Induction Machine Integrated Magnetic Gear Torque Density
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Solution Overview
Problem
Current technologies face challenges in integrating magnetic gears with induction machines, as induction machines are asynchronous, making them difficult to combine with synchronous magnetic gears, which are typically used with permanent magnet machines, limiting options for low-speed high-torque applications that require efficient and reliable solutions without mechanical gearboxes.
Innovation Solution
The integration of magnetic gears with induction machines involves a pseudo direct drive system, comprising an outer stator with AC windings, a high-speed rotor with ferromagnetic material and permanent magnet pole pieces, and a low-speed inner rotor, where the magnetic gearing is achieved through modulation harmonics, allowing for asynchronous coupling and optimized parameter design to achieve high torque density at low speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a mechanical gearbox is used to achieve high torque density, then torque transmission capability is improved, but reliability deteriorates due to mechanical wear, lubrication requirements, and maintenance needs
Solution Approach 1:
The patent replaces the mechanical gearbox with a magnetic gear system that uses magnetic field interactions instead of mechanical tooth engagement. The magnetic gear comprises a first rotor with permanent magnets, a second rotor with ferromagnetic pole pieces, and a stator, creating torque through magnetic coupling across an air gap without mechanical contact between gear teeth.
2Ease of manufacture
If a high-speed electrical machine is used with a mechanical gearbox to achieve desired speed and torque, then cost effectiveness is improved, but device complexity increases due to the additional gearbox components
Solution Approach 1:
The patent merges the electrical machine and magnetic gear into a single integrated unit where the magnetic gear's first rotor serves as the electrical machine rotor, the second rotor serves as the output shaft, and the stator serves as the electrical machine stator. This consolidation eliminates the need for separate gearbox housing, bearings, and coupling mechanisms.
3Reliability
If a magnetic gear system is used to eliminate mechanical contact, then reliability is improved, but manufacturing complexity increases due to precise alignment requirements of concentric rotors
Solution Approach 1:
The patent employs concentric cylindrical geometries for both rotors and the stator, with all components sharing a common rotational axis. This spherical/symmetrical arrangement simplifies manufacturing by allowing standardized radial mounting procedures and uniform air gap maintenance, rather than complex non-concentric alignments.
4Force
If direct drive machines are designed for high torque, then torque capability is improved, but size and mass increase making them infeasible for many applications
Solution Approach 1:
The patent introduces a magnetic field as an intermediary between the electrical machine and the load, allowing torque to be transmitted through the air gap via magnetic coupling rather than requiring direct mechanical contact. This magnetic intermediary enables high torque transmission without the need for a large-diameter rotor that would be required in a direct-drive mechanical system.
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 solution enables a compact, high-torque, low-speed drive system without mechanical gearboxes, offering improved reliability, efficiency, and reduced noise and vibration, suitable for applications like electric vehicles, wind turbines, and ship propulsion systems, with optimized parameters for desired performance.
Implementation Method 1
an outer stator (810) defining stator slots and having a plurality of pole pairs, the outer stator comprising AC windings (868, 870) located in the stator slots, the AC windings being operationally connected to a power supply operating at a supply frequency, the outer stator for producing a rotating magnetic field synchronized with the supply frequency
Implementation Method 2
a high speed rotor (844) positioned within the outer stator, the high speed rotor comprising ferromagnetic material and a combination of rotor bars (878) and permanent magnet pole pieces
Implementation Method 3
the magnetic gearing is achieved through modulation harmonics, allowing for asynchronous coupling and optimized parameter design to achieve high torque density at low speeds
Data Source
AI summary
An induction machine with integrated magnetic gears is disclosed. The machine comprises two rotors and two stators. An outer stator has ferromagnetic material, producing a rotating magnetic field with a defined number of pole pairs synchronized with a supply frequency. A high speed rotor has ferromagnetic material and a combination of rotor bars and permanent magnet pole pieces selected so that the permanent magnet pole pieces do not interact with the outer stator magnetic field. The high speed rotor rotation is asynchronously coupled to the outer stator magnetic field. An inner stator has ferromagnetic steel segments that modulate the field produced by the high speed rotor permanent magnets. A low speed inner rotor has ferromagnetic material and permanent magnet pole pieces, the low speed inner rotor counter-rotating to the high speed rotor. The low speed inner rotor is synchronously coupled to the high speed rotor using modulation harmonics.