Electric Machine Field Strengthening Against Magnet Demagnetization
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Solution Overview
Problem
Existing electric machines face demagnetization of permanent magnets due to high temperatures, leading to reduced performance or failure, as existing methods fail to effectively prevent demagnetization at elevated temperatures.
Innovation Solution
Implementing a field-strengthening mode by energizing the motor winding with a positive field-forming current component to support the magnetic field of permanent magnets, thereby preventing demagnetization and remagnetizing partially demagnetized magnets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the motor winding is energized with high motor current to generate desired torque at high temperatures, then the torque output is maintained, but the permanent magnets become demagnetized
Solution Approach 1:
The patent changes the current vector parameters by introducing a positive d-axis current component (Id > 0) in addition to the q-axis current component. This parameter change transforms the motor operating point from conventional torque-only control to a mode that simultaneously strengthens the magnetic field and prevents demagnetization, resolving the contradiction between maintaining torque and protecting magnetization at high temperatures
Solution Approach 2:
The patent applies preliminary anti-action by proactively introducing a field-forming current component before demagnetization occurs. The control unit detects temperature conditions and preemptively adjusts the current vector to create a strengthening magnetic field that counteracts the demagnetizing effect of high temperatures, preventing the harmful effect before it manifests
2Reliability
If the magnetic stator flux is reduced at high temperatures to protect permanent magnets, then demagnetization is prevented, but the torque generation capability is reduced
Solution Approach 1:
Instead of reducing the magnetic stator flux as in prior art, the patent changes the current vector parameters by adding a positive d-axis current component. This parameter change allows the system to maintain or even enhance the magnetic field strength while preventing demagnetization, thereby maintaining torque generation capability without sacrificing reliability
Solution Approach 2:
The patent inverts the conventional approach by not reducing but rather strengthening the magnetic field at high temperatures. Instead of lowering the magnetic stator flux to protect magnets, the system applies a field-forming current component that strengthens the magnetic field, simultaneously achieving protection and maintaining power output
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
Enhances the durability of electric machines by preventing demagnetization and remagnetizing affected magnets, ensuring continued operation and performance.
Implementation Method 1
the motor winding is energized or exposed to the motor current in such a way that a drive magnetic field is generated and the electric machine generates or provides the specified desired torque
Implementation Method 2
Due to the positive field-forming current component, a field strengthening of the magnetic field of the permanent magnet assembly is achieved
Implementation Method 3
the magnetic field is generated, which supports the correct alignment of micropoles of the permanent magnets of the permanent magnet assembly
Data Source
AI summary
The invention relates to a method for operating an electric machine (9) comprising a rotatably mounted rotor (10) and at least one motor winding (13). In said method, a temperature load of the machine (9) is ascertained, and an electric motor current is applied to the motor winding (13) to generate a specified desired torque (Ndesired) according to the temperature load. According to the invention, when a temperature load is ascertained that exceeds a specified load threshold, a field strengthening mode of the machine (9) is activated, in which field-strengthening mode the motor winding (13) is energized in such a way that the motor current has a positive field-forming current component (Id).