Electrical machine with cooled busbars

An electrical machine includes an electric motor, a cooling jacket over the electric motor, and a power inverter having multiple AC power outlets. The electrical machine also includes an elongated busbar having an end adjacent to and coupled to an AC power outlet. The other end of the elongated busbar is adjacent to and coupled to the electric motor. The elongated busbar traverses from one end of the electric motor to a second end of the electric motor over, and in thermal contact with, the cooling jacket so as to reduce a high temperature at the electric motor to a low temperature at the AC power outlet.

BACKGROUND

The efficient delivery of electrical power for use in driving an electric motor is of ever increasing importance as the transition from fossil fuel based vehicle technologies to green vehicle technologies continues. Electric and electric hybrid vehicles, for example, typically utilize one or more power inverters to convert DC power received from a battery to AC power for use by electric motors to propel the vehicle. One technical challenge posed by interfacing a power inverter with an electric motor is that the operating temperatures routinely generated by the electric motor can damage the heat sensitive transistors in the power inverter.

One conventional approach for transferring AC power to an electric motor utilizes relatively long, flexible cables to connect the AC outputs of the power inverter to the electric motor. Although such a conventional approach offers thermal protection to the power inverter by distancing it from the electric motor, a significant disadvantage of the approach is the amount of space required for its implementation. As demand for electric and hybrid vehicles continues to grow, the need for a more compact solution for interfacing a power inverter with an electric motor that concurrently provides thermal protection for the power inverter becomes increasingly important.

SUMMARY

The present disclosure is directed to electrical machines with cooled busbars, substantially as shown in and/or described in connection with at least one of the figures, and as set forth more completely in the claims.

DETAILED DESCRIPTION

As stated above, the efficient delivery of electrical power for use in driving an electric motor is of ever increasing importance as the transition from fossil fuel based vehicle technologies to green vehicle technologies continues. As further stated above, as demand for electric and hybrid vehicles continues to grow, the need for a more compact solution for interfacing a power inverter with an electric motor that concurrently provides thermal protection for the power inverter becomes increasingly important.

The present application addresses the electrical power delivery challenges described above by disclosing an efficient, compact, and low cost solution for interfacing an electric motor with a power inverter. By enabling a substantially direct connection between the AC outputs of a power inverter and the electric motor receiving the AC power, the present solution advantageously eliminates the cost and space requirements imposed by the conventional use of cables for accommodating a power inverter/motor interface. Moreover, by effectively cooling the high current carrying conductors connecting the power inverter to the motor, the present solution provides robust thermal protection for the transistors used to implement the power inverter.

FIG. 1shows a perspective view of exemplary electrical machine100. According to the exemplary implementation shown inFIG. 1, electrical machine100includes electric motor110having first motor endcap112adjacent first end102of electric motor110, and second motor endcap114adjacent second end104of electric motor110. As further shown inFIG. 1, electric motor110has cooling jacket120situated thereover. Cooling jacket120includes coolant inlet122, coolant outlet124, and at least one cooling channel (not visible from the perspective ofFIG. 1) for cooling electric motor110. In addition, cooling jacket120includes heat sink126having three conduct slots128thereon.

Also shown inFIG. 1are non-conductive blocks144adjacent first end102and second end104of electric motor110and electrical insulation layer140. Electrical machine100may be implemented as part of a power train of an electric or hybrid electric vehicle, for example. Thus, electric motor110may be a traction motor for driving a wheel axle of such a vehicle.

As shown inFIG. 1each of elongated busbars142a,142b, and142chas a first end adjacent first end102of electric motor110, and a second end adjacent second end104of electric motor110. In other words, elongated busbar142ahas first end146aand second end148a, while elongated busbars142band142chave respective first ends146band146c, and respective second ends148b, and148c.

Despite being referred to as “busbars” in the present application, elongated busbars142a,142b, and142cmay take any of several different forms. For example, although as shown inFIG. 1, elongated busbars142a,142b, and142cmay take the form of rectangular electrically conductive bars, in other implementations, elongated busbars142a,142b, and142cmay be cylindrical, such as electrically conductive rods. Moreover, in yet other implementations, elongated busbars142a,142b, and142cmay be triangular busbars, or may be curved between their respective first and second ends, such as by being implemented as spiral busbars, for example.

Elongated busbars142a,142b, and142cmay be implemented using any suitable materials. For example, in the exemplary electric or hybrid electric vehicle implementation described above, elongated busbars142a,142b, and142cmay include a metal such as copper, or a first metal coated with a second metal, such as copper coated with tin. Moreover, in that implementation, elongated busbars142a,142b, and142cmay have a length, i.e., the distance between their respective first and second ends, of approximately two hundred millimeters (200 mm), and a width of approximately 22 mm, for example.

According to the exemplary implementation shown inFIG. 1, each of elongated busbars142a,142b, and142cis situated in a respective conduct slot128of cooling jacket120, and is mechanically supported at its respective first and second ends by non-conductive blocks144, which may be plastic blocks, for example. In addition, each of second ends148a,148b, and148cof respective elongated busbars142a,142b, and142cis adjacent to and coupled to one phase of an end winding of electric motor110(end windings not visible from the perspective ofFIG. 1).

As further shown inFIG. 1, elongated busbars142a,142b, and142cmay be partially wrapped by electrical insulation layer140, which may be any electrically insulating but thermally conductive material, and may be implemented as a paper layer, such as a Nomex® paper layer, for example. It is noted that inFIG. 1, electrical insulation layer140underlies each of elongated busbars142a,142b, and142cin its respective conduct slot128of cooling jacket120. In other words, electrical insulation layer140is situated between each of elongated busbars142a,142b, and142cand cooling jacket120.

It is noted that, during operation, electric motor110generates substantial heat. Cooling jacket120is situated over electric motor110and provides cooling for electric motor110. Cooling jacket120may receive a flow of coolant, such as water or any suitable cooling fluid or fluid mix for example, through coolant inlet122, may circulate the coolant over surface portions of electric motor110, and may expel the heated coolant through coolant outlet124.

Despite the cooling provided to electric motor110by cooling jacket120, the end windings of electric motor110may reach a temperature of between approximately 150-160° C. during routine operation of electric motor110. Moreover, because each of second ends148a,148b, and148cof respective elongated busbars142a,142b, and142cis coupled to an end winding of electric motor110adjacent second end104of electric motor110, second ends148a,148b, and148cof respective elongated busbars142a,142b, and142ctoo may be at or near a temperature of 150° C.

According to the exemplary implementation shown inFIG. 1, elongated busbars142a,142b, and142ctraverse electric motor110from first end102to second end104, over, and in thermal contact with, cooling jacket120. Cooling jacket120, including heat sink126and conduct slots128, removes heat from and thereby cools elongated busbars142a,142b, and142cbetween second end104and first end102of electric motor110. Consequently, elongated busbars142a,142b, and142creduce a high temperature at second ends148a,148b, and148cof respective elongated busbars142a,142b, and142cto a low temperature at first ends146a,146b, and146cof respective elongated busbars142a,142b, and142c.

FIG. 2shows an exploded view of exemplary electrical machine200with power inverter230, according to one implementation. As shown inFIG. 2, electrical machine200includes electric motor210, and power inverter230interfaced with electric motor210by inverter busbars232a,232b, and232c, and respective elongated busbars242a,242b, and242c.

According to the exemplary implementation shown inFIG. 2, electric motor210includes first motor endcap212adjacent first end202of electric motor210, and second motor endcap214adjacent second end204of electric motor210. As further shown inFIG. 2, electric motor210has cooling jacket220including coolant inlet222, coolant outlet224, and at least one cooling channel216for cooling electric motor210. In addition, cooling jacket220includes heat sink226having three conduct slots228thereon. Also shown inFIG. 2are non-conductive blocks244adjacent first end202and second end204of electric motor210, electrical insulation layer240, thermally conductive cover250situated over elongated busbars242a,242b, and242c, and AC power outlets234a,234b, and234cof power inverter230.

Non-conductive blocks244and electrical insulation layer240correspond in general to non-conductive blocks144and electrical insulation layer140inFIG. 1, and each of those corresponding features may share any of the characteristics attributed to either corresponding feature in the present disclosure. Also, electric motor210, cooling jacket220, elongated busbars242a,242b, and242c, and conduct slots228correspond respectively in general to electric motor110, cooling jacket120, elongated busbars142a,142b, and142c, and conduct slots128inFIG. 1, and each of those corresponding features may share any of the characteristics attributed to either corresponding feature in the present disclosure. That is to say, each of elongated busbars242a,242b, and242cis situated in a respective conduct slot228on heat sink226of cooling jacket220.

Electrical machine200may be implemented as part of a power train of an electric or hybrid electric vehicle, for example. Thus, electric motor110/210may be a traction motor for driving a wheel axle of such a vehicle. In such an implementation, power inverter230may be used to receive DC power from a battery of the vehicle, to convert the DC power to AC power, and to output the AC power to electric motor110/210via AC power outlets234a,234b, and234cconnected respectively to inverter busbars232a,232b, and232c. As a specific example, power inverter230may provide an AC output at AC power outlets234a,234b, and234chaving an output voltage of about three hundred and fifty volts (350V), and an output current of about three hundred and eighty amperes (380 A). More generally, however, the inventive principles disclosed herein may be implemented in high power transfer applications, such as megawatt (MW) power transfer applications, for example.

In some implementations, power inverter230may utilize an array of power switches, such as insulated-gate bipolar transistors (IGBTs) for example, to convert a DC input to AC power for delivery to electric motor110/210. As noted above, during operation, electric motor110/210generates substantial heat. Despite the cooling provided to electric motor110/210by cooling jacket120/220, the end windings of electric motor110/210(end windings not visible from the perspective ofFIG. 1) may reach a temperature of between approximately 150-160° C. during routine operation of electric motor110.

Moreover, because each of elongated busbars142a/242a,142b/242b, and142c/242cis coupled to one phase of an end winding of electric motor110/210adjacent second end104/204of electric motor110/210, those elongated busbars too may be at or near a temperature of 150° C. at their respective second ends148a,148b, and148c. However, the IGBTs or other power switches utilized to implement power inverter230may experience thermal damage and/or failure at temperatures substantially lower than 150° C., such as at a temperature of approximately 110° C.

Elongated busbars142a/242a,142b/242b, and142c/242ctraverse electric motor110/210from first end102/202to second end104/204, over, and in thermal contact with, cooling jacket120/220. Cooling jacket120/220, including heat sink126/226and conduct slots128/228, removes heat from and thereby cools elongated busbars142a/242a,142b/242b, and142c/242cbetween second end104/204and first end102/202of electric motor110/210. Additional cooling of elongated busbars142a/242a,142b/242b, and142c/242cbetween second end104/204and first end102/202of electric motor110/210may be provided by thermally conductive cover250situated over elongated busbars142a/242a,142b/242b, and142c/242c. Consequently, elongated busbars142a/242a,142b/242b, and142c/242creduce a high temperature at the motor end windings adjacent second end104/204of electric motor110/210to a low temperature at AC power outlets234a,234b, and234cof power inverter230adjacent first end102/202of electric motor110/210.

FIG. 3shows an unexploded perspective view of an exemplary electrical machine300with power inverter330, according to one exemplary implementation. Electrical machine300includes electric motor310, and power inverter330interfaced with electric motor310by inverter busbars332a,332b, and332cand respective elongated busbars342a,342b, and342c. As shown inFIG. 3, electric motor310has first motor endcap312and second motor endcap314, and includes cooling jacket320thereover. Cooling jacket320includes coolant inlet322, coolant outlet324, and heat sink326. Also shown inFIG. 3are non-conductive blocks344, electrical insulation layer340, and AC power outlets334a,334b, and334cof power inverter330.

Electric motor310, cooling jacket320, inverter busbars332a,332b, and332c, and elongated busbars342a,342b, and342ccorrespond respectively in general to electric motor110/210, cooling jacket120/220, inverter busbars232a,232b, and232cand elongated busbars142a/242a,142b/242b, and142c/242c, inFIGS. 1 and/or 2, and each of those corresponding features may share the characteristics attributed to any corresponding feature in the present disclosure. That is to say, like electric motor110/210, electric motor310, inFIG. 3, has first end102/202adjacent first motor endcap312, second end104/204adjacent second motor endcap314.

Analogously, in addition to coolant inlet322, coolant outlet324, and heat sink326, cooling jacket320includes one or more cooling channels corresponding to cooling channel216, inFIG. 2. Furthermore, like cooling jacket120/220, cooling jacket320includes multiple conduct slots such as conduct slots128/228. In addition, electrical insulation layer340and non-conductive blocks344correspond respectively in general to electrical insulation layer140/240and non-conductive blocks144/244, inFIGS. 1 and 2, and each of those corresponding features may share the characteristics attributed to any corresponding feature in the present disclosure. Thus, non-conductive blocks344may be plastic blocks, and electrical insulation layer340may be an electrically insulating but thermally conductive paper layer, such as a Nomex® paper layer, for example.

Power inverter330including AC power outlets334a,334b, and334ccorresponds in general to power inverter230including AC power outlets234a,234b, and234c, inFIG. 2, and each of those corresponding features may share any of the characteristics attributed to either corresponding feature in the present disclosure. That is to say, power inverter330may utilize an array of power switches, such as IGBTs for example, to convert a DC input to AC power for delivery to electric motor310via AC power outlets334a,334b, and334c. It is noted that electrical machine300is depicted inFIG. 3as though seen through power inverter330and as though seen through a thermally conductive cover corresponding to thermally conductive cover250, inFIG. 2.

Inverter busbars232a/332a,232b/332b, and232c/332cmay assume any of a variety of forms, and may be implemented using any materials and having any dimensions suitable to support the AC power delivered to electric motor310via AC power outlets234a/334a,234b/334b, and234c/334c. Each of inverter busbars232a/332a,232b/332b, and232c/332chas a first end adjacent to and connected to a respective one of AC power outlets234a/334a,234b/334b, and234c/334c, and a second end adjacent to and coupled to a first end of a respective one of elongated busbars142a/242a/342a,142b/242b/342b, and142c/242c/342c. In other words, inverter busbar232a/332ahas first end336aadjacent to and connected to AC power outlet234a/334a, and second end338aadjacent to and connected to first end146a/346aof elongated busbar142a/242a/342a. Inverter busbars232b/332band232c/332care similarly connected to respective AC power outlets234b/334band234c/334cof power inverter130/330at their own respective first ends, and similarly have their second ends adjacent to and connected to the first ends of respective elongated busbars142b/242b/342b, and142c/242c/342c.

FIG. 4shows an exemplary temperature gradient of elongated busbar442when used as part of an electrical machine with a power inverter, according to one implementation. As shown inFIG. 4, elongated busbar442has first end446and opposite second end448. Also shown inFIG. 4is shading indexed temperature key460corresponding to temperatures measurable along a length of elongated busbar442between second end448and first end446.

Elongated busbar442corresponds in general to any of elongated busbars142a/242a/342a,142b/242b/342b, and142c/242c/342c, inFIGS. 1, 2, and 3, and each of those corresponding features may share the characteristics attributed to any corresponding feature in the present disclosure. That is to say, in operation, elongated busbar442is implemented so as to have first end446adjacent to and connected to a second end of any of inverter busbars232a/332a,232b/332b, or232c/332c, and so as to have second end448adjacent to and coupled to one phase of an end winding of electric motor110/210/310adjacent second end104/204of electric motor110/210/310.

As noted above, despite the cooling provided to electric motor110/210/310by cooling jacket120/220/320, the end windings of electric motor110/210/310may reach a temperature of between approximately 150-160° C. during routine operation of electric motor110/210/310. In addition, and due to its vicinity to and coupling to an end winding of electric motor110/220/310, second end448of elongated busbar442may also be at or near a temperature of 150° C. However, and as further noted above, the IGBTs or other power switches used to implement power inverter130/330may experience thermal damage and/or failure at temperatures substantially lower than 150° C., such as at a temperature of approximately 110° C.

Due to its traversal of electric motor110/210/310from first end102/202to second end104/204, over, and in thermal contact with, cooling jacket120/220/320, elongated busbar442is cooled between second end448and first end446. Additional cooling of elongated busbar442between second end448and first end446may be provided by thermally conductive cover250situated over elongated busbar442(i.e. any of elongated busbars142a/242a/342a,142b/242b/342b, and142c/242c/342c). Consequently, elongated busbar442has a high temperature T1at second end448, and a low temperature T2at first end446.

Moreover, the low temperature T2at first end446, which is thermally coupled to AC power outlets234a/334a,234b/334b,234c/334cvia respective inverter busbars232a/332a,232b/332b,232c/332cis sufficiently low to prevent thermal damage to power switching module456. In other words, low temperature T2at first end446of elongated busbar442can be less than approximately 110° C. Thus AC power outlets234a/334a,234b/334b,234c/334cof power inverter130/330are effectively cooled despite being interfaced with electric motor110/210/310.

FIG. 5shows electrical machine500, according to another exemplary implementation. As shown inFIG. 5, electrical machine500includes electric motor510having first motor endcap512and second motor endcap514, cooling jacket520having coolant inlet522, coolant outlet524, and heat sink526, and elongated busbars542a,542b, and542c. In addition, electrical machine500includes non-conductive blocks544and electrical insulation layer540. According to the exemplary implementation shown inFIG. 5, elongated busbars542a,542b, and542cinclude one or more curves between their respective first and second ends. Moreover, in some implementations, elongated busbars542a,542b, and542cmay take the form of spiral busbars, for example.

Electric motor510and cooling jacket520correspond respectively in general to electric motor110/210/310and cooling jacket120/220/320, inFIGS. 12and3, and each of those corresponding features may share the characteristics attributed to any corresponding feature in the present disclosure. That is to say, like electric motor110/210/310, electric motor510has first end102/202adjacent first motor endcap512, second end104/204adjacent second motor endcap514, and end windings coupled to second ends548a,548b, and548cof respective elongated busbars542a,542b, and542cadjacent second end104/204of electric motor510.

Analogously, in addition to coolant inlet522, coolant outlet524, and heat sink526, cooling jacket520includes one or more cooling channels corresponding to cooling channel216, inFIG. 2. Furthermore, like cooling jacket120/220, cooling jacket520includes multiple conduct slots128/228. It is noted that, according to the exemplary implementation shown inFIG. 5, each of elongated busbars542a,542b, and542cis situated in a respective conduct slot on heat sink526of cooling jacket520. It is further noted that electrical machine500is depicted inFIG. 5as though seen through a thermally conductive cover corresponding to thermally conductive cover250, inFIG. 2.

As further shown inFIG. 5, each of elongated busbars542a,542b, and542chas a first end adjacent the first end of electric motor510, and a second end adjacent the second end of electric motor510. In other words, elongated busbar542ahas first end546aand second end548a, while elongated busbars542band542chave respective first ends546band546c, and respective second ends548b, and548c. As shown inFIG. 5, according to the present exemplary implementation, elongated busbars542a,542b, and542cmay take the form of curved busbars.

Elongated busbars542a,542b, and542cmay be implemented using any materials, and having any dimensions, suitable to support the AC power delivered to electric motor510by a power inverter corresponding to power inverter230/330, inFIGS. 2 and 3. For example, in the exemplary electric or hybrid electric vehicle implementation described above, elongated busbars542a,542b, and542cmay include a metal such as copper, or a first metal coated with a second metal, such as copper coated with tin. Moreover, in that implementation, elongated busbars542a,542b, and542cmay have a length, i.e., the distance between their respective first and second ends, of less than approximately 200 mm, and/or a width of less than approximately 22 mm, for example.

According to the exemplary implementation shown inFIG. 5, each of elongated busbars542a,542b, and542cis situated in a conduct slot of cooling jacket620corresponding to conduct slots128and228, inFIGS. 1 and 2, and is mechanically supported at its respective first and second ends by non-conductive blocks544, which may be plastic blocks, for example. As further shown inFIG. 5, each of elongated busbars542a,542b, and542cmay be partially wrapped by electrical insulation layer540, which may be any electrically insulating but thermally conductive material, and may be implemented as a paper layer, such as a Nomex® paper layer, for example. It is noted that inFIG. 5, electrical insulation layer540underlies each of elongated busbars542a,542b, and542cin its respective conduct slot of cooling jacket520. In other words, electrical insulation layer540is situated between each of elongated busbars542a,542b, and542cand cooling jacket520.

Due to their respective traversals of electric motor510from first end102/204to second end104/204, over, and in thermal contact with, cooling jacket520, elongated busbars542a,542b, and542care cooled between their respective second ends548a,548b, and548cand their respective first ends546a,546b, and546c. Additional cooling of busbars542a,542b, and542cbetween their respective second and first ends may be provided by thermally conductive cover250situated over elongated busbars542a,542b, and542c. Consequently, and referring toFIG. 4, elongated busbars542a,542b, and542chave a high temperature T1at their respective second ends548a,548b, and548c, and a low temperature T2at their respective first ends546a,546b, and546c.

It is noted that the heat dissipation efficiency of elongated busbars542a,542b, and542cis determined by their effective length and width. By implementing elongated busbars542a,542b, and542cas curved or spiral busbars, the effective length of elongated busbars542a,542b, and542cmay be increased without increasing the linear distance between first ends546a,546b, and546c, and respective second ends548a,548b, and548c. As a result, considerable design variations are enabled.

For example, elongated busbars542a,542b, and542cmay be narrower while still providing the same amount of heat dissipation. Alternatively, elongated busbars542a,542b, and542ccan be utilized with a more compact electric motor, i.e., one for which first end102/202and second end104/204inFIGS. 1 and 2are more closely situated. As yet another variation, curved or spiral busbars having substantially the same linear length and width as elongated busbar442, for example, may deliver more AC power while providing adequate heat dissipation.

Thus, the present application discloses an efficient, compact, and low cost solution for interfacing an electric motor with one or more power inverters. By enabling a substantially direct connection between the AC outputs of a power inverter and the electric motor receiving the AC power, the present solution advantageously eliminates the cost and space requirements imposed by the conventional use of cables for mediating an inverter/motor interface. Moreover, by effectively cooling the high current carrying conductors, for example the busbars, connecting the power inverter to the motor, the present solution provides robust thermal protection for the transistors used to implement the power inverter.

It is noted that the inventive electrical machine with cooled busbars disclosed by the present application can advantageously be implemented with a variety of different types of power inverters having different cooling capabilities. Furthermore, the solution for interfacing an electric motor with a power inverter disclosed herein advantageously enables direct connection of the electric motor and the power inverter regardless of the cooling capability of the power inverter. It is further noted that in various implementations of the present disclosure, the various busbars may be flat busbars (rectangular or curved), or cylindrical busbars, such as electrically conductive rods, triangular busbars, or even spiral busbars.