Rotating Inverter DC Synchronous Machine Harmonic Reduction
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Solution Overview
Problem
Synchronous machines face inefficiencies due to current harmonics, large volumetric and power density, and thermal losses associated with rectifiers when converting AC to DC, affecting generator efficiency.
Innovation Solution
A DC synchronous machine design featuring a rotating inverter coupled to an AC field winding, which adjusts current frequency to synchronize with the rotating portion, improving efficiency by reducing the need for high power rectifiers and enhancing power transfer across an air gap.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a rectifier is used to convert AC to DC output, then DC current is produced, but current harmonics adversely affect generator efficiency and thermal losses increase
Solution Approach 1:
The patent extracts the inverter function from the stationary rectifier system and relocates it to the rotating portion of the synchronous machine. By placing the inverter on the rotor, the system eliminates the need for a large stationary rectifier, thereby reducing current harmonics and improving generator efficiency without the harmful thermal losses associated with conventional rectification methods
Solution Approach 2:
Instead of using a conventional rectifier to convert AC to DC at the stator, the patent inverts the approach by using an inverter on the rotating portion to generate synchronized AC current that directly produces DC output through the air gap, effectively reversing the traditional power conversion sequence and eliminating rectifier-related harmonics
2Loss of energy
If a rectifier is used to convert AC to DC output, then DC current is produced, but thermal losses increase requiring thermal management
Solution Approach 1:
The patent removes the thermal management burden from the stationary portion by extracting the inverter function to the rotating portion. This eliminates the need for large stationary rectifiers that generate significant thermal losses, thereby reducing temperature rise and minimizing thermal management requirements in the overall system
3Power
If a conventional synchronous machine design is used, then AC to DC conversion is achieved, but volumetric and power density are large
Solution Approach 1:
The patent inverts the conventional design by placing the power electronic converter (inverter) on the rotating portion rather than using a large stationary rectifier. This inversion allows for more compact integration of power conversion functions, significantly improving power density while reducing the overall volumetric requirements of the synchronous machine
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 enhances generator efficiency by stabilizing DC output, reducing thermal and electronic management requirements, and improving power density through synchronized current frequency adjustment.
Implementation Method 1
Synchronous machines include a stationary portion and a rotating portion, where the rotating portion and the stationary portion each have at least one winding
Implementation Method 2
The rotating inverter is configured to communicate current to the AC field winding such that a frequency of the current is adjusted to approach synchronization with a position of the rotating portion
Data Source
AI summary
An assembly for a direct current (DC) synchronous machine, according to an exemplary aspect of the present disclosure includes, among other things, a stationary portion including a direct current (DC) armature winding and a rotating portion including alternating current (AC) field winding configured to supply DC output to the DC armature winding. A rotating inverter is configured to selectively communicate current to the AC field winding such that a frequency of the current is adjusted to approach synchronization with a position of the rotating portion. A method for generating DC output from a DC synchronous machine is also disclosed.