Segmented Rotor Permanent Magnet Machine Flux Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current PM synchronous machines face issues with high magnetic material costs, poor voltage regulation, distorted waveforms under load, and difficulty in starting as synchronous motors due to flux drag effects, particularly in low pole number designs, limiting their use in small-scale power applications.
Innovation Solution
The design incorporates a rotor with angularly spaced permanent magnets, triangularly shaped voids, and slots in the rotor pole pieces to optimize flux flow and reduce harmonic distortion, along with a wound stator, which helps in minimizing magnetic material usage and improving voltage regulation and torque efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If surface-mount magnet types are used in 2- and 4-pole PM synchronous machines, then the machine structure is simplified and manufacturing is easier, but the output voltage and current waveforms become distorted under load and demagnetization occurs at high loads
Solution Approach 1:
The rotor magnet structure is segmented into multiple sections with different orientations. Each segment produces a specific flux component, and their combination creates a sinusoidal back-EMF waveform while preventing demagnetization. This segmentation allows the machine to maintain good waveform quality and reliability under load conditions.
2Reliability
If one-piece PM rotors are used to achieve acceptable waveform and voltage regulation, then voltage regulation improves, but magnet material volume increases up to six times compared to surface-mount designs
Solution Approach 1:
The rotor is divided into multiple segments with strategically oriented magnets. This segmentation allows achieving sinusoidal back-EMF and good voltage regulation without requiring a solid one-piece magnet structure, thereby reducing magnet material volume significantly while maintaining waveform quality.
Solution Approach 2:
Different regions of the rotor are given different magnetic properties and orientations. The magnet segments are positioned and oriented to create specific flux distributions in different zones, optimizing both waveform quality and material efficiency locally throughout the rotor structure.
3Volume of moving object
If low pole number (2- and 4-pole) PM synchronous machines are designed with conventional structures, then the machine size is reduced for small-scale applications, but flux drag effect causes severe waveform distortion under load
Solution Approach 1:
The rotor magnet structure is segmented into multiple sections with different orientations. Each segment produces a specific flux component, and their combination creates a sinusoidal back-EMF waveform while preventing demagnetization. This segmentation allows the machine to maintain good waveform quality and reliability under load conditions.
4Device complexity
If surface-mounted magnet segments with large arc segments are used, then the rotor structure is simplified, but manufacturing waste increases and monetary cost increases
Solution Approach 1:
The rotor magnet structure is segmented into multiple smaller sections with different orientations. This segmentation allows for more efficient use of magnet material, reducing waste during manufacturing while maintaining structural simplicity and achieving the desired sinusoidal flux distribution.
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 configuration reduces magnetic material volume by 50% for 2-pole machines and 38% for 4-pole machines, achieving near-sinusoidal output waveforms, improved voltage regulation, and enhanced torque efficiency, making them more cost-effective and efficient for both generator and motor applications.
Implementation Method 1
PM synchronous machines are robust, reliable and efficient... The need to save energy and increase the efficiency of motors and generators means PM synchronous machines are becoming a popular candidate because of their no-loss rotors.
Implementation Method 2
When operated as synchronous motors they are difficult to start without some form of sensor feedback.
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
A 2-pole machine arrangement (10) has a stator (100) with windings (101) in conventional form, wound either in a single phase or three phase configuration. The rotor is formed of stacked laminations. The laminations include rotor pole pieces (107) located between the two magnetic poles. Each pole is formed by a pair of (embedded) permanent magnets (103), angularly spaced-apart by inter-magnet segments (106). The rotor pole pieces (107) include a series of evenly-spaced slots (109) and a central void (108). The slots (109) are of various lengths to direct the flux from the magnets (103) into the air gap (121) at a desired angle normal to the rotor surface. The slots 109 may be varied in width and angle to achieve the desired lowest waveform distortion under load and the highest air gap flux. The slots (109) also contribute to changing the saliency of the rotor.