Abstract:
An operating structure for an electrically operated vehicle is disclosed, in which the windings of the electric motor are used as inductors for power factor correction during charging of the vehicle by means of the vehicle-dedicated convertor. The windings are interconnected in such a way that little or no torque is generated in the motor during the charging operation.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a U.S. National Stage Application of International Application No. PCT/EP2011/065854 filed Sep. 13, 2011, which designates the United States of America, and claims priority to DE Patent Application No. 10 2010 040 972.3 filed Sep. 17, 2010 The contents of which are hereby incorporated by reference in their entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The disclosure relates to an operating structure for an electrically operated vehicle having one or more electric motors, an accumulator or battery for supplying energy to the electric motor and a converter that is connected to the electric motor for supplying the electric motor with electrical energy from the accumulator. 
       BACKGROUND 
       [0003]    Electrically operated vehicles such as electric cars are driven by means of one or more electric motors in place of the conventional combustion engine. In contrast to rail-borne vehicles or trolley buses, the electric energy cannot be drawn continuously from a line, but rather said electrical energy must be provided from an energy storage device (=accumulator, battery). 
         [0004]    For this purpose, the energy storage device is part of an electronic power operating structure that comprises at least one converter between the energy storage device and the electric motor. The converter generates a typically three-phase voltage from the DC voltage of the energy storage device. Conversely, the converter is also mainly able to feed back into the energy storage device any energy that is generated during the brake applications and to perform for this purpose a voltage rectification procedure. 
         [0005]    The energy storage device must be charged occasionally. For future electrically operated vehicles, the energy storage device can store extremely large quantities of energy in order to provide an acceptable travel range for the electrically operated vehicles. In order to be able to charge these large quantities of energy in turn in an acceptable time into the energy storage device, a charging capacity is required that is high in comparison to present-day capacities in private households. For this purpose, it may be preferred that high-power rated controlled converters that comprise power factor control (PFC) filters are used. 
         [0006]    An external charging device that is embodied accordingly can be used to charge the energy storage device. It is also known to use as a charging device the converter that is provided in the vehicle. For this purpose, said converter is connected to the supply network by way of suitable impedances. It may be preferred in this case that the three-phase connection is selected, since otherwise the energy that can be drawn off is considerably less and the charging procedure is extremely long. 
         [0007]    A disadvantage of using an external charging device is the lack of flexibility. It is necessary for the electrically operated vehicle to be connected continuously to the charging device in order to be able to perform the charging procedure. A disadvantage of a charging device in the form of the converter having the PFC impedances being provided in the vehicle itself has the disadvantage that although the converter can to a great extent remain unchanged, it is, however, necessary to install impedances that are large and heavy due to the high power rating and this makes the car heavier. 
       SUMMARY 
       [0008]    One embodiment provides an operating structure for an electrically operated vehicle having: at least one electric motor, an accumulator for storing and supplying electrical energy, a converter that is connected to the electric motor for supplying the electric motor with electrical energy from the accumulator, and connection options for connecting a three-phase supply network and the operating structure, embodied in such a manner that for a motor operation the windings of the motor for the phases can be connected to a neutral point, and for a charging operation for charging the accumulator at least two of the phases of the supply network can be connected to the converter by way of in each case at least one winding of the electric motor, wherein the connection to the neutral point can be interrupted. 
         [0009]    In a further embodiment, switching options are provided with which during the charging operation the windings of the electric motor can be connected in such a manner that as a result of the current flow during the charging operation no torque or only an extremely small amount of torque is generated in the electric motor. 
         [0010]    In a further embodiment, the electric motor is multi-pole and its stator winding comprises a plurality of part windings, during the motor operation first part windings are allocated to a first phase, second part windings are allocated to a second phase and third part windings are allocated to a third phase, and the switching options are embodied in such a manner that during the charging operation a part of the first part windings and also a part of the second part windings can be connected to the first phase of the supply network and a further part of the first part windings and also a further part of the second part windings can be connected to the second phase of the supply network. 
         [0011]    Another embodiment provides an operating method for an electrically operated vehicle, wherein at least one electric motor is supplied by means of a converter that is connected to the electric motor with energy from an accumulator for storing and supplying electrical energy, during a motor operation the windings of the motor are connected for the phases to a neutral point, and during a charging operation for charging the accumulator at least two of the phases of a supply network that is to be connected are connected to the converter by way of in each case at least one winding of the electric motor, wherein the connection to the neutral point is interrupted. 
         [0012]    In a further embodiment, during the charging operation the windings of the electric motor are connected in such a manner that as a result of the current flow during the charging operation no torque or only an extremely small amount of torque is generated in the electric motor. 
         [0013]    In a further embodiment, a multi-pole electric motor is used, the stator winding of which comprises a plurality of part windings, wherein during the motor operation first part windings are allocated to a first phase, second part windings are allocated to a second phase and third part windings are allocated to a third phase, and wherein during the charging operation a part of the first part windings and also a part of the second part windings are connected to the first phase of the supply network and a further part of the first part windings and also a further part of the second part windings are connected to the second phase of the supply network. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    Exemplary embodiments will be explained in more detail below based on the schematic drawings, wherein: 
           [0015]      FIG. 1  shows a greatly simplified operating structure for an electric vehicle, 
           [0016]      FIG. 2  shows a connection diagram for charging the battery, 
           [0017]      FIG. 3  shows an operating structure having a multi-pole motor connected for the drive operation, 
           [0018]      FIG. 4  shows an operating structure having a multi-pole motor connected for the motor operation, 
           [0019]      FIG. 5  shows an operating structure having a multi-pole motor connected for the charging operation, and 
           [0020]      FIG. 6  shows an operating structure having a multi-pole motor connected for the motor operation. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    Embodiments of the present disclosure provide an operating structure for an electrically operated vehicle that avoids the mentioned disadvantages. In so doing, it is to be assumed that no external charging device is to be used, in other words the vehicle&#39;s own converter is to be used. 
         [0022]    Some embodiments provide an operating structure for an electrically operated vehicle that comprises at least one electric motor, an accumulator for storing and supplying electrical energy and at least one converter that is connected to the electric motor for supplying the electric motor with electrical energy from the accumulator. 
         [0023]    Furthermore, connection options are included for connecting a three-phase supply network and the operating structure, wherein said options are embodied in such a manner that for a charging operation for charging the accumulator at least two of the phases of the supply network can be connected to the converter by way in each case of at least one winding of the electric motor, wherein the connection to the neutral point can be interrupted. Furthermore, it is possible for a motor operation to connect the windings of the motor for the phases to a neutral point. 
         [0024]    It has been recognized that the windings of the electric motor can be used also for controlling the power factor. As a consequence, it is possible to omit the additional impedances and thus reduce the weight and installation space in electrically operated vehicles, which in turn increases their travel range. 
         [0025]    In one embodiment, connection options are provided, with which it is possible during the charging operation to connect the windings of the motor in such a manner that as a result of the current flow during the charging operation no torque or only an extremely small amount of torque is generated in the motor. As a consequence, any unintentional movement of the vehicle is prevented and it is not necessary to provide a special design in order to prevent such movements. 
         [0026]    For this purpose, it may be preferred in the case of a multi-pole electric motor, in which the stator winding comprises a plurality of part windings, that the following embodiment is selected: during the motor operation, first part windings are allocated to a first phase, second part windings are allocated to a second phase and third part windings are allocated to a third phase. Furthermore, the connection options are embodied in such a manner that during the charging operation a part of the first part windings and also a part of the second part windings can be connected to the first phase of the supply network and a further part of the first part windings and a further part of the second part windings can be connected to the second phase of the supply network. 
         [0027]    In other words, a cross-over connection of in each case a part of the part windings of two of the three phases can be performed for the charging operation. In so doing, in each case half of the part windings are expediently connected. As a consequence, the structure of a rotating field is avoided and the generated torque is reduced to extremely small values. 
         [0028]    In the case of the operating method for an electrically operated vehicle at least one electric motor is supplied by means of a converter that is connected to the electric motor with energy from an accumulator for storing and supplying electrical energy. Furthermore, the windings of the motor are connected for the phases to a neutral point during a motor operation and during a charging operation for charging the accumulator at least two of the phases of a supply network that is to be connected are connected to the converter by way of in each case at least one winding of the electric motor, wherein the connection to the neutral point is interrupted. It may be preferred that during the charging operation the windings of the motor are connected in such a manner that that as a result of the current flow during the charging operation no torque or only an extremely small amount of torque is generated in the motor. 
         [0029]      FIG. 1  illustrates an operating structure that is greatly schematic and reduced to the essential elements for operating an electric vehicle in accordance with the prior art. The structure comprises in this case an electric motor  1  that is illustrated schematically by means of its three windings. The electric motor  1  is embodied in a three-phase manner and is connected to a converter  2  by way of a first to third phase line  37  . . .  39 . The converter is connected on the DC side to an accumulator  3  that is used as a drive accumulator. 
         [0030]    The converter  2  is embodied to supply energy to the electric motor  1  from the accumulator  3  and to render it possible to feedback electrical energy into the accumulator  3 . The energy is fed back, for example, during brake applications. It is necessary to perform further measures when charging the accumulator  3  from outside the vehicle. 
         [0031]      FIG. 2  illustrates a diagram of a connection to a supply network  5  for charging the battery. Furthermore, the elements: electric motor  1 , converter  2  and accumulator  3  are provided. In addition, the operating structure is then connected to a supply network  5 . This connection is advantageously performed on the side of the electric motor  1  that is remote from the converter  2 . As a consequence, the windings of the electric motor  1  can be used as impedances for controlling a power factor (PFC). As a consequence, the energy consumption of the converter  2  is in turn less of a loading for the supply network  5 . 
         [0032]    Owing to the fact that the supply network  5  is connected by way of the windings of the electric motor  1 , it is necessary to disconnect the connection of the windings in the neutral point. A switching device  4  is provided for this purpose. The switching device  4  comprises a first switch between the first phase line  37  and the second phase line  38 . Furthermore, the switching device  4  comprises a switch between the second phase line  38  and the third phase line  39 . Both switches of the switching device  4  are open for a charging operation.  FIG. 2  and  FIGS. 4 and 6  illustrate the connection to the supply network  5  as a fixed connection. However, the connection is naturally performed by way of a plug-in system. 
         [0033]    A problem of the further greatly schematized structure in accordance with  FIG. 2  is that the windings of the electric motor  1  in the case of the charging operation generate a rotating field, as a consequence of which a torque is generated as is also the case during the drive operation. In order to greatly reduce this rotating field or to prevent it completely, a structure is used that is illustrated in  FIGS. 3 to 6  and explained herein under. 
         [0034]      FIG. 3  illustrates an example structure in accordance with one embodiment of the present invention. In this case,  FIG. 3  indicates the drive operation, i.e. the vehicle is not connected to the supply network  5 . The switching device  4  provides a connection of the phase lines  37  . . .  39  to the neutral point. For this purpose, the two switches of the switching device  4  are closed. The accumulator  3  is not illustrated in  FIG. 3 . 
         [0035]    It is assumed in the structure in accordance with  FIG. 3  that the electric motor  1  is a multi-pole machine having accordingly a plurality of windings  31  . . .  36  for each phase. The windings  31  . . .  36  for each phase are in this case connected in parallel. In so doing, the windings  31  . . .  36  for each phase symbolize in each case half of the actual windings of the electric motor  1 . 
         [0036]    There is no change in the third phase line  39  with respect to the known operating structure. However, changes have been introduced in the first and second phase line  37 ,  38 . 
         [0037]    In this case, a first winding  31  is connected in the first phase line  37  as it would be connected also in the known structure. However, the second winding  32  is connected in a different manner. Thus, the neutral point-side connection of the second winding  32  is connected not to the first phase line  37  but rather instead of that to the second phase line  38 . The converter-side connection of the second winding  32  is connected to a second switching device  40 . Two switches are provided in the second switching device  40  and by means of said two switches the converter-side connection of the second winding  32  is connected to the first phase line  37  and to the second phase line  38 . 
         [0038]    In the driving operation mode illustrated in  FIG. 3 , the converter-side connection of the second winding  32  in this case is connected to the first phase line  37  and its connection to the second phase line  38  is interrupted. Since the switching device  4  connects the phase lines  37  . . .  39  on the neutral point side, a parallel connection of the second winding  32  to the first winding  31  is effectively achieved as a consequence thereof. 
         [0039]    A fourth winding  34  is connected in the second phase line  38  as it would be connected also in the known structure. However, the connection of the third winding  33  remains unchanged. Thus, the neutral point-side connection of the third winding is connected not to the second phase line  38  but rather instead thereof to the first phase line  37 . The converter-side connection of the third winding  33  is likewise connected to the second switching device  40 . Two further switches are provided in the second switching device  40  and by means of said two switches the converter-side connection of the third winding  33  is connected to the first phase line  37  and the second phase line  38 . 
         [0040]    In the driving operation mode illustrated in  FIG. 3 , the converter-side connection of the third winding  33  in this case is connected to the second phase line  38  and its connection to the first phase line  37  is interrupted. Since the switching device  4  connects the phase lines  37  . . .  39  on the neutral point side, a parallel connection of the third winding  33  to the fourth winding  34  is effectively achieved as a consequence thereof. 
         [0041]    The mode and the connection during the charging operation are outlined in  FIG. 4 . It is evident in  FIG. 4  that the supply network  5  is connected to the phase lines  37  . . .  39 . As has already been indicated with respect to  FIG. 2 , the phase lines  37  . . .  39  must be disconnected from the neutral point and this is achieved by means of the switching device  4 . 
         [0042]    The switch positions in the second switching device  40  are then interchanged with respect to the mode in  FIG. 3 . Thus, the connection of the converter-side connection of the second winding  32  to the first phase line  37  is interrupted and said second winding is connected to the second phase line  38 . Furthermore, the connection of the converter-side connection of the third winding  33  to the second phase line  38  is interrupted and said third winding is connected to the first phase line  37 . 
         [0043]    The cross-over connection of a part of the windings  31  . . .  36  prevents the formation of a rotational field during the charging process. As a consequence, the build-up of a disturbing torque in the electric motor  1  is prevented at least to a great extent. 
         [0044]    A different structure is produced if the windings  31  . . .  36  for each phase in the multi-pole electric motor  1  are connected in series. In order to reduce the formation of the rotational field in the case of this arrangement, an exemplary structure is illustrated in  FIGS. 5 and 6 . In this case,  FIG. 5  illustrates the structure again during the driving operation and  FIG. 6  illustrates the structure during the charging operation. 
         [0045]    In the structure in accordance with  FIG. 5 , the first and second winding  31 ,  32  are arranged in series in the first phase line  37 , wherein the first winding  31  is connected directly to the converter  2  and the second winding  32  is connected directly to the switching device  4 . The third and fourth winding  33 ,  34  are arranged in series in the second phase line  38 , wherein the third winding  33  is connected directly to the converter  2  and the fourth winding  34  is connected directly to the switching device  4 . The fifth and sixth windings  35 ,  36  are arranged in series in the third phase line  39 , wherein the fifth winding  35  is connected directly to the converter  2  and the sixth winding  36  is connected directly to the switching device  4 . No further change is made in the third phase line  39 . 
         [0046]    A third switch  50  is provided in the first phase line  37 . The third switch  50  is arranged between the first and second winding  31 ,  32 . The third switch  50  renders it possible to provide the connection between the first and second winding  31 ,  32  or alternatively to provide the connection between the neutral point-side connection of the first winding  31  and the converter-side connection of the fourth winding  34 . 
         [0047]    A fourth switch  51  is provided in the second phase line  38 . The fourth switch  51  is arranged between the third and fourth winding  33 ,  34 . The fourth switch  51  renders it possible to provide the connection between the third and fourth winding  33 ,  34  or alternatively to provide the connection between the neutral point-side connection of the third winding  33  and the converter-side connection of the second winding  32 . 
         [0048]    During the driving operation in accordance with  FIG. 5 , the connection is provided between the first and second winding  31 ,  32 . Likewise, the connection between the third and fourth winding  33 ,  34  is provided. The switching device  4  connects the phase lines  37  . . .  39  on the neutral point side. 
         [0049]    During the charging operation in accordance with  FIG. 6 , the supply network  5  is connected in turn to the phase lines  37  . . .  39 . At the same time, the switches of the switching device  4  are open in order to eliminate the short circuit in the phase lines  37  . . .  39 . 
         [0050]    Furthermore, the switch positions of the third and fourth switches  50 ,  51  are interchanged. The third switch  50  represents a connection between the neutral point-side connection of the first winding  31  and the converter-side connection of the fourth winding  34 . The fourth switch  51  provides a connection between the neutral point-side connection of the third winding  33  and the converter-side connection of the second winding  32 . 
         [0051]    Also in the case of the structure in accordance with  FIG. 6 , the windings  31  . . .  36  are therefore connected during the charging operation partially in a crosswise manner in order to prevent the build-up of a rotational field. Consequently, the generation of a torque is in turn suppressed to a great extent.