Large Electric Generator Cooling for Part-Load Thermal Stress
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Solution Overview
Problem
High-voltage power generation equipment, such as generators, face inefficiencies and increased thermal stresses due to part-load and varying-load operations, leading to sub-optimal performance and reduced winding life, particularly in air-cooled systems which are limited in capacity and complexity by hydrogen cooling requirements.
Innovation Solution
A gas-cooled generator system with a low-pressure pressurizing unit that adjusts cooling gas pressure between 0 to 2 bar gauge to optimize heat transfer and efficiency, combined with liquid cooling of stator coils, allowing for variable output and reduced thermal stresses, and utilizing non-explosive gases like air, helium, or nitrogen for enhanced performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If hydrogen cooling is used to increase power output capability, then the generator can achieve higher capacity, but the device complexity and operational cost increase significantly
Solution Approach 1:
The patent changes the cooling parameter from hydrogen to air, operating at atmospheric pressure rather than high pressure. This parameter change simplifies the cooling system while maintaining adequate cooling performance for the generator's power output capability.
Solution Approach 2:
The patent uses air, which is freely available and costs nothing, replacing expensive hydrogen cooling systems. This substitution reduces both capital investment and operational costs while providing sufficient cooling for the generator operation.
2Device complexity
If air cooling is used to reduce complexity, then the generator structure is simpler, but the power output capability is limited
Solution Approach 1:
The patent introduces a variable speed fan that can dynamically adjust its operation based on load conditions. The fan speed varies with generator output, providing optimized cooling performance across different operating conditions and enabling higher power output capability without proportionally increasing cooling system complexity.
Solution Approach 2:
The cooling system operates periodically based on generator loading conditions. The variable speed fan activates and adjusts its speed according to the thermal load, providing cooling only when and where needed, thereby maintaining power output capability while minimizing unnecessary cooling system complexity.
3Power
If the generator is sized for maximum power output, then it can meet peak demand, but efficiency decreases during part-load operation
Solution Approach 1:
The variable speed fan dynamically adjusts cooling provision to match the generator's actual power output. During part-load operation, the fan runs at lower speeds, reducing energy consumption and improving overall system efficiency while still providing adequate cooling. At full load, the fan operates at maximum capacity to support peak power output.
Solution Approach 2:
The cooling system parameter (fan speed) is changed from fixed to variable, allowing the system to adapt to different operating conditions. This parameter change enables the generator to maintain higher efficiency during part-load operation while retaining the capability to deliver maximum power output when needed.
4Ease of operation
If fixed cooling pressure is used to simplify control, then the system is easier to operate, but thermal stresses increase during varying-load conditions
Solution Approach 1:
The cooling system transitions from fixed pressure to variable pressure control, where the fan speed and resulting cooling pressure dynamically follow the generator load. This dynamic adjustment reduces thermal stresses on windings during varying-load conditions by providing appropriate cooling levels, while the control system remains relatively simple by using load-sensing feedback.
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 system achieves improved efficiency and extended winding life by optimizing cooling gas pressure and using liquid cooling, resulting in a smaller, more efficient generator with increased power output capabilities and reduced windage losses, while minimizing thermal stresses and operational costs.
Implementation Method 1
a gas cooled generator comprises a rotor arranged along a centerline of the generator; a stator core arranged coaxially with the rotor and at least partially surrounding the rotor
Implementation Method 2
a low pressure pressurizing unit configured to vary an operating pressure of a non-explosive cooling gas between atmospheric pressure and 1 to 2 bar above atmospheric pressure
Implementation Method 3
combined with liquid cooling of stator coils, allowing for variable output and reduced thermal stresses
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
Disclosed is an improved life large electric generator comprising a rotor arranged along a centerline of the generator; a core arranged coaxially and surrounding the rotor; a plurality of stator windings arranged within the core; a stator frame arranged to fixedly support the core and rotationally support the rotor; a gas cooling system that circulates a cooling gas within the generator; a liquid cooling system that circulates a cooling liquid to cool the stator windings wherein the cooling ability of the liquid cooling system is a function of a required generator parameter; and a pressure boundary member that surrounds a plurality of the rotor and an entirety of the core and stator windings, the frame configured to operatively contain an internal pressure of two (2) bar relative to atmospheric pressure.