Abstract:
A capacitor comprising first and second end sprays respectively located at distal ends of a capacitor cell, a positive polarity bus bar extending from a first wound conductive layer of the capacitor cell adjacent to the first end spray, a negative polarity bus bar extending from a second wound conductive layer of the capacitor cell adjacent to the second end spray, and a capacitor film wrapped around an area between the first and second conductive layers.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure relates to a capacitor that may be utilized with electrical components to reduce inductance of the capacitor. 
       BACKGROUND 
       [0002]    Electric and hybrid electric vehicles may use high voltage sources (e.g. battery packs or fuel cells) that deliver direct current (DC) to drive motors, electrical traction systems, and other vehicle systems. Such systems may utilize power inverters to convert the DC input from the power source to alternating current (AC) output compatible with electric motors and other electrical components. Such inverters may include both capacitor modules and power modules interconnected by a capacitor system that distributes current throughout the inverter. A typical inverter may incur voltage spikes when currents flowing through the power module abruptly change, such as when the inverter is switched off. The magnitudes of these voltage spikes are related to the inductance of the capacitor. 
         [0003]    Voltage spikes are intensified for systems that have a high inherent inductance. That is, even relatively small changes in current can produce relatively large voltage spikes if the inductance is high. A capacitor may contribute substantially to the total inductance of an inverter system because of the relatively long current pathway between its various input and output nodes. A low inductance capacitor may reduce voltage spikes when power modules are switched off. The capacitor may provide for distributing current within a power inverter that has fewer parts and minimizes material costs. 
       SUMMARY 
       [0004]    A first illustrative embodiment a capacitor comprising a body including a conductive layer wound around a spiral capacitor film, first and second end sprays respectively located at opposite ends of the body, a first bus bar attached to and extending from the first end spray; and 
         [0005]    a second bus bar attached to and extending from the conductive layer at a location between the first bus bar and the second end spray. 
         [0006]    A second illustrative embodiment a capacitor comprising a first bus bar extending from a first end spray and a second bus bar, having a polarity opposite the first bus bar, extending from a conductive layer that is wrapped around a capacitor film and an insulation layer of a body of the capacitor, wherein the conductive layer is disposed between the capacitor film and second end spray. 
         [0007]    A third illustrative embodiment discloses a capacitor comprising first and second end sprays respectively located at distal ends of a capacitor cell, a positive polarity bus bar extending from a first wound conductive layer of the capacitor cell adjacent to the first end spray, a negative polarity bus bar extending from a second wound conductive layer of the capacitor cell adjacent to the second end spray, and a capacitor film wrapped around an area between the first and second conductive layers. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a schematic diagram of an example of an electrified vehicle. 
           [0009]      FIG. 2  is a schematic diagram of a variable voltage converter and power inverter. 
           [0010]      FIG. 3  illustrates a perspective view of a capacitor. 
           [0011]      FIG. 4  illustrates a side view of a capacitator. 
           [0012]      FIG. 5  illustrates a front cross-sectional of a capacitor. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may 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 to variously employ the present invention. 
         [0014]    An example of a PHEV is depicted in  FIG. 1 , referred to generally as a vehicle  16  herein. The vehicle  16  may include a transmission  12  and is an example of an electric vehicle propelled by an electric machine  18  with assistance from an internal combustion engine  20 . The vehicle  16  may be connectable to an external power grid. The electric machine  18  may be an AC electric motor depicted as a motor  18  in  FIG. 1 . The electric machine  18  receives electrical power and provides torque for vehicle propulsion. The electric machine  18  may also function as a generator for converting mechanical power into electrical power through regenerative braking. 
         [0015]    The transmission  12  may be a power-split configuration. The transmission  12  may include the first electric machine  18  and a second electric machine  24 . The second electric machine  24  may be an AC electric motor depicted as a generator  24  in  FIG. 1 . Similar to the first electric machine  18 , the second electric machine  24  may receive electrical power and provide output torque. The second electric machine  24  may also operate as a generator for converting mechanical power into electrical power and optimizing power flow through the transmission  12 . In other embodiments, the transmission may not have a power-split configuration. 
         [0016]    The transmission  12  may include a planetary gear unit (not shown) and may operate as a continuously variable transmission and without any fixed or step ratios. The transmission  12  may also include a one-way clutch (O.W.C.) and a generator brake  33 . The O.W.C. may be coupled to an output shaft of the engine  20  to control a direction of rotation of the output shaft. The O.W.C. may prevent the transmission  12  from back-driving the engine  20 . The generator brake  33  may be coupled to an output shaft of the second electric machine  24 . The generator brake  33  may be activated to “brake” or prevent rotation of the output shaft of the second electric machine  24  and of the sun gear  28 . Alternatively, the O.W.C. and the generator brake  33  may be replaced by implementing control strategies for the engine  20  and the second electric machine  24 . The transmission  12  may be connected to a driveshaft  46 . The driveshaft  46  may be coupled to a pair of drive wheels  48  through a differential  50 . An output gear (not shown) of the transmission may assist in transferring torque between the transmission  12  and the drive wheels  48 . The transmission  12  may also be in communication with a heat exchanger  49  or an automatic transmission fluid cooler (not shown) for cooling the transmission fluid. 
         [0017]    The vehicle  16  includes an energy storage device, such as a traction battery  52  for storing electrical energy. The battery  52  may be a HV battery capable of outputting electrical power to operate the first electric machine  18  and the second electric machine  24  as further described below. The battery  52  may also receive electrical power from the first electric machine  18  and the second electric machine  24  when they are operating as generators. The battery  52  may be a battery pack made up of several battery modules (not shown), where each battery module contains a plurality of battery cells (not shown). Other embodiments of the vehicle  16  contemplate alternative types of energy storage devices, such as capacitors and fuel cells (not shown) that may supplement or replace the battery  52 . 
         [0018]    A high voltage bus may electrically connect the battery  52  to the first electric machine  18  and to the second electric machine  24 . For example, the vehicle  16  may include a battery energy control module (BECM)  54  for controlling the battery  52 . The BECM  54  may receive input indicative of certain vehicle conditions and battery conditions, such as battery temperature, voltage, and current. The BECM  54  may calculate and estimate parameters of the battery  52 , such as a battery state of charge (BSOC) and a battery power capability (Pcap). The BECM  54  may provide output that is indicative of the BSOC and Pcap to other vehicle systems and controllers. 
         [0019]    The vehicle  16  may include a DC-DC converter or variable voltage converter (VVC)  10  and an inverter  56 . The VVC  10  and the inverter  56  may be electrically connected between the battery  52  and the first electric machine  18  and the second electric machine  24 . The VVC  10  may “boost” or increase a voltage potential of electrical power provided by the battery  52 . The VVC  10  may also “buck” or decrease voltage potential of the electrical power provided to the battery  52 . The inverter  56  may invert DC power supplied by the battery  52  via the VVC  10  to AC power for operating each of the electric machines  18  and  24 . The inverter  56  may also rectify AC power provided by each of the electric machines  18  and  24  to DC for charging the battery  52 . In other examples, the transmission  12  may operate with multiple inverters, such as one invertor associated with each of the electric machine  18  and  24 . The VVC  10  includes an inductor assembly  14  (further described in relation to  FIG. 2 ). 
         [0020]    The transmission  12  is shown in communication with a transmission control module (TCM)  58  for controlling the electric machines  18  and  24 , the VVC  10 , and the inverter  56 . The TCM  58  may be configured to monitor conditions of each of the electric machines  18  and  24  such as position, speed, and power consumption. The TCM  58  may also monitor electrical parameters (e.g., voltage and current) at various locations within the VVC  10  and the inverter  56 . The TCM  58  provides output signals corresponding to this information for other vehicle systems to utilize. 
         [0021]    The vehicle  16  may include a vehicle system controller (VSC)  60  that communicates with other vehicle systems and controllers for coordinating operations thereof. Although shown as a single controller, it is contemplated that the VSC  60  may include multiple controllers to control multiple vehicle systems and components according to an overall vehicle control logic or software. 
         [0022]    The vehicle controllers, such as the VSC  60  and the TCM  58 , may include various configurations of microprocessors, ASICs, ICs, memory (e.g., FLASH, ROM, RAM, EPROM and/or EEPROM), and software code to cooperate with one another to perform vehicle operations. The controllers may also include predetermined data, or “look up tables,” which are accessible from the memory and may be based on calculations and test data. This predetermined data may be utilized by the controllers to facilitate control of the vehicle operations. The VSC  60  may communicate with other vehicle systems and controllers (e.g., the BECM  54  and the TCM  58 ) over one or more wired or wireless connections using bus protocols such as CAN and LIN. The VSC  60  may receive input (PRND) that represents a current position of the transmission  12  (e.g., park, reverse, neutral or drive). The VSC  60  may also receive input (APP) that represents an accelerator pedal position. The VSC  60  may provide outputs representative of a desired wheel torque, desired engine speed, and a generator brake command to the TCM  58 ; and contactor control to the BECM  54 . 
         [0023]    The vehicle  16  may include an engine control module (ECM)  64  for controlling the engine  20 . The VSC  60  provides output, such as desired engine torque, to the ECM  64  that may be based on a number of input signals including APP and may correspond to a driver&#39;s request for vehicle propulsion. 
         [0024]    The battery  52  may periodically receive AC energy from an external power supply or grid via a charge port  66 . The vehicle  16  may also include an on-board charger  68  which receives the AC energy from the charge port  66 . The charger  68  may include AC/DC conversion capability to convert the received AC energy into DC energy suitable for charging the battery  52  during a recharge operation. Although illustrated and described in the context of a PHEV, it is contemplated that the inverter  56  may be implemented with other types of electrified vehicles, such as a FHEV or a BEV. 
         [0025]    Referring to  FIG. 2 , an example of an electrical schematic of the VVC  10  and the inverter  56  is shown. The VVC  10  may include a first switching unit  70  and a second switching unit  72  for boosting the input voltage (V_bat) to provide output voltage (V_dc). The first switching unit  70  is shown with a first transistor  74  connected in parallel to a first diode  76  and with their polarities switched (referred to as anti-parallel herein). The second switching unit  72  is shown with a second transistor  78  connected anti-parallel to a second diode  80 . Each of the transistors  74  and  78  may be a type of controllable switch (e.g., an insulated gate bipolar transistor (IGBT) or field-effect transistor (FET)). Additionally, each of the transistors  74  and  78  may be individually controlled by the TCM  58 . The inductor assembly  14  is depicted as an input inductor that is connected in series between the battery  52  and the switching units  70  and  72 . The inductor assembly  14  may generate magnetic flux when a current is supplied. When the current flowing through the inductor assembly  14  changes, a time-varying magnetic field is created and a voltage is induced. Other embodiments of the VVC  10  may include alternative circuit configurations (e.g., more than two switches). 
         [0026]    The inverter  56  may include a plurality of half-bridges  82  stacked in an assembly. Each of the half-bridges  82  may be packaged as a power stage. In the illustrated example, the inverter  56  includes six half-bridges (though  FIG. 2  labels only one complete half-bridge  82 ), three for the motor  18  and three for the generator  24 . Each of the half bridges  82  may include a positive DC lead  84  that is coupled to a positive DC node from the battery  52  and a negative DC lead  86  that is coupled to a negative DC node from the battery  52 . Each of the half bridges  82  may also include a first switching unit  88  and a second switching unit  90 . The first switching unit  88  includes a first transistor  92  connected in parallel to a first diode  94 . The second switching unit  90  includes a second transistor  96  connected in parallel to a second diode  98 . The first transistor  92  and the second transistors  96  may be IGBTs or FETs. The first switching unit  88  and the second switching unit  90  of each of the half-bridges  82  converts the DC power of the battery  52  into a single phase AC output at the AC lead  100 . Each of the AC leads  100  is electrically connected to the motor  18  or generator  24 . In this example, three of the AC leads  100  are electrically connected to the motor  18  and the other three AC leads  100  are electrically connected to the generator  24 . 
         [0027]    A film capacitor is a component that is used for electrified vehicle applications. Capacitors with low self-inductance may be used to reduce the over-design of semiconductor devices and save the component cost. Conductive material, such as metallized film, aluminum or copper foil, etc., is wound together with the insulation layer to provide shielding of the inner part. By adding the conductive layers outside the metallized film, the self-inductance of the capacitor cell can be effectively lowered without introducing 
         [0028]      FIG. 3  illustrates a sectional view of a capacitor. The capacitor  101  may be used in automotive applications or any other type of electrical applications. In the automotive environment, a capacitor  101  may be a component used in traction inverter used in an electrical vehicle (EV) or hybrid vehicle. The capacitor may be used in the traction inverter to absorb the ripple current and smooth voltage in a direct current (DC) link or bus bar. The capacitor  101  includes a capacitor cell  103  that may be used to store energy. The capacitor cell  103  may also include a plurality of bus bars attached to it. The bus bars are utilized to pass current between an inverter, and other electrical components (e.g. converter, etc.), and a capacitor cell  103 . The bus bars may be attached to a conductive layer of the capacitor cell. The bus bars themselves may be neutral, however, when used in an electrical application, the bus bars may then have a defined polarity dependent on the electrical component the capacitor  101  is connected to. For example, the capacitor cell may include both a negative polarity bus bar  105  and a positive polarity bus bar  107 . Each capacitor may include multiple bus bars that have varying length and width. For example, the positive polarity bus bar  107  may include a wider dimension or may be lengthier than the negative polarity bus bar  105 , and vice versa. Each of the bus bars may be separated by a defined distance between one another. The bus bars may extend generally parallel to one another in generally core extensive planes, although it is not required. For example, the bus bars may extend outwards along opposite sides of the capacitor  101 . While the bus bars may be both located at each of the end sprays, it is not required. For example, the bus bars may be attached to conductive layers that are adjacent to each end spray, but the bus bars themselves may not be directly attached to the end sprays. Additionally, the self-inductance may increase as the distance between the two bus bars increases and they are further away from each other. In some applications, it may be beneficial to minimize the self-inductance between the bus bars, thus minimizing the distance between the two bus bars could accomplish lowering the self-inductance. 
         [0029]    In one embodiment, the positive polarity bus bar  107  may be attached to the end spray  109  of the capacitor. An electrical connection to a metallized film may be made with a layer of molten metal droplets sprayed on each end of the capacitor, with lead wires welded to each end spray  109 . The connection of the metallized film to the end spray  109  may not be continuous, as small metal particles may contact the metallized layer at discrete locations. The bus bars may be used to pass current inside of electronic devices. The bus bar may be used as a lead to the electronic component. 
         [0030]    Between the positive polarity bus bar  107  and the negative polarity bus bar  105  may be a capacitor film  111 , which may be a wound metallized film that is wrapped around the body of the capacitor or the capacitor cell  103 . The capacitor cell  103  or body of the capacitor may also be covered with a conductive layer  113 . The conductive layer  113  may be multiple layers of conductive material, such as metallized film, aluminum foil, copper foil, etc. The conductive material may be wound together with the insulation layer outside of the capacitor film  111  to provide shielding of an inner part of the capacitor  101  that includes a wound metallized film layer. By adding the conductive layers  113  outside the wound metallized film, the self-inductance of the capacitor cell can be effectively lowered, without introducing or minimizing additional manufacturing processing. As an example, the self-inductance of the capacitor  101  may be lower than 1 nanoHenry (nH). 
         [0031]      FIG. 4  illustrates a side view of a capacitor  101 . In one illustrative embodiment, the capacitor  101  may include a positive polarity bus bar  107  attached to one end spray, and a negative polarity bus bar  105  attached to a conductive layer  113 . The negative polarity bus bar  105  may be attached to any part of the conductive layer  113  along the capacitor cell  103 . However, the negative polarity bus bar  105  that is at the opposite end spray  109  than that of the positive polarity bus bar  107  may allow for increased self-inductance due to the distance between each bus bar. For example, the negative polarity bus bar  105  may touch any surface of the conductive layer  113  and not necessarily the portion of the conductive layer  113  that is closest to the positive polarity bus bar  107 . Furthermore, each of the bus bars is not required to be on the same side of the capacitor cell  103 . Instead, the bus bars may be located on opposite surfaces. For example, the positive polarity bus bar  107  may be on the top surface of the capacitor cell  103 , while the negative polarity bus bar  105  may be on the bottom surface of the capacitor cell  103 . 
         [0032]      FIG. 5  illustrates a front cross-sectional of a capacitor that includes a conductive layer. The capacitor may be first wrapped with a wound metallized film  117  that is a polymer that includes a metallization layer. There may be multiple layers of the wound metallized film that are made up of the core of the capacitor in one embodiment. The wound metallization film is a functional portion to form the film capacitor. The capacitor may require a non-conductive dielectric layer and two conductive layers on both sides of the dielectric. The property of the dielectric layer may determine the performance of the capacitor, as well as the capacitance value. For a film capacitor, the capacitor may utilize a thin polymer film with a double-sided metallization layer, such as a wound metallized film. 
         [0033]    Next, the capacitor&#39;s layer of wound metallized film  117  may be wrapped in a blank film  115  for insulation. The blank film  115  may include materials similar to those as the wound metallized film, however, it should not be metallized or conductive. Thus, the blank film may be a thin polymer film. The blank film  115  or capacitor film  115  may be utilized to protect the inside functioning layers of the capacitor from electrical, mechanical, and/or chemical damage. 
         [0034]    The conductive layer  113  may be wrapped around the blank film  115 , which may be also referred to as an insulation layer. The conductive layer may be thick enough to conduct current, utilizing metals to pass current. The thickness may need to meet a specific current level of 50-60 amperes. In another embodiment, the conductive layer  113  may also be wrapped with another insulation layer or blank film layer. 
         [0035]    While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, 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 invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.