Internal Air Cooling for Rotor Magnets in Sealed Electrical Machines
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Solution Overview
Problem
Existing rotary electrical machines face inefficiencies in cooling, particularly in enclosed systems, where air cooling methods are inadequate for high-power applications, leading to performance degradation and overheating issues due to limited heat dissipation within the machine.
Innovation Solution
An enclosed rotary electrical machine with a cooling system featuring internal fans mounted on the rotor shaft, creating dual air flows through flux barriers surrounding permanent magnets, and external cooling options such as air or liquid cooling to effectively manage heat within a sealed enclosure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If air cooling is used for enclosed electrical machines, then the machine can maintain IP protection and sealed enclosure, but the cooling efficiency is insufficient for high-power applications
Solution Approach 1:
The internal air cooling system segments the cooling function by introducing multiple cooling air inlets distributed around the enclosure and multiple outlet openings, creating localized cooling zones that target specific heat-generating components (stator windings, rotor magnets, bearings) independently, thereby improving overall cooling efficiency while maintaining the sealed enclosure
Solution Approach 2:
Cooling air acts as an intermediary substance that absorbs heat from internal components through convection and conduction, then transports this heat to external cooling fins or heat sinks where it is dissipated to the environment, enabling effective heat removal while maintaining the IP-rated sealed enclosure
2Ease of operation
If forced air convection is used in enclosed machines with fan on shaft, then some cooling is achieved, but heat generated at rotor is not adequately discharged
Solution Approach 1:
The cooling system transitions from one-dimensional radial cooling (fan pushing air outward) to multi-dimensional cooling by adding axial cooling paths through inlet openings at one end and outlet openings at the other end, creating three-dimensional air flow patterns that efficiently transport heat from the rotor and stator to external dissipation points
Solution Approach 2:
Instead of relying solely on the rotor fan to push hot air outward (conventional approach), the system introduces cool air from the opposite direction through inlet openings, creating a counter-flow cooling pattern that enhances heat removal efficiency by establishing a pressure-driven air flow from cold to hot zones
3Temperature
If liquid cooling systems are used, then cooling efficiency improves for high-power machines, but the system becomes more aggressive and complex
Solution Approach 1:
The system utilizes pneumatic cooling (air-based cooling) with carefully designed flow paths, pressure differentials, and velocity distributions to achieve cooling efficiency previously only attainable with liquid systems, avoiding the complexity of liquid circulation pumps, seals, and coolant management while maintaining IP protection
Solution Approach 2:
The cooling system optimizes air flow parameters (velocity, pressure, temperature, flow rate) through strategic placement of inlet/outlet openings and internal bafles to maximize heat transfer coefficients and cooling effectiveness, enabling air cooling to perform at levels previously requiring liquid cooling
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 provides efficient cooling of the rotor, permanent magnets, and windings, reducing mechanical losses and ensuring high IP protection, while maintaining performance and extending the machine's lifespan by effectively dissipating heat within the sealed environment.
Implementation Method 1
a cooling system comprising a pair of internal fans, each internal fan being fixedly mounted on the rotating shaft between the rotor body and one of the bearings to create, upon rotation of the shaft, a first two-way air flow in the second recesses of the rotor
Implementation Method 2
The system provides efficient cooling of the rotor, permanent magnets, and windings, reducing mechanical losses and ensuring high IP protection, while maintaining performance and extending the machine's lifespan by effectively dissipating heat within the sealed environment
Data Source
AI summary
The invention relates to an enclosed rotary electrical machine including a cooling system comprising two internal fans (181, 182) fixedly mounted on shaft (160) at both ends of rotor (150). The rotor and stator (190) are contained in an enclosure sealed by two flanges. The fans allow dual air circulation in flux barriers surrounding the rotor magnets and formed by axial recesses running throughout the rotor, and also air circulation in the space created between the internal fans and the inner faces of the flanges comprising fins (113, 123) which orient the air flows created by the fans to capture the heat thereof. External cooling allows the enclosure and the flanges to be cooled, by air or liquid cooling.