Dielectric Stator Isolation for Bearing Current Reduction
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Solution Overview
Problem
Common mode electrical power generated in electric multi-phase rotary motor/generators can lead to deterioration of bearings, causing noise, vibration, and reducing the service life of the rotary electric machine.
Innovation Solution
A multi-phase, multi-pole permanent magnet motor/generator with an insulator system that includes a dielectric layer between the stator core and the housing, effectively isolating the stator core from the electrical ground return path and reducing common mode currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the stator core is directly connected to the housing (electrical ground), then the electrical circuit is complete and simple, but common mode currents flow through the bearings causing deterioration, noise, and vibration
Solution Approach 1:
A dielectric layer is introduced as an intermediary component between the stator core and the housing. This dielectric layer blocks the electrical path that would otherwise allow common mode currents to flow through the bearings, thereby protecting the bearings from deterioration while maintaining the electrical functionality of the motor system.
Solution Approach 2:
The electrical connection between the stator core and housing is segmented by introducing the dielectric layer. Instead of a direct continuous electrical path, the connection is divided into isolated segments, preventing the flow of common mode currents while allowing mechanical support and thermal management to continue.
2Ease of manufacture
If common mode currents are allowed to flow, then the electrical circuit is simple and continuous, but bearing deterioration occurs leading to noise and vibration
Solution Approach 1:
The dielectric layer serves as a mediator that is easily integrated into the existing motor assembly. It can be applied as a coating, insert, or integrated component during the manufacturing process, adding minimal complexity while effectively blocking harmful common mode currents from reaching the bearings.
Solution Approach 2:
The dielectric layer can be implemented as a thin film or coating on the stator core or housing surface. This thin dielectric barrier provides effective electrical isolation without adding significant thickness, weight, or manufacturing complexity to the motor assembly.
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 insulator system significantly reduces or eliminates common mode currents and associated deleterious effects, thereby extending the service life and improving the reliability of the rotary electric machine.
Implementation Method 1
an insulator system that includes a dielectric layer between the stator core and the housing, effectively isolating the stator core from the electrical ground return path and reducing common mode currents
Data Source
AI summary
A multi-phase, multi-pole permanent magnet motor/generator (electric machine) is described, and includes a rotor disposed on a rotor shaft within an annular stator, which may be arranged in a housing with an interposed insulator system. The insulator system is arranged to mitigate and isolate common mode currents in a shaft bearing system by insulating the stator core from an electrical ground return path of an electrical driving source. The electric machine includes a rotor rotatably disposed within a stator, and the stator is secured to the housing with the insulator system interposed therebetween.