Permanent Magnet Rotor Bridge Segmentation for High-Speed Torque
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Solution Overview
Problem
Permanent magnet type rotating electrical machines face challenges in suppressing peak voltage induced during low-speed rotation and efficiently utilizing magnetic fluxes while ensuring durability against high-speed rotation, especially when nonmagnetic portions are present on both sides of the permanent magnet in the circumferential direction.
Innovation Solution
The design incorporates a specific configuration where the circumferential pitch of teeth cores and the opening angle between magnetic path portions are optimized, with the permanent magnet divided into parts and a bridge portion formed between them, allowing for effective magnetic flux utilization and mechanical strength against centrifugal forces. This configuration adjusts the waveform of the induced voltage to increase the basic wave component while suppressing the peak value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the permanent magnet type rotating electrical machine is designed to generate high output voltage, then the output increases, but the peak induced voltage exceeds the withstand voltage of semiconductor devices in the inverter
Solution Approach 1:
The patent applies parameter changes by optimizing the opening angle θ between magnetic path portions and the circumferential width of permanent magnets to control the induced voltage waveform. By adjusting these geometric parameters, the basic wave component is maximized while the peak value is suppressed to remain within inverter withstand voltage limits, thus resolving the contradiction between output power and semiconductor device reliability.
2Reliability
If nonmagnetic portions are added on both sides of the permanent magnet to suppress peak voltage, then the peak induced voltage is reduced, but the magnetic flux utilization efficiency decreases
Solution Approach 1:
The patent optimizes the opening angle θ (set to specific ranges like 18°-42° or 72°-108°) and the circumferential width of permanent magnets to achieve the best balance. This parameter optimization ensures that nonmagnetic portions effectively suppress peak voltage while minimizing their negative impact on magnetic flux utilization, thereby resolving the contradiction between voltage suppression and productivity.
Solution Approach 2:
The patent introduces auxiliary salient poles that can perform field weakening control and utilize reluctance torque in the high-speed rotation range. This dynamic capability allows the system to adapt to different operating conditions, compensating for the reduced magnetic flux utilization caused by nonmagnetic portions while maintaining overall system performance.
3Strength
If the permanent magnet is divided into parts with bridge portions to enhance mechanical strength, then durability against centrifugal forces improves, but the device complexity increases
Solution Approach 1:
The patent divides the permanent magnet into multiple parts along the circumferential direction and connects them with bridge portions formed in the rotor core. This segmentation approach enhances mechanical strength and durability against centrifugal forces during high-speed rotation, while the bridge portions provide a practical and relatively simple structural solution to hold the divided magnets in place.
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 increases the basic wave component of induced voltage while maintaining a suppressed peak value, enhancing torque output and durability against high-speed rotation, thus improving the performance of permanent magnet type rotating electrical machines for vehicle driving applications.
Implementation Method 1
a voltage is induced in stator windings due to magnetic fluxes of permanent magnets during deceleration with coasting or braking of a vehicle
Implementation Method 2
measures for reducing the windage loss and wind roar (noise) are required
Data Source
AI summary
A permanent magnet type rotating electrical machine that is capable of producing a higher output and is suitable for high-speed rotation. A pair of nonmagnetic portions are formed in a rotor core at opposite ends of each pole. The waveform of induced voltage and a motor voltage are adjusted based on two parameters, i.e., an angle covering minimum magnetic path portions formed by the nonmagnetic portions and a magnet width. Assuming that a circumferential pitch of teeth cores with respect to a rotor axis is τs (degree) and an opening angle contained by a circumferential width between radial width minimum points of the pair of magnetic path portions with respect to the rotor axis is θ (degree), θ≈(n+Y)×τs (n: integer larger than 0) is met. Y=0.5 is set when the stator windings are wound in a distributed winding way, and Y=0.9-1.2 is set when they are wound in a concentrated winding way. The magnet forming one pole is divided into two parts, and a bridge portion is formed between the two divided magnet parts.