Double Stator PM Machine Layout for Heat and Demagnetization
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Solution Overview
Problem
Double stator electric machines face issues with heat generation and demagnetization, particularly in the inner stator, which can lead to performance degradation and structural rigidity concerns, limiting their suitability for high-torque density applications.
Innovation Solution
A high torque density double stator permanent magnet electric machine design featuring tangentially magnetized permanent magnets with complex topology profiles and optimized air-gaps between stators, along with winding configurations that reduce mutual inductance and current density, to manage heat and prevent demagnetization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the inner stator is isolated within the rotor away from convection with ambient air to maintain structural rigidity, then structural rigidity is improved, but heat build-up occurs causing temperature to increase
Solution Approach 1:
A thermal management system acts as an intermediary between the isolated inner stator and the external environment. The system includes cooling channels formed in the rotor that allow coolant to flow through, and thermal coupling elements that transfer heat from the inner stator to the coolant without compromising the structural isolation and rigidity of the inner stator within the rotor.
2Power
If spoke type configuration with tangentially orientated permanent magnets is used to generate high torque density, then torque density is improved, but demagnetization occurs causing performance to degrade
Solution Approach 1:
The patent modifies the magnetic parameters by using radially orientated permanent magnets instead of tangential orientation, and adjusts the flux distribution through specific pole configurations. This changes the magnetic field parameters to reduce demagnetization risk while maintaining high torque density through optimized flux paths and dual stator arrangements.
Solution Approach 2:
The patent employs a composite magnetic circuit design combining permanent magnets with electromagnets in the dual stator configuration. This composite approach allows the permanent magnets to provide baseline flux while electromagnets provide controllable flux, reducing the burden on permanent magnets and preventing demagnetization while maintaining high torque density.
3Power
If double stator configuration is used to utilize available space effectively, then torque density is improved, but heat generation increases causing reliability to worsen
Solution Approach 1:
The thermal management system is segmented into multiple independent cooling channels distributed throughout the rotor structure. Each channel serves a specific region, allowing localized heat removal from different parts of the double stator configuration. This segmentation enables effective thermal management while maintaining the high power density benefits of the double stator 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 effectively reduces heat buildup in the inner stator while maintaining high torque density and structural rigidity, preventing demagnetization and ensuring efficient thermal management, making it suitable for applications requiring high power and torque density.
Implementation Method 1
the rotor has a plurality of permanent magnets and a plurality of rotor segments located between the permanent magnets, where the inner stator, the rotor and the outer stator are coaxial, each of the plurality of permanent magnets is tangentially magnetized with respect to the rotor axis
Implementation Method 2
both the inner stator windings and outer stator windings can be wound around every other tooth of the stators to eliminate mutual inductance, decouple energizing phases and provide fault tolerance
Data Source
AI summary
A novel high torque density double stator permanent magnet electric machine is provided. An outer stator is provided which has complex teeth and optionally can have windings every tooth or every other tooth. A rotor is provided having a plurality of magnet receivers, each with a complex topology. Magnets are provided in the rotor which are tangentially magnetized with alternating polarities and a complex topology to increase torque density. An inner stator is provided having a plurality of teeth with complex topologies. Windings are provided around every tooth or every other tooth, alternatively. Air-gaps are provided between the outer stator and the rotor and between the rotor and inner stator. The air-gap between the inner stator and the rotor is smaller than the air-gap between the outer stator and the rotor. A lower current density in certain windings improves thermal response without comprising average torque.