Separately Excited Electric Machine Magnetic Circuit Design
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Solution Overview
Problem
Reversible electric machines using permanent magnets face limitations such as high cost, demagnetization at high temperatures, and inefficiencies due to resisting torque, which restrict their performance and reliability, especially in applications requiring high power-to-weight ratios and safety.
Innovation Solution
A separately excited electric machine design featuring a primary magnetic circuit and two secondary magnetic circuits, with annular windings and C-shaped yokes, allows for efficient magnetic flux circulation and torque generation without permanent magnets, optimizing performance and reducing weight and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If permanent magnets are used in reversible electric machines, then high torque and power density are achieved, but cost increases, demagnetization occurs at high temperatures, and resisting torque reduces efficiency
Solution Approach 1:
The patent extracts and removes permanent magnets from the electric machine design, replacing them with electromagnetic windings on the stator that generate the magnetic field dynamically. This eliminates the problems of demagnetization at high temperatures and high cost while maintaining the ability to generate high torque through controlled electromagnetic interaction between stator and rotor windings
Solution Approach 2:
The machine generates its own magnetic field through electromagnetic windings that can be controlled independently, eliminating dependence on permanent magnets. The stator windings create the magnetic field that interacts with rotor windings to produce torque, and the system can self-regulate the magnetic field strength and polarity through control of the winding currents
2Force
If permanent magnets are used, then high torque is generated, but weight increases and cost increases
Solution Approach 1:
The patent removes permanent magnets from the rotor assembly, replacing the magnetic field source with electromagnetic windings on the stator. This significantly reduces rotor weight while maintaining torque generation capability through controlled electromagnetic interaction, directly addressing the weight-torque tradeoff
Solution Approach 2:
The patent replaces the mechanical/magnetic system based on permanent magnets with an electromagnetic system using controlled windings. This substitution allows dynamic control of the magnetic field and eliminates the need for heavy permanent magnet materials, achieving high torque with reduced weight
3Power
If permanent magnets are used, then high power-to-weight ratio is achieved, but cost increases and reliability decreases due to demagnetization risk
Solution Approach 1:
The patent extracts permanent magnets from the design and replaces them with standard electromagnetic windings, eliminating the need for expensive rare earth materials and complex magnet assembly processes. This reduces manufacturing cost while maintaining high power-to-weight ratio through efficient electromagnetic design
Solution Approach 2:
The patent uses conventional electromagnetic windings instead of expensive permanent magnets, accepting that the magnetic field is generated dynamically rather than permanently. This approach uses cheaper, more readily available materials and manufacturing processes while achieving comparable or superior performance
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 enhances torque generation by up to 25% and improves the power-to-weight ratio while maintaining equivalent dimensions to machines with permanent magnets, offering improved reliability and safety without the drawbacks of permanent magnet usage.
Implementation Method 1
allows for efficient magnetic flux circulation and torque generation without permanent magnets
Implementation Method 2
A separately excited electric machine design featuring a primary magnetic circuit and two secondary magnetic circuits
Implementation Method 3
The rotor is caused to rotate by interaction between two magnetic fields, associated respectively with the stator and with the rotor, thereby creating magnetic torque on the rotor
Data Source
AI summary
A separately excited electric machine having a stator provided with at least one exciter unit and a rotor provided with strips. Each exciter unit comprises two secondary magnetic circuits and one primary magnetic circuit. Each secondary magnetic circuit comprises a stator exciter winding and two annular yokes provided with teeth. The primary magnetic circuit comprises a rotor exciter winding and an annular ring. First magnetic fluxes generated by the primary magnetic circuit circulate around loops in each strip and second magnetic fluxes generated by the secondary magnetic circuits circulate around loops in the strips, the teeth, and the ring. Each strip thus has a first north pole and a first south pole, with the teeth comprising in alternation second north poles and second south poles.