Coolant Passage Sealing for VPI-Protected Electric Machine Stators
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Solution Overview
Problem
The buildup of heat in rotor and stator components of electric machines due to disrupted or damaged coolant passages during the application of insulating varnish/resin, and the risk of foreign object debris in the cooling system, limit the power output of electric machines.
Innovation Solution
The implementation of coolant passage seals, such as extended core end rings, sealing plugs, and threaded sealing plugs, to protect coolant passages during the vacuum pressure impregnation process, ensuring the passages remain intact and debris-free.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If coolant passages are opened during the VPI process to allow resin penetration, then the insulating varnish/resin can penetrate and encapsulate the stator effectively, but the coolant passages may be disrupted or damaged and blocked by foreign object debris
Solution Approach 1:
Coolant passage seals are installed in the coolant passages before the VPI process begins. These seals preliminarily close the passages to prevent resin penetration and debris ingress during the impregnation process, then are removed afterward to restore the passages. This preliminary protective action resolves the contradiction by maintaining passage integrity during manufacturing while allowing effective resin encapsulation.
Solution Approach 2:
The coolant passage seals act as intermediary elements that temporarily block the coolant passages during the VPI process. These seals mediate between the need for resin penetration into the stator windings and the need to protect the coolant passages from damage and debris. The seals are removed after VPI to restore normal coolant flow, thus resolving the manufacturing complexity versus reliability contradiction.
2Reliability
If the stator is fully encapsulated with insulating varnish/resin during VPI, then the electrical insulation is improved, but the coolant passages may be blocked or significantly reduced in size
Solution Approach 1:
The coolant passage seals are installed before the VPI process to preliminarily protect the passages. This allows the stator to be fully encapsulated with insulating varnish/resin during VPI, achieving excellent electrical insulation, while the seals prevent resin from entering and blocking the coolant passages. After VPI, the seals are removed to restore full coolant flow and heat transfer efficiency, thus resolving the contradiction between insulation reliability and heat transfer productivity.
3Ease of manufacture
If coolant passages are left open during manufacturing, then the cooling system is simple and easy to manufacture, but foreign object debris may enter and compromise the cooling system
Solution Approach 1:
Coolant passage seals are installed as a preliminary protective measure before the VPI and machining processes. This allows the cooling system to remain simple in design while the seals temporarily prevent foreign object debris from entering the passages during manufacturing. After manufacturing is complete, the seals are removed to restore the simple, open cooling system, thus resolving the contradiction between manufacturing simplicity and protection from harmful debris ingress.
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 coolant passage seals maintain the integrity and functionality of internal coolant passages, enhancing heat transfer and preventing debris ingress, thereby improving the power output and efficiency of electric machines.
Implementation Method 1
a vacuum pressure impregnation (VPI) process applies an insulating varnish and/or resin to the stator. During the VPI process, the varnish/resin is applied in a liquid form and a vacuum is applied to force the varnish/resin to penetrate and encapsulate the stator
Implementation Method 2
A pressurization process and a thermal curing process then may be used to cure the insulating varnish/resin. Both vacuum and pressure help the resin to penetrate within the stator
Implementation Method 3
A pressurization process and a thermal curing process then may be used to cure the insulating varnish/resin
Data Source
Figure 1
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AI summary
The present application provides a stator suitable for an application of an insulating varnish or resin in a vacuum pressure impregnation process. The stator includes a number of conductive windings and a coolant passage extending through the stator. The coolant passage is sealed via a coolant passage seal.