Overlapping Busbar Capacitor Layout for Low ESL at High Frequencies
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Solution Overview
Problem
Metallized film DC-link capacitors face challenges in operating at high frequencies above 10 kHz due to parasitic inductances and resistances, leading to resonance effects and high losses in power electronics applications with wide-bandgap semiconductors.
Innovation Solution
The capacitor design features overlapping busbars and winding elements arranged in a specific stack configuration to minimize parasitic inductances and resistances, ensuring homogeneous impedance and reducing magnetic fields, thereby maintaining low equivalent series resistance and inductance across frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional busbar arrangements are used in capacitors, then the structure is simple and easy to manufacture, but parasitic inductances and resistances increase leading to high losses at high frequencies
Solution Approach 1:
The busbars are arranged in an overlapping configuration where they extend in different spatial dimensions. Specifically, first and second busbars overlap each other, while third and fourth busbars overlap each other, creating a three-dimensional arrangement that reduces parasitic inductance by canceling magnetic fields through opposing current directions in the overlapping regions.
Solution Approach 2:
The overlapping busbar arrangement converts the potentially harmful magnetic fields generated by high-frequency currents into a beneficial effect. By arranging busbars with opposite current directions to overlap, the magnetic fields cancel each other out, reducing parasitic inductance and transforming what would be energy-loss-generating fields into a field-cancellation mechanism that lowers losses.
2Reliability
If busbars are arranged to overlap each other to reduce parasitic inductance, then losses at high frequencies are reduced, but the manufacturing complexity and assembly difficulty increase
Solution Approach 1:
The capacitor is divided into multiple independent capacitor units, each with its own set of overlapping busbars and winding elements. This segmentation allows each unit to be manufactured and assembled separately with standardized overlapping busbar configurations, reducing overall manufacturing complexity while maintaining the reliability benefits of the overlapping arrangement.
3Object-affected harmful factors
If winding elements are connected to busbars in a conventional manner, then the connection is simple, but equivalent series inductance increases leading to resonance effects
Solution Approach 1:
The overlapping busbar arrangement acts as an intermediary structure between the winding elements and the external circuit. The busbars with opposing current directions create canceling magnetic fields that mediate the connection, reducing parasitic inductance and preventing resonance effects while maintaining electrical connectivity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design allows for efficient operation at high frequencies with reduced losses and resonance effects, providing a stable performance across the bandwidth and enabling the use of capacitors in applications with voltages above 600 V and switching frequencies over 10 kHz.
Implementation Method 1
The first busbar and the second busbar are arranged such that they overlap each other... a current flowing through the first busbar generates a first magnetic field and a current flowing through the second busbar generates a second magnetic field, wherein the first magnetic field and the second magnetic field compensate each other
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The present invention concerns a capacitor comprising at least one capacitor unit, wherein the capacitor unit comprises at least two winding elements (1a, 1b), a first busbar (7), a second busbar (8), a third busbar (107) and a fourth busbar (108), wherein all winding elements (1a, 1b) of the capacitor unit are arranged in a single stack, wherein the first busbar (7) and the second busbar (8) are arranged such that they overlap each other, wherein the first busbar (7) and the second busbar (8) are arranged at a first lateral face (6a) of the stack which has a surface normal perpendicular to a stacking direction (S) of the stack, wherein, in a stacking direction (S), alternatingly either the first busbar (7) or the second busbar (8) is connected to a top face of the winding elements (1a, 1b), wherein the third busbar (107) and the fourth busbar (108) are arranged such that they overlap each other, wherein the third and the fourth busbar (108) are arranged on a second lateral face (6b) of the stack opposite to the first lateral face (6a), wherein, in a stacking direction (S), alternatingly either the third busbar (107) or the fourth busbar (108) is connected to a bottom face of the winding elements (1a, 1b), such that the third busbar (107) is connected to the bottom faces of the winding elements (1a, 1b) which have a top face that is connected to the second busbar (8) and that the fourth busbar (108) is connected to the top faces of the winding elements (1a, 1b) which have a bottom face that is connected to the first busbar (7).