Composite Permanent Magnet Temperature Control for Motor Dragging Loss
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Solution Overview
Problem
In variable magnetic flux motors used for automobiles, high counter electromotive voltage at high rotation speeds leads to increased dragging loss, and existing solutions require generating a magnetic flux in the reverse direction to reduce this loss, which increases the load on the inverter.
Innovation Solution
A motor control method utilizing a composite permanent magnet with two different Curie temperatures, where the temperature of the magnet is controlled to achieve self-demagnetization and self-remagnetization, reducing dragging loss without generating a reverse magnetic flux.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a permanent magnet with high magnetic flux is used to obtain high torque during starting, then high torque is achieved during starting, but dragging loss increases during normal running at high rotation
Solution Approach 1:
The patent changes the magnetic flux parameter dynamically by controlling the temperature of the permanent magnet. At low speeds, the magnet operates at room temperature for high flux and high torque. At high speeds, the magnet is heated to reduce its magnetic flux, thereby reducing the counter electromotive voltage and dragging loss. This parameter change resolves the contradiction between needing high torque at starting and low dragging loss during normal running.
Solution Approach 2:
The patent makes the magnetic flux dynamic rather than static by introducing temperature control. The magnetic flux automatically adjusts based on operating conditions: high flux at low speed for high torque, and reduced flux at high speed for low dragging loss. This dynamic adaptation resolves the contradiction between high torque requirement during starting and low dragging loss requirement during normal running.
2Loss of energy
If a stator coil generates a magnetic flux in the reverse direction to reduce magnetic flux at high rotation, then dragging loss is reduced, but the load on the inverter increases
Solution Approach 1:
The patent replaces the electrical method (generating reverse magnetic flux through stator coil) with a thermal method (heating the permanent magnet to reduce its magnetic flux). Instead of using the inverter to generate a demagnetizing magnetic field, the system uses a heating device to thermally demagnetize the permanent magnet. This substitution eliminates the additional inverter load while achieving the same goal of reducing dragging loss at high rotation speeds.
Solution Approach 2:
The patent introduces temperature as an intermediary parameter to control magnetic flux. Rather than directly controlling magnetic flux through electrical means (which increases inverter load), the system uses temperature as an intermediate control variable. By heating the permanent magnet, the magnetic flux is reduced indirectly through thermal effects, avoiding the need for high inverter power while still reducing dragging loss.
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 approach effectively reduces dragging loss at high rotation speeds by controlling the temperature of the composite permanent magnet, allowing for efficient motor operation without the need for a reverse magnetic flux, thus minimizing inverter load.
Implementation Method 1
the Curie temperature of one of the core part and the shell part is Tc1 K, the Curie temperature of another is Tc2 K
Data Source
AI summary
To provide a motor control method ensuring that dragging loss at the time of high rotation can be reduced.A motor control method, wherein a composite permanent magnet has a core part and a shell part, the Curie temperature of one of the core part and the shell part is Tc1 K, and the Curie temperature of another is Tc2 K, and wherein when the magnitude of the reluctance torque is equal to or greater than the magnitude of the magnet torque, the temperature of the composite permanent magnet is set at Ts K that is (Tc1−100) K or higher and lower than Tc2 K and when the magnitude of the reluctance torque is less than the magnitude of the magnetic torque, the temperature of the composite permanent magnet is set at lower than the temperature Ts K or Tc1 K, whichever is lower.