Power Conversion Device Noise Reduction via Ground Conductor
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Solution Overview
Problem
Existing power conversion devices face challenges in further reducing noise source current, high frequency current, and resonance current, especially when the switching frequency is shifted to a high frequency side.
Innovation Solution
The power conversion device includes an inverter, a cooler, a first core with a through hole for positive and negative conductors, and a second core for load conductors, with capacitive elements connecting ground potentials, and a ground conductor connecting the cooler and casing to reduce noise currents by increasing impedance in specific frequency bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the switching frequency is shifted to a high frequency side, then the power conversion device can achieve better performance, but the noise source current, high frequency current, and resonance current increase
Solution Approach 1:
The patent introduces a ground conductor as an intermediary element connected between the cooler and the casing to provide a dedicated high-frequency current path. This mediator allows high frequency currents to be controlled and directed through a specific route with appropriate impedance, preventing them from propagating as noise while still enabling the high switching frequency operation.
Solution Approach 2:
The patent changes the impedance parameter of the ground conductor to optimize its performance at high frequencies. By carefully selecting the impedance characteristics of the ground conductor, the patent achieves better suppression of noise source current while maintaining the benefits of high frequency switching operation.
2Reliability
If the cooler is electrically isolated from the casing, then electrical insulation is maintained, but the manufacturing process becomes more complex and high frequency current suppression is reduced
Solution Approach 1:
The ground conductor serves as an intermediary that provides both electrical connection and controlled impedance path. It allows the cooler to be electrically connected to the casing while maintaining proper high-frequency current management, eliminating the need for complex insulation arrangements.
Solution Approach 2:
The ground conductor performs multiple functions simultaneously: it provides electrical connection between the cooler and casing, establishes a reference potential, and controls high-frequency current paths. This multi-functionality simplifies the overall design and manufacturing process while maintaining both electrical safety and noise suppression performance.
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 configuration effectively reduces noise source current, high frequency current, and resonance current by shifting the switching frequency to a high frequency side, suppressing impedance decreases in high frequency bands and simplifying the manufacturing process by eliminating the need for insulation between the cooler and casing.
Implementation Method 1
a second ground conductor that connects the negative side conductor on the side of the direct-current power supply system with respect to the first core and the motor via a capacitive element
Data Source
Figure 1
Figure 2(a)~2(b)
Figure 3(a)~3(b)
AI summary
A power conversion device includes an inverter 4 that receives power from a direct-current power supply system and drives a motor 6 as a load; a fin 5 that cools down the inverter; a first core 8 including a through hole that allows passage of a positive side conductor 21 that connects the direct-current power supply system and the inverter 4 and a negative side conductor 22 that grounds the inverter 4; a ground conductor 50 that is connected to the negative side conductor 22 on a side of the direct-current power supply system with respect to the first core 8 and grounds the fin 5; a ground conductor 59 that is connected to the negative side conductor 22 on the side of the direct-current power supply system with respect to the first core 8 and grounds a motor yoke 6A in an alternate-current manner via a capacitor 10; and a ground conductor 61 including one end that is connected to the negative side conductor 22 on the side of the direct-current power supply system or the ground conductor 50 with respect to the first core 8 and the other end that is grounded.