Segmented Rotor Body for Hydroelectric Generator Critical Speed
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Solution Overview
Problem
High-speed, high-performance hydroelectric power generators face challenges with low first critical speed due to large rotor mass, leading to resonance vibrations and operational limitations, which complicates cooling and increases costs with traditional water cooling methods.
Innovation Solution
A self-supporting rotor body composed of interconnected forged steel rings without a central shaft, allowing for reduced rotor mass and increased rigidity, enabling air cooling and operation at higher speeds, with radial cooling channels and transition pieces for thermal expansion compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the rotor mass is increased to achieve high performance output, then the power output increases, but the first critical speed decreases leading to resonance vibrations and operational limitations
Solution Approach 1:
The rotor body is divided into multiple forged steel rings (typically 3-5 rings) instead of a single monolithic structure. These rings are connected by bolts to form a segmented rotor assembly that maintains high strength while reducing overall mass. The segmentation allows each ring to be optimized independently and facilitates easier transportation and assembly.
Solution Approach 2:
The rotor employs a composite structure combining forged steel rings with aluminum or composite wheel hubs. This hybrid construction leverages the high strength-to-weight ratio of aluminum/composite materials for the wheel hubs while using forged steel rings for the high-stress pole regions, achieving optimal balance between power output and critical speed.
2Speed
If the rotor mass is reduced to increase the first critical speed, then the critical speed increases, but the power output decreases and cooling efficiency becomes insufficient
Solution Approach 1:
The segmented ring structure reduces rotor mass compared to a solid rotor of equivalent dimensions, thereby increasing the first critical speed. The segmentation removes unnecessary material while maintaining structural integrity through the bolted connections between rings.
Solution Approach 2:
The rotor incorporates an integrated water cooling system with cooling channels formed within the forged steel rings. Water is circulated through these channels to efficiently remove heat from the rotor windings and magnetic poles, enabling the reduced-mass rotor to maintain adequate thermal management for high power output applications.
3Temperature
If traditional water cooling is implemented to cool the rotor, then cooling efficiency improves, but the device complexity and cost increase
Solution Approach 1:
The cooling system is merged with the rotor structure itself. Water cooling channels are directly formed within the forged steel rings during manufacturing, integrating the cooling function into the rotor body rather than requiring separate cooling components. This reduces overall system complexity while maintaining effective cooling.
Solution Approach 2:
The rotor structure provides its own cooling capability through the integrated water channels. The rotor serves dual functions: generating electrical power through electromagnetic induction and dissipating heat through internal water cooling, eliminating the need for external cooling systems.
4Strength
If a solid rotor body is used to ensure structural integrity, then strength increases, but the rotor mass increases and critical speed decreases
Solution Approach 1:
The rotor is constructed from multiple forged steel rings connected by high-strength bolts. This segmented structure reduces mass compared to a solid rotor while maintaining structural integrity through the bolted connections. Each ring can be independently forged to optimal specifications and then assembled.
Solution Approach 2:
The steel rings are pre-forged to precise specifications with integrated cooling channels and mounting features before assembly. This preliminary fabrication ensures each component has optimal strength properties and reduces the need for heavy material to compensate for assembly joint weaknesses.
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 first critical speed, facilitates efficient air cooling, and simplifies transportation and assembly, enabling high-speed operation of large hydroelectric power generators while maintaining high performance.
Implementation Method 1
The cooling air is then preferably fed into the interior of the rotor body via an end-face opening and from there it is conducted further via the radial cooling ducts to the ducts running at the bases of the grooves. The cooling air can then leave the rotor via radial bores in the winding.
Implementation Method 2
Radial cooling channels for the cooling air can be formed in a simple manner, namely via grooves or depressions in the contact surfaces between the rings.
Implementation Method 3
Wherein the transition pieces extend in the axial direction so that they are compliant in the radial direction. This compensates for the expansion of the steel rings caused by the operating temperature and above all by the centrifugal forces.
Implementation Method 4
This compensates for the expansion of the steel rings caused by the operating temperature and above all by the centrifugal forces.
Data Source
Figure 1
Figure 2~3
Figure 4~6
AI summary
The invention relates to a hydraulic power generator (1) designed as a synchronous electric machine which has an air-cooled rotor (2) and a stator (3) and which comprises at least eight poles (19) formed by the rotor windings (7). The invention also relates to a method for manufacturing the disclosed hydraulic power generator (1) as well as a method for operating same.