Drive Filter for Adjustable Speed Drives with Low DC Bus Capacitance
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Solution Overview
Problem
Adjustable speed motor drives with lower DC bus capacitance face challenges in reducing total harmonic current distortion (THID) to meet IEEE Standard 519 limits, as existing filters fail to achieve the required 5% or less THID at both full and reduced loads.
Innovation Solution
The implementation of a drive filter with a plurality of electrical connections, comprising line capacitors and resistors, which connect input and output contacts to reduce THID by minimizing harmonic current flow and detuning shunt filtering, using specific capacitance values and inductance calculations to achieve the desired harmonic distortion reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If existing filters are used with adjustable speed drives having low DC bus capacitance (1-30 uF), then the device complexity remains simple, but the total harmonic current distortion (THID) cannot be reduced to 5% or less as required by IEEE Standard 519
Solution Approach 1:
The filter is segmented into multiple independent branches (first branch with capacitor C1 and inductor L1, second branch with capacitor C2 and inductor L2, third branch with capacitor C3 and inductor L3) that can be individually designed and tuned. This segmentation allows each branch to target specific harmonic frequencies, achieving comprehensive THID reduction while maintaining modular simplicity in the overall structure.
Solution Approach 2:
The patent applies parameter changes by specifically selecting capacitance values (C1, C2, C3) and inductance values (L1, L2, L3) to tune the filter's resonant frequencies. The capacitance values are chosen based on the drive's DC bus capacitance range (1-30 uF) to detune shunt filtering and minimize harmonic current flow, thereby reducing THID to meet IEEE Standard 519 requirements without increasing structural complexity.
2Use of energy by moving object
If the DC bus capacitance is reduced to 1-30 microfarads for energy efficiency, then the use of energy is improved, but the harmonic control becomes difficult to meet IEEE Standard 519 limits
Solution Approach 1:
The filter acts as an intermediary device between the low-capacitance DC bus and the power source. The capacitors C1, C2, and C3 in the filter branches provide additional capacitance that compensates for the reduced DC bus capacitance, enabling the system to maintain proper harmonic control and meet IEEE Standard 519 limits while keeping the main DC bus capacitance low for energy efficiency.
Solution Approach 2:
The patent changes the electrical parameters of the filter components, specifically selecting capacitance values (C1, C2, C3) and inductance values (L1, L2, L3) that are optimized for low DC bus capacitance applications (1-30 uF). These parameter changes enable the filter to effectively detune shunt filtering and reduce harmonic currents, achieving both energy efficiency and harmonic control precision.
3Manufacturing precision
If conventional filter designs are used, then the ease of manufacture is maintained, but the total harmonic current distortion cannot be reduced to 5% or less at both full and reduced loads
Solution Approach 1:
The filter design is segmented into three independent branches, each with its own capacitor and inductor. This segmentation simplifies the manufacturing process as each branch can be designed and assembled separately using standard components, while still achieving the complex function of reducing THID to 5% or less across varying load conditions.
Solution Approach 2:
The patent provides specific guidance on selecting capacitance values (C1, C2, C3) and inductance values (L1, L2, L3) to achieve the desired THID reduction. By changing and optimizing these electrical parameters, the filter can meet IEEE Standard 519 requirements at both full and reduced loads without requiring complex custom-manufactured components, thus maintaining ease of manufacture.
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 effectively reduces THID to 5% or less, meeting IEEE Standard 519 requirements, even at reduced loads, by minimizing harmonic currents and resonant frequencies, thereby improving harmonic control in adjustable speed motor drives with lower DC bus capacitance.
Implementation Method 1
each of the plurality of electrical connections consists of an electrical component, where the electrical component is selected from the group consisting of: i) one or more line capacitors
Implementation Method 2
the electrical component is selected from the group consisting of: i) one or more line capacitors and ii) the one or more line capacitors and one or more resistors
Data Source
AI summary
In some embodiments, the instant invention provides a drive filter that includes: a plurality of input contacts configured for receiving an initial three-phase alternative current from a three-phase alternative current power source; a plurality of output contacts configured for outputting an output current to a respective phase of an adjustable speed drive, where the adjustable speed drive has a direct current bus capacitance between 1 and 30 microfarads (uF); and a plurality of electrical connections, where each electrical connection is configured to connect each input contact of the plurality of input contacts to a respective output contact of the plurality of output contacts; and where each electrical connection consists of at least one line capacitor; and where the at least one capacitor has a capacitance value such that a total harmonic current distortion (THID) of the output current is reduced to 5 percent or less.