Autotransformer Rectifier Unit With Multiple AC Level Outputs
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Solution Overview
Problem
In shipboard and aircraft applications, the use of higher rectified DC voltage to reduce feeder weight leads to increased common mode voltages on the DC bus, which is a significant challenge as it requires larger common mode inductors, increasing weight and complexity.
Innovation Solution
A three-phase to two twelve-phase output transformer with specific winding configurations and diode pairs is employed to efficiently convert 230 Vrms to 115 Vrms AC and +/-135 Vdc and +/-270 Vdc, reducing common mode voltage and eliminating the need for a large common mode inductor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If a higher rectified DC voltage is used to reduce feeder weight, then the weight of feeders is decreased, but the common mode voltage on the DC bus increases
Solution Approach 1:
The patent divides the single DC bus into multiple isolated DC buses with different voltage levels (+270V, -270V, +135V, -135V). Each bus operates independently with its own common mode voltage reference, effectively segmenting the common mode voltage problem. This allows the system to use higher voltages for power transmission (reducing feeder weight) while preventing common mode voltage from propagating across the entire system.
Solution Approach 2:
The patent introduces a transformer with a neutral point as an intermediary element between the high voltage and low voltage DC buses. The neutral point serves as a common reference that isolates the common mode voltages of different buses while enabling power transfer. This intermediary structure allows high voltage operation for weight reduction while the neutral reference prevents common mode voltage propagation.
2Object-generated harmful factors
If a larger common mode inductor is used to reduce common mode voltage, then the common mode voltage is reduced, but the weight and complexity of the power system increase
Solution Approach 1:
The patent extracts the common mode voltage problem from the main power transmission path by creating separate isolated DC buses. Instead of using a large common mode inductor to suppress common mode voltage on a single bus, the design removes the common mode issue entirely by isolating each voltage level on its own bus with its own neutral reference, eliminating the need for large common mode filtering components.
Solution Approach 2:
Instead of trying to suppress common mode voltage after it is generated (using large inductors), the patent inverts the approach by preventing common mode voltage propagation through structural isolation. The system design inherently prevents common mode issues rather than correcting them, eliminating the need for heavy common mode filtering components.
3Object-generated harmful factors
If a larger common mode inductor is used to reduce common mode voltage, then the common mode voltage is reduced, but the device complexity increases
Solution Approach 1:
The transformer with neutral point performs multiple functions simultaneously: it transforms voltage levels between +270V and +135V, provides isolated DC buses for each voltage level, establishes neutral references for common mode voltage elimination, and enables power transfer between buses. This multi-functionality eliminates the need for separate common mode inductors and other filtering components, reducing overall system complexity.
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 solution effectively reduces common mode voltage, minimizing the size of the common mode inductor and thereby decreasing the overall weight and complexity of the power system, while maintaining efficient power delivery to motor controllers and other equipment.
Implementation Method 1
a three-phase to two twelve-phase output transformer includes a plurality of first primary winding groupings, a plurality of second primary winding groupings, a plurality of secondary windings
Implementation Method 2
A first set of diode pairs is provided. Each diode pair has a first diode end, a second diode end, and an inner connection
Data Source
AI summary
An electric power system is provided that includes a three-phase to two twelve-phase transformer. The transformer includes first and second primary winding groupings, secondary winding groupings, and third, fourth, and fifth windings. The groupings can include sub windings. First primary winding groupings are coupled to form a wye configuration and coupled to second primary winding groupings and the windings. The first of the two twelve-phase outputs at the same voltage as the input voltage while the second twelve-phase output is at a lower voltage. Diode pairs are connected to each other, each diode pair having an inner connection connected to one of the outputs of the transformer and first and second ends respectively connected to a positive dc bus and a negative dc bus. The diode pairs operatively rectify the transformer output voltage to form a DC voltage with a reduced common mode voltage.