Patent Publication Number: US-2023150353-A1

Title: Lightweight high-efficiency, high temperature electric drive system

Description:
RELATED APPLICATIONS 
     This patent arises from a divisional of U.S. patent application Ser. No. 17/097,871, (now U.S. Pat. No. ______) entitled “Lightweight High-Efficiency, High Temperature Electric Drive System” which was filed on Nov. 13, 2020, and claims the benefit of, and priority to, U.S. Provisional Application Ser. No. 63/027,828, entitled “Lightweight High-Efficiency, High Temperature Electric Drive System” which was filed on May 20, 2020. U.S. patent application Ser. No. 17/097,871 and U.S. Provisional Patent Application No. 63/027,828 are hereby incorporated herein by reference in their entireties. Priority to U.S. patent application Ser. No. 17/097,871 and U.S. Provisional Patent Application No. 63/027,828 is hereby claimed. 
    
    
     FIELD OF THE DISCLOSURE 
     This disclosure relates generally to electric drive systems, and, more particularly, to a lightweight high-efficiency, high temperature electric drive system. 
     BACKGROUND 
     Motor drive system can generate mechanical (rotational) energy to drive a mechanical load using power electronics. Applications of the motor drive systems include electric vehicles, hybrid electric vehicles, among others. Power electronics in a motor drive system could include direct current (DC) to DC converters, DC to alternating current (AC) inverters, AC to DC rectifiers, and AC to AC converters. Power electronic manufacturers can manufacture power electronics using semiconductor materials such a silicon carbide (SiC). 
     A highly integrated motor drive system includes a power electronics system (DC to AC inverter), an electric motor (eMotor), and a combined thermal management system (TMS). The TMS is also integrated with the power electronics systems and the electric motor. Therefore, resulting system is termed an electric drive (eDrive) with built-in thermal management. This eDrive system could have very high-power density and could synergistically use common cooling media (water and/or oil) for the power electronics and the motor, resulting in a simplified system architecture that requires far less space and volume in electric and hybrid vehicles. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1 A  is a schematic illustration of an example eDrive system with a parallel flow of coolant enabled by the thermal management system in accordance with teachings disclosed herein. 
         FIG.  1 B  is a schematic illustration of an example electric drive (eDrive) system with a serial flow of coolant enabled by the thermal management system in accordance with teachings disclosed herein. 
         FIG.  2 A  is a perspective view of the eDrive system of  FIG.  1 A . 
         FIG.  2 B  is a perspective view of the eDrive system of  FIG.  1 B . 
         FIG.  2 C  is a perspective view of an alternative example of the eDrive system of  FIG.  2 B . 
         FIG.  3 A  is a perspective view of an example capacitor ring included in the example eDrive systems of  FIGS.  2 A,  2 B . 
         FIG.  3 B  is a perspective view of the example capacitor ring of  FIG.  3 A  including sections of capacitor ring that are aligned with the phases of an inverter included in the example eDrive systems of  FIGS.  2 A,  2 B . 
         FIG.  4    is close-up, cross-section view of the eDrive system of  FIGS.  2 A,  2 B  including an electric motor, an insulating sleeve, an inverter, among other things. 
         FIG.  5    is a perspective view of the example coolant pump included in the example eDrive systems of  FIGS.  2 A,  2 B . 
         FIG.  6    is a cross-section view of the example heat exchanger system (coolant channel in inverter and eMotor) of the example eDrive system of  FIG.  2 B . 
         FIG.  7    is a perspective view of an example cooling ring with the example electric motor and the example inverter of  FIGS.  2 A,  2 B . 
         FIGS.  8 A,  8 B, and  8 C  are perspective views of example lap joint connections between the example electric motor and the example inverter of  FIGS.  2 A,  2 B . 
     
    
    
     The figures are not to scale. Instead, the thickness of the layers or regions may be enlarged in the drawings. In general, the same reference numbers will be used throughout the drawing(s) and accompanying written description to refer to the same or like parts. As used in this patent, stating that any part (e.g., a layer, film, area, region, or plate) is in any way on (e.g., positioned on, located on, disposed on, or formed on, etc.) another part, indicates that the referenced part is either in contact with the other part, or that the referenced part is above the other part with one or more intermediate part(s) located therebetween. 
     Connection references (e.g., attached, coupled, connected, and joined) are to be construed broadly and may include intermediate members between a collection of elements and relative movement between elements unless otherwise indicated. As such, connection references do not necessarily infer that two elements are directly connected and in fixed relation to each other. Stating that any part is in “contact” with another part means that there is no intermediate part between the two parts. Although the figures show layers and regions with clean lines and boundaries, some or all of these lines and/or boundaries may be idealized. In reality, the boundaries and/or lines may be unobservable, blended, and/or irregular. 
     Descriptors “first,” “second,” “third,” etc. are used herein when identifying multiple elements or components which may be referred to separately. Unless otherwise specified or understood based on their context of use, such descriptors are not intended to impute any meaning of priority, physical order or arrangement in a list, or ordering in time but are merely used as labels for referring to multiple elements or components separately for ease of understanding the disclosed examples. In some examples, the descriptor “first” may be used to refer to an element in the detailed description, while the same element may be referred to in a claim with a different descriptor such as “second” or “third.” In such instances, it should be understood that such descriptors are used merely for ease of referencing multiple elements or components. 
     DETAILED DESCRIPTION 
     Conventional electric drive systems have incorporated a silicon inverter to eliminate technical barriers to achieving a lightweight, high-efficiency and high-temperature electric drive system. However, the silicon inverter based conventional electric drive system often requires a large space and runs at lower ambient temperature while offering far lower efficiency compared to examples disclosed herein. Examples disclosed herein propose a 250 kW lightweight, highly-efficient, thermally- and mechanically-robust integrated electric drive that could achieve the demands of applications such as heavy-duty all-electric and hybrid vehicles. 
     Examples disclosed herein involve a lightweight, high switching frequency Silicon Carbide (SiC) inverter fed by a greater than 1.0 kV DC bus to support the actuation of a lightweight motor with high fundamental frequency in excess of 3 kHz. Additionally, examples disclosed herein include a robust thermal management system to rapidly withdraw the heat generated by the inverter, the high-speed electric-motor (eMotor), and the gearbox. In examples disclosed herein, the inverter, the high-speed eMotor, and the gearbox are assembled in a single housing. Examples disclosed herein further include a mechanical pump that is integrated with the gearbox assembly system driven by eMotor, therefore, some examples disclosed herein have a thermal management system without any external tubes and hoses for the coolant flow. A separate thermal management system is often common with conventional eDrive systems, which is not integrated with the common assembly for inverter fed eMotor. Contrarily, examples disclosed herein include a 275 kW high switching frequency eDrive system that has a built-in thermal management system (TMS). The TMS includes a radiator that operates as a combined heat exchanger for eMotor and inverter, a radiator fan and a coolant pump that are both integrated with the gear-box assembly that is driven by the inverter fed eMotor. 
     Some examples disclosed herein achieve a high efficiency (e.g., greater than 93%) during 250 kW peak load condition such as, for example, hill climbing. Examples disclosed herein achieve a high efficiency (e.g., about 93%) during 85 kW constant loading that is expected during interstate cruising of a heavy-duty vehicle electrified with examples disclosed herein. In examples disclosed herein, it is assumed that a 1050 V battery-pack will be integrated as the energy source in the case of an all-electric heavy-duty vehicle. Examples disclosed herein, it is also assumed that a 1050 V energy source can be realized using fuel-cell with minimal size battery-pack to get desired dynamic response during acceleration and deacceleration of an all-electric heavy-duty vehicle. In examples disclosed herein, it is assumed that a hybrid heavy-duty vehicle could use diesel engine in conjunction with two embodiments of examples disclosed herein. For example, one embodiment for the source-side power/energy management and another embodiment for the load-side power/energy management. In this case, the thermal management system is integrated with an embodiment that is used to realize the source-side power/energy management system, and the load-side embodiment could have an optional TMS system. This design significantly simplifies the architecture of a hybrid heavy-duty vehicle because a common TMS system could be used to cool two electric motors, two inverters and circulates coolant through two cooling rings with each cooling ring having captured lap-joints between an inverter and an electric motor (eMotor). 
     Examples disclosed herein include an electric motor including an output shaft. Additionally, examples disclosed herein include power electronics electrically coupled to the electric motor, wherein the power electronics include an inverter. Additionally, example disclosed herein include a gearbox coupled to the output shaft. Examples disclosed herein additionally include a first heat exchanger coupled to a surface (with built-in coolant channels) of the electric motor, the first heat exchanger including coolant. Examples disclosed herein additionally include a second heat exchanger coupled to a surface (with built-in coolant channels) of the power electronics, the second heat exchanger including the coolant. In examples disclosed herein, the first heat exchanger and the second heat exchanger are coupled to a pump, and the pump is coupled to the output shaft. 
     In examples disclosed herein, the connection between the electric motor and the power electronics are lap joints. In examples disclosed herein, the electric motor, the power electronics, the gearbox, the first heat exchanger, and the second heat exchanger are included in one single housing. 
     Examples disclosed herein additionally include a fan to pull air through (draft-air) the electric-drive system, wherein the air is to cool coolant in a radiator. Additionally, examples disclosed herein include a coolant pump to receive the coolant from the radiator and provide the coolant to an electric motor and power electronics. In examples disclosed herein, the coolant pump includes three outlets, a first outlet to the power electronics, a second outlet to the electric motor, and a third outlet to cooling ring that encloses lap-joint-based electrical connections between the power electronics and the electric motor. In example disclosed herein, the coolant pump additionally includes at least one of a centrifugal impeller pump or a vane impeller pump. Additionally, examples disclosed herein include a first coolant channel to exchange heat from the electric motor to the coolant, the coolant channel coupled to the electric motor. Examples disclosed herein additionally include a second coolant channel to exchange heat from the power electronics to the coolant, the second coolant channel coupled to the power electronics. 
     Examples disclosed herein additionally include a reservoir to store coolant from the electric motor and power electronics, the reservoir to provide the stored coolant to the radiator. Additionally, examples disclosed herein include a first insulation material between the first coolant channel and the electric motor and a second insulation material between the second coolant channel and the power electronics. 
       FIG.  1 A  is a schematic illustration of an example electric drive system  100  including a parallel thermal management system in accordance with teachings disclosed herein, where parallel flow of coolant is enabled by the thermal management. The example electric drive system  100  includes an example high-speed permanent magnet (PM) electric motor (eMotor)  110 , an example motor drive system (SiC inverter)  115 , an example gearbox assembly coupled with mechanical load  120 , an example integrated drive heat exchanger  125 , an example integrated motor heat exchanger  130 , an example integrated oil pump  135 , an example system heat exchanger  140 , and an example reservoir  145 . 
     In the illustrated example of  FIG.  1 A , the example high-speed PM electric motor  110  generates mechanical energy to be used by the example gearbox assembly coupled with mechanical load  120  to drive the mechanical load. In the illustrated example of  FIG.  1 A , the example high-speed PM electric motor  110  is power-dense (e.g., 75.8 kW/L), lightweight (e.g., 62.5 kW/kg), and highly efficient (e.g., 97.28%). In the illustrated example of  FIG.  1 A , the example high-speed PM electric motor  110  includes 250 kW, 690 V root-mean-square (RMS) line-to-line, 4-pole, capable of operating at 60,000 rotations per minute (RPM). In some examples, the example high-speed PM electric motor  110  has a weight of 4.0 kg and a size of 3.3 L. 
     The example motor drive system  115  of the illustrated example  FIG.  1 A  includes a silicon carbide (SiC) inverter. The example motor drive system  115  provides power to the example high-speed PM electric motor  110 . In the illustrated example of  FIG.  1 A , the example motor drive system  115  is power-dense (e.g., 55 kW/L), lightweight (e.g., 45.8 kW/kg), and highly efficient (e.g., 97.35%). In the illustrated example of  FIG.  1 A , the SiC inverter of the example motor drive system  115  includes 275 kW, a 1050 VDC Bus, 3 kHz fundamental-frequency, and greater than or equal to 100 kHz switching-frequencies. In some examples, the SiC inverter of the example motor drive system  115  has a weight of 6.0 kg and a size of 5 L. In the illustrated example of  FIG.  1 A , the example motor drive system  115  is coupled to the example high-speed PM electric motor  110 . 
     In the illustrated example of  FIG.  1 A , the example gearbox assembly coupled with mechanical load  120  drives the mechanical load  120  with the mechanical energy from the example high-speed PM electric motor  110 . The example gearbox assembly coupled with mechanical load  120  keeps the speed of a mechanical load at less than or equal to 12,000 RPM. In the illustrated example of  FIG.  1 A , the example gearbox assembly coupled with mechanical load  120  is implemented as a 5× ratio gearbox between the example high-speed PM electric motor  110  and the mechanical load  120 . In some examples, the example gearbox assembly coupled with mechanical load  120  has a weight of 4.2 kg and a size of 3.5 L. In the illustrated example of  FIG.  1 A , the example gearbox assembly coupled with mechanical load  120  is coupled to the example high-speed PM electric motor  110 . 
     In the illustrated example of  FIG.  1 A , the example integrated oil pump  135  circulates gearbox-oil (coolant) across the example integrated drive heat exchanger  125  and the example integrated motor heat exchanger  130  to the example system heat exchanger  140 , separately. In examples disclosed herein, the coolant can include automatic transmission fluid (ATF) or other example synthetic dielectrics with high latent heat and high heat carrying capacity which still result in a light-weight electric drive system for heavy-duty vehicle applications (e.g., electric drive system  100 ). In the illustrated example of  FIG.  1 A , it is assumed that coolant is pumped in parallel (e.g., once to each of the objects to be cooled at the same time and inlet temperature of coolant for each of the object is similar). Therefore, in  FIG.  1 A , the integrated oil pump  135  collects cooled gear-box oil (about 82 degrees Celsius) from the example reservoir  145 . The example integrated oil pump  135  disperses the cooled gearbox-oil to the example integrated drive heat exchanger  125  and the example integrated motor heat exchanger  130  separately. The example integrated oil pump  135  drives the warmed gearbox-oil from the example integrated drive heat exchanger  125  and the example integrated motor heat exchanger  130  to the example system heat exchanger  140  separately where the heat is output into the external environment. In the illustrated example of  FIG.  1 A , the example integrated oil pump  135  is coupled to the example integrated drive heat exchanger  125 , the example integrated motor heat exchanger  130 , and the example system heat exchanger  140  through tubing (e.g., the lines with arrows in the example  FIG.  1 A ). 
     The example integrated drive heat exchanger  125  of the illustrated example  FIG.  1 A  exchanges heat from the example motor drive system  115  to the gear-box oil from the example integrate oil pump  135 . In the illustrated example of  FIG.  1 A , the example integrated drive heat exchanger  125  is coupled to the example motor drive system  115 . In the illustrated example, the example integrated drive heat exchanger  125  receives the gear-box oil at a maximum flow rate of 15 L/min. In the illustrated example of  FIG.  1 A , the example integrated motor heat exchanger  130  exchanges heat from the example high-speed PM electric motor  110  to the gear-box oil from the example integrate oil pump  135 . In the illustrated example of  FIG.  1 A , the example integrated motor heat exchanger  130  is coupled to the example high-speed PM electric motor  110 . 
     The example system heat exchanger  140  of the illustrated example  FIG.  1 A  cools the gear-box oil from the example integrated drive heat exchanger  125  and the example integrated motor heat exchanger  130 . The example system heat exchanger  140  removes the heat collected by the gear-box oil, and outputs the heat into the external environment. In the illustrated example of  FIG.  1 A , the example system heat exchanger  140  is coupled to the example integrated drive heat exchanger  125  and the example integrated motor heat exchanger  130 . In the illustrated example of  FIG.  1 A , the example reservoir  145  stores the cooled gearbox-oil for use by the example integrated oil pump  135 . In some examples, the example reservoir stores gearbox-oil at 82 degrees Celsius. In the illustrated example of  FIG.  1 A , the example reservoir  145  is coupled to the example system heat exchanger  140 . 
       FIG.  1 B  is a schematic illustration of an example electric drive system  150  with a serial thermal management system in accordance with teachings disclosed herein, where serial flow of coolant is enabled by the thermal management. The example electric drive system  150  includes the example high-speed PM electric motor  110 , the example motor drive system  115 , the example gearbox assembly coupled with mechanical load  120 , the example integrated drive heat exchanger  125 , the example integrated motor heat exchanger  130 , the example system heat exchanger  140 , and the example reservoir  145 . The example electric drive system  150  includes an example integrated oil pump  155 . 
     The example integrated oil pump  155  of the illustrated example  FIG.  1 B  circulates gearbox-oil (coolant) across the example integrated drive heat exchanger  125 , the example integrated motor heat exchanger  130 , and the example system heat exchanger  140 . In examples disclosed herein, the coolant can include ATF or other example synthetic dielectrics with high latent heat and high heat carrying capacity which still result in a light-weight electric drive system for heavy-duty vehicle applications (e.g., electric drive system  150 ). In the illustrated example of  FIG.  1 B , it is assumed that coolant is pumped serially (e.g., one after other objects to be cooled). Therefore, in  FIG.  1 B , the integrated oil pump  155  collects cooled gear-box oil (about 82 degrees Celsius) from the example reservoir  145 . The example integrated oil pump  155  disperses the cooled gearbox-oil to the example integrated drive heat exchanger  125  and the example integrated motor heat exchanger  130 . In the illustrated example of  FIG.  1 B , the temperature of the gearbox-oil after the example integrated drive heat exchanger is about 98 degrees Celsius. In the illustrated example of  FIG.  1 B , the temperature of the gearbox-oil after the example integrated motor heat exchanger  130  is about 114 degrees Celsius. The example integrated oil pump  155  drives the warmed gearbox-oil from the example integrated drive heat exchanger  125  and the example integrated motor heat exchanger  130  to the example system heat exchanger  140  where the heat is output into the external environment. In the illustrated example of  FIG.  1 B , the example integrated oil pump  155  is coupled to the example integrated drive heat exchanger  125 , the example integrated motor heat exchanger  130 , and the example system heat exchanger  140  through tubing (e.g., the lines with arrows in the example  FIG.  1 B ). 
     The example integrated oil pump  155  of the illustrated example of  FIG.  1 B  includes a planetary gear-coupled with the example high-speed PM electric motor  110  to pump gearbox-oil through the example electric drive system  150 . The example integrated oil pump  155  eliminates the need for an electric pump to circulate the gearbox-oil, which results in weight reduction and increased reliability due to the elimination of the electronic circuit needed to drive a conventional electric pump. In the illustrated example, the maximum power consumed by the planetary gear-coupled integrated oil pump  155  is about 300 watts at the targeted operating temperatures of  FIG.  1 B . In the illustrated example of  FIG.  1 B , the example integrated oil pump  155  is coupled with the example integrated drive heat exchanger  125 , the example integrated motor heat exchanger  130 , and the example system heat exchanger  140  that have a combined weight of 6.5 kg and a size of 5 L. 
       FIG.  2 A  is a perspective view of the example electric drive system  100  of  FIG.  1 A . The example highly-integrated electric drive system  200  of  FIG.  2 A  includes an example electric motor  205 , an example insulating sleeve  210 , an example inverter  215 , an example inverter phase  217 , an example coolant channel  220 A for example electric motor  205 , an example coolant channel  220 B for example inverter  215 , an example cooling ring  225 , an example capacitor ring  230 , example power inputs  232 A,  232 B, an example air filter  235 , an example motor shaft  240 , an example driver gear  245 , an example idle (coupling) gear  250 , an example coolant pump  255 , an example cooled coolant input  260 , example coolant pump outputs  265 A- 265 C, an example load gear  270 , an example common shaft  275 , an example fan  280 , an example radiator  285 , an example reservoir  290 , example used coolant collection channels  295 A- 295 C, an example rigid portion of an outer jacket  297 A, and an example flexible portion of the outer jacket  297 B. The outer jacket ensures draft-air flow over the example highly-integrated electric drive system  200  to keep temperature of example capacitor ring  230  closely tied to air-ambient around the example highly-integrated electric drive system  200 . 
     The example electric motor  205  of the illustrated example of  FIG.  2 A  generates mechanical energy to drive a mechanical load. In the illustrated example of  FIG.  2 A , the electric motor  205  is a permanent magnet electric motor. The example electric motor  205  is electrically coupled to the example inverter  215 . A first portion of the outer surface of the example electric motor  205  is coupled to the inner surface of the example coolant channel  220 A. In the illustrated example of  FIG.  2 A , the first portion is on the right side of the example electric motor  205 . The example coolant channel  220 A provides coolant to the example electric motor  205 . The coolant in the example coolant channel  220 A absorbs heat generated by the example electric motor  205 . 
     The example inverter  215  of the illustrated example of  FIG.  2 A  supplies high-frequency current and voltages to the example electric motor  205 . In the illustrated example of  FIG.  2 A , the inverter  215  is a silicon carbide (SiC) inverter. The inner surface of the example inverter  215  is coupled to the outer surface of the example coolant channel  220 B. The example coolant channel  220 B provides coolant to the example inverter  215 . The coolant in the example coolant channel  220 B absorbs heat generated by the example inverter  215 . In the illustrated example of  FIG.  2 A , the example inverter phase  217  represents a phase of the example inverter  215 . The example inverter  215  includes three phases that are substantially similar to the example inverter phase  217 . The three phases of the example inverter  215  are further described in connection with  FIG.  7    below. 
     In the illustrated example of  FIG.  2 A , the example insulating sleeve  210  is coupled to the outer surface of the example coolant channel  220 A and the inner surface of the example coolant channel  220 B. The example insulating sleeve  210  is coupled between the coolant channel  220 A and the coolant channel  220 B to separate the heat exchange between the example electric motor  205  and the example coolant channel  220 A from the heat exchange between the example inverter  215  and the example coolant channel  220 B. 
     In the illustrated example of  FIG.  2 A , the example cooling ring  225  is coupled to a second portion of the outer surface of the example electric motor  205 . In the illustrated example of  FIG.  2 A , the second portion of the outer surface of the example electric motor  205  is to the left of the first portion of the outer surface that is coupled to the example coolant channel  220 B. In some examples, the cooling ring  225  captures the lap-joints for electrical power connections between the example electric motor  205  and the example inverter  215 . The example cooling ring  225  includes a coolant channel. The coolant in the coolant channel of the example cooling ring  225  absorbs the heat generated due to resistive nature of electrical power connection between the example electric motor  205  and the example inverter  215 . The example cooling ring  225  captures the electrical power lap joints between the example inverter  215  and the example electric motor  205  and provides cooling to make sure that heat does not travel from the example inverter  215  and the example electric motor  205  and vice versa. 
     In the illustrated example of  FIG.  2 A , the example capacitor ring  230  generates high-frequency, time-varying power for the example inverter  215 . In the illustrated example of  FIG.  2 A , the example capacitor ring  230  includes the example power inputs  232 A,  232 B. The example power input  232 A provides negative direct current (DC) power and the example power input  232 B provides positive DC power to the example capacitor ring  230 . In the illustrated example of  FIG.  2 A , the example power inputs  232 A,  232 B receive the negative DC power and positive DC power respectively from an external source such as, for example, a battery, a fuel-cell, etc. In the illustrated example, the example capacitor ring  230  is mounted on the outer surface of the example electric motor  205 . The capacitor ring  230  is coupled between the example cooling ring  225  and the example inverter  215 . In the illustrated example of  FIG.  2 A , the example capacitor ring  230  is coupled to the example inverter  215  using pressurized connections for positive and negative DC voltage. The connections between the example capacitor ring  230  and the example inverter  215  are described in further detail below in connection with  FIG.  7   . In the illustrated example of  FIG.  2 A , the example capacitor ring  230  is cooled by the external air (draft-air contained by example outer jacket  297 ) that has passed through the example air filter  235 . 
     The example air filter  235  of the illustrated example of  FIG.  2 A  is provided to filter the external air pulled into the example electric drive system  200 . The example air filter  235  is coupled to a third portion of the outer surface of the example electric motor  205 . In the illustrated example of  FIG.  2 A , the third portion is to the left of the second portion of the outer surface that is coupled to the example cooling ring  225 . 
     In the illustrated example of  FIG.  2 A , the example electric motor  205  is coupled to the example motor shaft  240 . The example motor shaft  240  is driven by the example electric motor  205 . In the illustrated example of  FIG.  2 A , the example motor shaft  240  is coupled to the example driver gear  245 . The example motor shaft  240  drives the example driver gear  245  using the mechanical output from the example electric motor  205 . In the illustrated example of  FIG.  2 A , the example driver gear  245  is coupled to the example idle (coupling) gear  250 . The example idle (coupling) gear  250  is coupled to the example common shaft  275 . The example idle (coupling) gear  250  is driven by the example driver gear  245 . The example idle (coupling) gear  250  drives the example common shaft  275 . 
     In the illustrated example of  FIG.  2 A , the example coolant pump  255  is coupled to the example common shaft  275 . The example coolant pump  255  is coupled to one end of the example common shaft  275 . In the illustrated example, the example coolant pump  255  is coupled to the left end of the example common shaft  275 . In the illustrated example, the left end of the common shaft  275  is the end closest to the example electric motor  205 . The example coolant pump  255  is coupled to the left of the example common shaft  275  to prevent any coolant leaks because the end of the example common shaft  275  allows appropriate sealing of the example coolant pump  255 , thereby preventing any coolant leak from the example coolant pump  255 . The example coolant pump  255  is driven by the example common shaft  275 . The example coolant pump  255  collects coolant from the example radiator  285  and disperses the coolant to the example coolant channels  220 A,  220 B and the coolant channel of the example cooling ring  225 . In some examples, the coolant pump  255  can be implemented as a centrifugal impeller style pump. In some examples, the coolant pump  255  can be implemented as a vane impeller style pump. 
     In the illustrated example of  FIG.  2 A , the example coolant pump  255  collects coolant from the example radiator  285  through the example cooled coolant input  260 . The example cooled coolant input  260  is coupled to an opening on the outer surface of the example coolant pump  255 . In the illustrated example of  FIG.  2 A , the example coolant pump  255  disperses the coolant to the example coolant channel  220 A through the example coolant pump output  265 A. The example coolant pump output  265 A is coupled to an opening on the outer surface of the example coolant pump  255 . The example coolant pump output  265 A is coupled to an opening to the example coolant channel  220 A. 
     In the illustrated example of  FIG.  2 A , the example coolant pump  255  disperses the coolant to the example coolant channel  220 B through the example coolant pump output  265 B. The example coolant pump output  265 B is coupled to an opening on the outer surface of the example coolant pump  255 . The example coolant pump output  265 B is coupled to an opening to the example coolant channel  220 B. In the illustrated example of  FIG.  2 A , the example coolant pump  255  disperses the coolant to the coolant channel in the example cooling ring  225  through the example coolant pump output  265 C. The example coolant pump output  265 C is coupled to an opening on the outer surface of the example coolant pump  255 . The example coolant pump output  265 C is coupled to an opening on the outer surface of the example cooling ring  225 . 
     In the illustrated example of  FIG.  2 A , the example load gear  270  is coupled to the example common shaft  275 . The example load gear  270  drives an output mechanical load for the electric drive system  200  of  FIG.  2 A . The example load gear  270  is driven by the example common shaft  275 . In the illustrated example of  FIG.  2 A , the example load gear  270  is coupled to the example common shaft  275  to the right of the example idle (coupling) gear  250 . 
     In the illustrated example of  FIG.  2 A , the example fan  280  is coupled to the example common shaft  275 . The example fan  280  is driven by the example common shaft  275 . The example fan  280  produces air flow (draft-air) within the example electric drive system  200 . The example fan  280  pulls in external air through the example air filter  235 . The example fan  280  propels the external air through the example radiator  285  as shown by the arrows present in the illustrated example of  FIG.  2 A . The example fan  280  is coupled to the right end of the example common shaft  275 . In the illustrated example of  FIG.  2 A , the example fan  280  is coupled to the common shaft  275  to the right of the example load gear  270 . 
     The example radiator  285  of the illustrated example of  FIG.  2 A  cools coolant using the air propelled by the example fan  280 . The example radiator  285  collects coolant from the example reservoir  290  to cool. The example radiator  285  provides the cooled coolant to the example coolant pump  255  through the example cooled coolant input  260 . In the illustrated example, the example radiator  285  is coupled to the example reservoir  290 . The example reservoir  290  is coupled to the top surface of the example radiator  285 . 
     In the illustrated example of  FIG.  2 A , the example reservoir  290  collects and stores coolant. The example reservoir  290  collects coolant from the example used coolant collection channels  295 A- 295 C. In the illustrated example of  FIG.  2 A , the used coolant collection channel  295 A collects used coolant from the example coolant channel  220 A. In the illustrated example of  FIG.  2 A , the used coolant collection channel  295 B collects used coolant from the example coolant channel  220 B. In the illustrated example of  FIG.  2 A , the used coolant collection channel  295 C collects used coolant from the coolant channel in the example cooling ring  225 . 
     In the illustrated example of  FIG.  2 A , the example rigid portion of the outer jacket  297 A and the example flexible portion of the outer jacket  297 B encloses the example electric drive system  200 . The example rigid portion of the outer jacket  297 A and the example flexible portion of the outer jacket  297 B provide an enclosed space for the air flow (draft-air) forced by the example fan  280 . In the illustrated example of  FIG.  2 A , the example rigid portion of the outer jacket  297 A is coupled to the example air filter  235  and the non-drive end of the example electric motor  205 . In the illustrated example of  FIG.  2 A , the example flexible portion of the outer jacket  297 B is coupled to the drive end of the example electric motor  205  and the example radiator  285 . 
       FIG.  2 B  is a perspective view of the example electric drive system  150  of  FIG.  1 B . The example highly-integrated electric drive system  202  of  FIG.  2 B  includes the example electric motor  205 , the example insulating sleeve  210 , the example inverter  215 , the example inverter phase  217 , the example coolant channel  220 A for example electric motor  205 , the example coolant channel  220 B for example inverter  215 , the example cooling ring  225 , the example capacitor ring  230 , the example power inputs  232 A,  232 B, the example air filter  235 , the example motor shaft  240 , the example driver gear  245 , the example idle (coupling) gear  250 , the example coolant pump  255 , the example cooled coolant input  260 , the example load gear  270 , the example common shaft  275 , the example fan  280 , the example radiator  285 , the example reservoir  290 , the example rigid portion of an outer jacket  297 A, and the example flexible portion of the outer jacket  297 B of the example highly-integrated electric drive system  200  of  FIG.  2 A . The example highly-integrated electric drive system  202  of  FIG.  2 B  further includes an example coolant channel input  262  and an example coolant channel output  292 . 
     In the illustrated example of  FIG.  2 B , the example coolant pump  255  collects coolant from the example radiator  285  through the example cooled coolant input  260 . The example cooled coolant input  260  is coupled to an opening on the outer surface of the example coolant pump  255 . In the illustrated example of  FIG.  2 A , the example coolant pump  255  disperses the coolant to the example coolant channel  220 B for the example inverter  215  through the example coolant channel input  262 . The example coolant channel input  262  is coupled to an opening on the outer surface of the example coolant pump  255 . The example coolant channel input  262  is coupled to an opening to the example coolant channel  220 B. 
     In the illustrated example of  FIG.  2 B , the example coolant pump  255  disperses the coolant to the coolant channel in the example cooling ring  225  from the example coolant channel  220 B. In the illustrated example of  FIG.  2 B , the example coolant pump  255  disperses the coolant to the example coolant channel  220 A for the example electric motor  205  from the example coolant channel in the example cooling ring  225 . In the illustrated example of  FIG.  2 B , the example coolant pump  255  disperses the coolant from the example coolant channel  220 A to the example radiator  285  through the example coolant channel output  292 . The example coolant pump  255  disperses the coolant used by the example coolant channel  220 B, the coolant channel in the cooling ring  225 , and the coolant channel  220 A back to the radiator  285  through the example coolant channel output  292 . The example coolant channel output  292  is coupled to an opening to the example coolant channel  220 A. 
       FIG.  2 C  is a perspective view of an alternative example of the example eDrive system  202  of  FIG.  2 B . The example highly-integrated electric drive system  204  of  FIG.  2 C  includes the example electric motor  205 , the example insulating sleeve  210 , the example inverter  215 , the example inverter phase  217 , the example coolant channel  220 A for example electric motor  205 , the example coolant channel  220 B for example inverter  215 , the example cooling ring  225 , the example capacitor ring  230 , the example power inputs  232 A,  232 B, the example air filter  235 , the example motor shaft  240 , the example driver gear  245 , the example idle (coupling) gear  250 , the example coolant pump  255 , the example cooled coolant input  260 , the example common shaft  275 , the example fan  280 , the example radiator  285 , the example reservoir  290 , the example rigid portion of an outer jacket  297 A, and the example flexible portion of the outer jacket  297 B of the example highly-integrated electric drive system  200  of  FIG.  2 A . The example highly-integrated electric drive system  204  of  FIG.  2 C  includes the example coolant channel input  262  and the example coolant channel output  292  of the example highly-integrated electric drive system  202  of  FIG.  2 B . The example highly-integrated electric drive system  204  of  FIG.  2 C  further includes an example load gear  247 . 
     In the illustrated example of  FIG.  2 C , the example load gear  247  is coupled to the example motor shaft  240 . The example load gear  247  is coupled to the example motor shaft unlike the example load gear  270  that is coupled to the example common shaft  275  of  FIG.  2 B . The example load gear  247  drives an output mechanical load for the electric drive system  204  of  FIG.  2 C . The example load gear  247  is driven by the example motor shaft  240 . In the illustrated example of  FIG.  2 C , the example load gear  247  is coupled to the example motor shaft  240  to the left of the example electric motor  205 , the example cooling ring  225 , the example capacitor ring  230 , and the example air filter  235 . 
       FIG.  3 A  is a perspective view of an example capacitor ring  230  included in the example electric drive system  200  of  FIG.  2 A . The example capacitor ring  230  of  FIG.  3 A  shows a side view of the example electric motor  205 . The example capacitor ring  230  includes an example insulating ring  305 , an example DC positive power connection  310 , an example DC negative power connection  315 , an example DC positive bus bar  320 , an example DC negative bus bar  325 , and an example capacitor element  330 . In the illustrated example of  FIG.  3 A , the example capacitor ring  230  is slid over the example electric motor  205  and is connected with the example inverter  215  using three pairs (DC+ and DC−) of pressurized connections, one for each phase of the example inverter  215 . 
     The example insulating ring  305  of the illustrated example of  FIG.  3 A  protects the example DC positive bus bar  320 , the example DC negative bus bar  325 , and the example capacitor element  330  from heat generated by the example electric motor  205  of the example electric drive system  200  of  FIG.  2 A . The example insulating ring  305  reduces the heat exchange between the example electric motor  205  and the example DC positive bus bar  320 , the example DC negative bus bar  325 , and the example capacitor element  330 . The example insulating ring  305  is coupled to the outer surface of the example electric motor  205  and the inner surface of the example DC positive bus bar  320 . 
     The example DC positive bus bar  320  and the example DC negative bus bar  325  of the illustrated example of  FIG.  3 A  provides direct current (DC) power to the example capacitor element  330 . The example DC negative bus bar  325  includes the example DC negative power connection  315 . The example DC positive bus bar  320  includes the example DC positive power connection  310 . In some examples, the example DC positive power connection  310  and the example DC negative power connection  315  receive the DC power supply from an external power supply such as, for example, a battery, a fuel-cell, etc. In some examples, the external power supply to provide DC power could be a similar embodiment connected with engine-driven system in hybrid-vehicles. In some examples, the example DC positive power connection  310  and the example DC negative power connection  315  are substantially similar to the example power inputs  232 A,  232 B in the illustrated example of  FIG.  2 A . In the illustrated example of  FIG.  3 A , the example DC positive bus bar  320  and the example DC negative bus bar  325  are flexible laminated bus bar made of Al 2 O 3  (alumina) coated copper or aluminum sheets. 
     The example capacitor element  330  of the illustrated example of  FIG.  3 A  provides high-frequency, time-varying power to the example inverter  215  of the example electric drive system  200  of  FIG.  2 A . The example capacitor element  330  receives positive and negative DC voltage from the example DC positive bus bar  320  and the example DC negative bus bar  325 , respectively. The example capacitor element  330  stores the DC power from the example DC positive bus bar  320  and the example DC negative bus bar  325  and provides high-frequency, time-varying power for proper function and switching of the example inverter  215 . The example capacitor ring  230  is not limited to the number of capacitor elements illustrated. The example capacitor ring  230  can include a plurality of capacitor elements with similar features to provide high-frequency, time-varying power to the example inverter  215  to provide stable voltage across the DC bus bar of the example inverter  215  and to fulfill switching ripples current (time varying current) requirement of the example inverter  215 . Capacitor elements are inserted in the flexible DC positive bus bar  320  and DC negative bus bar  325  and then folded in the ring-shape and the inner surface of this ring shape capacitor module is the example insulating ring  305 . 
       FIG.  3 B  is a perspective view of the example capacitor ring  230  of  FIG.  3 A  including the phases of the example inverter  215  included in the example eDrive systems of  FIGS.  2 A,  2 B . The example capacitor ring  230  of  FIG.  3 B  shows side view of the example electric motor  205 . The example capacitor ring  230  includes the example insulating ring  305 , the example DC positive power connection  310 , the example DC negative power connection  315 , the example DC positive bus bar  320 , the example DC negative bus bar  325 , and the example capacitor element  330 . The example DC positive bus bar  320 , the example DC negative bus bar  325  are coated with Al 2 O 3  to make sure necessary insulation and voltage withstand capability exists between the example DC positive bus bar  320 , the example DC negative bus bar  325 . The example capacitor ring  230  of  FIG.  3 B  further includes an example section of first phase  340 , an example section of second phase  345 , and an example section of third phase  350 . The example phases  340 ,  345  and  350  of the example capacitor ring  230  are electrically connected with the example inverter phases  705 ,  710 ,  715  of  FIG.  7   , respectively. 
     In the illustrated example of  FIG.  3 B , the example first phase  340 , the example second phase  345 , and the example third phase  350  refer to the three phases of the example inverter  215 . The three phases of the example inverter  215  are further described below in connection with the illustrated example of  FIG.  7   . In the illustrated example of  FIG.  3 B , the capacitor elements are associated with one of the example first phase  340 , the example second phase  345 , and the example third phase  350 . In the illustrated example of  FIG.  3 B , the example capacitor ring  230  is connected with the example first phase  340 , the example second phase  345 , and the example third phase  350  of the example inverter  215  using three pairs (DC+ and DC−) of pressurized connections, one for each phase of the example inverter  215 . 
       FIG.  4    is a close-up, cross-section view of the example electric motor  205 , the example insulating sleeve  210 , the example inverter  215 , the example coolant channel  220 A, the example coolant channel  220 B, and the example capacitor ring  230  of  FIG.  2 A . The illustrated example of  FIG.  4    includes the example DC positive power connection  310  and the example capacitor element  330 . The illustrated example of  FIG.  4    further includes the example capacitor ring layers  410 . 
     In the illustrated example of  FIG.  4   , the example capacitor ring layer  410  include the example the example insulating ring  305 , the example DC positive bus bar  320 , and the example DC negative bus bar  325  of the illustrated example of  FIGS.  3 A,  3 B . The illustrated example of  FIG.  4    provides a cross-section view of the example capacitor ring  230  of  FIGS.  3 A,  3 B  in connection with the example electric drive system  200  of  FIG.  2 A . The connections between the example capacitor ring  230  and the example inverter  215  are described below in connection with  FIG.  7   . 
       FIG.  5    is a perspective view of an example coolant pump  500  included in the example electric drive system  200  of  FIG.  2 A . The example coolant pump  500  is directly driven by electric drive system  200  and forces coolant through three major components of electric drive system  200 : the electric motor  205 , the inverter  215 , and the cooling ring  225 . The example coolant pump  500  of  FIG.  5    includes an example coolant input port  510 , an example blade  515 , an example coolant output port  520  to force coolant through inverter, an example coolant output port  525  to force coolant through motor, and an example coolant output port  530  to forces coolant through cooling ring. 
     The example coolant input port  510  of the illustrated example of  FIG.  5    collects coolant from the example radiator  285  of the example electric drive system  200  of  FIG.  2 A . The example coolant input port  510  receives cooled coolant from the example radiator  285  and provides the cooled coolant to the example coolant pump  500  to be distributed to other components of the example electric drive system  200  of  FIG.  2 A . 
     The example blade  515  of the illustrated example of  FIG.  5    circulates the cooled coolant from the example coolant input port  510  in the example coolant pump  500 . The example blade  515  in the example coolant pump  500  forces the cooled coolant through the inverter, motor, and cooling ring via coolant output ports  520 ,  525  and  530 , respectively. The example blade  515  circulate the coolant by spinning in the example coolant pump  500 . The example blade  515  is spun by the example common shaft  275  of the example electric drive system  200  of  FIG.  2 A . The example coolant pump  500  is not limited to the number of blades illustrated. The example coolant pump  500  can include a plurality of blades with similar features to circulate the cooled coolant from the example coolant input port  510  to the example coolant output ports  520  (for inverter),  525  (for electric motor), and  525  (for cooling ring). 
     The example coolant output port  520  of the illustrated example of  FIG.  5    provides coolant to the example inverter  215  of the example electric drive system  200  of  FIG.  2 A . The example coolant output port  520  collects cooled coolant from the example coolant pump  500 . The example coolant output port  520  provides the collected cooled coolant to the coolant channel for the example inverter  215 . 
     The example coolant output port  525  of the illustrated example of  FIG.  5    provides coolant to the example electric motor  205  of the example electric drive system  200  of  FIG.  2 A . The example coolant output port  525  collects cooled coolant from the example coolant pump  500 . The example coolant output port  525  provides the collected cooled coolant to the coolant channel for the example electric motor  205 . 
     The example coolant output port  530  of the illustrated example of  FIG.  5    provides coolant to the example cooling ring  225  of the example electric drive system  200  of  FIG.  2 A . The example coolant output port  530  collects cooled coolant from the example coolant pump  500 . The example coolant output port  530  provides the collected cooled coolant to the coolant channel built-in the example cooling ring  225 . 
       FIG.  6    is a cross-section view of the example heat exchanger system  600  of the example electric drive system  202  of  FIG.  2 B . The illustrated example of  FIG.  6    is a cross-section view of a serial thermal management system illustrated in the example  FIG.  2 B . The example heat exchanger system  600  includes the example electric motor  205 , the example cooling ring  225 , the example power input  232 A,  232 B, the example motor shaft  240 , and only partial view of the example rigid portion of the outer jacket  297 A. In the illustrated example of  FIG.  6   , the example heat exchanger system  600  includes an example coolant inlet  605 , an example inverter coolant channel  610 , an example electric motor coolant channel  615 , an example coolant outlet  620 , example capacitor elements  630 A,  630 B,  630 C, example inverter phases  635 A,  635 B,  635 C, example power boards  640 A,  640 B,  640 C, an example power output  645 , an example control board  650 , an example control input  655 , example flying leads  660 A,  660 B,  660 C, and an example gearbox  665 . 
     The example inverter coolant channel  610  of the illustrated example of  FIG.  6    provides coolant to the example inverter phases  635 A,  635 B,  635 C. The coolant in the example inverter coolant channel  610  absorbs heat generated by the example inverter phases  635 A,  635 B,  635 C. The example inverter coolant channel  610  obtains the coolant through the example coolant inlet  605 . In the illustrated example of  FIG.  6   , the example inverter coolant channel  610  is coupled to the inner surface of the example inverter phases  635 A,  635 B,  635 C. In some examples, the example inverter coolant channel  610  is similar to the example coolant channel  220 B. In some examples, the example coolant inlet  605  is similar to the example coolant channel input  262 . 
     In the illustrated example of  FIG.  6   , cooled coolant is received at the coolant inlet  605  from the example coolant pump  255 . The example coolant flows through the example inverter coolant channel  610 . The coolant from the example inverter coolant channel  610  then flows to the coolant channel of the example cooling ring  225 . In the illustrated example of  FIG.  6   , the example coolant flows from the example cooling ring  225  to example electric motor coolant channel  615 . In the illustrated example, the coolant from the example electric motor coolant channel  615  is returned to the example radiator  285  through the example coolant outlet  620 . The illustrated example of  FIG.  6    represents the example serial thermal management system described above in connection with  FIG.  2 B . 
     In the illustrated example of  FIG.  6   , the example electric motor coolant channel  615  provides coolant to the example electric motor  205 . The coolant in the example electric motor coolant channel  615  absorbs heat generated by the example electric motor  205 . The example electric motor coolant channel  615  obtains the coolant from the coolant channel in the example cooling ring  225 . In the illustrated example of  FIG.  6   , the example electric motor coolant channel  615  is coupled to the outer surface of the example electric motor  205 . In the illustrated example of  FIG.  6   , the example coolant outlet  620  is coupled to the example electric motor coolant channel  615  through an opening in the example inverter  215  and the example electric motor coolant channel  615 . In some examples, the example electric motor coolant channel  615  is similar to the example coolant channel  220 A. 
     In the illustrated example of  FIG.  6   , the example capacitor elements  630 A,  630 B,  630 C generate high-frequency, time-varying power for the example inverter phases  635 A,  635 B,  635 C. In some examples, the example capacitor elements  630 A,  630 B,  630 C are included in the example capacitor ring  230  of  FIG.  2 B . In some examples, the example inverter phases  635 A,  635 B,  635 C are similar to the example inverter phase  217  of  FIG.  2 B . 
     In the illustrated example of  FIG.  6   , the example inverter phases  635 A,  635 B,  635 C include the example power boards  640 A,  640 B,  640 C. In some examples, the example power boards  640 A,  640 B,  640 C obtains power from the example inverter phases  635 A,  635 B,  635 C. In some examples, the power boards  640 A,  640 B,  640 C obtain the AC power generated by the example inverter phases  635 A,  635 B,  635 C. In some examples, the example power boards  640 A,  640 B,  640 C output the power via an example power output. For examples, the example power board  640 A outputs the power from the example inverter phase  635 A via the example power output  645 . In the illustrated example of  FIG.  6   , the example power boards  640 B and  640 C are illustrated using dashed lines to show placement in the example heat exchanger system  600  since they are not visible in the illustrated cross-section view of  FIG.  6   . 
     In the illustrated example of  FIG.  6   , the example control board  650  controls the example power boards  640 A,  640 B,  640 C of the example inverter phases  635 A,  635 B,  635 C. In some examples, the example power boards  640 A,  640 B,  640 C include control inputs. For example, the example power board  640 A includes the example control input  655 . In some examples, the example control board  650  provides control inputs to the example power boards  640 A,  640 B,  640 C via the example flying leads  660 A,  660 B,  660 C. In the illustrated example of  FIG.  6   , portions of the example flying leads  660 B and  660 C are illustrated using dashed lines to show placement in the example heat exchanger system  600  since they are not visible in the illustrated cross-section view of  FIG.  6   . 
     In the illustrated example of  FIG.  6   , the example electric motor  205  is coupled to the example motor shaft  240 . The example motor shaft  240  is coupled to the example gearbox  665 . In the illustrated example, the gearbox  665  is representative of the example driver gear  245 , the example idle (coupling) gear  250 , the example load gear  270 , and the example common shaft  275  of  FIG.  2 B . 
       FIG.  7    is a perspective view of the three phases of the example inverter  215  of the example electric drive system  200  of  FIG.  2 A . The assembly  700  of  FIG.  7    includes the example electric motor  205 , the example cooling ring  225 , the example capacitor ring  230 , the example motor shaft  240 , and the example gearbox  630 . The illustrated example of  FIG.  7    includes an example first inverter phase  705 , an example second inverter phase  710 , an example third inverter phase  715 , and an example pressurized connection  720  between example first inverter phase  705  and example capacitor ring  230 . 
     In the illustrated example of  FIG.  7   , the first inverter phase  705 , the second inverter phase  710 , and the third inverter phase  715  are coupled to the electrical output of the example electric motor  205 . The example first inverter phase  705  is located one hundred twenty degrees from the example second inverter phase  710  on one side of the first inverter phase  705  and one hundred twenty degree from the example third inverter phase  715  on the other side of the first inverter phase  705 . In the illustrated example of  FIG.  7   , the example second inverter phase  710  is located one hundred twenty degrees clockwise from the example first inverter phase  705 , and the third inverter phase  715  is located one hundred twenty degrees counterclockwise from the example first inverter phase  705 . The example second inverter phase  710  and the example third inverter phase  715  are also located one hundred twenty degrees from each other on the surface of the example electric motor  205 . In the illustrated example of  FIG.  7   , the first inverter phase  705 , the second inverter phase  710 , and the third inverter phase  715  are equally spaced around the surface of the example electric motor  205 . In some examples, the example first inverter phase  705 , the example second inverter phase  710 , and the example third inverter phase  715  are substantially similar to the example inverter  215  of the example electric drive system  200  of  FIG.  2 A . In the illustrated example of  FIG.  7   , the example first inverter phase  705 , the second inverter phase  710 , and the third inverter phase  715  are open cylindrical shapes to fit over the cylindrical shape of the example electric motor  205 . 
     In the illustrated example of  FIG.  7   , the example pressurized connection  720  represents the connection between the example capacitor ring  230  and the example first inverter phase  705 . The example pressurized connection  720  includes a pressurized connection for positive DC power and a pressurized connection for negative DC power. In the illustrated example, the second inverter phase  710  and the third inverter phase  715  have connections with the example capacitor ring  230  that are substantially similar to the example pressurized connection  720 . 
     In the illustrated example of  FIG.  7   , the example cooling ring  225  covers the connection between the example first inverter phase  705  and the example electric motor  205 , the connection between the example second inverter phase  710  and the example electric motor  205 , and the connection between the example third inverter phase  715  and the example electric motor  205 . In the illustrated example, the first inverter phase  705  has a terminal that connects with a first terminal from the example electric motor  205 . In the illustrated example, the second inverter phase  710  has a terminal that connects with a second terminal from the example electric motor  205 . In the illustrated example, the third inverter phase  715  has a terminal that connects with a third terminal from the example electric motor  205 . The connections of the example first inverter phase  705 , the example second inverter phase  710 , and the example third inverter phase  715  with the example electric motor  205  are described in further detail below in connection with  FIG.  8   . 
       FIGS.  8 A,  8 B, and  8 C  are perspective views of example lap joint connections between the example electric motor  205  and the example inverter  215  the example electric drive system  200  of  FIG.  2 A . The assembly  800  of  FIG.  8 A  includes the example electric motor  205 , the example cooling ring  225 , the example first inverter phase  705 , the example second inverter phase  710 , and the example third inverter phase  715 . The assembly  800  of  FIG.  8 A  includes example stator windings  805 , an example inverter power terminal  810 , and example motor power terminal  815 , and an example lap joint connection  820 . 
     In the illustrated example of  FIG.  8 A , the example electric motor  205  includes example stator windings  805  that help to produce a magnetic field for the example electric motor  205 . In the illustrated example of  FIG.  8 A , the stator windings  805  are represented as stator coils placed in stator slots of the example electric motor  205 . In some examples, the example stator windings  805  include copper, however, other conductive materials may additionally or alternatively be used including stator body fabricated using 3-D printing technology and magnet wire-based winding placed in uniquely created stator slots using flexibilities of the 3-D printing technology to print metal forms. 
     In the illustrated example of  FIG.  8 A , the example first inverter phase  705  is coupled to the example inverter power terminal  810 . The example inverter power terminal  810  collects AC power from the example first inverter phase  705 . In the illustrated example of  FIG.  8 A , the example electric motor  205  is coupled to the example motor power terminal  815 . The example motor power terminal  815  provides the AC power from the example first inverter phase  705  to the example electric motor  205 . In the illustrated example of  FIG.  8 A , the example inverter power terminal  810  is coupled to the example motor power terminal  815  using the example lap joint  820 . The example lap joint  820  is described in further detail below in connection with  FIGS.  8 B and  8 C . In the illustrated example of  FIG.  8 A , the example second inverter phase  710  and the example third inverter phase  715  include lap joint connections to the example electric motor  205  that are substantially similar to the example lap joint  820 . 
       FIG.  8 B  is an illustrated example of the lap joint  820  of  FIG.  8 A . The illustrated example of  FIG.  8 B  includes the example before joining  823  representation and example after joining  826  representation. The illustrated example of  FIG.  8 B  includes example bolts  830 ,  835 , an example inverter power terminal  840 , an example motor power terminal  845 , and example guiding pins  850 A,  850 B. In some examples, the example inverter power terminal  840  is substantially similar to the example inverter power terminal  810 . In some examples, the example motor power terminal  845  is substantially similar to the example motor power terminal  815 . 
     The illustrated example of  FIG.  8 B  is representative of an example grooved-style lap joint. In the illustrated example of  FIG.  8 B , the surface of the example inverter power terminal  840  and the surface of the example motor power terminal  845  are grooved. The grooved surfaces of the example inverter power terminal  840  and the example motor power terminal  845  help to increase the surface area of the lap joint connection, resulting in substantial decrease in the electrical resistance for the connection between example inverter power terminal  840  and example motor power terminal  845 . In the illustrated example of  FIG.  8 B , the example motor power terminal  845  includes the example guiding pins  850 A,  850 B. The example guiding pins  850 A,  850 B help to align the example inverter power terminal  840  and the example motor power terminal  845 . In the illustrated example of  FIG.  8 B , the example bolts  830 ,  835  secure the lap joint connection between the example inverter power terminal  840  and the example motor power terminal  845 . In the illustrated example of  FIG.  8 B , the example before joining  823  represents the lap joint between the example inverter power terminal  840  and the example motor power terminal  845  before the connection is made. In the illustrated example of  FIG.  8 B , the example after joining  826  represents the lap joint between the example inverter power terminal  840  and the example motor power terminal  845  after the connection is made and the example bolts  830 ,  835  are secured. 
       FIG.  8 C  is an alternative example of the lap joint  820  of  FIG.  8 A . The illustrated example of  FIG.  8 C  includes the example before joining  850  representation and example after joining  855  representation. The illustrated example of  FIG.  8 C  includes the example bolts  830 ,  835 , an example inverter power terminal  860 , an example motor power terminal  865 , and example guiding pins  870 A,  870 B. In some examples, the example inverter power terminal  860  is substantially similar to the example inverter power terminal  810 . In some examples, the example motor power terminal  865  is substantially similar to the example motor power terminal  815 . 
     The illustrated example of  FIG.  8 C  is representative of an example smooth-style lap joint. In the illustrated example of  FIG.  8 C , the surface of the example inverter power terminal  860  and the surface of the example motor power terminal  865  are smooth. The smooth surfaces of the example inverter power terminal  860  and the example motor power terminal  865  help make aligning the surfaces for the lap joint connection easier. In the illustrated example of  FIG.  8 C , the example motor power terminal  865  includes the example guiding pins  870 A,  870 B. The example guiding pins  870 A,  870 B help to align the example inverter power terminal  860  and the example motor power terminal  865 . In the illustrated example of  FIG.  8 C , the example bolts  830 ,  835  secure the lap joint connection between the example inverter power terminal  860  and the example motor power terminal  865 . In the illustrated example of  FIG.  8 C , the example embodiment before joining  850  represents the lap joint between the example inverter power terminal  860  and the example motor power terminal  865  before the connection is made. In the illustrated example of  FIG.  8 C , the example embodiment after joining  855  represents the lap joint between the example inverter power terminal  860  and the example motor power terminal  865  after the connection is made and the example bolts  830 ,  835  are secured. 
     “Including” and “comprising” (and all forms and tenses thereof) are used herein to be open ended terms. Thus, whenever a claim employs any form of “include” or “comprise” (e.g., comprises, includes, comprising, including, having, etc.) as a preamble or within a claim recitation of any kind, it is to be understood that additional elements, terms, etc. may be present without falling outside the scope of the corresponding claim or recitation. As used herein, when the phrase “at least” is used as the transition term in, for example, a preamble of a claim, it is open-ended in the same manner as the term “comprising” and “including” are open ended. The term “and/or” when used, for example, in a form such as A, B, and/or C refers to any combination or subset of A, B, C such as (1) A alone, (2) B alone, (3) C alone, (4) A with B, (5) A with C, (6) B with C, and (7) A with B and with C. As used herein in the context of describing structures, components, items, objects and/or things, the phrase “at least one of A and B” is intended to refer to implementations including any of (1) at least one A, (2) at least one B, and (3) at least one A and at least one B. Similarly, as used herein in the context of describing structures, components, items, objects and/or things, the phrase “at least one of A or B” is intended to refer to implementations including any of (1) at least one A, (2) at least one B, and (3) at least one A and at least one B. As used herein in the context of describing the performance or execution of processes, instructions, actions, activities and/or steps, the phrase “at least one of A and B” is intended to refer to implementations including any of (1) at least one A, (2) at least one B, and (3) at least one A and at least one B. Similarly, as used herein in the context of describing the performance or execution of processes, instructions, actions, activities and/or steps, the phrase “at least one of A or B” is intended to refer to implementations including any of (1) at least one A, (2) at least one B, and (3) at least one A and at least one B. 
     As used herein, singular references (e.g., “a,” “an,” “first,” “second,” etc.) do not exclude a plurality. The term “a” or “an” entity, as used herein, refers to one or more of that entity. The terms “a” (or “an”), “one or more,” and “at least one” can be used interchangeably herein. Furthermore, although individually listed, a plurality of means, elements or method actions may be implemented by, e.g., a single unit or processor. Additionally, although individual features may be included in different examples or claims, these may possibly be combined, and the inclusion in different examples or claims does not imply that a combination of features is not feasible and/or advantageous. 
     From the foregoing, it will be appreciated that example methods, apparatus and articles of manufacture have been disclosed for electric drive systems. The disclosed methods, apparatus and articles of manufacture improve the efficiency of electric drive systems. 
     Although certain example methods, apparatus and articles of manufacture have been disclosed herein, the scope of coverage of this patent is not limited thereto. On the contrary, this patent covers all methods, apparatus and articles of manufacture fairly falling within the scope of the claims of this patent. 
     The following claims are hereby incorporated into this Detailed Description by this reference, with each claim standing on its own as a separate embodiment of the present disclosure.