Stator Core Magnetic Permeability Gradient for Rotating Electrical Machine Cooling
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Solution Overview
Problem
In large-sized rotating electrical machines, particularly those with turbine-driven generators, the cooling effect near the axial center is decreased due to high magnetic flux density and increased heat generation, leading to reliability issues and inefficiencies in temperature distribution.
Innovation Solution
The stator core is formed using magnetic steel sheets with varying magnetic permeability, where grain-oriented sheets are used at the axial ends and non-oriented sheets at the axial center, and the thickness of the sheets is adjusted to optimize magnetic flux passage and cooling medium flow, reducing heat generation and improving temperature distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the number of cooling ducts per unit axial length is increased in the vicinity of the axial center to improve cooling effect, then the cooling effect is improved, but the magnetic flux density of the core is increased and loss is increased
Solution Approach 1:
The patent applies local quality by using grain-oriented magnetic steel sheets specifically at the axial end portions where cooling ducts are concentrated, while using non-oriented sheets in other regions. This local differentiation allows the high-permeability grain-oriented sheets to compensate for the increased magnetic flux density caused by additional cooling ducts, thereby reducing core loss in the specific high-stress region without compromising overall cooling effectiveness.
Solution Approach 2:
The patent changes the magnetic permeability parameter by selecting grain-oriented magnetic steel sheets with higher magnetic permeability for the axial end portions. This parameter change enables the core material to better conduct magnetic flux in regions where cooling ducts reduce the effective magnetic path area, thus maintaining lower magnetic flux density and reducing iron loss while preserving the enhanced cooling capability.
2Loss of energy
If grain-oriented magnetic steel sheets are used at axial end portions, then magnetic flux passage is improved and loss is reduced, but manufacturing complexity increases
Solution Approach 1:
The patent segments the stator core into distinct regions: axial end portions using grain-oriented magnetic steel sheets and central/portion regions using non-oriented sheets. This segmentation allows each region to be optimized for its specific functional requirements while maintaining manufacturing feasibility through standardized production processes for each sheet type and modular assembly approaches.
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 configuration enhances the reliability of the rotating electrical machine by improving temperature distribution near the stator winding, reducing heat generation, and minimizing losses associated with magnetic flux density and eddy currents.
Implementation Method 1
magnetic steel sheets which are different in magnetic permeability in a diametrical direction between at an axial end of and at an axial central portion of the stator core
Implementation Method 2
grain-oriented sheets are used at the axial ends and non-oriented sheets at the axial center
Implementation Method 3
minimizing losses associated with magnetic flux density and eddy currents
Implementation Method 4
the stator core is formed by punching a split piece... from a magnetic steel sheet, and laminating a plurality of those circular configurations in an axial direction
Implementation Method 5
a cooling medium is caused to flow diametrically of the cooling ducts 5 to cool the core and an armature winding 6
Data Source
AI summary
A rotating electrical machine includes: a rotor comprising a rotor core and a field winding wound round the rotor core; and a stator comprising a stator core and a stator winding wound round the stator core. The stator is arranged in opposition to the rotor with a predetermined spacing therebetween. the stator core is formed by punching a split piece, which comprises teeth for insertion of the stator winding thereinto and a core back on an outer periphery thereof, from a magnetic steel sheet, and laminating a plurality of those circular configurations in an axial direction, in which a plurality of the split pieces are arranged in a circle in a circumferential direction. The stator core has magnetic steel sheets, which are different in magnetic permeability in a diametrical direction, laminated at an axial end region of and in an axial central region of the stator core.