Electric Motor Winding-Free Space Reduces Capacitive Coupling
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Solution Overview
Problem
Electric motors controlled by frequency converters experience increased bearing wear due to high-frequency harmonics, which lead to reduced service life, as these harmonics cause capacitive coupling between the stator and rotor, particularly in motors with ball-bearing rotors.
Innovation Solution
The design incorporates a stator with deep winding integration into slots to create a significant winding-free space and uses shielding rings between the winding overhangs and rotor, with the shielding rings being conductively attached to the stator core, to reduce capacitive coupling. This configuration, combined with a laminated stator core and slot insulation, effectively decouples high-frequency currents, reducing bearing load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If frequency converters are used to control electric motors, then speed control precision is improved, but high-frequency harmonics cause capacitive coupling between stator and rotor leading to increased bearing wear
Solution Approach 1:
The patent introduces an intermediary substance (insulating material) filled in the winding-free space between the stator winding and rotor. This intermediary increases the electrical insulation distance and reduces capacitive coupling, thereby blocking the harmful high-frequency current paths while maintaining the speed control function of the frequency converter
Solution Approach 2:
The patent extracts the harmful capacitive coupling effect by creating a winding-free space and filling it with insulating material. This removes the direct electrical coupling path between stator and rotor that causes bearing currents, while preserving the motor's electromagnetic conversion function
2Reliability
If shielding plates are added between end winding and rotor, then bearing wear is reduced, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent merges the insulation function with the existing winding-free space in the stator slot. Instead of adding separate shielding plates, the insulating material is integrated into the slot structure, combining the electrical insulation function with the mechanical structure and reducing overall device complexity
Solution Approach 2:
The patent utilizes the existing winding-free space in the stator slot for dual purposes: maintaining winding insulation and reducing capacitive coupling. This self-service approach eliminates the need for additional shielding components while achieving bearing protection
3Object-affected harmful factors
If winding-free space is increased in stator slot, then capacitive coupling is reduced, but winding density decreases
Solution Approach 1:
The patent applies local quality by concentrating the winding-free space specifically in the slot region where capacitive coupling occurs, while maintaining normal winding density in the active electromagnetic conversion areas. The insulating material is locally placed only where needed to block harmful currents
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 solution significantly reduces capacitive coupling by at least 40%, thereby minimizing bearing wear and extending the motor's service life, while maintaining high winding density and simplifying production processes.
Implementation Method 1
Due to capacitive coupling, these high-frequency signal components first travel from the stator to the rotor
Implementation Method 2
Shielding rings are provided between the rotor and the stator heads, which form electrostatic shielding and are conductively attached to the stator
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
The electric motor comprises a stator (2) and a rotor (6) rotatably mounted therein. The stator (2) has a stator core (10) and motor windings (11) arranged in stator slots. The winding heads (12) of these windings extend beyond the ends of the slots, with winding head shields (13) arranged between the winding heads (12) and the rotor (6). The stator slots are open towards the rotor and, in addition to the winding-free gap required for inserting the wire, have a winding-free space in the area between the winding sections located in the slots and the respective gap. This winding-free space, in conjunction with the shields (13), serves to reduce the capacitive coupling between the rotor and the stator.