POWER ELECTRONIC CIRCUIT AND METHOD FOR ITS FABRICATION

Abstract

Current busbars may be made of copper and have at least one nominal bending point which has been locally heated and thereby softened prior to being installed. Such components may be used in power electronic circuits, especially an inverter, in fully electrical and partially electrical (hybrid) vehicles.

Claims

1. A power electronic circuit, comprising: current busbars made of copper, each having at least one nominal bending point which has been locally heated and thereby softened prior to being installed.

2. The power electronic circuit according to claim 1, wherein the yield strength of the copper at the at least one nominal bending point is not more than 120 MPa.

3. The power electronic circuit according to claim 2, wherein the yield strength of the copper at the at least one nominal bending point is not more than 70 MPa.

4. The power electronic circuit according to claim 1, wherein the power electronic circuit is a component of an inverter of a hybrid or electric vehicle.

5. The power electronic circuit according to claim 1, wherein the power electronic circuit is a component of a switching cell of an inverter of a hybrid or electric vehicle.

6. The power electronic circuit according to claim 1, further comprising at least one semiconductor power module and at least one intermediate circuit capacitor which are connected to each other by current busbars.

7. A method for the fabrication of a power electronic circuit including current busbars made of copper, each having at least one nominal bending point which has been locally heated and thereby softened prior to being installed, the method comprising: locally heating and thereby softening at least one nominal bending point of the current busbar prior to the installing of the current busbar.

8. The method according to claim 7, wherein the current busbar is heated to at least 300° C. at the nominal bending point.

9. The method according to claim 7, wherein the local heating reduces the yield strength of the copper of the current busbar at the nominal bending point, determined by ISO 6892-1, from 180 MPa to a value in the range of 70 MPa to 120 MPa.

10. The method according to claim 7, in which the local heating of the nominal bending point is done by inductive heating.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0021] FIG. 1 shows a force/bending diagram for copper samples each bent to the same degree: (a) soft annealed and (b) rolled;

[0022] FIGS. 2a-2c show a comparison of the critically stressed points in the plastic casting compound after bending the current busbars.

DETAILED DESCRIPTION

[0023] FIG. 1 shows a force/bending diagram for two copper samples each bent to the same degree: (a) soft annealed and (b) rolled. Soft annealing serves here as an extreme example for achieving a stationary, maximum softening. As can be seen from the diagram, a significantly lower force is needed for the deformation of the sample after the soft annealing. Softening of the copper generally results in a reduced yield strength.

[0024] FIGS. 2a-2c show a comparison of the critically stressed points in the plastic casting compound (mold) after bending the current busbars.

[0025] FIG. 2a shows the stress at the critical points when the current busbars are untreated. Each time, the stress at the critical points is set at 100%.

[0026] FIG. 2b shows the stress at the critical points when the current busbars have been subjected to a local heat treatment at the position where they are supposed to be bent. Under the assumption of a reduction in the yield strength of the copper to 120 Mpa, the stress at the critical points of the casting compound is reduced to 79% to 93%.

[0027] FIG. 2c shows the stress at the critical points when the current busbars have been subjected to a local heat treatment at the position where they are supposed to be bent, further reducing the yield strength of the copper. Under the assumption of a reduction in the yield strength of the copper to 70 Mpa, the stress at the critical points of the casting compound is reduced to 49% to 69%.

[0028] Accordingly, with the aid of the local heat treatment of the current busbars the stress in the critical points of the plastic casting compound is reduced to half of the original stress level.

[0029] German patent application no. 10 2021 122724.0, filed Sep. 2, 2021, to which this application claims priority, is hereby incorporated herein by reference, in its entirety. Aspects of the various embodiments described above can be combined to provide further embodiments. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled.