Electric Machine Thermal Management via Silpad Shims
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Solution Overview
Problem
Existing rotary electric machines, especially sealed types, face significant energy losses and overheating issues due to Joule heating, which deteriorate the conductivity of windings and insulation, leading to potential short circuits and costly maintenance.
Innovation Solution
The electric machine employs Silpad® shims made of thermally conductive and electrically insulating material between the windings and the casing, providing effective heat exchange through conduction while maintaining electrical insulation, and uses elastic elements to ensure constant pressure and secure fixation, preventing overheating and short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If windings are placed in a sealed environment, then protection against dust and contamination is improved, but heat dissipation deteriorates causing overheating
Solution Approach 1:
A heat sink is introduced as an intermediary component between the windings and the external environment. The heat sink receives heat from the windings through thermal conduction and dissipates it to the surrounding air, acting as a mediator that enables heat transfer while maintaining the sealed protective environment.
Solution Approach 2:
The heat sink utilizes phase transition of water (evaporation/condensation cycle) to enhance heat dissipation. Water is circulated through channels in the heat sink, absorbing heat from windings and releasing it through phase change, allowing effective cooling while the casing remains sealed against dust and contamination.
2Power
If high current passes through windings, then power output is improved, but Joule heating increases causing conductivity deterioration
Solution Approach 1:
The heat sink serves as a thermal intermediary that intercepts heat generated by high current before it can deteriorate the winding conductivity. By providing a dedicated heat transfer path through the heat sink, the system can sustain higher currents without the harmful thermal effects accumulating in the windings.
Solution Approach 2:
The system changes the thermal parameters of the winding environment by introducing active cooling through the heat sink. This allows the windings to operate at higher temperatures temporarily during high power output without suffering permanent conductivity loss, as the heat is continuously removed by the heat sink's phase transition cooling mechanism.
3Reliability
If insulation layer is placed between winding and polar expansion, then electrical insulation is improved, but thermal conduction deteriorates
Solution Approach 1:
The heat sink acts as a thermal conduit that bypasses the insulating layer. While the insulation layer remains necessary for electrical isolation between windings and polar expansions, the heat sink provides an alternative thermal pathway from the winding to the external environment, eliminating the need for the insulation layer to also serve as a thermal barrier.
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 effectively manages heat exchange, maintaining the conductivity and insulation of windings, reducing energy losses, and enhancing the reliability and longevity of the electric machine by preventing overheating and ensuring constant thermal and electrical insulation.
Implementation Method 1
employs Silpad® shims made of thermally conductive and electrically insulating material between the windings and the casing, providing effective heat exchange through conduction
Implementation Method 2
uses elastic elements to ensure constant pressure and secure fixation
Implementation Method 3
Electric currents, including high ones, pass through the winding and cause heating due to the Joule effect which extends through the entire winding and adjacent areas of the electric machine
Data Source
Figure 1
Figure 2
Figure 3a~3b
AI summary
An electric machine comprises an outer casing (2), a rotor and a stator (3) having at least one polar expansion (5) and at least one winding (8) having an annular shape and placed around the polar expansion (5). The casing (2) has a plurality of protrusions (13) each of which holds, by supporting, a corresponding portion (12) of a stator winding (8) to enable heat exchange between the winding (8) and the protrusion (13). Each portion (12) of the winding (8) is electrically insulated from the respective protrusion (13).