Autotransformer-Rectifier Output Layout for Low Harmonic Distortion
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Solution Overview
Problem
Existing autotransformer-rectifier units (ATRUs) fail to meet the requirement of low harmonic distortion rate for electrical equipment connected to a 115 V AC grid, especially when adding new electrical functions that consume significant power.
Innovation Solution
An autotransformer with five outputs per output group, including a main output and four auxiliary outputs, is designed to provide a low overall size and cost-effective solution. The autotransformer is configured such that the main output voltage has an amplitude greater than the input amplitude, and all output voltages belong to the same Reuleaux polygon in a Fresnel diagram, ensuring low harmonic distortion after rectification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If an ATRU comprising an 18-pulse converter is used, then the overall size is reduced and manufacturing cost is lowered, but the harmonic distortion rate exceeds acceptable levels (greater than 1%)
Solution Approach 1:
The invention segments the output voltages into three groups of five voltages each, where each group is derived from a different input phase. This segmentation allows the rectifier to process voltages with optimized phase relationships, reducing harmonic distortion while maintaining a compact transformer structure with fewer windings compared to traditional solutions.
Solution Approach 2:
The invention changes the voltage amplitude parameters by configuring the autotransformer to provide main output voltages with amplitudes greater than the input amplitude. This parameter optimization, combined with specific phase shifts (integer multiples of 12°), enables the rectifier to operate with reduced harmonic distortion without requiring a larger or more complex transformer design.
2Power
If the main output voltage amplitude is increased to be greater than input amplitude, then power delivery capability is improved, but transformer winding complexity increases
Solution Approach 1:
The invention merges multiple functions into the autotransformer structure: voltage transformation, phase shifting, and voltage grouping. By combining these functions into a single transformer device with a specific winding configuration, the design achieves enhanced power delivery capability while avoiding the need for separate components that would increase overall complexity.
Solution Approach 2:
The autotransformer is designed with universal functionality to provide both voltage transformation and the specific phase relationships required for low harmonic distortion. Each winding group serves multiple purposes: transforming voltage, creating phase shifts, and contributing to the five-voltage groups, thereby reducing the need for additional dedicated components.
3Object-generated harmful factors
If five outputs per output group are provided instead of traditional configurations, then harmonic distortion is reduced below 1%, but the number of windings and connections increases
Solution Approach 1:
The invention applies local quality by providing different voltage amplitudes and phase relationships for different output groups. Each of the three output groups is tailored with specific characteristics (main output with higher amplitude, four auxiliary outputs with specific phase shifts) to optimize the overall harmonic performance while using a manageable number of windings per group.
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 autotransformer-rectifier unit achieves a low harmonic distortion rate compatible with stringent requirements, providing a compact, cost-effective, and energy-efficient solution for connecting electrical equipment to a three-phase grid.
Implementation Method 1
the windings of a same winding group being magnetically coupled to each other, each winding group being associated with a respective phase
Data Source
AI summary
A three-phase autotransformer including three output groups and three inputs each connected to each of the outputs of a respective output group by windings, the windings being configured so that, when each input has a respective input voltage applied thereto, the three input voltages having the same input amplitude, being 120° out of phase with each other and defining a neutral point: for each output group, a main output voltage, taken between a main output of said output group and the neutral point, has an amplitude greater than the input amplitude; and output voltages of the autotransformer belong to a same Reuleaux polygon, each output voltage being associated with a respective output and being equal to a voltage between said output and the neutral point.