Grounded Ring Shield Layout for Common-Mode Bearing Protection
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Solution Overview
Problem
Existing electrical machines face issues with protection from common mode voltage effects, which can lead to increased wear and damage in bearing arrangements due to parasitic capacitances, particularly when operated with converters that create timely varying common mode voltages.
Innovation Solution
The implementation of an electrical machine design featuring electrically conductive shielding units connected to earth or a reference potential, with ring-shaped parts extending around the rotation axis and mechanically connected to the central body, creating a shielded space that reduces capacitive coupling between the stator winding, rotor, and bearings, thereby minimizing detrimental electrical currents and voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the electrical machine is connected to a converter that comprises a direct current link, then the electrical machine can be controlled with a frequency converter, but a timely varying common mode voltage is created between the stator winding and ground potential, leading to increased wear and damage in the bearing arrangement due to parasitic capacitances
Solution Approach 1:
A shield arrangement is introduced as an intermediary component between the stator winding and the bearing arrangement. This shield is electrically connected to the stator winding and positioned to reduce parasitic capacitances, thereby mediating the harmful electrical effects before they reach the bearings. The shield acts as a protective intermediary that blocks common mode voltages and electrical stresses from affecting the bearing lubricant and rolling elements.
Solution Approach 2:
The shield arrangement is positioned and configured to preemptively counteract common mode voltages before they can cause damage to the bearings. By being electrically connected to the stator winding and strategically positioned relative to both the stator and bearings, the shield creates opposing electrical fields that neutralize harmful voltages in advance, preventing breakthroughs and light arcs before they occur.
2Reliability
If a shielding arrangement is placed between the stator winding and the bearing outer rings, then protection against common mode voltage effects is improved, but the device complexity increases
Solution Approach 1:
The shield arrangement is designed to perform multiple functions simultaneously: it reduces parasitic capacitances, blocks common mode voltages, and protects the bearing arrangement. By integrating these functions into a single component structure that is electrically connected to the stator winding, the design avoids the need for multiple separate protective components, thereby reducing overall device complexity while maintaining comprehensive bearing protection.
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 design effectively reduces the risk of voltage flashovers and wear at the bearings by minimizing parasitic capacitances and capacitive coupling, providing enhanced protection against common mode voltage effects.
Implementation Method 1
a timely varying common mode voltage can be created between the stator winding and a reference potential (e.g. ground or earth). Due to this common mode voltage, parasitic capacitances may become effective in the electrical machine
Implementation Method 2
The implementation of an electrical machine design featuring electrically conductive shielding units connected to earth or a reference potential, with ring-shaped parts extending around the rotation axis and mechanically connected to the central body, creating a shielded space that reduces capacitive coupling
Data Source
AI summary
An electrical machine including a stator, a rotor and a bearing arrangement having a first bearing and a second bearing on opposite sides of the stator as well as a shielding arrangement comprising a first shielding unit and a second shielding unit. The rotor is rotatably supported around a rotation axis by means of bearings. The shielding units are electrically conductive and comprise a ring part in each case that extends originating from a radial inner end to a radial outer end away from the rotation axis. Preferably each shielding unit has a circumferential part on its radial outer end that extends in a continuous ring-shaped manner around rotation axis and is arranged in overlapping manner with the adjacent axial end of stator winding in axial direction. The circumferential parts are preferably completely closed, whereas the ring parts can comprise through holes.