Current-Shaping Bus Bar Connectors for Balanced Switch Currents
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Solution Overview
Problem
Power converters in locomotive and OHV applications face challenges in maintaining electrical and thermal balance among semiconductor power switches, leading to uneven current distribution, resistive and inductive losses, and potential thermal stress-related failures due to cyclic thermal stresses and differing thermal properties of materials used in switch fabrication.
Innovation Solution
The design of bus bars with strategically reshaped supply and load terminal connectors to create balanced current paths and minimize stray inductance, using laminated structures and optimized geometries to ensure all terminals experience the same current flow and thermal environment, thereby reducing switching heat loss and improving response time and uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional terminal connectors are used to connect multiple switch terminals, then electrical connections are established, but uneven current distribution and electrical imbalance occur among terminals
Solution Approach 1:
The terminal connector is divided into multiple separate terminal elements rather than using a single common connector. Each terminal element connects to a specific switch terminal, allowing independent optimization of current paths for each terminal to achieve balanced current distribution and minimize stray inductance.
Solution Approach 2:
Each terminal element is designed with specific local geometric features and material properties optimized for its position in the circuit. The terminal elements have different shapes, sizes, and conductive path configurations tailored to their specific electrical and thermal requirements, ensuring uniform current distribution across all terminals.
2Area of stationary object
If terminal connectors are designed for compact arrangement, then space is saved, but thermal stress and cyclic thermal stresses increase due to uneven thermal distribution
Solution Approach 1:
Each terminal element incorporates local thermal management features such as heat sinks, thermal vias, or heat dissipation structures optimized for its specific thermal load. The terminal elements are designed with varying thermal masses and heat transfer characteristics to compensate for positional differences, ensuring uniform thermal stress distribution across all terminals despite compact arrangement.
Solution Approach 2:
The terminal elements are designed with asymmetric geometries that compensate for their positions relative to the heat sink and other thermal sources. This asymmetric design ensures that each terminal experiences similar thermal cycling conditions despite different locations in the compact layout, preventing thermal stress-related failures.
3Ease of manufacture
If standard terminal connector geometries are used, then manufacturing is simplified, but stray inductance and switching heat loss increase
Solution Approach 1:
The terminal elements incorporate optimized geometric parameters such as trace widths, via diameters, layer thicknesses, and path lengths that are specifically tuned to minimize stray inductance and resistive losses. These parameter optimizations are achieved while maintaining compatibility with standard PCB manufacturing processes and existing fabrication capabilities.
Data Source
AI summary
A bus bar includes a load terminal connector comprising a conductive plate that extends from a first edge to an opposite second edge and extends from a third edge to an opposite fourth edge. The third and fourth edges extend from the first edge to the second edge. The plate includes a window opening located between the first and second edges and between the third and fourth edges. The plate also includes a slot extending into the plate from the first edge to the window opening. The plate includes first and second sets of openings configured to receive connections with first and second power terminals of switch packages. The first set of openings and the second set of openings are located on opposite sides of the slot.