Voltage-Balanced Stator Wave Winding With Fewer Branch Connections
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Solution Overview
Problem
High-pole pair electric machines face efficiency reduction and overheating due to voltage unbalance in wave windings, primarily caused by uneven inductances of parallel branches, which is exacerbated by the solid cross-section of wires and high frequencies, leading to circular currents and insulation deterioration.
Innovation Solution
A design that ensures all parallel branches are equally represented in layers and circumferential sections with a minimum number of connections by strategically positioning and connecting uninterrupted conductor segments, following specific rules to achieve voltage balance without interweaving, suitable for both wave and pseudo-helical windings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If wave winding topology is used in high-pole pair machines, then high efficiency and superior heat removal are achieved, but voltage unbalance occurs due to differing inductances of parallel branches
Solution Approach 1:
The winding is divided into multiple radial layers with conductors distributed across different layers. Each layer contains conductors from different phases, and the segmentation ensures that parallel branches are evenly distributed across layers to balance inductances and eliminate voltage unbalance while maintaining wave winding topology
Solution Approach 2:
Different radial layers are assigned specific phase conductors to ensure that each local region (layer) contains a balanced representation of all phases. This local quality distribution ensures that inductances of parallel branches are equalized, preventing circulating currents while preserving the high efficiency characteristics of wave winding
2Reliability
If multiple connections are made to balance voltage in parallel branches, then voltage unbalance is reduced, but production time and cost increase
Solution Approach 1:
Multiple conductor ends from different phases are merged together in each radial layer to form connection points. This merging approach balances voltage across parallel branches while minimizing the number of discrete connections required, thereby reducing production time and cost compared to traditional methods that require more extensive inter-layer connections
3Quantity of substance
If solid cross-section wires are used in wave windings, then high fill factors are achieved, but circulating currents occur due to voltage unbalance
Solution Approach 1:
The winding configuration ensures that all parallel branches have equal inductance by distributing conductors evenly across radial layers. This equipotentiality in terms of inductance values prevents potential differences between parallel branches, thereby eliminating the driving force for circulating currents while maintaining the high fill factor advantage of solid cross-section wires
4Force
If high pole pair number is used, then high torque is achieved, but slot leakage flux increases causing voltage unbalance
Solution Approach 1:
The solution moves from a single-layer winding configuration to a multi-radial-layer configuration. By distributing conductors across multiple radial layers, the patent addresses the voltage unbalance problem in high-pole pair machines without reducing the pole pair number, thus maintaining high torque while eliminating the harmful effects of slot leakage flux through improved spatial distribution
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 results in a voltage-balanced winding with reduced connections, minimizing efficiency losses, overheating, and production costs, while enhancing reliability and heat management in high-pole pair electric machines.
Implementation Method 1
Stators for electrical machines used in modern traction applications have to exhibit highly efficient conversion of electric current into magnetic flux in the air gap of the machine
Data Source
AI summary
A voltage balanced winding for a stator of an electric machine with a high number of pole pairs is distributed over several circumferential sections and several radial layers of the stator. The winding consists of at least two phases and each phase of the winding comprises a plurality of conductor segments, one conductor segment for each layer in each sector. Each of the conductor segments comprises a plurality of straight conductor portions arranged in an axial direction of the stator and a plurality of end-windings connecting the straight conductor portions to a wave pattern. The voltage balanced winding is characterized in that the plurality of conductor segments is divided into branches of series connected conductor segments, wherein each branch includes at least D conductor segments selected from D different sections d and D different layers j such that (j+d) mod D equals a predefined number, with D being the number of circumferential sections. At least a first conductor segment of layer j1 and sector d1 and a second conductor segment of layer j2 and sector d2 with j1+d1=j2+d2 are integrally formed as an uninterrupted conductor segment.