Patent Publication Number: US-2015070027-A1

Title: Method and apparatus for detecting disconnection of three-phase cable

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of Korean Patent Application No. 10-2013-0110023, filed on Sep. 12, 2013, entitled “Method and apparatus for detecting disconnection of 3-phase cable”, which is hereby incorporated by reference in its entirety into this application. 
     BACKGROUND 
     1. Technical Field 
     The present invention relates to a method and an apparatus that detect a disconnection of a three-phase cable, and more particularly, to a method and an apparatus for detecting disconnection of a three-phase cable that detect which three-phase cable is disconnected by performing switching one time. 
     2. Description of the Related Art 
     Generally, three-phase motors are required for operating hybrid vehicles. Although vehicles may have different systems, it is common that motors are used for driving a vehicle and charging a battery. In particular, direct-current (DC) voltage from a battery is delivered to a three-phase motor via an inverter that converts the DC voltage into alternating-current (AC) voltage to drive the motor. Since three-phase cables that transfer power between the output of the inverter and the input of the motor are generally located within an engine room, the cables may be exposed to environmental influence such as varying temperature, humidity and external impact. Therefore, damage to the cables may occur causing disconnection of the cables. When even one of the three-phase cables is disconnected, the three-phase motor may not be controlled normally (e.g., without error or failure) causing the motor to become unpredictable and increasing driver danger. 
     SUMMARY 
     The present invention provides a method and an apparatus for detecting disconnection of three-phase cables that may determine in which of phases disconnection occurs by switching the switching elements connected to the three-phase cables one time. 
     According to an exemplary embodiment of the present invention, a method for detecting disconnection of a three-phase cable may include: switching a plurality of switching elements within switching units each corresponding to the respective phases of three-phase circuits configuring an output stage based on a predetermined criteria; applying a current generated in an input stage to the switching elements determined to be switched on and off based on the switching; detecting current flow from the plurality of switching elements based on the applied current; and determining, by a processor, which of the three-phase circuits at the output stage is in an open phase based on the detecting result. 
     Furthermore, the switching may be performed one time. The method may be performed when a vehicle is started or a brake pedal of the vehicle is engaged. The determination of the disconnected three-phase circuit may include determining that one of the three-phase circuits is an open phase when no current flow is detected from the plurality of the switching elements. In addition, the determination may include determining that any one phase is an open phase when current flow is detected from the switching elements connected to two of the three-phase circuits. The determination may also include determining that one phase is an open phase from which no current flow is detected when current flow is detected from the switching elements connected to two of the three-phase circuits. 
     The three-phase circuits may include first, second and third phases, each of the three switching units connected to the first, second and third phases may include an upper switching element and a lower switching element. The switching may include switching on the upper switching element connected to the first phase, the lower switching element connected to the second phase, and the lower switching element connected to the third phase. 
     Additionally, the determination of the disconnected three-phase circuits may include: determining that the first phase is an open phase when no current flow is detected from any of the switching elements; determining that the second phase is an open phase when no current flow is detected from the switching unit connected to the second phase; and determining that the third phase is an open phase when no current flow is detected from the switching unit connected to the third phase. 
     According to another exemplary embodiment of the present invention, an apparatus for detecting disconnection of a three-phase cable, may include: three-phase circuits operating as an output stage; switching units that each correspond to the respective phases of the three-phase circuits; a plurality of switching elements included within the switching units and switched based on a predetermined criteria; an input stage applying generated current to the switching elements determined to be switched on and off based on the switching; a detecting unit configured to detect current flow from the plurality of switching elements based on the applied current; and a determining unit (e.g., a processor) configured to determine which of the three-phase circuits at the output stage is an open phase based on the detecting result. 
     The three-phase circuits may include first, second and third phases, each of the three switching units connected to the first, second and third phases may include an upper switching element and a lower switching element. The upper switching element connected to the first phase, the lower switching element connected to the second phase, and the lower switching element connected to the third phase may be switched on. In addition, determining unit may be configured to determine that the first phase is an open phase when no current flow is detected from any of the switching elements, determine that the second phase is an open phase when no current flow is detected from the switching unit connected to the second phase only, and determine that the third phase is an open phase when no current flow is detected from the switching unit connected to the third phase only. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features and advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is an exemplary table illustrating current flows in switching elements connected to phases of a three-phase cable when one of the phases is an open phase according to an exemplary embodiment of the present invention; 
         FIG. 2  is an exemplary view illustrating an apparatus for detecting disconnection of a three-phase cable according to an exemplary embodiment of the present invention; 
         FIG. 3A to 3C  are exemplary views illustrating a process for detecting disconnection of a three-phase cable according to an exemplary embodiment of the present invention; and 
         FIG. 4  is an exemplary flowchart illustrating a method for detecting disconnection of a three-phase cable according to an exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     It is understood that the term “vehicle” or “vehicular” or other similar term as used herein is inclusive of motor vehicles in general such as passenger automobiles including sports utility vehicles (SUV), buses, trucks, various commercial vehicles, watercraft including a variety of boats and ships, aircraft, and the like, and includes hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles and other alternative fuel vehicles (e.g. fuels derived from resources other than petroleum). As referred to herein, a hybrid vehicle is a vehicle that has two or more sources of power, for example both gasoline-powered and electric-powered vehicles. 
     Although exemplary embodiment is described as using a plurality of units to perform the exemplary process, it is understood that the exemplary processes may also be performed by one or plurality of modules. Additionally, it is understood that the term controller/control unit refers to a hardware device that includes a memory and a processor. The memory is configured to store the modules and the processor is specifically configured to execute said modules to perform one or more processes which are described further below. 
     Furthermore, control logic of the present invention may be embodied as non-transitory computer readable media on a computer readable medium containing executable program instructions executed by a processor, controller/control unit or the like. Examples of the computer readable mediums include, but are not limited to, ROM, RAM, compact disc (CD)-ROMs, magnetic tapes, floppy disks, flash drives, smart cards and optical data storage devices. The computer readable recording medium can also be distributed in network coupled computer systems so that the computer readable media is stored and executed in a distributed fashion, e.g., by a telematics server or a Controller Area Network (CAN). 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term “and/of” includes any and all combinations of one or more of the associated listed items. 
     Specific descriptions on structure and function of exemplary embodiments of the present invention described herein are merely illustrative and not construed to limit the invention thereto. Since the present invention may be variously modified and have several exemplary embodiments, specific exemplary embodiments will be shown in the accompanying drawings and be described in detail. However, it is to be understood that the present invention is not limited to the specific exemplary embodiments, but includes all modifications, equivalents, and substitutions included in the spirit and the scope of the present invention. 
     Terms such as ‘first’, ‘second’, etc., may be used to describe various components, but the components are not to be construed as being limited to the terms. The terms are used only to distinguish one component from another component. For example, the ‘first’ component may be named the ‘second’ component and the ‘second’ component may also be similarly named the ‘first’ component, without departing from the scope of the present invention. 
     It is to be understood that when one element is referred to as being “connected to” or “coupled to” another element, it may be connected directly to or coupled directly to another element or be connected to or coupled to another element, having the other element intervening therebetween. On the other hand, it is to be understood that when one element is referred to as being “connected directly to” or “coupled directly to” another element, it may be connected to or coupled to another element without the other element intervening therebetween. Other expressions describing a relationship between components, that is, “between,” “directly between,” “neighboring to,” “directly neighboring to” and the like, should be similarly interpreted. 
     Terms used in the present specification are used only in order to describe specific exemplary embodiments rather than limiting the present invention. Singular forms used herein are intended to include plural forms unless explicitly indicated otherwise. It will be further understood that the terms “comprises” or “have” used in this specification, specify the presence of stated features, steps, operations, components, parts, or a combination thereof, but do not preclude the presence or addition of one or more other features, numerals, steps, operations, components, parts, or a combination thereof. 
     Unless indicated otherwise, it is to be understood that all the terms used in the specification including technical and scientific terms have the same meaning as those that are understood by those who skilled in the art. It must be understood that the terms defined by the dictionary are identical with the meanings within the context of the related art, and they should not be ideally or excessively formally defined unless the context clearly dictates otherwise. 
     Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Like reference numerals denote like components throughout the drawings. 
       FIG. 1  is an exemplary table illustrating current flows in switching elements connected to phases of a three-phase cable when one of the phases is an open phase according to an exemplary embodiment of the present invention. Referring to  FIG. 1 , when all of the phases of the three-phase cable are normally connected (e.g., when none of the phases are disconnected), currents may be generated in all of the switching elements connected to the three-phase cable. In other words, when U-phase, V-phase and W-phase cables are normally connected (e.g., not disconnected), current flows in the switching elements connected to the U-phase, V-phase and W-phase. 
     In addition, when the U-phase of the three-phase cable is an open phase, no current flows in the switching elements connected to the U-phase, V-phase and W-phase cables. When the V-phase is an open phase, currents flow in the switching elements connected to the U-phase and the W-phase but no current flows in the switching element connected to the V-phase. When the W-phase is an open phase, currents flow in the switching elements connected to the U-phase and the V-phase but no current flows in the switching element connected to the W-phase. 
       FIG. 2  is an exemplary view illustrating an apparatus for detecting disconnection of a three-phase cable according to an exemplary embodiment of the present invention. The apparatus  200  may include a three-phase cable  250 ,  260  and  270 ; switching units  220 ,  230  and  240  connected to the respective phases of a three-phase circuits  250 ,  260  and  270 ; a plurality of switching elements  220   a ,  220   b ,  230   a ,  230   b ,  240   a  and  240   b  included within the switch units  220 ,  230  and  240  to be switched based on a predetermined criteria; an input terminal (not shown) to apply a generated current I to the switching elements  220   a ,  220   b ,  230   a ,  230   b ,  240   a  and  240   b  which have been switched on and off based on switching; detecting units (e.g., sensors)  222 ,  224 ,  232 ,  234 ,  242  and  244  configured to detect a current flow from the plurality of switching elements  220   a ,  220   b ,  230   a ,  230   b ,  240   a  and  240   b  based on the applied current I; and a determining unit or a processor (not shown) configured to determine an open circuit from among the three-phase circuits  250 ,  260  and  270  at an output stage based on the detection result in the detecting units  222 ,  224 ,  232 ,  234 ,  242  and  244 . The three-phase circuits  250 ,  260  and  270  may be connected to a load  290 . 
     Specifically, the three-phase circuits  250 ,  260  and  270  may include a U-phase cable  250 , a V-phase cable  260 , and a W-phase cable  270  and the U-phase cable  250  may be connected to the first switching unit  220 . The first switching unit  220  may include an upper switching element  220   a  and a lower switching element  220   b  and may include detecting units  222  and  224  disposed near (e.g., adjacent to) the switching elements  220   a  and  220   b , respectively, to detect current flow in the corresponding switching elements. When the upper switching element  220   a  is switched on and when a path exists via which current may return from the load, the input current I may pass through the upper switching element  220   a  connected to the U-phase cable  250  to enter the load. 
     The V-phase cable  260  may be connected to the second switching unit  230 . The second switching unit  230  may include an upper switching element  230   a  and a lower switching element  220   b  and may include detecting units  232  and  234  disposed near (e.g., adjacent to) the switching elements  230   a  and  230   b , respectively, to detect current flow in the corresponding switching elements. When the upper switching element  230   a  is switched on and when a path exists via which current may return from the load, the input current I may pass through the upper switching element  230   a  connected to the V-phase cable  260  to enter the load. In addition, the W-phase cable  270  may be connected to the third switching unit  240 . The third switching unit  240  may include an upper switching element  240   a  and a lower switching element  240   b  and may include detecting units  242  and  244  disposed near (e.g., adjacent to) the switching elements  240   a  and  240   b , respectively, to detect current flow in the corresponding switching elements. When the upper switching element  240   a  is switched on and when a path exists via which current may return from the load, the input current I may pass through the upper switching element  240   a  connected to the W-phase cable  270  to enter the load. 
       FIG. 3A to 3C  are exemplary views illustrating a process for detecting disconnection of a three-phase cable according to an exemplary embodiment of the present invention. A plurality of switching elements  220   a ,  220   b ,  230   a ,  230   b ,  240   a  and  240   b  included within the switching units  220 ,  230  and  240  may each correspond to the respective phases of the three-phase circuits  250 ,  260  and  270 . Connection states of the plurality of switching elements may be set one time (e.g., avoiding multiple adjustments), to determine whether disconnections are present in the three-phase cable  250 ,  260  and  270  in the set switching state. 
     In particular, with regards to the switching states of the switching elements  220   a ,  220   b ,  230   a ,  230   b ,  240   a  and  240   b , an upper switching element  220   a  connected to the U-phase cable  250 , a lower switching element  230   b  connected to the V-phase cable  260 , and a lower switching element  240   b  connected to the W-phase cable  270  may be switched on to close the switching elements, while a lower switching element  220   b  connected to the U-phase cable  250 , an upper switching element  230   a  connected to the V-phase cable  260 , and an upper switching element  240   a  connected to the W-phase cable  270  may be switched off to open the switching elements. 
     Referring to  FIG. 3A  in which the U-phase cable  250  is disconnected, the switching element  220   a  may be switched on and the U-phase cable  250  may be disconnected to prevent an input current I from flowing in the upper switching element  220   a . Since no current is input to the load, (i.e., a motor) no current flows in any of the switching elements connected to the U-phase, V-phase, and W-phase  250 ,  260  and  270 . 
     As a result, when no current flow is detected from the plurality of switching elements  220   a ,  220   b ,  230   a ,  230   b ,  240   a  and  240   b , the U-phase cable  250  among the three-phase cable  250 ,  260  and  270  may be determined to be an open phase. In other words, when no current is detected in any of the switching elements upon the input current I being applied, the U-phase cable  250  may be determined to be disconnected. In addition, when current flow is detected from the switching elements connected to two phases of the three-phase cable  250 ,  260  and  270 , any one of the phases may be determined to be an open phase. When current flow is detected from the switching elements connected to two phases of the three-phase cable  250 ,  260  and  270 , the one phase from which no current flow is detected may be determined to be an open phase. 
     In particular, referring to  FIG. 3B  in which the V-phase cable  260  is disconnected, since only the switching element  220   a  that is connected to the U-phase  250  is switched on, the input current I may enter the load through the U-phase cable  250 . Although the V-phase cable  260  is disconnected, the W-phase cable  270  may connect the load to the input terminal and the current entering the load through the U-phase cable  250  may flow to the input terminal through the W-phase cable  270 . Accordingly, current may flow through the upper switching element  220   a  connected to the U-phase cable  250  and the lower switching element  240   b  connected to the W-phase cable  270 , and such current flow may be detected by the detecting units  222  and  224  to determine that the V-phase cable  260  is disconnected. 
     Further, referring to  FIG. 3C  in which the W-phase cable  270  is disconnected, since only the switching element  220   a  that is connected to the U-phase cable  250  is switched on, the input current I may enter the load through the U-phase cable  250 . Although the W-phase cable  270  is disconnected, the V-phase cable  260  may connect the load to the input terminal and the current entering the load through the U-phase cable  250  may flow to the input terminal through the V-phase cable  260 . 
     Accordingly, current may flow through the upper switching element  220   a  connected to the U-phase cable  250  and the lower switching element  230   b  connected to the V-phase cable  260 , and the current flow may be detected by the detecting units  222  and  234  to determine that the W-phase cable  270  is disconnected. In other words, when no current flow is detected in any of the switching elements  220   a ,  220   b ,  230   a ,  230   b ,  240   a  and  240   b , the U-phase cable  250  may be determined to be disconnected and that the U-phase is an open phase. When no current flow is detected in the switching units  230   a  and  230   b  connected to the V-phase cable  260 , the V-phase cable  260  may be determined to disconnected and that the V-phase is an open phase. In addition, when no current flow is detected in the switching units  240   a  and  240   b  connected to the W-phase cable  270 , the W-phase cable  270  may be determined to be disconnected and that the W-phase is an open phase. 
       FIG. 4  is an exemplary flowchart illustrating a method for detecting disconnection of a three-phase cable according to an exemplary embodiment of the present invention. Referring to  FIG. 4 , the method for detecting disconnection of a three-phase cable may include: when a vehicle enters the ignition (IG) on state or a braking state, that is, when the vehicle is started or a brake pedal is engaged (S 401 ), as shown in  FIGS. 3A to 3C , the connection states of the switching elements  220   a ,  220   b ,  230   a ,  230   b ,  240   a  and  240   b  may be connected to the three-phase cable  250 ,  260  and  270  (S 403 ). In other words, the upper switching element  220   a  connected to the U-phase cable  250 , a lower switching element  230   b  connected to the V-phase cable  260 , and a lower switching element  240   b  connected to the W-phase cable  270  may be switched on, while a lower switching element  220   b  connected to the U-phase cable  250 , an upper switching element  230   a  connected to the V-phase cable  260 , and an upper switching element  240   a  connected to the W-phase cable  270  may be switched off. 
     When the input current I is applied to a circuit having the set switching (e.g., set only once) (S 405 ), the applied current I may be detected in the corresponding switching elements among the detecting units (e.g., sensors)  222 ,  224 ,  232 ,  234 ,  242  and  244  connected to the U-phase cable  250 , the V-phase cable  260  and the W-phase cable  270  based on which of the U-phase cable  250 , the V-phase cable  260  and the W-phase cable  270  is disconnected (S 407 ). Based on the detection result of current flow in the switching elements, the determining unit (e.g., the processor) may be configured to determine that which of the three-phase cable is an open phase. 
     In the conventional structure, three individual tests were necessary to determine in which of the phases the cable was in an open phase. In contrast, according to an exemplary embodiment of the present invention, by switching on the upper switching element  220   a  and switching off the lower switching element  220   b  connected to the U-phase cable  250 , switching off the upper switching element  230   a  and switching on the lower switching element  230   b  connected to the V-shape cable  260 , and switching off the upper switching element  240   a  and switching on the lower switching element  240   b  connected to the W-phase cable  270 , it may be possible to determine which of the three-phase cable  250 ,  260  and  270  is an open phase at one time, thus preventing multiple adjustments. Therefore, the time consumed to detect disconnection may be reduced, and thus the degree of freedom of applying disconnection detecting may be increased. 
     According to an exemplary embodiment, when a vehicle is turned on or when a brake pedal is engaged, the algorithm to detect disconnection of a three-phase cable may be initiated. In response to determining that one of the cables among the three-phase cable connected to a motor is disconnected, the motor may no longer be operable, and therefore the vehicle may enter an engine driving mode in which an engine is driven instead or a service lamp may be lit to notify the driver of the failure. When the service lamp is lit, the driver may become aware that one of the three-phase cable connected to the motor is disconnected and that the motor has failed. 
     Although the present invention has been described with reference to the exemplary embodiment shown in the drawings, they are merely illustrative. It will be appreciated by those skilled in the art that various modifications and equivalent other embodiments are possible from the present invention. Accordingly, the true technical protection scope of the present invention must be defined by the spirit of the accompanying claims.