Dual-Input 18-Pulse Autotransformer Rectifier for Harmonic Reduction
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Solution Overview
Problem
Aircraft electric power systems face challenges in converting AC power to DC power efficiently, resulting in substantial current harmonics due to the use of diode pairs, which pollute the electric power generation and distribution system, and existing multi-phase autotransformers do not effectively address this issue for both 230V and 115V AC inputs.
Innovation Solution
A lightweight dual-input nine-phase eighteen-pulse Autotransformer Rectifier Unit that converts three-phase AC inputs to nine-phase AC outputs, utilizing an autotransformer with a 40° phase shift and break-before-make switches to reduce harmonics and maintain a constant DC output voltage, and filters the inputs to synthesize an 18-step current waveform approximating a sine-wave, effectively canceling undesirable harmonic currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If diode pairs are used for AC-DC conversion, then the conversion is simple, but substantial current harmonics are generated that pollute the electric power system
Solution Approach 1:
The patent divides the three-phase AC input into nine-phase outputs by segmenting the transformer windings into multiple sections with different tap positions. Each phase is further divided into multiple windings that are connected in series, creating nine distinct phase outputs from the original three phases. This segmentation enables the rectifier to draw current from multiple phases simultaneously, reducing harmonic distortion.
Solution Approach 2:
The patent transitions from a three-phase system to a nine-phase system by adding phase dimensionality. The autotransformer creates nine-phase outputs spaced at 40° electrical angles, effectively adding phases as a new dimension to the power conversion system. This dimensional expansion allows for smoother current draw and reduced harmonics.
2Object-generated harmful factors
If multi-phase autotransformers are employed to reduce current harmonics, then harmonics are reduced, but the device complexity and weight increase
Solution Approach 1:
The patent combines the autotransformer and rectifier functions into a single integrated unit. The autotransformer windings are configured to directly feed the rectifier diodes, eliminating the need for separate transformer and rectifier assemblies. This merging reduces overall system weight while maintaining the nine-phase harmonic-reduction capability.
Solution Approach 2:
The autotransformer is designed with multiple tap positions and winding configurations that enable it to serve multiple functions: voltage transformation, phase multiplication, and harmonic reduction. The same transformer structure handles both 230V and 115V AC inputs by reconfiguring the winding connections, providing universal operation across different voltage standards.
3Object-generated harmful factors
If a nine-phase autotransformer is used to convert three-phase AC to nine-phase AC, then harmonics are reduced, but the device complexity increases
Solution Approach 1:
The patent implements a nested winding structure where multiple windings are placed on the same transformer core legs. The autotransformer contains primary windings, secondary windings, and tertiary windings nested on shared magnetic paths. This nesting approach achieves nine-phase output without requiring nine separate transformer cores, reducing overall structural complexity.
Solution Approach 2:
The patent achieves nine-phase output by changing the connection parameters and tap positions of the windings rather than creating entirely separate winding sets. By adjusting the electrical angle spacing of taps along the windings and changing connection configurations, the system generates nine phases from three input phases, simplifying the physical structure while achieving the desired phase multiplication.
4Adaptability or versatility
If break-before-make switches are used to handle both 230V and 115V AC inputs, then adaptability is improved, but the switching complexity increases
Solution Approach 1:
The patent employs dynamically reconfigurable winding connections that can switch between different voltage modes. The break-before-make switches dynamically reconfigure the autotransformer winding connections to accommodate either 230V or 115V input. This dynamic reconfiguration allows a single device to adapt to different voltage standards without requiring completely separate circuit paths.
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 provides a reliable and efficient AC-DC conversion with reduced harmonic currents, ensuring a constant DC output voltage and minimizing harmonic pollution across both 230V and 115V AC inputs, enhancing the overall performance of aircraft electric power systems.
Implementation Method 1
an 18-pulse passive AC-DC converter in which a three-phase to nine-phase autotransformer converts a three-phase AC input into a nine-phase AC output
Implementation Method 2
a nine-phase rectifier converts the nine-phase AC power into DC power
Data Source
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AI summary
A dual-input 18-pulse autotransformer rectifier unit for more electric aircraft AC-DC converter uses an autotransformer with a nine-phase output to condition AC power prior to DC rectifying the AC power.