Magnetic Pole Module Structure for Low-Cogging Motor Rotors
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Solution Overview
Problem
Conventional electric machine designs face challenges in reducing cogging torque and torque pulsation, particularly in large-scale wind power generators, leading to increased manufacturing complexity, cost, and reliability issues due to inclined magnetic poles and inadequate magnetic pole fixation, which are prone to rust and powder under high-temperature and high-humidity conditions.
Innovation Solution
A magnetic pole module with offset structural features, where adjacent magnetic pole units in different modules are spaced apart by varying distances, and are sealed and fixed using a housing and adhesive, with resin infusion for complete sealing and mechanical fastening to the rotor yoke, ensuring reliable fixation and protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the rotor has inclined poles to reduce cogging torque and torque pulsation, then generator performance is improved, but manufacturing difficulty and cost increase significantly
Solution Approach 1:
The magnetic pole is divided into multiple magnetic pole units (first magnetic pole unit and second magnetic pole unit) that can be manufactured separately as conventional cuboid shapes, then assembled together. This segmentation allows each unit to be produced using standard manufacturing processes while the combined structure achieves the inclined pole effect needed to reduce cogging torque and torque pulsation.
Solution Approach 2:
The magnetic pole units are arranged asymmetrically with different axial offsets - the first magnetic pole unit is offset by a first axial distance while the second magnetic pole unit is offset by a second axial distance that differs from the first. This asymmetric arrangement creates the inclined pole configuration that reduces cogging torque and torque pulsation without requiring complex manufacturing of each individual pole.
2Reliability
If multiple conventional magnetic poles are offset axially to form segmented inclined poles, then cogging torque is reduced, but assembly dimensional control accuracy requirements increase, reducing yield and assembly efficiency
Solution Approach 1:
A dedicated mounting structure comprising a base plate and housing serves as an intermediary component between the magnetic pole units and the rotor yoke. The base plate provides a common reference plane for positioning both magnetic pole units, and the housing maintains precise axial distances between them. This intermediary structure eliminates the need for high-precision direct assembly of multiple offset poles, as the mounting structure itself ensures the required dimensional accuracy.
3Ease of manufacture
If surface pasting type magnetic pole fixing is used, then magnetic pole is bonded to rotor yoke surface, but sealing weak points occur leading to rust and powder under high-temperature high-humidity conditions
Solution Approach 1:
The magnetic pole units are nested within a housing that forms an enclosed space, which is then mounted to the rotor yoke. This nested structure provides inherent sealing protection, as the housing encloses the magnetic pole units and prevents direct exposure to the harsh environment. The mounting structure creates a protective barrier that eliminates sealing weak points and prevents rust and powder formation under high-temperature high-humidity operating conditions.
4Strength
If insertion type magnetic pole fixing is used with groove and end plate, then magnetic pole is reliably fixed, but sealing remains insufficient causing rust and powder accumulation
Solution Approach 1:
The fixing and sealing functions are merged into a single integrated mounting structure consisting of the base plate and housing. The base plate provides mechanical fixation by mounting to the rotor yoke, while the housing simultaneously provides comprehensive sealing protection for the magnetic pole units. This merged design eliminates the separate groove and end plate structure that failed to provide adequate sealing, achieving both reliable fixation and effective protection against rust and powder.
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 design effectively reduces cogging torque and torque pulsation, provides reliable sealing and mechanical fixation of magnetic poles, enhancing generator performance and durability under harsh conditions.
Implementation Method 1
a housing mounted to the first magnetic pole unit, the second magnetic pole unit and the base plate
Implementation Method 2
sealed and fixed using a housing and adhesive
Implementation Method 3
with resin infusion for complete sealing and mechanical fastening to the rotor yoke
Data Source
Figure 1
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AI summary
The present disclosure relates to a magnetic pole module, an electric motor rotor and a method for manufacturing the electric motor rotor. The electric motor rotor comprises a rotor yoke and multiple magnetic pole modules disposed on the rotor yoke, each of the magnetic pole modules comprising a base plate, a housing, and a pair of magnetic pole units that are accommodated in an accommodating space formed by the base plate and the housing and have opposite polarities, wherein a pair of magnetic pole units in each of the magnetic pole modules are spaced apart from each other by a first distance in a circumferential direction of the rotor yoke. The electric motor rotor according to the present disclosure can give consideration to the properties, such as cogging torque and torque pulsation, of a generator, the protection of magnetic poles and the mechanical fixation of the magnetic poles.