Sealed Permanent Magnet Machine Cooling via Internal Airflow
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Solution Overview
Problem
Existing cooling methods for permanent magnet electric machines are inefficient, particularly when the machines need to be sealed from the outside environment, leading to demagnetization and increased costs, size, and complexity due to ancillary component cooling solutions.
Innovation Solution
A closed-loop air cooling system that uses a centrifugal blower to circulate air across the permanent magnets and stator, with cooling channels and a heat exchanger to transfer thermal energy to a coolant, and diverting airflow to ancillary components like inverters through power lead housings for effective thermal management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a fan is used to introduce cool air to permanent magnet surfaces, then cooling effectiveness is improved, but the machine cannot be sealed from the outside environment
Solution Approach 1:
The patent combines the cooling function with the sealed environment requirement by integrating a centrifugal blower that circulates air within the sealed housing, eliminating the need for external air intake while maintaining both sealing and cooling effectiveness
Solution Approach 2:
The patent introduces a heat exchanger as an intermediary component that transfers heat from the permanent magnets to a coolant fluid, enabling cooling without direct external air flow and thus maintaining the sealed environment
2Temperature
If coolant is flooded into the rotor cavity, then cooling of permanent magnets is improved, but windage losses increase severely
Solution Approach 1:
The patent uses a controlled hydraulic cooling system with cooling channels that deliver coolant precisely where needed, avoiding the need to flood the entire rotor cavity and thus eliminating excessive windage losses while maintaining effective cooling
3Temperature
If active cooling systems with spray nozzles are used, then cooling effectiveness is improved, but system complexity and cost increase
Solution Approach 1:
The patent extracts the complex spray nozzle system and replaces it with a simpler cooling channel architecture integrated into the rotor structure, maintaining cooling effectiveness while significantly reducing system complexity and eliminating the need for separate lubrication and scavenge systems
4Reliability
If excess capability is designed into the machine, then demagnetization is prevented, but machine size increases
Solution Approach 1:
The patent implements preliminary cooling action through integrated cooling channels and active temperature management, allowing the machine to operate at higher power densities without requiring excess physical size, while still preventing demagnetization through proactive thermal control
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 solution prevents demagnetization, reduces the size and complexity of the machine, and enhances the efficiency of the cooling process while maintaining the machine's sealed environment, allowing for smaller gauge power leads and improved reliability.
Implementation Method 1
a pumping element configured to urge an airflow across the plurality of permanent magnets of the rotor of the electric machine to remove thermal energy therefrom
Implementation Method 2
a plurality of cooling channels disposed in the housing of the electric machine configured to transfer thermal energy from the stator of the electric machine to a flow of fluid coolant through the plurality of cooling channels
Implementation Method 3
a plurality of cooling channels disposed in the housing of the electric machine configured to transfer thermal energy from the stator of the electric machine to a flow of fluid coolant through the plurality of cooling channels
Implementation Method 4
a heat exchanger in thermal communication with the plurality of cooling channels to transfer thermal energy from the airflow to the fluid coolant
Data Source
Figure 1
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AI summary
A cooling system for a sealed permanent magnet electric machine (10) includes a fan element (40) configured to urge an airflow across a plurality of permanent magnets (16) of a rotor (12) of the electric machine to remove thermal energy therefrom. A plurality of cooling channels (32) are located in a housing (26) of the electric machine and are configured to transfer thermal energy from a stator (18) of the electric machine to a flow of liquid coolant through the plurality of cooling channels. A heat exchanger (42) is located in thermal communication with the plurality of cooling channels to transfer thermal energy from the airflow to the liquid coolant. One or more coolant supply conduits (48) are configured to divert a portion of the airflow from the heat exchanger to an ancillary component (44) of the electric machine to allow for transfer of thermal energy from the ancillary component to the airflow.