Capacitor Overlapping Busbars Magnetic Field Cancellation
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Solution Overview
Problem
Metallized film DC-link capacitors face significant losses due to parasitic inductances and resistances at high switching frequencies, which are exacerbated by the increased demands of wide-bandgap semiconductor applications, leading to resonance effects and inefficiencies in power conversion.
Innovation Solution
The design incorporates overlapping busbars with opposite polarities to cancel out magnetic fields, resulting in reduced inductance and homogeneous impedance across winding elements, minimizing parasitic inductances and resistances, and ensuring stable performance at frequencies above 10 kHz.
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 at high switching frequencies, causing losses and resonance effects
Solution Approach 1:
The busbars are arranged asymmetrically with different lengths and positions, where the first busbar connects to one terminal and the second busbar connects to the other terminal with deliberately different path lengths. This asymmetric arrangement creates opposing magnetic fields that cancel each other, reducing parasitic inductance and energy losses at high switching frequencies
Solution Approach 2:
The invention converts the harmful magnetic fields generated by current flow through busbars into a beneficial effect by arranging the busbars such that their magnetic fields oppose and cancel each other. The parasitic inductance that would normally cause losses is transformed into a magnetic cancellation mechanism, turning the harmful electromagnetic effect into a solution that reduces overall parasitic inductance
2Productivity
If high switching frequencies above 10 kHz are used in power converters, then power density and efficiency improve, but losses due to parasitic inductances and resistances in capacitors increase
Solution Approach 1:
The busbar arrangement uses asymmetric path lengths and configurations to create opposing magnetic fields. The first busbar and second busbar are deliberately designed with different geometries so that their magnetic fields cancel each other at high switching frequencies, enabling the capacitor to operate efficiently at frequencies above 10 kHz without excessive losses
Solution Approach 2:
The invention changes the geometric parameters of the busbars, specifically their lengths, positions, and arrangement patterns. By optimizing these parameters, the magnetic fields generated by each busbar are made to oppose and cancel each other, reducing parasitic inductance and enabling high-frequency operation with minimal energy losses
3Device complexity
If the magnetic fields of busbars are not cancelled, then the busbar arrangement is simpler, but inductance of the capacitor increases, resulting in resonance effects and high losses
Solution Approach 1:
The busbars are arranged asymmetrically with the first busbar connecting to one terminal and the second busbar connecting to the other terminal with deliberately different path lengths and configurations. This asymmetric design creates opposing magnetic fields that cancel each other, reducing the capacitor's inductance and eliminating resonance effects while maintaining manufacturing simplicity
Solution Approach 2:
The invention converts the potentially harmful magnetic fields generated by the busbars into a beneficial cancellation effect. By arranging the busbars to generate opposing magnetic fields, the harmful inductance and resonance effects are transformed into a self-canceling mechanism, reducing parasitic inductance without requiring complex additional components
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 approach significantly reduces losses and resonance effects, providing a low equivalent series resistance (ESR) and inductance (ESL) while maintaining homogeneous impedance, enabling efficient operation at high frequencies and voltages, thus enhancing the capacitor's performance in power applications.
Implementation Method 1
When a current flows through the first busbar, a magnetic field is generated by the current. Further, when a current flows through the second busbar, another magnetic field is generated by this current.
Implementation Method 2
Due to the overlap of the busbars, the magnetic fields have opposite orientations and, therefore, weaken or even cancel each other.
Data Source
AI summary
A capacitor is disclosed. In an embodiment a capacitor includes at least two winding elements, a first busbar and a second busbar, wherein the first busbar and the second busbar connect the winding elements in parallel to each other, and wherein the first busbar and the second busbar are arranged such that they overlap each other.