Exciterless Synchronous Machine Rotor Design
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing synchronous machines require a separate exciter machine and associated power stage, which increases weight, size, and reduces critical speed, making it desirable to provide excitation to the main machine without the need for an exciter machine.
Innovation Solution
A synchronous machine design where the rotor includes a rotating DC power supply coupled to exciter windings adjacent the air gap, utilizing air gap harmonics to induce current in the exciter windings, which is then rectified and supplied to the rotor field windings, eliminating the need for a separate exciter machine.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separate exciter machine and power stage are used to provide excitation to the main machine, then reliable excitation control is achieved, but the total weight and size of the system increases and the shaft length increases reducing critical speed
Solution Approach 1:
The patent combines the excitation function with the main machine by integrating exciter windings into the rotor structure. The exciter windings are placed in the rotor and utilize the main machine's air gap flux to generate excitation current, eliminating the need for a separate exciter machine and power stage while maintaining reliable excitation control
Solution Approach 2:
The rotor structure is designed to serve multiple functions: it provides the main machine's magnetic field through field windings and simultaneously generates excitation power through exciter windings that interact with the air gap harmonics. This multi-functional design eliminates the separate exciter system
2Reliability
If a separate exciter machine and power stage are used to provide excitation to the main machine, then reliable excitation control is achieved, but the system complexity increases with additional components such as transformers, breakers and active power electronics
Solution Approach 1:
The patent merges the excitation control function directly into the main machine's rotor and stator structure. The exciter windings in the rotor interact with harmonics in the air gap flux produced by the stator, generating excitation current that is rectified by a simple rotating rectifier. This eliminates the need for complex external power stages, transformers, and breakers
Solution Approach 2:
The main machine's own air gap flux and harmonics are utilized to generate the excitation current for the field windings. The system essentially excites itself by converting a portion of the main machine's electromagnetic energy into excitation power through the exciter windings, eliminating the need for external excitation equipment
3Power
If a separate exciter machine is used to provide excitation to the main machine, then sufficient excitation power is available, but the shaft length increases which reduces the critical speed of the rotor
Solution Approach 1:
The patent integrates the excitation system within the main machine's rotor structure, placing exciter windings in the rotor that utilize the air gap flux. This eliminates the need for a separate exciter machine coupled to the shaft, thereby reducing shaft length and increasing critical speed while still providing sufficient excitation power through the combined action of air gap harmonics and controlled DC power supply
Solution Approach 2:
The patent employs a dynamic control approach where a rotating DC power supply provides controllable excitation current to the field windings, and additional harmonics can be superimposed on the stator winding current to induce prescribed currents in the exciter windings. This dynamic control ensures sufficient excitation power while maintaining a compact rotor design
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 design results in a more compact synchronous machine capable of achieving desired current levels in the rotor field windings, reducing weight and size while maintaining performance, and allowing for efficient power extraction to the field windings, effectively eliminating the need for a separate exciter system.
Implementation Method 1
Power from air gap harmonics, including air gap slot harmonics induce current in the exciter windings
Implementation Method 2
which is rectified and supplied to the rotor field windings
Data Source
AI summary
A synchronous machine and related systems include a stator and rotor separated by an air gap. The rotor includes a rotating DC power supply coupled to exciter windings disposed adjacent the air gap. Power from air gap harmonics, including air gap slot harmonics induce current in the exciter windings, which is rectified and supplied to the rotor field windings. In operation, a desired current level in the rotor field windings can be achieved through control of the DC power supply or superposition of harmonics into the stator winding current which induces the prescribed current in exciter windings.