[0040] The current calculation method in the current detector described above, the calculation method of the calculation unit, the configuration of the calculator, and the temperature correction method of the calculation unit can also be applied to the embodiment of the voltage detection bus bar described later.

[0041] The structure of the voltage detection busbar, the design method of the voltage detection busbar, and the calculation method of the calculation unit have been described for one embodiment of the current detector of the present invention. As described above, the design method of the voltage detection busbar and the calculation method of the calculation unit do not change even if the structure of the voltage detection busbar is changed, but various forms of the structure of the voltage detection busbar are possible. These forms are shown below as other embodiments.

[0042] (Embodiment 2) FIG. 4 is a perspective view showing an external shape of a voltage detection busbar 14 used in a current detector according to a second embodiment of the present invention, viewed from above on one side.

[0043] 4, the voltage detection busbar 14 includes two types of conductor parts 14a and 14b that are different in length (longitudinal direction in FIG. 4) and width (short-side height direction in FIG. 4) and have the same thickness (depth direction in FIG. 4). The length of the conductor part 14a is longer than the length of the conductor part 14b, and the width of the conductor part 14a is wider than the width of the conductor part 14b. A shallow notch 17 is provided at the upper part of the width direction of the conductor part 14a, and a deep notch 18 is provided at the upper part of the width direction of the conductor part 14b so as to be separated from the shallow notch 17. As a result, the two conductor parts 14a and 14b have electrical characteristics in which the resistance value R is different and the inductance value L is the same. That is, the voltage detection busbar 14 has electrical characteristics due to the shape in which the notches 17 and 18 are provided in the metal material. The conductor portion 14a and the conductor portion 14b in this embodiment are an example of the two conductor portions in the claims.

[0044] Moreover, the voltage detection busbar 14 has voltage detection parts 16a, 16b, 16c, and 16d provided at both ends of a portion dividing one conductor part 14a and a portion dividing the other conductor part 14b. That is, the voltage detection busbar 14 has voltage detection parts 16a and 16b at both ends corresponding to one conductor part 14a and voltage detection parts 16c and 16d at both ends corresponding to the other conductor part 14b. In this embodiment, it is sufficient to select one of the voltage detection parts 16a and 16b as the reference potential part of the conductor part 14a, and it is sufficient to select one of the voltage detection parts 16c and 16d as the reference potential part of the conductor part 14b. In other words, the difference between this embodiment and the voltage detection busbar 11 of the first embodiment is that the voltage detection parts do not have a common reference potential part. Due to this difference, the length between the voltage detection part 16b and the voltage detection part 16c can be freely changed, and it can be said that the degree of freedom in terms of structure is higher than that of the first embodiment.

[0045] (Embodiment 3) FIG. 5 is a perspective view showing an external shape of a voltage detection busbar 20 used in a current detector according to a third embodiment of the present invention, viewed from above on one side.

[0046] 5, the voltage detection busbar 20 includes two types of conductor parts 20a and 20b that are different in length (longitudinal direction in FIG. 5) and width (short-side height direction in FIG. 5) and have the same thickness (depth direction in FIG. 5). The length of the conductor part 20a is longer than the length of the conductor part 20b, and the width of the conductor part 20a is wider than the width of the conductor part 20b. In addition, a shallow notch 23a is provided at the upper part of the width direction of the conductor part 20a, and a notch 23 is provided at the upper part of the width direction of the conductor part 20b, in which the deep notch 23b is connected to the shallow notch 23a to form a step. As a result, the two conductor parts 20a and 20b have electrical characteristics in which the resistance value R is different and the inductance value L is equal. That is, the voltage detection busbar 20 has electrical characteristics due to the shape obtained by providing the notch 23 in the metal material. The conductor portion 20a and the conductor portion 20b in this embodiment are an example of the two conductor portions in the claims.

[0047] Moreover, the voltage detection busbar 20 has voltage detection portions 22a, 22c and a reference potential portion 22b provided at both ends of a portion dividing one conductor portion 20a and a portion dividing the other conductor portion 20b. That is, the voltage detection busbar 20 has voltage detection portion 22a and reference potential portion 22b at both ends corresponding to one conductor portion 20a, and voltage detection portion 22c and reference potential portion 22b at both ends corresponding to the other conductor portion 20b. In this embodiment, the reference potential portions are at the same potential as in the first embodiment.

[0048] In all of the above-described embodiments, a current detector comprising the voltage detection bus bar and the calculation unit is provided. In all of the above-described embodiments, a magnetic core and an amplifier circuit are not required compared to a current detector using a Hall element, and the current detector can be expected to be smaller in size. In addition, all of the above-described embodiments are bus bars formed from a single material, and therefore can be said to require less cost and labor than shunt resistors.

[0049] (Examples) Finally, an example in which the current detector of the present invention is applied to a power conversion device will be described. Fig. 6 is a diagram illustrating a basic configuration of a power conversion device 100 in which the current detector according to each of the above-mentioned embodiments is applied to the output stage of an inverter circuit section 100a.

[0050] 6, a power conversion device 100 generally has a function of converting DC power supplied from a DC power source 101 into AC power by an inverter circuit unit 100a and supplying the AC power to a load 102. In the case of this power conversion device 100, specifically, a DC current supplied from the DC power source 101 is converted into a three-phase AC current by the inverter circuit unit 100a and supplied to the load 102. The power conversion device 100 is configured by interposing a current detector 100b between the output side of the inverter circuit unit 100a and the load 102 connected to the output side. The current detector 100b here is configured by using a total of three voltage detection bus bars 11 for three AC phases, which are connected to a calculation unit 110.

[0051] The inverter circuit unit 100a is configured with a DC capacitor C and power semiconductor devices M1, M2, and M3 provided on a main circuit wiring board, and the input side is connected to a DC power supply 101 via input terminals P and N. The power semiconductor devices M1, M2, and M3 have input terminals P1, P2, and P3 respectively connected to the input terminal P, and input terminals N1, N2, and N3 respectively connected to the input terminal N. In addition, the power semiconductor devices M1, M2, and M3 have output terminals O1, O2, and O3 respectively connected to output terminals u, v, and w for the u-phase, v-phase, and w-phase of the inverter circuit unit 100a.

[0052] Next, voltage detection in the voltage detection busbar 11 will be described with reference to Figs. 7 to 8. Figs. 7 to 8 show one phase of current flowing through the power conversion device 100 and the load 102. Fig. 7 shows the current output from the power conversion device 100 to the load 102 and the waveform of that current detected by the voltage detection busbar 11 of the present invention and calculated by the calculation unit 110. Fig. 7(a) shows the output current of the inverter circuit unit 100a in Fig. 6. Fig. 7(b) shows a current waveform calculated by the calculation unit 110 of the current detector based on the differential voltage (VB-VA) of the voltages generated at the busbars A and B of the voltage detection busbar 11 when the current in Fig. 7(a) flows through the voltage detection busbar 11.

[0053] Fig. 8 shows waveforms when the current of Fig. 7(a) flows through busbars A and B of two conductor portions 11a and 11b included in voltage detection busbar 11. Fig. 8(a) shows the waveform of a first voltage VA [V] detected at busbar A, and Fig. 8(b) shows the waveform of a second voltage VB [V] detected at busbar B. Fig. 8(c) shows the waveform of a differential voltage (VB-VA) [V] obtained by subtracting the first voltage VA of Fig. 8(a) from the second voltage VB of Fig. 8(b).

[0054] The output current of the inverter circuit section 100a shown in Fig. 7(a) contains not only a sine wave component current controlled by the inverter circuit section 100a but also a high frequency component current generated by the switching operation of the inverter. The high frequency component generated by the switching operation is a current with a large time change compared to the sine wave component current controlled by the inverter circuit section 100a. When such a current flows through the voltage detection busbar 11, a high frequency voltage with a high peak value is generated in the two conductor sections 11a and 11b due to the inductance components parasitic on the busbars A and B according to the relational expressions (C) and (D). Therefore, the waveform is one in which the high frequency component is superimposed on the sine wave component, as shown in Figs. 8(a) and 8(b).

[0055] In contrast, referring to Figure 8(c), we can see that the differential voltage (VB-VA) between busbars A and B has a sine waveform. This is because the inductance values ​​L of busbars A and B are equivalent, and therefore the inductance component voltages of busbars A and B cancel each other out according to relational expression (E).

[0056] Also, referring to Fig. 7(b), it can be seen that the detection current IC calculated based on the relational expression (F) calculated by the calculation unit 110 coincides with the actual output current IOUT in Fig. 7(a). From the above, it can be said that the output current of the inverter can be detected with high accuracy by applying the present invention. Note that Figs. 7(a)-(b) and Figs. 8(a)-(c) have been described for one phase of a three-phase AC current, but the other phases can be measured in the same manner.

[0057] The above describes, using Figures 6 to 8, an example in which the current detector of the present invention is applied between the output part of an inverter that outputs AC current and a load, i.e., a location where AC current flows. However, the current detector of the present invention can be applied between an AC power source and the input part of a converter to which AC current from the AC power source is supplied, i.e., any location where AC current flows. [Explanation of symbols]

[0058] 11, 14, 20 Voltage detection busbars 11a, 11b, 14a, 14b, 20a, 20b Conductor part 12, 15, 21 holes 13a, 13c, 16a, 16b, 16c, 16d, 22a, 22c Voltage detection unit 13b, 22b Reference potential section 17, 18, 23, 23a, 23b Cutout 100 Power conversion device 100a Inverter circuit section 100b Current Detector 101 DC power supply 102 Load 110 Arithmetic section

Claims

1. A voltage detection bus bar that is conductively connected to a portion of a power conversion device through which an AC current flows, the voltage detection busbar includes two conductor portions each having a first and second reference potential portion, a first voltage detection portion, and a second voltage detection portion; the two conductor portions have a ratio of a first resistance value between the first voltage detection portion and the first reference potential portion and a second resistance value between the second voltage detection portion and the second reference potential portion different from a ratio of a first inductance value between the first voltage detection portion and the first reference potential portion and a second inductance value between the second voltage detection portion and the second reference potential portion; The voltage detection busbar has one or more types of notches in a base made of a metal material so that the electrical characteristics of the two conductor portions are different. A voltage detection bus bar comprising:

2. The two conductors are each formed of one or more kinds of metal materials, and have a shape obtained by changing at least two or more elements among the length, width, and thickness that define the shape.

2. The voltage detection bus bar according to claim 1 .

3. A voltage detection busbar that is conductively connected to a portion of a power conversion device through which an alternating current flows, the voltage detection busbar is made of one type of metal material and includes two conductor portions having first and second reference potential portions and a first voltage detection portion and a second voltage detection portion; In the two conductor portions, a ratio of a first resistance value between the first voltage detection portion and the first reference potential portion and a second resistance value between the second voltage detection portion and the second reference potential portion is different from a ratio of a first inductance value between the first voltage detection portion and the first reference potential portion and a second inductance value between the second voltage detection portion and the second reference potential portion. A voltage detection bus bar comprising:

4. The voltage detection busbar has a shape obtained by providing one or more types of notches in the base body made of the metal material.

4. The voltage detection bus bar according to claim 3.

5. The first and second reference potential units are Same potential 5. The voltage detection bus bar according to claim 1, wherein the voltage detection bus bar is a voltage detection bus bar having a width of 100 mm or less.

6. A voltage detection bus bar according to any one of claims 1 to 5, a calculation unit that performs current detection by dividing a differential voltage between a first voltage between the first voltage detection unit and the first reference potential unit and a second voltage between the second voltage detection unit and the second reference potential unit by a differential resistance value between the first resistance value and the second resistance value; A current detector comprising:

7. The current detector according to claim 6 is provided at a location where an AC current flows. A power conversion device comprising:

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