CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This PCT International Patent Application claims the benefit of and priority to U.S. Provisional Patent Application Serial No. 63/353,324, filed June 17, 2022, titled “Low- Inductance Bus Bar With Dual-Sided Welding Connection,” the entire disclosure of which is hereby incorporated by reference.

FIELD

[0002] The present disclosure relates generally to electrical conductors. More specifically, the present disclosure relates to bus bar type electrical conductors with low inductance for high-voltage direct current applications.

BACKGROUND

[0003] Electrical conductors in the form of bus bars including elongate strips of solid metal are used in a variety of applications. Bus bars are commonly used in electrified vehicle applications for transmitting alternating current (AC) and direct current (DC) power. In one application, bus bars may provide an interconnect between a power module that generates and/or regulates a high-voltage DC power, and one or more sources and/or loads, such as a battery pack, a rectifier, and/or an inverter that converts the high-voltage DC power to and from an AC power for application to a motor or a motor/generator.

[0004] Such a high-voltage DC bus may include separate bus bar conductors for each of a DC positive (DC+) and DC negative (DC-) nodes. One or more DC-link capacitors may be connected between the DC+ and DC- bus bars to regulate the DC power thereupon.

[0005] In conventional designs, the high-voltage (HV) DC+ and DC- bus bars may be be arranged side-by-side to enable a physical connection between a DC power module and a DC-link capacitor by e.g. screwing or welding from one side. This side by side arrangement can cause a high induction loop, which results in high current overshoots during switching.

[0006] It is an object of the present disclosure to provide a HV DC bus bar interconnection between a power module and a DC-link capacitor with minimum/as-low-as- possible induction. The reduced induction may enable low overshoot semiconductor switching. It is a further object of the present disclosure to provide a connection method for such a low- induction HV DC bus bar interconnection.

SUMMARY

[0007] The present disclosure provides a direct current (DC) bus assembly. The DC bus assembly includes a positive bus bar configured to be energized with a positive DC voltage. The positive bus bar extends along a first length and has a first width perpendicular to the first length and a first thickness in a direction perpendicular to each of the first width and the first length. The first thickness is substantially shorter than each of the first width and the first length. The DC bus assembly also includes a negative bus bar configured to be energized with a negative DC voltage. The negative bus bar extends along a second length and has a second width perpendicular to the second length and a second thickness in a direction perpendicular to each of the second width and the second length. The second thickness is substantially shorter than each of the second width and the second length. The positive bus bar and the negative bus bar are stacked one over the other. The DC bus assembly also includes a separator of electrically insulating material. The separator is formed as a thin film and is disposed between the positive bus bar and the negative bus bar to provide electrical isolation therebetween. The first thickness and the second thickness together may substantially comprise a total thickness of the DC bus assembly. For example, the thickness of the separator may be negligible compared to the thicknesses of the positive bus bar and the negative bus bar. [0008] The present disclosure also provides a power module for an electrified vehicle. The power module includes a direct current (DC) bus assembly configured to be energized with a high-voltage DC power. The DC bus assembly includes a positive bus bar configured to be energized with a positive DC voltage. The positive bus bar extends along a first length and has a first width perpendicular to the first length and a first thickness in a direction perpendicular to each of the first width and the first length. The first thickness is substantially shorter than each of the first width and the first length. The DC bus assembly also includes a negative bus bar configured to be energized with a negative DC voltage. The negative bus bar extends along a second length and has a second width perpendicular to the second length and a second thickness in a direction perpendicular to each of the second width and the second length. The second thickness is substantially shorter than each of the second width and the second length. The positive bus bar and the negative bus bar are stacked one over the other with the first thickness and the second thickness together comprising a total thickness of the DC bus assembly. The DC bus assembly also includes a separator of electrically insulating material. The separator is formed as a thin film and is disposed between the positive bus bar and the negative bus bar to provide electrical isolation therebetween.

[0009] The present disclosure also provides a method of assembling a DC bus assembly. The method includes: stacking a positive bus bar and a negative bus bar in one-over- the-other configuration with a thin film separator of electrically insulating material disposed therebetween; and energizing the bus bars with a high-voltage direct current (DC) power.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Further details, features and advantages of designs of the invention result from the following description of embodiment examples in reference to the associated drawings.

[0011] FIG. 1 shows a perspective fragmentary view of a DC bus assembly in a power module;

[0012] FIG. 2 shows a cross-section of the DC bus assembly of FIG. 1 and through section A-A;

[0013] FIG. 3 shows a flow chart of steps in a method of assembling a DC bus assembly in accordance with some embodiments of the present disclosure.

DETAILED DESCRIPTION

[0014] Referring to the drawings, the present invention will be described in detail in view of following embodiments.

[0015] An aim of the bus bar design of the present disclosure is to minimize the induction loop by a one-over-the-other bus bar design in the entire power module and a joining technique (e.g., welding) which allows a low inductive connection to a DC-link capacitor (e.g. dual-sided welding). The needed clearance and creepage distance at the one-over-the-other busbar will be provided by an isolation layer (e.g. foil) between the DC+ and DC- bus bars.

[0016] FIG. 1 shows a perspective fragmentary view of a DC bus assembly 10 in a power module 20. The power module 20 may be a component of an electrified vehicle. The power module 20 may generates and/or regulate a high-voltage DC power for supply to one or more loads, such as a battery pack and/or an inverter that converts the high-voltage DC power to an AC power for application to a motor or a motor/generator. The power module 20 may include a printed circuit board 22 having one or more electronic components (not shown), such as power transistors, for regulating power to and/or from the DC bus assembly 10. The DC bus assembly 10 may be energized with a high-voltage DC power, which may have a voltage, for example, of 600 Volts DC or 800 Volts DC. However, other DC voltages may be used.

[0017] The DC bus assembly 10 includes a negative bus bar 30a configured to be energized with a negative DC voltage and extending along a first length and having a first width perpendicular to the first length and a first thickness in a direction perpendicular to each of the first width and the first length and substantially shorter than each of the first width and the first length. For example, the positive bus bar 30a may have a first thickness of 2.0 mm and a first width of 10 to 12 mm, and a first length that is two or more centimeters. These are merely examples, and any of the dimensions may be different, depending on several factors such as the physical layout of a given system and the current carrying requirements for the DC bus assembly 10.

[0018] The DC bus assembly 10 also includes a positive bus bar 30b configured to be energized with a positive DC voltage and extending along a second length and having a second width perpendicular to the second length and a second thickness in a direction perpendicular to each of the second width and the second length and substantially shorter than each of the second width and the second length. For example, the negative bus bar 30b may have a second thickness of 2.0 mm and a second width of 10 to 12 mm, and a second length that is two or more centimeters. These are merely examples, and any of the dimensions may be different, depending on several factors such as the physical layout of a given system and the current carrying requirements for the DC bus assembly 10.

[0019] The negative bus bar 30a and the positive bus bar 30b are stacked one over the other with the first thickness and the second thickness together comprising a total thickness of the DC bus assembly 10. The negative bus bar 30a is shown in the FIGs. as being stacked on top of the positive bus bar 30b, with the positive bus bar 30b located between the negative bus bar 30a and the printed circuit board 22. However, the DC bus assembly 10 of the present disclosure could have an opposite arrangement, with the positive bus bar 30b stacked on top of the negative bus bar 30a.

[0020] The power module 20 also includes a capacitor 24 that is coupled to the DC bus assembly 10. The capacitor 24 may also be called a DC link capacitor and may function to regulate the DC voltage between the negative bus bar 30a and the positive bus bar 30b. The power module 20 may include several such capacitors 24. However, one of the capacitors 24 is shown for ease of description. The capacitor 24 includes a first conductor tab 40a that overlies and located flush against a flat upper surface of the positive bus bar 30a and which is joined thereto for conducting electrical current therebetween. The capacitor 24 also includes a second conductor tab 40b disposed below and flush against a flat lower surface of the negative bus bar 30b and which is joined thereto for conducting electrical current therebetween. The conductor tabs 40a, 40b of the capacitor 24 may have a width that is approximately equal to a width of the bus bars 30a, 30b. The conductor tabs 40a, 40b of the capacitor 24 may each have a thickness of, for example, 1.0 mm. However, the conductor tabs 40a, 40b of the capacitor 24 may have a different width and/or thickness.

[0021] The negative bus bar 30a extends to a first terminal end 34a, defining an end of the length thereof. The positive bus bar 30b extends to a second terminal end 34b, defining an end of the length thereof. In some embodiments, and as shown in FIG. 1, first terminal end 34a and the second terminal end 34b are aligned with one-another, defining a common terminal end 34a, 34b. Alternatively, negative bus bar 30a and the positive bus bar 30b may not share a common terminal end 34a, 34b. Instead, one of the negative bus bar 30a or the positive bus bar 30b may extend for a distance beyond the other one of the bus bars 30a, 30b, with the first terminal end 34a spaced apart from the second terminal end 34b. In some embodiments, the conductor tabs 40a, 40b of the capacitor 24 are each joined to the DC bus assembly 10 adjacent to corresponding ones of the terminal ends 34a, 34b. However, in other embodiments, the conductor tabs 40a, 40b of the capacitor 24 may be joined to the DC bus assembly 10 at one or more locations that are spaced away from the corresponding ones of the terminal ends 34a, 34b. Each of the negative bus bar 30a and the positive bus bar 30b includes side edges that extend between a flat upper surface and a flat tower surface thereof. The side edges may each define a rectangular shape that extends substantially perpendicularly to each of the a flat upper surface and the flat tower surface. However, the side edges may have another shape. For example, the side edges may include flat ends including the terminal ends 34a, 34b, and elongated intermediate sides which may have a bulbous or convex shape.

[0022] FIG. 1 also shows the DC bus assembly 10 including an insulative cover 42, 44 that at least partially surrounds and covers the negative bus bar 30a and the positive bus bar 30b. The insulative cover 42, 44 includes a sheath portion 42 having a tubular shape that is disposed above a flat upper surface of the negative bus bar 30a, and which and wraps under a flat tower surface of the positive bus bar 30b. The insulative cover 42, 44 also includes a peripheral guard 44 that extends around at least a portion of the sides edges of the bus bars 30a, 30b and which overlies the terminal ends 34a, 34b. In some embodiments, the peripheral guard 44 may extend around an entire periphery of the sides edges of the bus bars 30a, 30b. Alternatively, the peripheral guard 44 may extend around only a portion of the sides edges of the bus bars 30a, 30b, including at least the terminal ends 34a, 34b.

[0023] FIG. 2 shows a cross-section of the DC bus assembly 20 of FIG. 1 and through section A-A. FIG. 2 shows a separator 50 of electrically insulating material formed as a thin fdm and disposed between the negative bus bar 30a and the positive bus bar 30b to provide electrical isolation therebetween. The separator 50 must be able to withstand forces and temperatures that can be applied including, for example, force and heat applied as part of a welding process. In some embodiments, and as shown in FIG. 1, the separator 50 extends beyond the terminal ends 34a, 34b and into the peripheral guard 44. [0024] Referring back to FIG. 2, the first conductor tab 40a of the capacitor 24 includes an upward bent edge 42a, and the second conductor tab 40b of the capacitor 24 includes a downward bent edge 42b. These bent edges 42a, 42b may aid in assembly and aligning the bus bars 30a, 30b between the conductor tabs 40a, 40b of the capacitor 24.

[0025] FIG. 2 also shows a first joint 44a, as indicated by a red X, between the first conductor tab 40a and the negative bus bar 30a underlying the first conductor tab 40a. The first joint 44a may provide for enhanced physical and electrical bonding therebetween. The first joint 44a may include a weld that melts together metal of the first conductor tab 40a and the negative bus bar 30a. A first laser beam 46a may be used to form the first joint 44a via a laser welding process. However, other welding methods may be used, such as resistance welding, to form the first joint 44a.

[0026] FIG. 2 also shows a second joint 44b, as indicated by a red X, between the second conductor tab 40b and the positive bus bar 30b overlying the second conductor tab 40b. The second joint 44b may provide for enhanced physical and electrical bonding therebetween. The second joint 44b may include a weld that melts together metal of the second conductor tab 40b and the positive bus bar 30b. A second laser beam 46b may be used to form the second joint 44b via a laser welding process. However, other welding methods may be used, such as resistance welding, to form the second joint 44b.

[0027] A method 100 of assembling a DC bus assembly 10 is shown in the flow chart of FIG. 3. The method 100 includes stacking a positive bus bar and a negative bus bar in one- over-the-other configuration with a thin film separator of electrically insulating material disposed therebetween at step 102.

[0028] The method 100 also includes energizing the positive bus bar and the negative bus bar with a high-voltage direct current (DC) power at step 104. [0029] The method 100 also includes placing a first conductor tab of a capacitor overlying a flat upper surface of an upper one of the bus bars at step 106.

[0030] The method 100 also includes placing a second conductor tab of the capacitor disposed below a flat lower surface of a lower one of the bus bars at step 108.

[0031] The method 100 also includes joining each of the first conductor tab and the second conductor tab to adjoining ones of the positive bus bar and the negative bus bar at step 110. In some embodiments, step 110 may include using a welding process for joining each of the first conductor tab and the second conductor tab to adjoining ones of the positive bus bar and the negative bus bar.

[0032] In some embodiments, the welding process of step 110 may include directing a first laser beam toward a junction of the first conductor tab and a corresponding one of the bus bars to melt the junction therebetween. Additionally or alternatively, the welding process of step 110 may include directing a second laser beam toward a junction of the second conductor tab and a corresponding one of the bus bars to melt the junction therebetween.

[0033] The foregoing description is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.