Variable Speed Constant Frequency Generator Using Rotating Inverter
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Solution Overview
Problem
Conventional variable speed AC generator systems are large and heavy due to large exciter assemblies and require additional rotating signal transformers for voltage/frequency control and engine starting, which complicates the design and increases size and weight.
Innovation Solution
A variable speed constant frequency (VSCF) power generator design that excludes rotary signal transformers, utilizing a permanent magnet generator with rotating three-phase windings, a rotating rectifier, and a rotating inverter to generate DC power for an electronic PLC controller, which communicates and controls the main generator field windings to maintain constant frequency and voltage, enabling engine start without additional rotating transformers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional exciter assemblies are used in variable speed AC generator systems, then the generator can provide variable speed operation, but the size and weight of the system significantly increase
Solution Approach 1:
The patent extracts and eliminates the large conventional exciter assembly from the generator system by implementing a solid-state excitation system using power electronic converters (rectifier and inverter) that can generate the required field current without a physical exciter. This removal directly reduces system weight while maintaining variable speed capability through electronic control.
Solution Approach 2:
The invention changes the operating parameters of the generator by using power electronic converters to independently control field current magnitude and frequency, allowing the generator to operate at variable speeds while maintaining constant output frequency. This parameter control through electronics replaces the need for mechanical exciter components.
2Adaptability or versatility
If rotating signal transformers are added to drive voltage/frequency controller, then engine start function is enabled, but device complexity and size increase
Solution Approach 1:
The patent merges the engine start function with the existing power electronic control system by using the same inverter and controller to provide both voltage/frequency control for generation mode and controlled rectification for motor mode operation. This integration eliminates the need for separate rotating signal transformers and simplifies the overall system architecture.
Solution Approach 2:
The control system is designed with multi-functionality, where the power electronic converters and controller can operate in multiple modes: generating mode with variable speed constant frequency output, and motor mode for engine starting. This universal control approach enables diverse functions without adding dedicated hardware for each function.
3Adaptability or versatility
If large exciter assemblies are used to provide low frequency AC power, then variable speed operation is achieved, but the overall size of the generator system increases
Solution Approach 1:
The patent replaces the mechanical exciter assembly with an electrical/electronic solution using power electronic converters. The rectifier-converter system electronically generates the required field current from the generator output, eliminating the need for mechanical exciter components and reducing overall generator size while maintaining variable speed capability.
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 VSCF power generator reduces size and weight compared to conventional systems, enabling efficient engine starting and constant frequency output without the need for additional rotating signal transformers, thus simplifying the design and improving performance.
Implementation Method 1
power generators convert mechanical energy to electrical energy via the interaction of rotating magnetic fields and coils of wire
Implementation Method 2
a rotating rectifier that converts the initial AC power into a DC power
Data Source
Figure 1A
Figure 1B
Figure 1B
AI summary
A variable speed constant frequency (VSCF) power generator includes a rotating direct current (DC) power source, rotating multi-phase generator main field windings 114 to generate a rotating alternating current (AC) power, and a rotating inverter 112 configured to control alternating current (AC) generator field windings in response to output AC power generated by the VSCF power generator and DC power from the rotating DC power source. At least one generator main field sensor 124, 126 outputs a generator main field feedback signal based on the rotating AC power applied to the rotating multi-phase generator main field windings. Stationary multi-phase generator armature windings 128 output constant voltage constant frequency AC power controlled by the rotating AC power. An electronic rotating power line communication (PLC) controller 116 generates a control signal that adjusts the rotating AC power based on the rotating generator feedback signal, where the output AC power is controlled by adjusting the rotating AC power.