Piezoelectric Output Filter for Motor Drive dv/dt and Common-Mode Currents
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing solutions for mitigating transmission line effects in power train systems, such as those in AC motor drives, often result in excessive losses, weight, and reliability concerns due to the use of capacitors, and fail to effectively manage common mode currents, which can lead to motor damage and non-compliance with EMI requirements.
Innovation Solution
A power train system utilizing piezoelectric transformers and inductors as an output filter to replace capacitive components, allowing for energy recycling and minimizing losses without capacitors, thereby addressing transmission line effects and common mode currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If passive filters (RC or RLC) are provided at the inverter output or motor terminals to mitigate transmission line effects, then voltage surges are reduced, but excessive energy losses occur and heat sink size increases
Solution Approach 1:
The active filter recycles the energy required to damp voltage overshoot by capturing it during negative voltage transitions and making it available during positive transitions, rather than dissipating it as heat. This energy recovery mechanism eliminates the need for large heat sinks and reduces overall energy losses in the system.
Solution Approach 2:
The patent replaces passive RC or RLC filters with an active filter implementation that uses controlled switching devices (such as MOSFETs or IGBTs) and energy storage elements. This substitution transitions from a passive energy-dissipating system to an active energy-managing system, reducing energy losses while maintaining voltage surge mitigation.
2Speed
If wide band-gap rapid switching components (SiC and GaN) are used to improve switching properties, then switching speed is enhanced, but transmission line effects occur even in shorter cables
Solution Approach 1:
The active filter acts as an intermediary between the rapid switching components and the motor, managing the high dv/dt transitions. By actively controlling voltage transitions and providing a controlled impedance path, the filter mitigates transmission line effects caused by fast switching while preserving the benefits of wide band-gap devices.
Solution Approach 2:
The active filter preemptively manages voltage transitions by preparing energy storage elements and switching devices to counteract transmission line effects before they manifest. The filter proactively controls dv/dt rates and prevents voltage surges from developing, rather than reacting after problems occur.
3Object-affected harmful factors
If RC components are selected to provide terminating resistance to avoid high frequency components, then voltage rise rate is controlled, but energy dissipation increases
Solution Approach 1:
Instead of using RC components that continuously dissipate energy as heat to control voltage rise rate, the active filter captures energy during voltage transitions and recycles it. This approach maintains controlled dv/dt while minimizing energy dissipation through intelligent energy management rather than resistive damping.
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 proposed solution efficiently manages transmission line effects and common mode currents, reducing energy losses and weight, while enabling the full exploitation of fast-switching devices like SiC and GaN, and ensuring compliance with EMI standards.
Implementation Method 1
A power train system utilizing piezoelectric transformers and inductors as an output filter to replace capacitive components, allowing for energy recycling and minimizing losses without capacitors
Implementation Method 2
A power train system utilizing piezoelectric transformers and inductors as an output filter to replace capacitive components
Data Source
Figure 1
Figure 2a~2b
Figure 3
AI summary
An output filter for a power train (3), comprising a piezoelectric transformer (11), a load element (12) connected across the output of the piezoelectric transformer and an inductor (13) connected to an input of the piezoelectric transformer.