Patent Publication Number: US-2023142008-A1

Title: Current sensor assembly

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is the National Stage filing under 35 U.S.C. 371 of International Application No. PCT/KR2020/005500, filed on Apr. 27, 2020, the contents of which are all hereby incorporated by reference herein in their entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a current sensor assembly included in an inverter. 
     BACKGROUND ART 
     Recently, there is a rapid advance in development of technology of electric vehicles driving using electricity that is green energy. Electric vehicles refer to vehicles operated using electricity, and may be largely classified into a battery powered electric vehicle and a hybrid electric vehicle. 
     Here, the battery powered electric vehicle travels only using electricity, and is generally referred to as an electric vehicle. The hybrid electric vehicle refers to a vehicle that travels using electricity and fossil fuels. 
     Most electric vehicles include a motor configured to generate rotational power, a battery configured to supply power to the motor, an inverter configured to control a number of rotations of the motor, a battery charger configured to charge electricity to the battery, and a low-voltage direct current (DC)/DC converter (LDC) for a vehicle. 
     Among the elements described above, the inverter includes a sensor configured to sense current to precisely control the motor. 
     A sensor in the related art configured to sense current is provided separately from a bus bar. In detail, a bus bar, a current sensor, and a shield are combined with each other to thereby provide at least two configurations. Accordingly, an error may occur when the current sensor measures current flowing through the bus bar. 
     In addition, as the bus bar, the current sensor, and the shield are combined with each other to thereby provide the at least two configurations, it may be difficult to structurally change a location relationship therebetween. 
     DISCLOSURE OF INVENTION 
     Technical Problem 
     Therefore, to obviate those problems, an aspect of the detailed description is to provide a current sensor assembly in which a bus bar, a current sensor, and a shield may be combined with each other as one configuration. 
     Another aspect of the detailed description is to provide a current sensor assembly in which relative positions and distances between the bus bar, the current sensor, and the shield may be optimized. 
     Solution to Problem 
     To achieve these and other advantages and in accordance with the purpose of the present disclosure, as embodied and broadly described herein, there is provided a current sensor assembly including: a housing; a plurality of shields which are accommodated inside the housing and open toward a top of the housing; a plurality of bus bars to which current with three phases is applied and which are arranged spaced apart from each other to go past the plurality of shields, respectively; and a current sensor unit comprising a printed circuit board and a plurality of current sensors disposed on the printed circuit board to measure the current applied to the plurality of bus bars, wherein the plurality of shields, the plurality of bus bars, and the current sensor unit are configured to be accommodated inside the housing, and the current sensors are spaced apart from the plurality of bus bars and disposed in inner spaces of the plurality of shields. 
     The current sensor assembly may further include a housing cover arranged at an upper end of the housing to cover the inside of the housing, wherein the housing cover extends in a downward direction to include a support protrusion portion in contact with the printed circuit board. 
     The plurality of current sensors may be disposed on the printed circuit substrate to be spaced apart from each other, and grooves through which the plurality of shields may pass are provided in the printed circuit board. 
     The plurality of shields may include: inner side surfaces (base) arranged at an inner side of the housing; and protruding surfaces (protruding sides) protruding from opposite sides of the inner side surfaces, wherein the plurality of bus bars are disposed near the inner side surfaces and pass through the plurality of shields, the plurality of current sensors are spaced apart from the plurality of bus bars and arranged between the protruding surfaces, and the inside of the housing is spaced apart from the plurality of shields to provide a first axis in a direction in which the plurality of bus bars pass over the inner side surfaces of the plurality of shields, a second axis in a direction in which the inner side surfaces of the plurality of shields extend, and a third axis in which the plurality of protruding surfaces extend from both ends of the plurality of shields. 
     Volumes of the plurality of shields may be estimated according to widths and thicknesses of the plurality of shields and lengths of the protruding surfaces, and included in a range in which linearity in a numerical range, in which the plurality of current sensors measure the current applied to the plurality of bus bars, is ensured within a range of current passing through the plurality of bus bars. 
     The plurality of shields and the plurality of bus bars may be spaced apart from each other in a direction of the third axis by a first distance to ensure the linearity in the numerical range in which the plurality of bus bars measure the current applied to the plurality of bus bars, within the range of the current passing through the plurality of bus bars. 
     The plurality of current sensors may be spaced apart from the plurality of bus bars in a direction of the third axis by a second distance to maintain the linearity in the measured current within the range of the current passing through the plurality of bus bars. 
     The plurality of current sensors may be arranged in correspondence to the plurality of the bus bars providing the three phases, respectively, and arranged adjacent to centers between the protruding surfaces of the plurality of shields surrounding of the plurality of current sensors, respectively. 
     The plurality of current sensors may be arranged spaced apart from surfaces of the inner side surfaces of the plurality of shields in a direction of the third axis by a third distance. 
     The plurality of current sensors may be disposed spaced apart from centers of the plurality of bus bars in a direction of the second axis by a fourth distance. 
     The plurality of current sensors may be disposed spaced apart from surfaces of the plurality of bus bars in a direction of the third axis by a constant distance. 
     Advantageous Effects of Invention 
     In accordance with the detailed description, effects of the present disclosure described herein may be obtained. 
     Since a support protrusion portion of a housing cover is in contact with a printed circuit board, vibration of a current sensor in a current sensor unit, which may be caused by vibration of a current sensor assembly when an inverter vibrates according to driving of the inverter, may be reduced. Thus, an error that may be caused by the vibration of the current sensor during detection of current supplied to a bus bar may be reduced. 
     An optimum volume of the shield such that the current sensor may linearly measure current flowing through the bus bar may be easily determined. Further, a range in which the current sensor may linearly measure current according to a position relationship between the bus bar and a current sensor center portion may be easily determined, and thus, positions of the bus bar and the current sensor may be optimized. 
     Current flowing through the bus bar may be accurately detected by easily determining a position of the current sensor for minimizing a crosstalk effect generated by an adjacent bus bar and adjusting positions of the current sensor and the shield, by measuring and taking into account respective crosstalk effects of the current sensor positioned inside protruding surfaces of the shield with respect to first to third axes. 
     The current sensor may be arranged near the bus bar by taking into account a change in a magnetic flux density according to a skin effect of the bus bar, and as the current sensor is arranged near an end portion of the bus bar, a phase delay effect that may be caused by a magnetic flux density difference may be reduced. 
     A mold unit is not arranged to excessively surround the protruding surfaces, and a large portion of the protruding surfaces is exposed from the mold unit. Accordingly, an inner width w between the protruding surfaces is maintained, and thus, a volume of the shield and a shielding ability of the shield may be maintained to be constant. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a diagram illustrating an integrated power equipment according to an embodiment of the present disclosure. 
         FIG.  2    is a diagram illustrating an inverter assembly according to an embodiment of the present disclosure. 
         FIG.  3    is an exploded perspective view illustrating the inverter assembly of  FIG.  2   . 
         FIGS.  4  and  5    are diagrams for explaining a direction in which current flows in the inverter assembly. 
         FIG.  6    is a diagram illustrating a current sensor assembly according to an embodiment of the present disclosure. 
         FIGS.  7  and  8    are exploded perspective views illustrating the current sensor assembly of  FIG.  6   . 
         FIG.  9    is a diagram for explaining that a housing cover coupled to a rear surface of a housing and a support protrusion portion protruding from the housing cover support a printed circuit board. 
         FIG.  10    is a cross-sectional view for explaining the current sensor assembly of  FIG.  6   . 
         FIGS.  11  and  12    are diagrams for explaining a range of current that may be measured by a current sensor according to locations of a bus bar and the current sensor and a volume of a shield. 
         FIGS.  13  and  14    are diagrams for explaining a crosstalk generated in one current sensor according to relative positions of the shield and the current sensor. 
         FIGS.  15  and  16    are diagrams for explaining a skin effect and phase delay, both being generated according to a frequency of current passing through the bus bar. 
         FIGS.  17  and  18    are diagrams for explaining positions of and distances between the shield, the bus bar, and a current sensor unit. 
         FIG.  19    is a diagram for explaining a mold unit configured to fix fixing the shield and the bus bar to inside of the housing. 
     
    
    
     MODE FOR THE INVENTION 
     Description will now be given in detail according to exemplary embodiments disclosed herein, with reference to the accompanying drawings. For the sake of brief description with reference to the drawings, the same or equivalent components may be provided with the same or similar reference numbers, and description thereof will not be repeated. In general, a suffix such as “module” and “unit” may be used to refer to elements or components. Use of such a suffix herein is merely intended to facilitate description of the specification, and the suffix itself is not intended to give any special meaning or function. In describing the present disclosure, if a detailed explanation for a related known function or construction is considered to unnecessarily divert the gist of the present disclosure, such explanation has been omitted but would be understood by those skilled in the art. The accompanying drawings are used to help easily understand the technical idea of the present disclosure and it should be understood that the idea of the present disclosure is not limited by the accompanying drawings. The idea of the present disclosure should be construed to extend to any alterations, equivalents and substitutes besides the accompanying drawings. 
     It will be understood that although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are generally only used to distinguish one element from another. 
     It will be understood that when an element is referred to as being “connected with” another element, the element can be connected with the another element or intervening elements may also be present. In contrast, when an element is referred to as being “directly connected with” another element, there are no intervening elements present. 
     A singular representation may include a plural representation unless it represents a definitely different meaning from the context. 
     Terms such as “include” or “has” are used herein and should be understood that they are intended to indicate an existence of several components, functions or steps, disclosed in the specification, and it is also understood that greater or fewer components, functions, or steps may likewise be utilized. 
       FIG.  1    is a diagram illustrating an integrated power equipment according to an embodiment of the present disclosure.  FIG.  2    is a diagram illustrating an inverter assembly according to an embodiment of the present disclosure.  FIG.  3    is an exploded perspective view illustrating the inverter assembly  1  of  FIG.  2   .  FIGS.  4  and  5    are diagrams for explaining a direction in which current C 1  flows in the inverter assembly  1 . 
     Referring to  FIG.  1   , an integrated power device  1000  is illustrated. The integrated power device  1000  may include an auxiliary power module (APM) assembly, a charging module, the inverter assembly  1 , and a battery disconnect unit (BDU) assembly configured to distribute power to each module. The integrated power device  1000  is surrounded by a top cover assembly  1001  and an integrated module housing  1002 . 
     Referring to  FIGS.  2  and  3   , the inverter assembly  1  included in the integrated power device  1000  is illustrated. The inverter assembly  1  is configured to control current supplied to a motor, and may include a bulk capacitor  10  configured to store energy (power) for driving an inverter, a direct current bus bar assembly  20 , a control board  30 , a gate board  40 , a top compressor  50 , a power module assembly  60 , and a bottom compressor  70 . 
     In addition, current C 1  supplied from the bulk capacitor  10  to the motor may be delivered to a bus bar  300  via a power semiconductor module B (Insulated-gate bipolar transistor (IGBT)). In this process, the current C 1  flowing through the bus bar  300  may pass through a current sensor assembly A. 
       FIG.  6    is a diagram illustrating the current sensor assembly A according to an embodiment of the present disclosure.  FIGS.  7  and  8    are exploded perspective views illustrating the current sensor assembly A of  FIG.  6   .  FIG.  9    is a diagram for explaining that a housing cover  500  coupled to a rear surface of a housing  100  and a support protrusion portion  520  protruding from the housing cover  500  support a printed circuit board  420 .  FIG.  10    is a cross-sectional view for explaining the current sensor assembly A of  FIG.  6   . 
     Referring to  FIG.  6   , the current sensor assembly A according to an embodiment of the present disclosure is arranged in a process in which current flows from the bulk capacitor  10  configured to store energy (power) for driving an inverter to an assembly  390  of the bus bar  300 . The bulk capacitor  10 , the current sensor assembly A, and the assembly  390  of the bus bar  300  may be arranged to be coupled to a housing H. 
     Referring to  FIG.  7   , the current sensor assembly A according to an embodiment of the present disclosure includes the housing  100 , a shield  200 , the bus bar  300 , and a current sensor unit  400 . 
     The housing  100  has an approximate rectangular cross section. An inner space  120  in which the shield  200 , the bus bar  300 , and the current sensor unit  400  may be accommodated may be provided in the housing  100 . The shield  200 , the bus bar  300 , and the current sensor unit  400  may be sequentially accommodated in the inner space  120  in an upward direction. 
     The housing  100  may further include the housing cover  500 . The housing cover  500  may be coupled to an upper end of the housing  100  to cover the inner space  120  of the housing  100 . 
     In detail, a housing groove  110   h  may be provided in a rear surface of the housing  100 . In addition, the housing cover  500  may extend in a downward direction from a main body  510  of the housing cover  500 , and may include a fixing projection portion  530  provided to fit into the housing groove  110   h . As illustrated in  FIG.  9   , when the housing cover  500  is arranged to cover the inner space  120  of the housing  100 , the fixing projection portion  530  of the housing cover  500  may be connected to the housing groove  110   h  to engage the housing  100  with the housing cover  500 . 
     The housing cover  500  may extend in a downward direction to include the support protrusion portion  520  in contact with the printed circuit board  420 . 
     In detail, as illustrated in  FIG.  7   , the support protrusion portion  520  protrudes in a downward direction from the main body of the housing cover  500 . In addition, as illustrated in  FIG.  9 C , when the housing cover  500  is coupled to the housing  100 , the support protrusion portion  520  may be in contact with the printed circuit board  420 . 
     To do so, the support protrusion portion  520  may be provided to have a length slightly greater than a distance h 1  between an inner side of the main body of the housing cover  500  and the printed circuit substrate  420 . For example, the support protrusion portion  520  may be provided to be about 2 mm longer than the distance h 1  between the inner side of the main body of the housing cover  500  and the printed circuit substrate  420 . 
     Since the support protrusion portion  520  supports the printed circuit board  420 , vibration of the current sensor  410  in the current sensor unit  400 , which may be caused by vibration of the current sensor assembly A when the inverter vibrates according to driving of the inverter, may be reduced. Thus, an error that may be generated due to the vibration of the current sensor  410  during measurement of current supplied to the bus bar  300  may be reduced. 
     A plurality of shields  200  are provided. The shields  200  may be accommodated in the housing  100 , and arranged to open toward a top of the housing  100 . 
     The shields  200  include inner side surfaces (base)  210  arranged inside the housing  100  and protruding surfaces (protruding sides)  220  protruding from opposite sides of the inner side surfaces  210 . In this case, open portions of the shields  200  which are not surrounded by three surfaces of the shields  200  are arranged toward the top of the housing  100 . However, an installation direction of the housing  100  may vary according to a design. 
     Inner portions of the shields  200  refer to regions surrounded by the inner side surfaces  210  and the protruding surfaces  220  of the shields  200 . In addition, each of the regions provided by the inner portions of the shields  200  may be understood as a volume of each of the shields  200 . The volume of each of the shields  200  is relevant to a magnitude of current measured by the current sensor  410  arranged in each of the shields  200 . This will be described later in detail. The bus bar  300  is arranged to pass through inside of each of the shields  200 . 
     A plurality of bus bars  300  are provided. Three-phase current is applied to each of the bas bars  300 . The bus bars  300  are arranged near the inner side surfaces  210  and spaced apart from each other to pass through the shields  200 , respectively. 
     In detail, as illustrated in  FIG.  7   , first to third bus bars  300   a  to  300   c  may be arranged. Currents with different phase may flow to the bus bars  300 , respectively. For example, U-phase current may flow to the first bus bar  300   a , V-phase current may flow to the second bus bar  300   b , and W-phase current may flow to the third bus bar  300   c.    
     In detail, a power module including the bulk capacitor  10  may provide three-phase power by supplying three phase currents to drive the motor. 
     The three-phase power includes three symmetrical sine waves having different phases by an electrical angle of 120 degrees, respectively. For example, in a symmetrical three-phase power supply system, three conductors deliver alternate current with a same frequency and a same voltage amplitude but with a phase difference by ⅓ of a cycle, with reference to a common reference. Due to the phase difference, a voltage on an arbitrary conductor reaches a peak after ⅓ of a cycle of another conductor and before ⅓ of a cycle of the other conductor. Such phase delay provides constant power to a balanced linear load. In addition, a rotating magnetic field may be generated in an electric motor and another phase array may be generated using a transformer. 
     The current sensor unit  400  may include the printed circuit board  420  and a plurality of current sensors  410 . 
     The plurality of current sensors  410  are arranged on the printed circuit board  420 . The current sensors  410  measure current flowing through the bus bars  300 . According to a type of the current sensors  410 , a magnitude of current that may be measured may vary. For example, the current sensors  410  that may measure a magnetic flux density of 60 mT may be used, or a magnetic flux density equal to or greater than 60 mT or a magnetic flux density less than 60 mT may be measured. 
     The current sensors  410  are spaced apart from the bus bars  300  and arranged in the inner space  120  of the housing  100 . The current sensors  410  are arranged between the protruding surfaces  220  of the shields  200 . In detail, referring to  FIG.  7   , the shields  200  are inserted into the housing  100 . In addition, the bus bars  300  are arranged to pass over the shields  200 . In addition, the current sensor unit  400  is arranged to be apart from the bus bars  300  by a certain distance. In this case, the current sensors  410  are arranged in regions surrounded by three surfaces of the shields  200 . 
     The plurality of current sensors  410  are arranged to be apart from each other on the printed circuit board  420 . 
     Grooves through which the shields  200  may pass may be provided in the printed circuit board  420 . In detail, as illustrated in  FIG.  7   , first grooves  422  through which the shields  200  may pass may be provided in the printed circuit board  420 . 
     In addition, second holes  424  into which fixing protrusion portions  540  protruding from the housing cover  500  are inserted may be provided in the printed circuit board  420 . The printed circuit board  420  may be fixed to the inner space  120  of the housing  100  by using the fixing protrusion portions  540 . In addition, a mold unit and may be provided in the inner space  120  of the housing  100  to fix the housing  100 , the shields  200 , and the bus bars  300 . 
     In the current sensor assembly A according to an embodiment of the present disclosure, the shields  200 , the bus bars  300 , and the current sensor unit  400  are stacked and fixed in one housing  100 . Thus, an error that may occur when the current sensor assembly A is divided into two or more configurations may be reduced. In addition, a design may be performed such that the shields  200 , the bus bars  300 , and the current sensor unit  400  are arranged close to each other in the inner space  120  of one housing  100  to minimize various problems that may occur when the current sensors  410  measure current. 
       FIGS.  11  and  12    are diagrams for explaining a range of current that may be measured by the current sensors  410  according to locations of the bus bars  300  and the current sensors  410  and volumes of the shields  200 . 
     A volume of a shield  200  according to an embodiment of the present disclosure may be provided within a range in which a linearity in a numerical range, in which current supplied to the bus bar  300  is measured by the current sensor  410 , may be ensured within a range of current passing through the bas bar  300 . Thus, the volume of the shield  200  may be selected within a magnetic range in which the current sensor  410  may measure current. 
     The volume of the shield  200  is estimated by a width w and a thickness t of the shield  200  and a length h of the protruding surfaces  220 . In detail, referring to (c) of  FIG.  11   , a product of the width w, length l, and height h-t of the shield  200  may be the volume of the shield  200 . 
     Referring to (a) of  FIG.  11   , a vertical axis of the table indicates a magnetic flux density measured by the current sensor  410  according to volumes of the shields  200 . In detail, lines a to d each indicate a magnetic flux density measured by the current sensors  410 , according to lengths of inner widths of the shields  200  having a same thickness t of the shields  200  and a same height of the protruding surfaces  220 . In addition, a horizontal axis of the table indicates current supplied to the bus bars  300 . 
     For example, the line a indicates a case when the inner width of the shield  200  is about 15 mm, the line b indicates a case when the inner width of the shield  200  is about 20 mm, the line c indicates a case when the inner width of the shield  200  is about 25 mm, and the line d indicates a case when the inner width of the shield  200  is about 30 mm. 
     Lines e to f indicate magnitudes of magnetic flux densities measured at inner surfaces of the shields  200  when lengths of the inner side surfaces  210  of the shields  200  are about 15 mm, 20 mm, 25 mm, and 30 mm, respectively. When about 1200 A is exceeded, in all of the four cases described above, the magnetic flux density drastically decreases. 
     According sizes and performance of the current sensors  410 , the current sensors  410  may have a maximum magnetic density needed to linearly measure the current supplied to the bus bars  300 . For example, in a case of the current sensors  410  with a product name of MLX91208CAV, when the current supplied to the bus bars  300  is about 1200 A, the maximum magnetic density may be about 50 mT to about 100 mT according to lengths of the inner widths of the shields  200  measured by the current sensors  410 . 
     The current sensors  410  described above may linearly measure a magnetic flux density of up to about 60 mT. Accordingly, the lengths of the inner side surfaces  210  of the shields  200  may be desirably about 25 mm or about 30 mm. In addition, the volumes of the shields  200  may be selected within a range in which the current sensors  410  may linearly measure the current supplied to the bus bar  300 . In this example, the lines c and d may be selected. 
     First to third axes inside the housing  100  may be defined as follows. 
     The first axis is in a direction in which the bus bars  300  are spaced apart from the shields  200  and pass over the inner side surfaces  210  of the shields  200 . For example. referring to (a) of  FIG.  12   , the first axis is in a direction of an x-axis. The second axis is in a direction in which the inner side surfaces  210  of the shields  200  extend. Referring to (b) of  FIG.  12   , the second axis is in a direction of a y-axis. The third axis is in a direction in which the protruding surfaces  220  at both ends of the shields  200  extend. Referring to (c) of  FIG.  12   , the third axis is in a direction of a z-axis. 
     The shields  200  and the bus bars  300  may be spaced apart from each other in a direction of the third axis by a first distance to ensure linearity in a numerical range in which current supplied to the bus bars  300  is measured by the current sensors  410 , within a range of current passing through the bas bars  300 . In detail, referring to (b) of  FIG.  11   , a distance from inner surfaces of the shields  200  to the bus bars  300  may be referred to as a first distance in the direction of the third axis. This will be described later in detail with reference to  FIGS.  17  and  18   . 
     In addition, the current sensors  410  may be spaced apart from the bus bars  300  by a second distance in the direction of the third axis to maintain linearity of measured current within a range of the current passing through the bus bars  300 . In detail, in (b) of  FIG.  11   , a distance c from surfaces of the bus bars  300  to current sensor center portions  415  may be understood as the second distance in the direction of the third axis. 
       FIG.  12    illustrates an amount of current measured by the current sensors  410  according to changes in relative positions of the bus bars  300  and the current sensor center portions  415  along the first to third axes. 
     In detail, (a) of  FIG.  12    illustrates magnetic flux densities measured by the current sensor  410  in respective positions with reference to the first position  415   a  on the bus bar  300  along the first axis (the x-axis) when the current sensor center portion  415  is located in the respective different positions. 
     When the current sensor  410  is located in the first position  415   a , a second position  415   b , and a third position  415   c , magnetic flux densities measured by the current sensor  410  in the first to third positions  415   a  to  415   c  correspond to lines a to c, respectively. In this case, there is very little difference between the magnetic flux densities measured by the current sensor  410  in the first position  415   a , the second position  415   b , and the third position  415   c , respectively. 
     In detail, (b) of  FIG.  12    illustrates magnetic flux densities measured by the current sensor  410  in respective positions with reference to the first position  415   a  on the bus bar  300  along the second axis (the y-axis) when the current sensor center portion  415  is located in the respective different positions. In this case, there is very little difference between the magnetic flux densities measured by the current sensor  410  in the first position  415   a , the second position  415   b , and the third position  415   c , respectively. 
     In detail, (c) of  FIG.  12    illustrates magnetic flux densities measured by the current sensor  410  in respective positions with reference to the first position  415   a  on the bus bar  300  along the third axis (the z-axis) when the current sensor center portion  415  is located in the respective different positions. The first position  415   a  is a position of the current sensor center portion  415  being spaced apart from the bus bar  300  by a reference distance. The second position  415   b  is a position of the current sensor center portion  415  being spaced far apart from the bus bar  300 . The third position  415   c  is a position of the current sensor center portion  415  being arranged nearer the bus bar  300  than in the first position  415   a.    
     In a case when the current sensor center portion  415  is located in the third position  415   c  nearer the bus bar  300  than in the first position  415   a , when current of about 1200 A flows through the bus bar  300 , a magnetic flux density measured by the current sensor  410  may exceed 60 mT. This is because a magnetic field according to the current flowing through the bus bar  300  is strong when the current sensor center portion  415  is arranged near the bus bar  300 . Accordingly, with respect to the magnetic range, it is desirable that the current sensor center portion  415  is arranged apart from the bus bar  300  by a certain distance rather than being arranged near the bus bar  300 . 
     The current sensor assembly A according to an embodiment of the present disclosure may easily determine an optimum volume of the shield  200  such that the current sensor  410  may linearly measure current flowing through the bus bar  300 . Further, the current sensor assembly A may easily determine a range in which the current sensor  410  may linearly measure current according to a position relationship between the bus bar  300  and the current sensor center portion  415  to optimize positions of the bus bar  300  and the current sensor  410 . 
       FIGS.  13  and  14    are diagrams for explaining a crosstalk generated on one current sensor  410  according to relative positions of the shield  200  and the current sensor  410 . 
     Referring to  FIG.  13   , the bus bar  130  may include the first bus bar  300   a , the second bus bar  300   b , and the third bus bar  300   c  through which U-phase current, V-phase current, and W-phase current flow, respectively. In this case, the current sensor  410  arranged over one bus bar  300  such as the first bus bar  300   a , the second bus bar  300   b , or the third bus bar  300   c  may measure current flowing through another bus bar  300  adjacent to the bus bar  300  on which the current sensor  410  is arranged. This may be referred to a crosstalk. 
     To minimize the crosstalk, the plurality of current sensors  410  arranged in correspondence to the plurality of the bus bars  300  providing the three phases, respectively, may be arranged adjacent to centers between the protruding surfaces  220  of the plurality of shield  200  surrounding the current sensors  410 , respectively. 
     In detail, (a) of  FIG.  14    illustrates a degree of a crosstalk generated in the current sensor  410  in respective positions with reference to the first position  415   a  between the protruding surfaces  220  of the shield  200  along the first axis (the x-axis) when the current sensor center portion  415  is located in the respective different positions. 
     Points g 1  to g 4  indicate a crosstalk effect between the first bus bar  300   a  and the second bus bar  300   b , a crosstalk effect between the first bus bar  300   a  and the third bus bar  300   c , and a crosstalk effect between the second bus bar  300   b  and the third bus bar  300   c , respectively. In addition, crosstalk effects generated in a region a, a region b, and a region c indicate crosstalk effects generated in the first position  415   a , the second position  415   b , and the third position  415   c , respectively. 
     When the current sensor  410  is positioned in the first position  415   a , the second position  415   b , or the third position  415   c  between the protruding surfaces  220  of the shield  200 , respectively, a difference between the crosstalk effects generated in the first to third positions  415   a ,  415   b , and  415   c  is not significant. A crosstalk effect in the first position  415   a  that is a reference position is least. Accordingly, a crosstalk effect is least when the current sensor  410  is arranged in the first position  415   a  between the protruding surfaces  220  in a direction of the first axis. 
     In detail, (b) of  FIG.  14    illustrates a degree of a crosstalk generated in the current sensor  410  in respective positions with reference to the first position  415   a  between the protruding surfaces  220  of the shield  200  along the second axis (the y-axis) when the current sensor center portion  415  is located in the respective different positions. 
     A crosstalk effect in the second or third position  415   b  or  415   c  is great compared to a cross effect in the first position  415   a . Accordingly, the current sensor  410  may not measure an accurate current value of the corresponding bus bar  300 . Accordingly, a crosstalk effect is least when the current sensor  410  is arranged in the first position  415   a  between the protruding surfaces  220  in a direction of the second axis. 
     In detail, (c) of  FIG.  14    illustrates a degree of a crosstalk generated in the current sensor  410  in respective positions with reference to the first position  415   a  between the protruding surfaces  220  of the shield  200  along the third axis (the z-axis) when the current sensor center portion  415  is located in the respective different positions. 
     It may be understood that a crosstalk effect increases in an order from a case when the current sensor center portion  415  is located in the second position  415   b , a case when the current sensor center portion  415  is located in the first position  415   a , to a case when the current sensor center portion  415  is located in the third position  415   c . This is because a shield effect that may be exerted on the current sensor  410  by the protruding surfaces  220  is small when the current sensor center portion  415  is far apart from the inner side surface  210  of the shield  200 . Accordingly, an influence exerted on the current sensor  410  by current flowing through the adjacent bus bar  300  may be great. Accordingly, a crosstalk effect is least when the current sensor  410  is arranged in the second position  415   b  between the protruding surfaces  220  in a direction of the third axis. 
     That is, it may be desirable that the current sensor  410  is arranged to be apart from a surface of the inner side surface  210  of the shield  200  in the third axis by a third distance. In this case, the third distance will be described later in detail with reference to  FIGS.  17  and  18   . 
     The current sensor assembly A according to an embodiment of the present disclosure may measure and take into account respective crosstalk effects with respect to the first to third axes of the current sensor  410  positioned in the protruding surfaces  220  of the shield  200 . By doing so, the current sensor assembly A may accurately measure current flowing through the bus bar  300  by easily determining a position of the current sensor  410  for minimizing a crosstalk effect generated by the adjacent bus bar  300  and adjusting positions of the current sensor  410  and the shield  200 . 
       FIGS.  15  and  16    are diagrams for explaining a skin effect and phase delay generated according to a frequency of current passing through the bus bar  300 . 
     An upper drawing in  FIG.  15    illustrates a magnetic flux density generated according to each position of the bus bar  300  according to a frequency of current flowing through the bus bar  300 . Referring to the upper drawing in  FIG.  15   , as a frequency of current increases, a magnetic flux density in a central region  301  of the bus bar  300  drastically decreases. In addition, as the frequency of current increases, a magnetic flux density in an outer region  302  of the bus bar  300  greatly increases. This may be referred to a skin effect. 
     In addition, a lower drawing in  FIG.  15    illustrates phase delay generated in each position of the bus bar  300  according to a frequency of current flowing through the bus bar  300 . As described above, when a frequency of current increases, a magnetic flux density in the central region  301  of the bus bar  300  drastically decreases. Accordingly, when the frequency is high, phase delay in the central region  301  of the bus bar  300  may be greater than that in the outer region  302  of the bus bar  300 . 
     To reduce the phase delay described above, the current sensor  410  may be arranged apart from a center of the bus bar  300  along the second axis by a fourth distance. 
     In detail, (a) of  FIG.  16    illustrates a degree of phase delay generated for the current sensor  410  in respective positions with reference to the first position  415   a  apart from the bus bar  300  along the first axis (the x-axis) when the current sensor center portion  415  is located in the respective positions. The regions a to c indicate degrees of phase delay generated in the first position  415   a , the second position  415   b , and the third position  415   c , respectively. 
     When the current sensor  410  moves along the first axis, this indicates that the current sensor  410  moves along a central portion of the bus bar  300 . Thus, phase delay in the first position  415   a , the second position  415   b , and the third position  415   c  are identical to each other. Accordingly, a location of the current sensor  410  with reference to the first position  415   a  along the first axis does not affect phase delay within a certain distance. 
     In detail, (b) of  FIG.  16    illustrates a degree of phase delay generated for the current sensor  410  in respective positions with reference to the first position  415   a  on the bus bar  300  along the second axis (the y-axis) when the current sensor center portion  415  is located in the respective positions. 
     In this case, as the current sensor center portion  415  moves with reference to the first position  415   a  along the second axis, the current sensor center portion  415  may be moved from the central region  301  of the bus bar  300  to the outer region  302  of the bus bar  300 . As described above, a magnetic flux density is high and phase delay occurs little in the outer region  302  of the bus bar  300 . Thus, occurrence of phase delay may decrease when the current sensor  410  moves from the first position  415   a  that is a reference position, the second position  415   b , to the third position  415   c.    
     Accordingly, to reduce a phase delay effect, it may be desirable that the current sensor center portion  415 , that is, the current sensor  410  moves on the bus bar  300  along the second axis. 
     The current sensor  410  may be arranged apart from a surface of the bus bar  300  in the third axis by the third distance. 
     In detail, (c) of  FIG.  16    illustrates a degree of phase delay generated for the current sensor  410  in respective positions with reference to the first position  415   a  on the bus bar  300  along the third axis (the z-axis) when the current sensor center portion  415  is located in the respective positions. 
     It may be understood that phase delay decreases as the current sensor  410  moves from the first position  415   a  that is a reference position to the third position  415   c  arranged near the bus bar  300 . In addition, it may be understood that phase delay increases as the current sensor  410  moves from the first position  415   a  to the second position  415   b . This is caused by a reduction in phase delay that occurs in the current sensor  410  as a magnetic flux density of the bus bar  300  increases when the current sensor  410  is arranged near the bus bar  300 . 
     Accordingly, it may be understood that the current sensor center portion  415  may be desirably moved near the bus bar  300  on the bus bar  300  along the third axis to reduce a phase delay effect. 
     However, as described above, when the current sensor  410  is arranged too close to the bus bar  300 , as a magnetic flux density becomes too high, a magnetic flux density that may be linearly measured by the current sensor  410  may be exceeded. Accordingly, it is needed to set a distance for reducing phase delay while a condition for a magnetic flux density that may be measured by the current sensor  410  is met. 
     The current sensor assembly A according to an embodiment of the present disclosure may be configured such that the current sensor  410  is arranged near the bus bar  300 , by taking into account a change in the magnetic flux density according to a skin effect of the bus bar  300 . As the current sensor  410  is arranged near an end portion of the bus bar  300 , a phase delay effect caused by a magnetic flux density difference may be reduced. 
       FIGS.  17  and  18    are diagrams for explaining positions of and distances between the shields  200 , the bus bars  300 , and the current sensor  400 . 
     As described above, the shields  200 , the bus bars  300 , and the current sensors  410  may be spaced apart from each other in a direction of the first, second, or third axis by a certain distance. 
     In detail, the shields  200  and the bus bars  300  may be spaced apart from each other in a direction of the third axis by a first distance to ensure linearity of the numerical range in which the current sensors  410  measure current supplied to the bus bars  300  within a range of current passing through the bas bars  300 . Referring to  FIG.  17   , the first distance may be the distance g. 
     In addition, the current sensors  410  may be spaced apart from the bus bars  300  in a direction of the third axis by a second direction to maintain linearity of measured current within a range of current passing through the bus bars  300 . Referring to  FIG.  17   , the second distance may be the distance c. 
     That is, the current sensors  410  may be arranged apart from a surface of the inner side surface  210  of the shields  200  in the third axis by a third distance. Referring to  FIG.  17   , the third distance may be a distance obtained by adding the distances g, b, and c. 
     In addition, to reduce phase delay, the current sensors  410  may be arranged apart from centers of the bus bars  300  along the second axis by a fourth distance. Referring to  FIG.  17   , the fourth distance may be a distance f (refer to (a) of  FIG.  18   ). 
     When the thickness t of the shield  200  is 3 mm, a desirable distance obtained by taking into account all of a magnetic range in which the current sensors  410  may measure current, a crosstalk effect, and a phase delay effect is described below. 
     The inner width w between the protruding surfaces  220  of the shields  200  may be desirably about 25 mm. The length h of the protruding surfaces  220  of the shields  200  may be desirably about 18 mm. An inner side distance h′ between the shields  200  may be desirably about 20 mm. 
     A horizontal length a of the bus bars  300  may be desirably about 14 mm. A thickness b of the bus bars  300  may be desirably about 3 mm. A distance between surfaces of the bus bars  300  and the current sensor center portion  415  may be desirably about 4.7 mm. A distance i between the surfaces of the bus bars  300  and inner side surfaces of the protruding surfaces  220  at one side may be desirably about 2 mm. A distance j between a bus bar  300  and another bus bar  300  adjacent thereto may be desirably about 51 mm. A distance g between surface of the bus bar  300  and the inner side surface  210  of the shield  200  may be desirably about 2 mm. 
     A distance d between the current sensor center portion  415  and an end portion of the protruding surface  220  may be desirably about 8.3 mm. A distance e between the current sensor center portion  415  and the inner side surface  220  of the protruding surface  220  may be desirably about 12.5 mm. A distance k between the current sensor center portion  415  and an end portion of the shield  200  may be desirably about 4 mm. The distance f between the current sensor center portion  415  and a central portion of the bus bar  300  may be desirably about 3.5 mm. 
     However, a desirable distance between the respective elements described above may be changed according to a volume of the shield  200 , a measurement capability of the current sensor  410 , and a magnitude of current supplied and a frequency applied to the bus bar  300 . 
     In detail, In detail, (b) of  FIG.  18    is a diagram illustrating the bus bar  300  according to another embodiment of the present disclosure. 
     Referring to (b) of  FIG.  18   , a width of the bus bar  300  may be greater than that in the embodiment described above. In detail, the width of the bus bar  300  may be small in a section in which the bus bar  300  passes through the shield  200 . Thus, a magnetic flux density in the bus bar  300  may be increased in the section in which the bus bar  300  passes through the shield  200 . 
     In detail, in the section the bus bar  300  passes through the shield  200 , when a width a of the bus bar  300  is 14 mm, a width a′ of the bus bar  300  in sections before and after the bus bar  300  passes through the shield  200  may be greater than 14 mm, for example, 16 mm to 18 mm. To provide such a section, bus bar protruding portions  305  of the bus bar  300  may be provided. In addition, a concave portion  300 ′ of the bus bar  300  may be provided between the bus bar protruding portions  305 . 
     However, in the present embodiment, since a phase delay effect decreases in an outer region of the bus bar  300 , it may be desirable that the current sensor  410  is arranged at an end portion of the bus bar  300 . 
       FIG.  19    is a diagram for explaining a mold unit md configured to fix the shield  200  and the bus bar  300  to inside of the housing  100 . 
     The shield  200  and the bus bar  300  according to an embodiment of the present disclosure may be fixed inside the housing  100  by the mold unit md. In detail, after the shield  200  and the bus bar  300  are arranged in the inner space  120  of the housing  100 , the mold unit md may be arranged in the inner space  120  of the housing  100  to fix positions of the shield  200  and the bus bar  300 . 
     However, when the mold unit md is provided to surround a large portion of the protruding surfaces  220  of the shield  200  as illustrated in (a) of  FIG.  19   , a problem described below may occur. In a process in which the mold unit md in a liquid state coagulates to a solid, force f such as heat expansion or shrinkage may occur. The force f on the mold unit md may be applied to the protruding surfaces  220 . 
     A torque tq that is a bending force may occur on the protruding surfaces  220  at opposite sides of the shield  200  according to the force f applied to the protruding surfaces  220  by the mold unit md. According to the torque tq, the protruding surfaces  220  may become apart from each other or close to each other. Thus, a length of the inner width w between the protruding surfaces  220  may vary. When the length of the inner width w between the protruding surfaces  220  changes, a whole volume of the shield  200  may be changed. Accordingly, a magnetic flux density sensed by the current sensor  410  may be affected. 
     Referring to (b) of  FIG.  19   , the mold unit md may be provided not to cover the protruding surfaces  220  of the shield  200 . Thus, since the protruding surfaces  220  are not affected by heat expansion force or shrinkage force generated as the mold unit md is hardened, the length of the inner width w between the protruding surfaces  220  may be maintained to be constant. 
     In addition, referring to (c) of  FIG.  19   , a height a of the protruding portions  220  surrounded by the mold unit md may be provided as being less than 50% of a whole height b of the protruding surfaces  220 . Thus, a force provided by the mold unit md to fix the shield  200  may be maximized, and at same time, generation of the torque tq on the protruding surfaces  220  due to force generated by the hardening of the mold unit md may be reduced. 
     The current sensor assembly A according to an embodiment of the present disclosure is provided such that a large portion of the protruding surfaces  220  is exposed by the mold unit md, and the mold unit md does not excessively surround the protruding surfaces  220 . Accordingly, the inner width w between the protruding surfaces  220  is maintained, and thus, the volume of the shield  200  and a shielding ability of the shield  200  may be maintained to be constant. 
     The current sensor assembly A described above is not limited to the configurations and methods provided in the embodiments described above. A part or whole of the respective embodiments may be selectively combined and configured such that various modifications thereof can be made.