Multi-Layer Dielectric Rotor for PWM Motor Shaft Voltage Control
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Solution Overview
Problem
Electric motors using PWM inverters experience electric corrosion in bearings due to shaft voltage, leading to insulation breakdown and abnormal sounds, which existing solutions struggle to control effectively.
Innovation Solution
The electric motor incorporates a rotation body with an outer iron core, an inner iron core, and a dielectric layer comprising at least two dielectric bodies with different dielectric constants, allowing adjustable capacitance between the cores to set an appropriate shaft voltage, thereby reducing electric corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single dielectric layer is used to reduce shaft voltage, then the structure is simple, but the ability to control shaft voltage is insufficient
Solution Approach 1:
The dielectric layer is divided into multiple dielectric layers with different dielectric constants, arranged in series between the inner and outer iron cores. This segmentation allows independent control of capacitance contribution from each layer, enabling precise adjustment of the overall capacitance value to achieve effective shaft voltage control while maintaining reasonable structural complexity
Solution Approach 2:
Different dielectric layers are assigned different dielectric constants based on their position and function requirements. The first dielectric layer (closer to the inner core) and the second dielectric layer (closer to the outer core) have different dielectric constants, allowing localized optimization of the electric field distribution and capacitance characteristics to better control shaft voltage
2Productivity
If PWM inverter is used to drive the motor, then the motor efficiency is improved, but shaft voltage causes electric corrosion in bearings
Solution Approach 1:
The multi-layer dielectric structure acts as an intermediary between the inner and outer iron cores, introducing a controlled capacitance that serves as an electrical barrier. This intermediary structure reduces the shaft voltage by providing an alternative electrical path through the dielectric layers, thereby preventing high-frequency current from causing electric corrosion in the bearings while allowing the PWM inverter to maintain high motor efficiency
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 configuration effectively reduces electric corrosion in bearings by managing the shaft voltage, maintaining a low potential difference between the inner and outer rings and preventing high-frequency current-induced damage.
Implementation Method 1
The dielectric layer includes at least two dielectric bodies different in dielectric constant. By adjusting the capacitance between the inner and outer iron cores, the shaft voltage can be set to an appropriate value, reducing electric corrosion in bearings
Implementation Method 2
The dielectric layer includes at least two dielectric bodies different in dielectric constant. The dielectric materials are used to create capacitance between the iron cores to manage shaft voltage
Data Source
Figure 1
Figure 2A~2B
Figure 2C
AI summary
An electric motor (40) includes stator (10), rotor (14) including rotation body (20), a pair of bearings (15), and a pair of brackets (17, 24). Rotation body (20) includes outer iron core (25), inner iron core (26), and dielectric layer (23). Outer iron core (25) is located in the outer side of rotation body (20). Inner iron core (26) is fixed to shaft (16). Dielectric layer (23) is located between outer iron core (25) and inner iron core (26) and includes at least two dielectric bodies different in dielectric constant.