Flux Concentration Rotor Demagnetization Protection
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Solution Overview
Problem
Synchronous rotating electrical machines with permanent magnets and flux concentration are prone to demagnetization, especially under high temperature conditions, which poses a risk to their performance and reliability in variable automotive applications.
Innovation Solution
Incorporating a defluxing magnetic circuit with specific magnetic reluctance ratios within the rotor to prevent demagnetization, featuring slots and recesses that manage magnetic flux and mechanical stress, ensuring the permanent magnets are protected against short-circuit currents and high-speed operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a defluxing magnetic circuit is added to prevent demagnetization, then reliability is improved, but device complexity increases
Solution Approach 1:
The defluxing magnetic circuit is nested within the existing rotor structure, utilizing the magnetic body and slot arrangements to create the protection function without adding external components. The second slot and constriction are integrated into the rotor's magnetic body, forming a compact nested structure that provides demagnetization protection while maintaining space efficiency.
Solution Approach 2:
The defluxing magnetic circuit acts as an intermediary element between the permanent magnets and the external magnetic field. By introducing this intermediate magnetic path with controlled reluctance, the circuit mediates the interaction between the magnets and opposing magnetic fields, preventing direct demagnetizing effects while maintaining overall system functionality.
2Power
If magnets are arranged in radial configuration for flux concentration, then power-to-weight ratio is improved, but susceptibility to demagnetization increases
Solution Approach 1:
The patent applies local quality by creating different magnetic reluctance characteristics in different regions of the rotor. The defluxing magnetic circuit introduces specific local magnetic paths with controlled reluctance values, while the rest of the rotor maintains the high-flux-density radial configuration. This localized modification protects specific vulnerable areas without compromising the overall flux concentration performance.
Solution Approach 2:
The magnetic circuit employs composite structural elements combining magnetic materials with specific reluctance properties. The magnetic body incorporates regions with different magnetic characteristics - high permeability areas for flux concentration and controlled reluctance areas for demagnetization protection - creating a functionally composite magnetic structure that simultaneously achieves both performance and reliability goals.
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 solution effectively eliminates the risk of demagnetization, enhancing the reliability and performance of synchronous rotating electrical machines by optimizing magnetic flux management and mechanical stress distribution, thereby ensuring stable operation across varying conditions.
Implementation Method 1
a defluxing magnetic circuit allowing the circulation of a defluxing magnetic flux
Implementation Method 2
the defluxing magnetic circuit having a magnetic reluctance of the defluxing circuit determined as a function of an internal magnetic reluctance of the permanent magnet
Data Source
AI summary
A synchronous rotating electrical machine is disclosed, of the type including a stator (10) and a rotor (11). The rotor is of the flux concentration type and includes a plurality of alternate North and South poles formed from permanent magnets (PM). The magnets are housed in slots (E1) arranged in the magnetic body of the rotor. The rotor includes, for each permanent magnet, a magnetic circuit allowing the circulation of a defluxing magnetic flux. This magnetic circuit has a magnetic reluctance of the defluxing circuit (Rf) determined as a function of an internal magnetic reluctance of the magnet (Ra) such that the ratio (Rf/Ra) of the magnetic reluctance of the defluxing circuit on the internal magnetic reluctance of the magnet (Ra) is within a range of predetermined values guaranteeing the magnet against a risk of demagnetization. This range of predetermined values is from approximately 0.3 to approximately 3 depending on the type of magnet.