Patent Publication Number: US-2023145148-A1

Title: Stator switching module

Description:
TECHNICAL FIELD 
     This disclosure relates to wye-delta electric drive systems. 
     BACKGROUND 
     Electric machines are used to propel and brake vehicles. The electric machines are comprised of a number of windings that may be connected in a wye or delta configuration. The peak torque and power characteristics of the electric machine are dependent on the type of connection. 
     SUMMARY 
     An electric machine assembly has a stator including three or more phase hairpins and neutral hairpins, and a switching module attached directly to an end of the stator and over the phase hairpins and neutral hairpins. The switching module includes a housing defining a cavity containing platforms in contact with the some of the phase hairpins and neutral hairpins and switches connected with the platforms that selectively change connections of the phase hairpins between a wye configuration and a delta configuration. 
     A switching module for a stator includes a housing configured to be attached directly to an end of the stator and over line and neutral phase hairpins of the stator, electrically conductive platforms disposed in the housing and configured to contact some of the hairpins, switches disposed in the housing, connected with the platforms, and configured to selectively change connections of the hairpins between wye and delta configurations, and a conduit defining a coolant channel through the housing. 
     A method for mounting a switching module to an end of a stator includes arranging a housing of the switching module over an end of the stator such that line and neutral hairpins projecting from the end of the stator contact electrically conductive platforms of the switching module that are electrically connected with switches configured to selectively change connections of the hairpins between a wye configuration and a delta configuration, welding the platforms to the hairpins, and filling at least some of the housing with a resin that surrounds the platforms and portions of the hairpins and hardens. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic diagram of a vehicle. 
         FIG.  2    is a schematic diagram of a power electronics system; 
         FIGS.  3 A through  3 D  are schematic diagrams of a switching module. 
         FIG.  4    is a perspective view of a stator and the switching module of  FIGS.  3 A through  3 D . 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments are described herein. It is to be understood, however, that the disclosed embodiments are merely examples and other embodiments may take various and alternative forms. The figures are not necessarily to scale. Some features could be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art. 
     Various features illustrated and described with reference to any one of the figures may be combined with features illustrated in one or more other figures to produce embodiments that are not explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for typical applications. Various combinations and modifications of the features consistent with the teachings of this disclosure, however, could be desired for particular applications or implementations. 
     An electric machine includes a number of windings that are electrically driven to produce torque, and may be a three-phase machine that is driven by a three-phase inverter. The windings of the electric machine may be connected to the inverter in a delta or a wye configuration. In the wye-connected configuration, the windings are connected in a Y-shape with each winding connected to a neutral point. In the delta-connected configuration, each winding is connected to the other two windings forming a triangle of sorts. 
     The wye- and delta-connected electric machines have distinct torque and power capability due to the respective winding connection configuration. A wye wound motor has high torque and power characteristics at lower speeds, while a delta wound motor has high torque and power characteristics at higher speeds. Benefits may be derived from a dynamic electric machine connection strategy. The dynamic electric machine connection strategy may implement a control strategy to manage transitions between the types of connections to optimize vehicle performance. 
     Here, a stator winding switching module and manufacturing process that utilizes the unique wye and delta motor characteristics are contemplated. The hardware implementation and associated control allow for electric vehicle versatility. In one example, a high-power switching module is provided that can quickly switch stator winding configurations between a wye or delta winding set. The module contains the switching mechanism (e.g., high-power triacs for alternating current, etc.), a fluid cooling system, and control hardware. To reduce inductive switching transients, torque may be reduced to zero Nm prior to switching or based on a specific torque threshold. 
     The switches may be sized for the peak line voltage and current required for either motor configuration (including increased line voltage from regenerative braking). The module can be installed on the stator end windings to allow for easier access to line and neutral connections (wound or hairpin end winding connections). As an example, a dual parallel stator with hairpin end windings will have multiple neutral and line connections (e.g., six hairpin connections for each phase winding). If the module is not installed directly on the stator windings, there may need to be several bus bar extensions from the stator hairpin windings to the module (if mounted elsewhere) to rearrange the winding connection to either a wye or delta, which may be less practical. Further, mounting the module on the stator windings would improve loss efficiency (e.g., reduced bus bar power losses) and provide closer proximity to cooling channels used for motor stator cooling. These cooling channels can be used as an interface for the proposed module cooling ports. Cooling mediums may include, but not be limited to, glycol or transmission fluid. 
     An example module may contain the high-power switches, internal winding connections, cooling channels, heat exchanger interfaces, temperature sensors, and low voltage control hardware. The module could be received as a shell or module with terminal weld points, winding switches, cooling channels, sensors, etc., to be later filled with an epoxy or other suitable material. The module would first be mounted to the stator end windings. Weld spatter shields could be introduced and the module permanently laser welded to the end windings. After welding, the module could be filled with a thermal epoxy to rigidly affix it to the stator windings. After the motor is installed in a transmission, the low voltage harness could allow for low voltage power and control for the winding switches as well as sensor signals or other interfaces to the module. Since the resolver stator low voltage harness and transmission bulkhead connectors may be in close proximity to the motor stator, it could be possible to ‘tap’ into the low voltage harness connections to interface with the module. This would allow for connection of the module to the inverter and thereby vehicle-side controllers. 
     The high-power switches may be Silicon (Si) based semi-conductors. With Silicon Carbide (SiC) power devices being introduced to the market, switching device package size will continue to decrease over time. SiC devices are well suited for high current, high power, and high temperature operation in a small package. While the size of these switching devices decreases, this may allow for improved packaging and cooling mechanisms. 
     Switching control could be utilized by monitoring motor fundamental frequency, which is proportional to motor speed. As an example, when the fundamental motor frequency reaches 400 Hz, the switching module could automatically switch to the delta winding configuration or vice versa. 
     Wye-delta switching modules can utilize available low voltage control harnesses, which would interface with various other modules to handle switching related functions—creating a number of possibilities for motor control (e.g., torque-split, efficiency optimization, high-speed regenerative capture, noise, vibration, and harshness optimization, etc.). 
     Alternatively, a specific inverter high voltage AC switching frequency can be used as a type of control mechanism for an internal processing module (or filter) to signal a switch of the motor configuration. As an example, circuitry could change its switching frequency to 4500 Hz (for a short time) to signal a switch to the wye winding configuration. Conversely, the inverter could change its switching frequency to 5500 Hz to signal a delta winding configuration. An internal or external frequency filter or processing module could detect this switching frequency or such signals directly from vehicle communication channels (e.g., CAN communication). This can be used as a means for signaling a switching scenario to the motor to reduce low voltage harness wiring. 
     Referring to  FIG.  1   , a vehicle  100  is shown. The vehicle  100  may include a set of wheels  102 . The wheels  102  may be coupled to a front axle  104  or a rear axle  106  configured to drive the wheels  102 . The vehicle  100  may include one or more electric machines  112  that are coupled to a respective axle via a corresponding gearbox  110 . The vehicle  100  may include a front-drive electric machine  112 A that is mechanically coupled to a front axle gearbox  110 A. The vehicle  100  may include a rear-drive electric machine  112 B that is mechanically coupled to a rear axle gearbox  110 B. The front axle gearbox  110 A and the rear axle gearbox  110 B may be coupled to the front axle  104  and the rear axle  106 , respectively. The gearboxes  110  may include a differential for transferring torque from the corresponding electric machine  112  to the corresponding axle and wheels  102 . In other configurations, an electric machine may be coupled to each of the wheels directly or via an associated gearbox. Such a configuration would have four electric machines. Any number of electric machines and configurations thereof are contemplated and may be referred to collectively as an electric machine or a plurality of electric machines. 
     The electric machines  112  may be operated by one or more power electronics modules  122 . The power electronics modules  122  may be powered by a traction battery  124 . The power electronics modules  122  may be directed or controlled by a controller  140 . The controller  140  may include gate drivers or other hardware to drive switches of the power electronics module  122  along with processors, memory, and communications to perform logic functions and exchange information. The controller  140  may include one or more processors and controllers configured to perform such functions. The controller  140  may further include various types of computing apparatus in support of performance of the functions of the controller  140  described herein. In an example, the controller  140  may include one or more processors configured to execute computer instructions, and a storage medium on which the computer-executable instructions and/or data may be maintained. A computer-readable storage medium (also referred to as a processor-readable medium or storage) includes any non-transitory (e.g., tangible) medium that participates in providing data (e.g., instructions) that may be read by a computer (e.g., by the processor(s)). In general, a processor receives instructions and/or data, for example, from the storage, etc., to a memory and executes the instructions using the data, thereby performing one or more processes, including one or more of the processes described herein. The controller  140  may receive a control signal of a pedal(s)  142  from operators of the vehicle  100  or similar autonomous commands. The controller  140  may also determine autonomous commands and otherwise drive the vehicle  100  autonomously. 
     Referring to  FIG.  2   , a power electronics configuration is shown for operating the electric machines  112 . The traction battery  124  may be used to energize or receive energy from the power electronics configuration  200 . The power electronics configuration  200  may include one or more inverters  130  that include a set of switching elements configured to convert a direct current (DC) voltage from the traction battery  124  to an alternating current (AC) signal for the electric machines  112 . The traction battery  124  energizes terminals or rails  132 ,  134  of the inverters  130 . As shown, the inverters  130  may selectively energize the windings  114 A,  114 B,  114 C corresponding to the associated phases of the electric machine  112  by operation of the switching elements. The controller  140  may operate the inverters  130  to cause the electric machines  112  to generate torque. The controller  140  may implement various control strategies such as vector control or field-oriented control to control the torque output of the electric machines  112 . In the present example, the front-drive electric machine  112 A and the rear-drive electric machine  112 B may be driven by the inverters  130 . 
     The windings  114 A,  114 B,  114 C may be selectively arranged or configured in a delta or a wye configuration. One or more sets of switches may be configured to selectively connect each of the electric machines  112  in one of a wye and a delta connection. The windings  114 A,  114 B,  114 C may be associated with a set of delta switches  126  that configure the windings  114 A,  114 B,  114 C as a delta connection when closed. The windings  114 A,  114 B,  114 C may be associated with a set of wye switches  128  that configure the windings  114 A,  114 B,  114 C as a wye connection when closed. Other winding configurations may be used. That is, additional inverters  130  may be used to alternately power an additional set of windings such that the switches  126 ,  128  as shown are not necessary. Meaning, the electric machine  112  may be double wound with independent wye and delta windings, or the electric machine  112  may also be wound with independent wye and delta switches  126 ,  128  to selectively create wye and delta windings, or some combination thereof. Any configuration, combination, addition, or subtraction of inverters  130 , electric machines  112 , and windings  114 A,  114 B,  114 C known and unknown is contemplated. The controller  140  may be programmed to operate the switches  126 ,  128  to selectively connect each of the electric machines  112  in one of the wye and the delta connection based on various criteria (e.g., speed). 
     Referring to  FIGS.  3 A through  3 D , a switching module  146  is shown. To facilitate understanding,  FIGS.  3 A through  3 C  each show certain components of the switching module  146 , whereas  FIG.  3 D  shows all the components of  FIGS.  3 A through  3 C  together. The switching module  146  includes a housing  148 , line connections  150 ,  152 ,  154 , weld platforms  156 ,  158 ,  160  for corresponding U-phase, V-phase, and W-phase hairpins U, V, W respectively, weld platforms  162 ,  164 ,  166  for corresponding neutral phase hairpins N u , N v , Nw respectively, and weld platforms  168 ,  170 ,  172  for corresponding neutral phase hairpins N nu , N nv , N nw  respectively. The switching module  146  further includes a low voltage interface  174  and cooling ports  176 ,  178 . 
     The line connections  150 ,  152 ,  154  are respectively electrically connected with the hairpins U, V, W via bus bars  180 ,  182 ,  184 . The weld platform form  162  is electrically connected with the weld platform  168  via bus bar  186 . The weld platform  164  is electrically connected with the weld platform  170  via bus bar  188 . The weld platform  166  is electrically connected with the weld platform  172  via bus bar  190 . Unless otherwise stated, such electrical connections are separate. 
     Referring to  FIG.  3 B , the switching module  146  further includes the switches  128  and a thermistor  192 . One of the switches  128  is electrically connected between the weld platforms  162 ,  164 . The other of the switches  128  is electrically connected between the weld platforms  164 ,  166 . The switches  128  allow current flow in either direction, and each includes a control signal line  194  electrically connected with the low voltage interface  174 : Command signals from the controller  140  for the switches  128  can be provided via the low voltage interface  174 . The thermistor  192 , in this example, is mounted on the bus bar  190  and is electrically connected with the low voltage interface  174  such that signals therefrom are accessible via the low voltage interface  174 . 
     Referring to  FIG.  3 C , the switching module  146  further includes the switches  126 . One of the switches  126  is electrically connected between the weld platforms  156 ,  172 . One of the switches  126  is electrically connected between the weld platforms  158 ,  162 . And one of the switches  126  is electrically connected between the weld platforms  160 ,  170 . The switches  126  allow current flow in either direction, and each includes a control signal line  196  electrically connected with the low voltage interface  174 : Command signals from the controller  140  for the switches  126  can be provided via the low voltage interface  174 . 
     Referring to  FIG.  3 D , the housing  146  in this example is filled with a resin (e.g., epoxy)  198  that defines a cooling channel  200  between the cooling ports  176 ,  178 . A conduit may also be included for such purpose. Coolant can be directed through the housing  146  and in the vicinity of the switches  126 ,  128  to carry heat generated by them away from the switching module  146 . 
     Referring to  FIG.  4   , one of the electric machines  112  includes a stator  202  and the switching module  146  attached directly to an end of the stator  202  over some of the U, V, and W phase hairpins and neutral hairpins. 
     An electric machine connected in a wye configuration may be capable of generating higher peak torque and lower peak power than if the electric machine were connected in a delta configuration. In some configurations, the electric machine may be a permanent magnet synchronous motor (PMSM). The PMSM generates a torque that is proportional to the current supplied to the windings. When supplied current and peak generated torque are the same between a wye and delta connected electric machine, the increased phase voltage of a delta winding allows for higher power capability and thereby increased torque at higher speeds. The inverters  130  may be configured with voltage and frequency modulation capability. As such, the torque may be directly controlled in either a wye configuration or a delta configuration. 
     The algorithms, methods, or processes disclosed herein can be deliverable to or implemented by a computer, controller, or processing device, which can include any dedicated electronic control unit or programmable electronic control unit. Similarly, the algorithms, methods, or processes can be stored as data and instructions executable by a computer or controller in many forms including, but not limited to, information permanently stored on non-writable storage media such as read only memory devices and information alterably stored on writeable storage media such as compact discs, random access memory devices, or other magnetic and optical media. The algorithms, methods, or processes can also be implemented in software executable objects. Alternatively, the algorithms, methods, or processes can be embodied in whole or in part using suitable hardware components, such as application specific integrated circuits, field-programmable gate arrays, state machines, or other hardware components or devices, or a combination of firmware, hardware, and software components. 
     While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms encompassed by the claims. The words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the disclosure. 
     As previously described, the features of various embodiments may be combined to form further embodiments of the invention that may not be explicitly described or illustrated. While various embodiments could have been described as providing advantages or being preferred over other embodiments or prior art implementations with respect to one or more desired characteristics, those of ordinary skill in the art recognize that one or more features or characteristics may be compromised to achieve desired overall system attributes, which depend on the specific application and implementation. These attributes may include, but are not limited to strength, durability, marketability, appearance, packaging, size, serviceability, weight, manufacturability, ease of assembly, etc. As such, embodiments described as less desirable than other embodiments or prior art implementations with respect to one or more characteristics are not outside the scope of the disclosure and may be desirable for particular applications.