Rotor Lamination Design for High-Speed Asynchronous Machines
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Solution Overview
Problem
Asynchronous machine rotors are limited in maximum rotation speed and radial dimension reduction due to mechanical stresses from centrifugal and temperature-related loading, which are not adequately addressed by existing designs, leading to increased mass and production costs.
Innovation Solution
A rotor design featuring a laminated core with strategically strengthened rotor laminations at the ends, providing increased strength and rigidity to absorb centrifugal forces, allowing higher rotation speeds and reduced dimensions without increasing mass or production costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the rotor dimensions are reduced to increase power density, then the power density improves, but the mechanical strength of the webs decreases due to increased centrifugal forces
Solution Approach 1:
The patent applies local quality by differentiating the lamination structure between the end regions and the central region of the rotor core. The end regions utilize laminations with increased web thickness to provide enhanced mechanical strength where centrifugal forces are highest, while the central region maintains standard lamination dimensions to preserve power density. This localized structural differentiation allows the rotor to achieve compact dimensions without compromising the mechanical integrity of critical areas.
2Power
If the rotation speed is increased to improve power output, then the power output improves, but the centrifugal forces on the laminated core increase quadratically
Solution Approach 1:
The patent addresses the quadratic increase in centrifugal forces by implementing local quality enhancement at the rotor ends where these forces are most severe. By increasing the web thickness specifically in the end region laminations, the structure can withstand the intensified centrifugal loading at high rotation speeds without requiring a uniform increase in the entire rotor dimensions, thus maintaining power density while enabling higher operational speeds.
3Strength
If the web size is increased to improve mechanical strength, then the mechanical strength improves, but the radial dimensions of the rotor increase
Solution Approach 1:
The patent resolves this contradiction by applying the local quality principle, which dictates that the increased web thickness is implemented only in the end region laminations where mechanical strength is most critical due to higher centrifugal forces. The central region laminations maintain their standard, smaller dimensions. This selective approach ensures adequate mechanical strength in the critical end regions without increasing the overall radial dimensions of the rotor, thereby preserving compact size and power density.
4Stress or pressure
If steps are formed in the transition region to reduce stress peaks, then the local stress peaks are reduced, but the mass of the cage increases
Solution Approach 1:
The patent applies parameter changes by modifying the lamination geometry in the end regions, specifically increasing the web thickness parameter in these areas. This geometric parameter change strengthens the transition regions between the rotor bars and short-circuiting rings, reducing stress peaks without requiring additional mass from steps or other cage modifications. The parameter change is localized to the laminations rather than the cage structure itself.
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 design enhances the rotor's ability to achieve higher rotation speeds and more compact construction with reduced radial dimensions, improving power density and weight savings while maintaining mechanical integrity and production efficiency.
Implementation Method 1
The centrifugal force which occurs can be described by the following equation: F=m*ω2*r
Implementation Method 2
The cage of the rotor is generally manufactured from copper and therefore has a greater coefficient of thermal expansion than the laminated core. Consequently, the short-circuiting ring and rods of the cage expand to a greater extent than the laminated core when there is an increase in temperature during operation of the asynchronous machine.
Data Source
AI summary
A rotor for an asynchronous machine includes a laminated rotor core which is made of a plurality of rotor laminations that are stacked in a longitudinal direction of the rotor, an intended rotational axis of the rotor running in the longitudinal direction; and a rotor cage that has a number of rotor bars, which run through the rotor laminations in the longitudinal direction, and at least one short circuit ring, which is arranged on a laminated rotor core end lying in the longitudinal direction such that the short circuit ring electrically connects the rotor bars together. The laminated rotor core contains at least one rotor lamination in a region at the end. This rotor lamination has a greater strength and/or a greater rigidity in a radial direction with respect to the rotational axis than the other rotor laminations.