Copper Busbar Stepped Hole for Cable Lug Connection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for connecting copper busbars to cable lugs, such as self-tapping screws, self-clinching bolts, and push-through screw connections, face challenges like high manufacturing costs, complex assembly, and reliability issues due to threading and material deformation, especially in power converters with fast switching operations.
Innovation Solution
A copper busbar with a stepped hole design allows for a reliable and secure electrical connection using a screw connection, where the stepped hole has different radii sections to accommodate a press-in nut and cable lug, ensuring minimal clamping length and screw depth, reducing production complexity and tolerances, and enabling direct use of set nuts with combination screws.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If self-tapping screws are used to create a thread in the copper busbar, then a connection can be established, but the manufacturing precision and reliability are compromised due to material deformation and threading problems
Solution Approach 1:
The stepped hole is pre-formed in the copper busbar before the screw connection is assembled. The hole includes a first section with a first diameter and a second section with a second diameter smaller than the first diameter, creating a prepared pathway that guides the screw and prevents improper threading. This preliminary preparation ensures that the screw engages correctly with the busbar material without causing deformation or threading defects.
2Strength
If self-clinching bolts are used to connect the cable lug, then connection strength is improved, but the overall height becomes significant and manufacturing costs increase
Solution Approach 1:
The stepped hole design creates different local geometries within the same hole structure. The first section has a larger diameter to accommodate the screw head and provide material for engagement, while the second section has a smaller diameter to reduce the overall protrusion height. This local variation in diameter allows the connection to achieve sufficient strength while maintaining a compact overall height that does not significantly extend beyond the busbar surface.
3Ease of manufacture
If combination nuts are used with cable lugs, then connection can be established, but the contact surface area is reduced and assembly accessibility is limited
Solution Approach 1:
Instead of reducing the contact surface area in the planar dimension, the solution transitions to a three-dimensional stepped geometry. The stepped hole provides adequate contact surface area through its first section with larger diameter, while the second section with smaller diameter extends in the depth dimension. This dimensional transition allows the cable lug to maintain sufficient contact area with the busbar while enabling the use of set nuts for secure fastening.
4Ease of manufacture
If push-through screw connections are used, then connection can be established, but manufacturing costs increase and installation accessibility is insufficient
Solution Approach 1:
The hole is segmented into two distinct sections: a first section with a first diameter and a second section with a second diameter. This segmentation allows the screw connection to be assembled from one side only, as the stepped geometry provides sufficient material engagement in the first section and proper guidance in the second section. The segmentation eliminates the need for push-through installation from both sides, improving accessibility while maintaining connection reliability.
Data Source
Figure 1~2
Figure 3
AI summary
The invention relates to a copper busbar. To improve the connectability with a cable shoe (3), it is proposed that the copper busbar (1) has at least one stepped hole (2) for fastening a cable shoe (3) by means of a screw connection (4), wherein the stepped hole (2) extends from a first surface (11) of the copper busbar (1) to a second surface (12) of the copper busbar (1), wherein the stepped hole (2) has at least a first region (21), a second region (22) and a third region (23), wherein the first region (21) of the stepped hole (2) adjoins the first surface (11), wherein the radius of the stepped hole is constant over the length of the second region (22) with the second radius value (r2), wherein the third region (23) adjoins the second surface (12), wherein the third region (23) has at least at the second surface (12) a radius with a third radius value (r3), wherein the third radius value (r3) is less than the second radius value (r2). The invention also relates to a contact system (30) with such a copper busbar (1), and also to a converter with such a copper busbar (1) or such a contact system (30). The invention relates furthermore to a method for producing such a copper busbar (1).