Rotary Machine Stator Cooling via Gravity Guide
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Solution Overview
Problem
Existing cooling structures for rotary electric machines face challenges in efficiently cooling stator coils at low rotor speeds due to insufficient centrifugal force, leading to drag loss issues when liquid refrigerant remains on the rotor's outer peripheral surface.
Innovation Solution
A cooling structure featuring cooling holes in the stator core, a refrigerant supply mechanism, and a refrigerant guide that uses gravity to supply liquid refrigerant to stator coils, preventing it from attaching to the rotor by guiding it to the slots, thereby maintaining drag loss and ensuring efficient cooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If liquid refrigerant is supplied to stator coil using centrifugal force at high rotor speed, then cooling efficiency is improved, but drag loss decreases when rotor rotates at low speed or stands still
Solution Approach 1:
The patent employs dynamic cooling hole configurations where the number, position, and orientation of cooling holes are varied according to rotor speed conditions. At high speeds, centrifugal force drives refrigerant through all cooling holes for maximum cooling. At low speeds or standby, the system dynamically adjusts which cooling holes are active to prevent refrigerant accumulation on the rotor surface, thereby maintaining drag loss while providing adequate cooling when needed.
Solution Approach 2:
The system changes operational parameters including refrigerant supply pressure, cooling hole activation patterns, and refrigerant flow distribution based on rotor speed. By adjusting these parameters dynamically, the system optimizes the balance between cooling efficiency at high speeds and drag loss prevention at low speeds, transitioning between different cooling modes to match operational conditions.
2Temperature
If liquid refrigerant is supplied to stator coil by direct contact method, then cooling efficiency is improved, but refrigerant distribution becomes uneven at low rotor speeds
Solution Approach 1:
The stator core is divided into multiple segments with dedicated cooling holes in each segment. This segmentation allows independent control of refrigerant flow to different stator coil regions. By activating specific segments based on thermal load and rotor speed, the system achieves uniform refrigerant distribution even at low speeds where centrifugal force is insufficient to distribute refrigerant evenly across all segments.
Solution Approach 2:
The patent introduces intermediary structures such as refrigerant distribution channels and guide elements that mediate between the refrigerant supply source and the stator coils. These intermediaries actively direct and distribute refrigerant to ensure even coverage of all cooling holes, compensating for insufficient centrifugal force at low rotor speeds and preventing localized overheating.
3Temperature
If cooling holes are provided in stator core to supply refrigerant directly to stator coil, then cooling efficiency is improved, but device complexity increases
Solution Approach 1:
The cooling holes in the stator core serve multiple functions: they act as refrigerant supply channels, structural support elements, and thermal management pathways. By integrating these cooling functions into the existing stator core structure rather than adding separate cooling components, the system achieves efficient stator coil cooling while minimizing increases in device complexity. The same stator core structure that provides mechanical support also provides the cooling function.
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 configuration effectively cools the stator coil while preventing drag loss by ensuring consistent refrigerant supply and distribution, even at low rotor speeds, and prevents refrigerant from attaching to the rotor, thus maintaining efficiency and performance.
Implementation Method 1
the refrigerant supply mechanism is configured to supply liquid refrigerant to supply cooling holes among the cooling holes
Implementation Method 2
The refrigerant guide is configured to catch the liquid refrigerant falling down from the radially inner ends of the supply cooling holes through slots corresponding to the supply cooling holes among the respective slots and to guide the liquid refrigerant to slots placed on the lower side in the gravitational direction among the respective slots
Implementation Method 3
The liquid refrigerant is supplied to a stator coil in the slots via the cooling holes. Accordingly, it is possible to efficiently cool the stator coil
Data Source
AI summary
A cooling structure for a rotary electric machine includes: a plurality of cooling holes provided such that the cooling holes penetrate from an outer peripheral surface of a stator core to respective slots; a refrigerant supply mechanism configured to supply liquid refrigerant to supply cooling holes among the cooling holes, the supply cooling holes being configured such that radially outer ends of the supply cooling holes are placed above radially inner ends of the supply cooling holes in the gravitational direction; and a refrigerant guide provided between a rotor and a stator and configured to catch the liquid refrigerant falling down from the radially inner ends of the supply cooling holes through their corresponding slots and to guide the liquid refrigerant to slots placed on the lower side in the gravitational direction among the slots.