Polyphase AC Motor Partial Discharge Suppression via Winding Arrangement
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Solution Overview
Problem
High-speed inverter switching leads to increased surge voltage and higher frequencies, causing complex voltage distribution within coils and partial discharge issues in polyphase AC electric motors, which existing configurations fail to adequately address without increasing manufacturing costs or reducing space factor.
Innovation Solution
A polyphase AC electric motor with windings of different phases distributed and star-connected, featuring specific arrangements of partial conductors to reduce voltage between coils and suppress partial discharge, even under high-frequency inverter surges, by strategically placing conductors adjacent to those with extreme voltage values and maintaining the same winding direction for all phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If insulating paper is inserted into slots to partition coils, then insulation performance is improved, but coil space factor declines and slot length increases leading to increased motor size
Solution Approach 1:
The patent changes the dielectric constant parameter of the insulating layer from conventional high values to lower values (e.g., from 3-5 to 2-3). This parameter change allows the insulating layer to provide adequate insulation performance while occupying less space, thereby improving the coil space factor and reducing motor size without requiring additional insulating paper partitions
Solution Approach 2:
The insulating layer is designed to serve multiple functions simultaneously: it provides electrical insulation between coils, maintains slot filling efficiency, and eliminates the need for separate insulating paper partitions. This multi-functionality resolves the contradiction by achieving insulation performance improvement without the space penalty of additional partitioning components
2Volume of stationary object
If coil end portion length is shortened to reduce distance between conductors, then motor size is reduced, but voltage difference between conductors increases leading to partial discharge and insulation deterioration
Solution Approach 1:
By changing the dielectric constant parameter of the insulating layer to lower values, the patent reduces the electric field intensity for a given voltage, thereby suppressing partial discharge even when coil end portions are shortened. This allows motor miniaturization while maintaining insulation reliability
Solution Approach 2:
The insulating layer with optimized dielectric constant serves as a preventive measure against partial discharge before it can occur. By selecting materials with appropriate dielectric properties, the patent creates a cushioning effect that protects the insulation system from the harmful effects of high voltage differences that arise when coil end portions are shortened
3Reliability
If all insulating layers are configured with lower dielectric constant to suppress partial discharge, then insulation performance is improved, but manufacturing cost increases
Solution Approach 1:
The patent applies the lower dielectric constant insulating layer specifically in critical locations where partial discharge is most likely to occur (such as between adjacent coils in the same slot and at coil end portions), rather than uniformly across all insulating layers. This localized application maintains insulation performance while reducing material costs compared to configuring all insulating layers with low dielectric constant materials
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 effectively reduces voltage between coils, suppresses partial discharge, and simplifies manufacturing without reducing the space factor, even when high-frequency inverter surges are applied, thereby enhancing the motor's performance and reliability.
Implementation Method 1
the potential difference between the adjacent coils increases due to the effects of the surge voltage. Moreover, in cases where the potential difference between the adjacent coils exceeds the Partial Discharge Inception Voltage (PDIV), partial discharge occurs between the coils
Implementation Method 2
configuring all of the coils, including an entirety of an insulating layer provided around the periphery of the in-slot components, from an insulating layer having a dielectric constant that is lower than that of conventionally used insulating layers
Implementation Method 3
a stator in which windings of different phases are distribution wound and star-connected, and the polyphase AC electric motor is driven by an inverter
Data Source
AI summary
Object: To provide a polyphase AC electric motor whereby partial discharge can be suppressed.Resolution Means: The winding of each phase includes a first partial conductor that is an input side partial conductor; an nth partial conductor connected to a neutral point; and second to n-1th partial conductors. Moreover, a partial conductor disposed within the stator adjacent to the first partial conductor of each phase, or a partial conductor including a coil end portion disposed adjacent to a coil end portion where the first partial conductor extends out of the slot, is any of the following:(1) of the intermediate partial conductors, an ath (where a is a natural number greater than or equal to 2) partial conductor of the same phase or a different phase where voltage takes an extreme value when AC voltage is applied from the inverter;(2) any of an a-3th to a-1th partial conductors of the same phase or a different phase, or any of an a+1th to a+3th partial conductors of the same phase or a different phase connected to the intermediate partial conductor taking the extreme value;(3) any of a n-3th to nth partial conductors of the same phase or a different phase.