Input EMI Filter with Active Rectifier for Motor Drive
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Solution Overview
Problem
Existing motor drive systems face challenges with large physical size and weight due to high motor current requirements, leading to increased size and weight of EMI filters, which can be mitigated by incrementally increasing the input EMI filter at the active rectifier input and eliminating EMI filtering at the motor drive inverter output.
Innovation Solution
A poly-phase motor drive system with an input EMI filter that includes a poly-phase filter input and output, an active rectifier connected to the filter output, and a motor drive inverter connected to the DC output, featuring a T-type differential mode filter and multiple common mode chokes with different core materials to effectively filter common and differential mode noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the motor drive inverter operates at higher output current, then the power output is improved, but the weight of the EMI filter output section increases
Solution Approach 1:
The EMI filter is divided into two separate sections: an input section connected between the active rectifier and the power source, and an output section connected between the drive inverter and the motor. Each section is independently optimized for its specific function, allowing the input section to handle common mode filtering without being oversized for the higher motor current
Solution Approach 2:
The patent shifts the primary common mode filtering capability from the output section to the input section by increasing the common mode inductance in the input section. This dimensional shift in filtering strategy allows the output section to be sized according to actual motor current requirements rather than being oversized to compensate for insufficient input filtering
2Object-affected harmful factors
If additional common mode filtering is added to the EMI filter input section, then the common mode noise filtering is improved, but the size and weight of the filter increases
Solution Approach 1:
The patent changes the inductance parameter of the common mode choke in the input section to a higher value specifically optimized for filtering common mode noise from the active rectifier. By adjusting this parameter, the filter achieves effective common mode noise suppression without requiring excessive physical size, as the higher inductance provides better filtering efficiency per unit volume
3Reliability
If the common mode filter uses increased inductance instead of increased capacitance, then the insertion loss is improved, but the filter becomes bulky
Solution Approach 1:
The patent applies different quality characteristics to different parts of the filter system. The input section uses high inductance common mode chokes optimized for common mode noise rejection, while the output section uses components optimized for differential mode filtering and bearing current suppression. This localized optimization allows each section to achieve its filtering goals with minimal volume
Solution Approach 2:
The filter employs a composite structure with multiple common mode chokes having different core materials and characteristics. The input section uses chokes with cores optimized for high-frequency common mode noise from the active rectifier, while the overall filter structure combines multiple filtering mechanisms (inductive and capacitive elements) to achieve comprehensive EMI suppression without excessive size
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 reduces the size and weight of the EMI filter while effectively filtering high-frequency leakage currents and conducted electromagnetic interference, improving thermal performance and reducing switching losses in the motor drive inverter.
Implementation Method 1
common mode filters use an increased inductance of at least one common mode choke in a multi-stage common mode filter
Implementation Method 2
featuring a T-type differential mode filter and multiple common mode chokes
Implementation Method 3
Both the active rectifier and the motor drive inverter employ fast switching IGBT devices controlled using a pulse-width modulation (PWM) technique
Implementation Method 4
The high frequency voltage components of PWM converter (the active rectifier) and inverter cause high frequency leakage currents and conducted EMI in the power lines and ground system
Data Source
AI summary
A poly-phase motor drive includes an input EMI filter having a poly-phase filter input and a poly-phase filter output and an active rectifier connected to the filter output. The input EMI filter includes notch filters tuned at active rectifier and motor drive inverter switching frequencies and diverts common-mode current into DC bus. The active rectifier has a DC output. A motor drive inverter is connected to the DC output. The motor drive inverter has a poly-phase motor control output.