Stator End Insulation Structure for Motor Shaft Voltage Blocking
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Solution Overview
Problem
The generation of axis voltage between the shaft axis and bearing in IPM-type motors due to parasitic capacitance causes bearing corrosion, leading to noise, vibration, and motor failure, which is exacerbated by increasing power and carrier frequency requirements, and existing anti-corrosion solutions like ceramic bearings are costly.
Innovation Solution
An insulation structure is applied to the ends of the stator to block the electric field from reaching the motor shaft, using a conducting part and insulating part to redirect the electric field away from the rotor, thereby reducing the axis voltage and preventing corrosion without expensive ceramic bearings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ceramic bearings or SGR/RGC bearings are used to prevent bearing corrosion, then bearing corrosion resistance is improved, but material cost increases
Solution Approach 1:
An insulating structure comprising insulating paper and conducting parts is introduced as an intermediary between the end coil assembly and the bearing. This insulating structure blocks the electric field from reaching the bearing, preventing axis current flow and bearing corrosion while allowing the use of inexpensive steel ball bearings instead of costly ceramic or SGR/RGC bearings
2Temperature
If oil cooling method is used to cool the motor, then cooling efficiency is improved, but anti-corrosion effect significantly decreases due to oil film formation
Solution Approach 1:
The insulating structure is installed in advance between the end coil assembly and the bearing to block the electric field path. This preliminary protective measure ensures that even when oil cooling creates an oil film that would normally reduce anti-corrosion effectiveness, the bearing remains protected from axis current by the pre-established insulating barrier
3Power
If motor specifications are increased to meet higher performance requirements, then power output is improved, but axis voltage and axis current increase leading to more frequent bearing corrosion failures
Solution Approach 1:
The insulating structure serves as a mediator that blocks the electric field generated by high-power motor operation from reaching the bearing. This allows the motor to operate at higher power levels with increased axis voltage and current without proportionally increasing bearing corrosion failure rates
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 insulation structure effectively reduces the axis voltage by up to 69% and 28%, minimizing motor failures and maintaining durability while using inexpensive steel ball bearings, thus lowering production costs.
Implementation Method 1
a conducting part extending in a predetermined induction direction parallel to a direction in which the end coil assembly is pulled out from the stator and inducing the electric field of the end coil assembly to be directed in the induction direction
Implementation Method 2
an insulating part positioned between the conducting part and the end coil assembly to insulate the conducting part
Data Source
AI summary
An insulation structure applied to each of two ends of a stator in an axial direction to block an electric field of an end coil assembly from being applied to a motor shaft. The structure includes: a conducting part extending in a predetermined induction direction parallel to a direction in which the end coil assembly is pulled out from the stator; and an insulating part positioned between the conducting part and the end coil assembly to insulate the conducting part.