Motor Rotor Structure With Variable Pole States for Wide Speed Range
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Solution Overview
Problem
Permanent magnet motors face challenges in adjusting their internal magnetic field to balance efficiency at high and low frequencies, leading to increased copper loss, reduced efficiency, and limited speed regulation due to fixed magnetic flux, which is addressed by incorporating a motor rotor structure with permanent magnets of different coercivities to dynamically adjust the magnetic field based on operational conditions.
Innovation Solution
The motor rotor structure features first and second permanent magnet slots with magnets of varying coercivities, allowing for adjustments in magnetization direction via armature current to switch between more-magnetic-pole and fewer-magnetic-pole states, optimizing torque and speed according to operational conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If flux weakening control is used to expand the operating range of permanent magnet motors, then the speed regulation range is expanded, but motor copper loss increases and motor efficiency decreases
Solution Approach 1:
The rotor is segmented into multiple permanent magnet slots with different coercivity magnets, allowing independent control of magnetic flux from different magnet groups. This segmentation enables flexible flux adjustment without requiring high current flux weakening control, thus expanding speed regulation range while reducing copper losses.
Solution Approach 2:
The invention changes the magnetic field parameters by using permanent magnets with different coercivities (e.g., different remanence values) in different slots. By selectively controlling the magnetization states of these magnets through armature reaction, the total magnetic flux can be adjusted, enabling wide speed regulation without excessive copper loss.
2Device complexity
If permanent magnets with fixed magnetic flux are used, then the motor structure is simple, but it is difficult to adjust the internal magnetic field to balance efficiency at high and low frequencies
Solution Approach 1:
Different regions of the rotor (different permanent magnet slots) are assigned magnets with different local properties (different coercivities). This allows the magnetic field to be locally adjusted by controlling specific magnet groups, providing magnetic field adaptability while maintaining a relatively simple overall motor structure.
Solution Approach 2:
The invention transforms the static magnetic field from fixed permanent magnets into a dynamic adjustable field by utilizing the different coercivity characteristics of magnets in different slots. Through armature reaction control, the magnetic flux can be dynamically adjusted to optimize efficiency at different operating frequencies while keeping the physical structure simple.
3Device complexity
If fixed power supply voltage is used, then the system is simple, but the maximum operating frequency of the motor is limited
Solution Approach 1:
By changing the magnetic flux parameter through selective control of permanent magnets with different coercivities, the motor can operate at higher frequencies without requiring proportional increases in voltage. This allows the maximum operating frequency to be extended while maintaining a simple fixed voltage system.
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 solution enables the motor to expand its operating range and increase efficiency by dynamically adjusting the internal magnetic field, enhancing torque and speed regulation while minimizing copper loss and improving motor performance across different operational states.
Implementation Method 1
A permanent magnet motor adjusts the intensity of an internal magnetic field of the motor according to a load of the motor
Implementation Method 2
When identical polarities of adjacent two kinds of permanent magnets having different coercivities face each other, the rotor core is in a more-magnetic-pole state. When contrary polarities of adjacent two kinds of permanent magnets having different coercivities face each other, the rotor core is in a fewer-magnetic-pole state
Data Source
AI summary
A motor rotor structure including a rotor core. Multiple first permanent magnet slots are disposed in the rotor core in a circumferential direction. At least one second permanent magnet slot is disposed between every two adjacent first permanent magnet slots; each of the first permanent magnet slots and an adjacent second permanent magnet slot thereof are spaced a preset distance apart. Between two kinds of permanent magnets having different coercivities, a first kind of permanent magnet is mounted in each of the first permanent magnet slots and a second kind of permanent magnet is mounted in the second permanent magnet slot. When identical polarities of adjacent two kinds of permanent magnets having different coercivities face each other, the rotor core is in a more-magnetic-pole state. When contrary polarities of adjacent two kinds of permanent magnets having different coercivities face each other, the rotor core is in a fewer-magnetic-pole state.