Permanent Magnet Motor Ventilation Holes for Uniform Cooling
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Solution Overview
Problem
Permanent magnet motors in refrigeration compressors experience uneven cooling, leading to high temperatures and potential demagnetization of the rotor, due to inefficient heat exchange and thermal field non-uniformity.
Innovation Solution
A permanent magnet motor design featuring taper-shaped axial ventilation holes in the stator core, which enhance heat exchange efficiency by allowing heat-exchange fluids to effectively carry heat away from the teeth where it is generated most intensely, and a partition between the rotor and stator to manage airflow and reduce heat transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional cooling methods (spraying coolants or spiral flow channels) are used, then cooling is provided to the motor, but the cooling effect on the rotor is poor and the thermal field is non-uniform
Solution Approach 1:
The patent introduces axial ventilation holes specifically in the stator teeth regions where heat is generated most intensively. Each ventilation hole has a tapered shape with larger cross-section at the tooth head and smaller at the root, creating localized quality variation that optimizes heat extraction from high-temperature zones while maintaining overall thermal balance.
Solution Approach 2:
The stator core is segmented into multiple regions with axial ventilation holes distributed across different teeth. This segmentation allows independent heat management in each tooth region, enabling uniform heat extraction across the stator and preventing localized overheating that could lead to rotor demagnetization.
2Ease of manufacture
If axial ventilation holes are made with uniform cross-section, then manufacturing is simpler, but heat exchange efficiency is reduced and ventilation holes may be blocked during painting
Solution Approach 1:
The ventilation holes feature asymmetric tapered geometry with larger cross-sectional area at the tooth head and smaller area at the root. This asymmetry optimizes heat exchange by providing larger surface area at the high-temperature tooth head region while maintaining structural integrity at the root. The asymmetric shape also prevents painting blockage by ensuring the opening remains accessible.
3Reliability
If cooling intensity is increased to prevent demagnetization, then rotor temperature control improves, but thermal field non-uniformity increases with some regions too hot and others too cold
Solution Approach 1:
The patent applies local quality by placing ventilation holes specifically in stator teeth where heat is generated most intensively during motor operation. The tapered holes provide enhanced heat extraction capacity at these localized high-temperature regions, achieving uniform thermal field distribution by addressing heat generation patterns at their source rather than applying uniform cooling throughout.
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 solution stabilizes motor temperature, ensures uniform thermal fields, prevents demagnetization, and maintains open ventilation holes during painting, thereby improving cooling efficiency and reducing the risk of heat-related issues.
Implementation Method 1
axial ventilation holes in communication with the first inner cavity and with the second inner cavity are disposed in teeth of the stator core... enable the heat-exchange fluid to carry out heat exchange at the tooth, where heat is generated most intensively
Data Source
AI summary
A stator and a rotor are mounted inside a case of the permanent magnet motor, and separate the inner cavity of the case into a first inner cavity and a second inner cavity. Axial ventilation holes in communication with the first inner cavity and with the second inner cavity, are disposed in teeth of a stator core of the stator, and each axial ventilation hole is a taper hole extending in a height direction of each tooth. The width of one end of the axial ventilation hole, which is close to a head of the tooth, is greater than the width of the other end of the axial ventilation hole, which is close to a root of the tooth. The taper holes enable fluid to fully carry out exchange heat at the teeth where heat is generated most intensively.