Power Conversion Unit Grid Capacitor Array Noise Reduction
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Solution Overview
Problem
Existing power conversion units for three-phase AC motors face issues with noise voltage generation due to parasitic inductance and unequalized ripple currents in large-capacitor arrays, and increased risk of electric shock and size expansion with higher voltage systems.
Innovation Solution
A power conversion unit featuring a power smoothing capacitor assembly of conductive polymer solid or hybrid aluminum electrolytic capacitors connected in parallel on a circuit board, with copper bus bars for reduced impedance and noise, and a control circuit for managing three-phase AC voltages with variable frequency and phase difference, ensuring efficient energy storage and distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a large number of unit capacitors are intensively arrayed on a high current wiring board, then the capacitance is increased, but noise voltage is generated by parasitic inductance and ripple currents cannot be equalized
Solution Approach 1:
The capacitor assembly is segmented into multiple unit capacitors (first through fourth unit capacitors) arranged in a specific pattern on the wiring board. This segmentation allows for better current distribution and reduced parasitic inductance compared to intensive arraying, while achieving the required total capacitance for power smoothing.
2Quantity of substance
If a large number of unit capacitors are intensively arrayed on a high current wiring board, then the capacitance is increased, but ripple currents cannot be equalized
Solution Approach 1:
The wiring board is designed with specific trace arrangements and connection points that create equipotential regions, ensuring that ripple currents are evenly distributed across all unit capacitors. The symmetrical arrangement of capacitors and their connection to the power supply terminals ensures equalized current sharing, improving reliability.
3Quantity of substance
If a higher system voltage is set, then a capacitor with a smaller capacitance can be used, but a lower system voltage requires a larger capacitance and larger capacitor volume
Solution Approach 1:
The invention optimizes the capacitance value and physical arrangement parameters of the capacitor assembly to achieve effective power smoothing at lower system voltages. By using multiple unit capacitors in a specific configuration rather than a single large capacitor, the design achieves the required capacitance with reduced overall volume and improved current distribution.
4Object-generated harmful factors
If DC terminals are separately connected to electrode terminals of the capacitor by screwing, then dispersion of current and parasitic inductance are reduced, but the structure becomes more complex
Solution Approach 1:
The connection structure merges the capacitor terminals with the wiring board's power supply terminals through direct soldering or bonding. This integration eliminates the need for separate screw connections, reducing parasitic inductance by minimizing connection length and points, while simplifying the overall structure and assembly process.
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
The solution reduces capacitor size, minimizes temperature rise, and enhances reliability by equalizing ripple currents and reducing noise, while preventing electric shock and size expansion, thus improving the power conversion unit's efficiency and safety.
Implementation Method 1
Electrostatic energy stored in the above-mentioned capacitor is defined by the product of a square of a charged voltage and a capacitance
Implementation Method 2
copper bus bars for reduced impedance and noise
Data Source
AI summary
Provided is a power conversion unit, in which a power smoothing capacitor is configured such that a plurality of unit capacitors as conductive polymer hybrid aluminum electrolytic capacitors are arrayed in a grid pattern and connected in parallel on a circuit board, and also connected to a plurality of unit modules of different phases via positive and negative bus bars arranged on both sides of the circuit board so that each group of several unit capacitors and each unit module are arranged close to each other, to thereby reduce wiring impedance of a power supply circuit and suppress noise generation.