Magnetizing Permanent Magnet Segments Using Pulse DC
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Solution Overview
Problem
The assembly of permanent magnet rotors in electrical machines is cumbersome and prone to accidents due to the need for precise alignment and restraint of energized magnet segments, and metallic retaining rings induce eddy currents that impede magnetization, especially in larger machines.
Innovation Solution
A magnetizer system using pulse direct current for an optimal duration to magnetize non-magnetized permanent magnet segments, with a magnetization fixture and coils configured to suppress eddy currents in the retaining ring, ensuring complete flux penetration and alignment of magnet segments for efficient magnetization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If pre-magnetized permanent magnet segments are assembled around the rotor spindle, then the rotor can be constructed with permanent magnets, but the assembly process becomes cumbersome and time-consuming requiring substantial forcing and aligning by mechanical devices
Solution Approach 1:
The patent applies preliminary action by assembling the permanent magnet segments in their desired positions around the rotor spindle before magnetization. The segments are positioned and restrained by mechanical devices and a retaining ring prior to the magnetization process, so that when magnetized in place, they remain in the correct alignment without requiring post-magnetization adjustment or repositioning.
Solution Approach 2:
The patent merges the assembly and magnetization operations into a single integrated process. Instead of magnetizing segments separately and then assembling them, the segments are assembled in their final positions and then magnetized in place using a magnetization fixture that applies magnetic fields directly to the assembled segments, combining two previously separate operations into one efficient process.
2Ease of manufacture
If un-magnetized permanent magnet segments are assembled and then magnetized all at once, then assembly is simplified, but metallic retaining rings induce eddy currents that impede magnetization
Solution Approach 1:
The patent introduces a non-conductive coating on the metallic retaining ring as an intermediary layer. This coating acts as a barrier that prevents eddy currents from forming in the metallic retaining ring during the magnetization process, while still allowing the ring to perform its mechanical function of restraining the permanent magnet segments in their correct positions.
Solution Approach 2:
The patent changes the electrical parameter of the retaining ring by applying a non-conductive coating, which transforms it from a conductive material that generates eddy currents to a non-conductive barrier that prevents eddy current formation, thereby enabling successful magnetization of the segments.
3Strength
If a metallic retaining ring is used to prevent fracturing and scattering of permanent magnet segments, then mechanical strength is improved, but eddy currents are induced that impede magnetization of the segments
Solution Approach 1:
The non-conductive coating serves as an intermediary layer between the metallic retaining ring and the permanent magnet segments. It allows the metallic ring to maintain its mechanical strength and restraining function while preventing the induction of eddy currents during magnetization, thus resolving the conflict between mechanical strength and magnetization effectiveness.
Solution Approach 2:
The retaining ring system becomes a composite structure combining the metallic material (providing mechanical strength) with a non-conductive coating material (providing electrical insulation). This composite structure simultaneously achieves both mechanical strength for restraining the segments and electrical non-conductivity for preventing eddy currents during magnetization.
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 method simplifies the magnetization process, reduces the risk of accidents, and achieves a sinusoidal flux distribution with reduced AC harmonic losses, torque ripple, vibration, and acoustic noise, facilitating efficient assembly and operation of electrical machines.
Implementation Method 1
A magnetizer system using pulse direct current for an optimal duration to magnetize non-magnetized permanent magnet segments
Implementation Method 2
the metallic retaining ring or holding ring around the permanent magnet assembly is induced with eddy currents which impede the un-magnetized magnets from becoming magnetized
Implementation Method 3
achieves a sinusoidal flux distribution with reduced AC harmonic losses
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
A method for magnetizing a rotor of an electrical machine is provided. The method includes assembling an array of non-magnetized anisotropic permanent magnet segments (19) around a rotor spindle (18) encased in a metallic ring. The method also includes determining multiple optimal magnetization orientation directions of the non-magnetized anisotropic permanent magnet segments (19). Further, the method includes positioning the assembled non-magnetized anisotropic permanent magnet segments (19) around the rotor spindle (18) such that the optimal magnetization orientation directions of the anisotropic permanent magnet segments (19) are aligned with multiple flux lines produced by a magnetization fixture (12). Finally, the method includes energizing the magnetization fixture (12) for magnetizing the segments (19) via a pulse direct current for an optimal duration of the pulse.