Permanent Magnet Retainers on Rotor
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Solution Overview
Problem
Existing permanent magnet rotor arrangements in rotating electrical machines suffer from unacceptably high eddy current losses, particularly when flux passes through the rotor drum in a radial direction.
Innovation Solution
A rotor arrangement where magnet carriers are spaced apart from the rotor drum radially, with pole pieces located on the outer or inner surface, and enclosed by a non-magnetic retainer to prevent flux path into the drum, using laminated magnetic material and non-magnetic spacers to reduce eddy currents and allow for cooling air passages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If magnet carriers are affixed directly to the rotor drum to provide a flux path, then the rotor structure is simplified, but eddy current losses increase unacceptably
Solution Approach 1:
The rotor is segmented into distinct components: magnet carriers mounted on the rotor drum surface rather than affixed directly, with magnet carriers spaced apart to interrupt eddy current paths. This segmentation reduces eddy current losses while maintaining structural integrity and flux path functionality through the distributed magnet carrier arrangement.
2Power
If permanent magnet material is used to provide high energy product, then magnetic performance is improved, but the material becomes brittle and prone to fracture and corrosion
Solution Approach 1:
A pole piece retainer made of non-magnetic material is provided to enclose the permanent magnet pole piece beforehand, providing mechanical protection against fracture and corrosion. This protective enclosure is designed in advance to prevent damage to the brittle high-energy-product magnet material during operation and maintenance.
Solution Approach 2:
The rotor assembly uses composite material construction with non-magnetic retainers enclosing magnetic pole pieces. This composite structure combines the high energy product benefits of rare earth magnets with the mechanical strength and corrosion resistance of the non-magnetic retainer material, creating a reliable hybrid system.
3Loss of energy
If magnet carriers are spaced apart from the rotor drum to reduce eddy currents, then eddy current losses are reduced, but the rotor structure becomes more complex
Solution Approach 1:
Non-magnetic spacers or support members are introduced as intermediaries between the magnet carriers and the rotor drum. These intermediaries maintain the radial spacing required to reduce eddy current losses while simplifying the overall structure by providing a straightforward mounting solution that doesn't require complex integration of spacing features into the magnet carriers themselves.
4Reliability
If a pole piece retainer is provided to protect the permanent magnet material, then reliability is improved, but the device complexity increases
Solution Approach 1:
The pole piece retainer serves multiple functions simultaneously: it provides mechanical protection against fracture, corrosion resistance, structural support for the pole piece, and electrical isolation. By combining these functions into a single component, the design improves reliability without proportionally increasing device complexity.
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
Significantly reduces eddy current losses, simplifies construction, allows for easy assembly and replacement of pole pieces, and provides environmental protection for the magnets while maintaining efficient cooling.
Implementation Method 1
Each pole piece is enclosed by a pole piece wrapper or retainer made of a non-magnetic material... the flux path between adjacent pole pieces flows through the body or drum of rotor in the circumferential direction
Implementation Method 2
Each magnet carrier has a laminated construction... The magnet carriers are spaced apart from the rotor drum in the radial direction by the array of circumferentially spaced T-shaped fixing members to define a space or void therebetween
Implementation Method 3
The magnet carriers are spaced apart from the rotor drum in the radial direction... to define a space or void therebetween... provides environmental (and optionally also mechanical) protection for the permanent magnet material
Data Source
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AI summary
The present invention provides a permanent magnet rotor arrangement for a rotating electrical machine including a rotor (6) having an outer rim (4). A circumferential array of magnet carriers (8) is mounted to the rotor (6) by fixing members (16) and support members (18) and is spaced apart from the rotor body (6) in the radial direction to define a series of axially gaps or spaces (20) which can optionally be used as passages for cooling air. At least one pole piece (10) made of permanent magnet material is located adjacent to a surface of each magnet carrier (8). The magnet carriers (8) and pole pieces (10) preferably have a laminated or divided construction to virtually eliminate eddy currents that may be particularly problematic in certain types and construction of electrical machine. The flux path between adjacent pole pieces (10) flows in the circumferential direction within the magnet carriers (8) and does not use the rotor 6.