Polyphase Output Filter for Motor Drive Noise Suppression
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Solution Overview
Problem
Existing motor drive systems face challenges in effectively suppressing high-frequency noise and surge voltages at motor terminals, leading to resonance and degradation issues, particularly in high-frequency regions, which can cause electrolytic corrosion and require larger components for noise suppression.
Innovation Solution
A motor drive system incorporating a polyphase common-mode filter, a polyphase normal-mode filter, and a capacitor/resistor series-connected body, which connects the frame ground of the power converter to the polyphase common-mode filter, reducing impedance in high-frequency regions and suppressing common-mode voltages and surge voltages at motor terminals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a filter is designed to suppress high-frequency noise and surge voltages, then noise suppression performance is improved, but the filter size and component dimensions increase
Solution Approach 1:
The filter is divided into two distinct sections: a common-mode filter section with a first choke coil and capacitors, and a normal-mode filter section with a second choke coil and capacitors. This segmentation allows each section to be optimized for its specific function, reducing the overall size compared to a single monolithic filter design that would need to handle both modes simultaneously.
Solution Approach 2:
Different parts of the filter are designed with different characteristics tailored to their specific functions. The common-mode filter uses a first choke coil with specific inductance and first capacitors with specific capacitance values, while the normal-mode filter uses a second choke coil with different inductance and second capacitors with different capacitance values. This local optimization enables effective noise suppression without requiring oversized components throughout the entire filter.
2Object-affected harmful factors
If larger filter components are used to suppress high-frequency noise, then noise suppression performance is improved, but the device complexity and component count increase
Solution Approach 1:
The filter structure is segmented into common-mode and normal-mode sections, each handling specific types of noise and surge voltages. This functional segmentation allows for targeted suppression strategies rather than using a complex monolithic structure that attempts to handle all noise types simultaneously, thereby reducing overall device complexity.
Solution Approach 2:
The filter design achieves multi-functionality by combining common-mode and normal-mode filtering capabilities in a single integrated structure. The common-mode filter section handles common-mode noise and surges, while the normal-mode filter section handles differential-mode noise and surges, allowing one filter assembly to perform multiple suppression functions without requiring separate independent filter systems.
3Object-affected harmful factors
If conventional filter designs are used, then basic noise suppression is achieved, but resonance occurs between lines and at neutral point
Solution Approach 1:
The filter design applies different local characteristics to different frequency ranges and noise modes. The common-mode filter section is optimized for suppressing common-mode noise with specific capacitor and choke coil values, while the normal-mode filter section is optimized for differential-mode noise with different component values. This local optimization prevents resonant conditions that would occur with uniform filter characteristics across all modes and frequencies.
Solution Approach 2:
The filter design changes key parameters including the inductance values of the choke coils, the capacitance values of the capacitors, and the grounding configuration, to shift resonant frequencies away from operating frequencies. By carefully selecting these parameters, the filter suppresses noise effectively while avoiding resonance between lines and at the neutral point that would occur with conventional parameter selections.
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 effectively reduces high-frequency components of common-mode voltages, suppresses surge voltages, and minimizes the size of noise suppression components, thereby preventing electrolytic corrosion and improving the overall performance of the motor drive system.
Implementation Method 1
reducing impedance in high-frequency regions
Implementation Method 2
capacitor/resistor series-connected body
Implementation Method 3
polyphase common-mode filter connected to an output of the power converter
Implementation Method 4
polyphase common-mode filter
Implementation Method 5
polyphase normal-mode filter connected to the other end of the polyphase common-mode filter
Implementation Method 6
polyphase normal-mode filter
Data Source
AI summary
An output filter includes a polyphase common-mode filter having a polyphase common-mode choke connected to an output of a power converter at one end, a first polyphase capacitor connected to the other end of the polyphase common-mode choke at one end, and a neutral-point detecting transformer connected to the other end of the first polyphase capacitor at one end; a capacitor/resistor series-connected body connected to a frame ground of the power converter at one end and connected to the other end of the neutral-point detecting transformer at the other end; and a polyphase normal-mode filter having a polyphase normal-mode choke connected to the other end of the polyphase common-mode choke at one end, and a second polyphase capacitor connected to the other end of the polyphase normal-mode choke at one end and having the other ends connected together and further connected to the one end of the capacitor/resistor series-connected body.