Two-Phase Gap Cooling for Electrical Machine Rotor Thermal Management
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Solution Overview
Problem
In synchronous reluctance, interior permanent magnet, and surface permanent magnet motors, the rotor experiences excessive heat, leading to degraded magnet performance and increased stator temperature due to inefficient cooling methods, which result in high friction and windage losses when using liquid coolants.
Innovation Solution
A two-phase gap cooling system is implemented, where a mixture of gas and coolant (such as air and oil) is directed through the gap between the rotor and stator, controlled to maintain acceptable friction and windage losses, using a gas circulating system to generate pressure and ensure effective cooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If liquid coolant is used to cool the rotor, then cooling effectiveness is improved, but friction and windage losses increase significantly
Solution Approach 1:
The patent applies pneumatic cooling by introducing a gas coolant (such as nitrogen or air) into the rotor through coolant injection ports. The gas is pressurized and circulated through the rotor's internal passages, absorbing heat from the magnets and windings. This pneumatic approach replaces traditional liquid cooling, eliminating the friction and windage losses associated with liquid coolant while maintaining effective heat removal from the rotor components.
Solution Approach 2:
The patent changes the physical state parameter of the coolant from liquid to gas phase. By using gaseous coolant instead of liquid coolant, the system achieves effective cooling while avoiding the harmful effects of liquid presence in the rotor. The gas coolant can be circulated at controlled pressures and flow rates, providing adjustable cooling performance without increasing mechanical losses.
2Temperature
If internal volume is filled with oil for cooling, then cooling effectiveness is improved, but friction and windage losses become prohibitively high
Solution Approach 1:
The patent replaces liquid oil filling with a pneumatic cooling system. Gas coolant is introduced through injection ports and circulated through internal passages within the rotor, providing cooling to internal motor components without requiring the internal volume to be filled with liquid. This eliminates the high friction and windage losses that would result from liquid filling while maintaining effective thermal management of internal components.
Solution Approach 2:
The patent introduces a gas coolant as an intermediary substance to transfer heat from internal motor components. The gas circulates through internal passages, absorbing heat from the magnets and windings, and carries it away through the cooling system. This intermediary gas phase coolant provides the necessary thermal coupling without the mechanical interference and losses associated with liquid oil filling.
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 approach significantly enhances cooling of the electrical machine while minimizing friction and windage losses, effectively managing rotor and stator temperatures.
Implementation Method 1
excessive heat is transferred from the rotor to the stator through the gap between the rotor and the stator
Implementation Method 2
directing a mixture of gas and cooling liquid or coolant through the gap between the rotor and stator
Implementation Method 3
The gas may be pressurized to generate the flow of the gas and coolant mixture through the gap
Data Source
AI summary
An electro-dynamic machine has a rotor and stator with a gap therebetween. The machine has a frame defining a hollow interior with end cavities on axially opposite ends of the frame. A gas circulating system has an inlet that supplies high pressure gas to the frame interior and an outlet to collect gas passing therethrough. A liquid coolant circulating system has an inlet that supplies coolant to the frame interior and an outlet that collects coolant passing therethrough. The coolant inlet and gas inlet are generally located on the frame in a manner to allow coolant from the coolant inlet to flow with gas from the gas inlet to the gap. The coolant outlet and gas outlet are generally located on the frame in a manner to allow the coolant to be separated from the gas with the separated coolant and gas collected for circulation through their respective circulating systems.