Isolated Rotor Modulated Pole Machine for High Low-Speed Torque
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Solution Overview
Problem
Existing electrical machines face challenges with low torque or force densities and efficiency at low speeds, leading to the need for mechanical systems that introduce additional losses and maintenance costs.
Innovation Solution
A modulated pole machine design with multiple airgaps and magnetic gearing, where windings are arranged to encircle multiple poles, reducing winding resistance and increasing airgap area per unit volume, and using neodymium or ferrite magnets to enhance force density and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If standard electrical machine design is used, then the machine structure is simple, but the torque or force density is low
Solution Approach 1:
The rotor is divided into multiple isolated rotor sections (at least two) separated by non-magnetic material or air gaps. Each rotor section can be independently positioned relative to the stator sections, allowing the magnetic flux to be modulated as it passes through multiple air gaps. This segmentation enables the machine to achieve high torque or force density through magnetic gearing effects while maintaining a manageable structure through modular design
Solution Approach 2:
Multiple stator sections and rotor sections are nested interleaved with each other, with each rotor section positioned between stator sections. The magnetic flux passes through multiple nested air gaps in sequence, creating a multiplicative effect on the torque or force density. This nested arrangement allows the machine to achieve high force density without proportionally increasing the overall machine size
2Speed
If electrical machine operates at low speed, then the total power is low, but the resistive power losses become high
Solution Approach 1:
The winding is divided into multiple phase windings distributed across different stator sections, with each phase winding contributing to the total power output. This segmentation allows the machine to maintain high efficiency at low speeds by optimizing the current distribution across multiple phases, reducing the resistive losses in each individual phase while maintaining the required total power output
Solution Approach 2:
The machine operates by switching of magnetic flux through the isolated rotor sections, changing the magnetic circuit parameters dynamically. This flux switching mechanism allows the machine to maintain high power factor and low resistive losses at low speeds by optimizing the magnetic flux path and reducing the current required for a given torque output
3Force
If modulated pole machine design is used, then the torque or force density is high, but the leakage magnetic flux becomes large
Solution Approach 1:
The harmful leakage magnetic flux is extracted and redirected through the isolated rotor sections. By positioning non-magnetic material or air gaps between rotor sections, the leakage flux that would otherwise be lost is captured and channeled through the magnetic circuit, converting a harmful effect into a useful contribution to the torque or force density
Solution Approach 2:
The magnetic flux that would normally leak and cause losses is converted into a beneficial effect by passing it through multiple air gaps in the isolated rotor sections. The leakage flux is redirected to contribute to the magnetic gearing effect, increasing the torque or force density while reducing the harmful losses. This converts the previously harmful leakage flux into a useful component of the magnetic circuit
4Force
If mechanical systems are used to increase torque or force, then the torque or force density is high, but the maintenance requirements increase
Solution Approach 1:
The patent replaces mechanical gear systems with a magnetic gearing mechanism based on isolated rotor sections and flux switching. This substitution eliminates the need for mechanical gears, bearings, and lubrication systems, thereby reducing maintenance requirements while achieving high torque or force density through the magnetic circuit 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
The design achieves significantly higher torque or force density and efficiency, especially at low speeds, while maintaining a reasonable power factor, reducing the need for heavy structures and minimizing leakage magnetic flux.
Implementation Method 1
A rotating electrical machine operating by switching of magnetic flux comprises a rotor, a stator and a winding
Implementation Method 2
These machine types, for example the Vernier machine (VM), the Vernier hybrid machine (VHM) and different variants of the transverse flux machines (TFM) implement a geometrical effect known as magnetic gearing
Implementation Method 3
using neodymium or ferrite magnets to enhance force density and efficiency
Data Source
AI summary
An electrical machine (1) being a modulated pole machine operating by switching of magnetic flux comprises a rotor (10), a stator (20) and a winding (30). The rotor and stator have respective sections (12,22) interleaved with each other via more than 4 air gaps. At least two different sections each comprise a winding loop from the same phase winding. At least one of the sections that is part of the rotor is an isolated rotor section which comprises electrically non-conducting structure material.