Hairpin Stator Inner-Layer Segmentation for Balanced Current Density
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In electric machines with stator windings formed by hairpin conductors, higher AC copper losses occur in leg portions close to the rotor accommodation space, leading to increased current density and reduced performance and efficiency.
Innovation Solution
The stator design features first type leg portions that are electrically short-circuited at the axial first face side, with a smaller radial extent compared to second type leg portions, counteracting the proximity effect and achieving balanced current distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional single leg portion design is used in inner layer, then manufacturing is simple, but AC copper losses increase and current density becomes unbalanced
Solution Approach 1:
The stator winding is segmented into multiple first type leg portions (at least two) within the inner layer, each with smaller radial extent, instead of using a single large leg portion. This segmentation allows balanced current distribution and reduces AC copper losses by mitigating the proximity effect in the inner layer.
Solution Approach 2:
Different leg portions are designed with different radial extents according to their specific positions and current density requirements. The first type leg portions in the inner layer have smaller radial extent to reduce local current density and AC copper losses, while other leg portions maintain larger radial extent for their functional requirements.
2Temperature
If leg portions with uniform radial extent are used, then manufacturing is easier, but current density distribution becomes unbalanced causing overheating
Solution Approach 1:
The leg portions are designed with non-uniform radial extents tailored to their specific locations. First type leg portions in the inner layer have smaller radial extent to reduce local current density and prevent overheating, while other leg portions have larger radial extent appropriate for their positions and thermal requirements.
Solution Approach 2:
The radial extent parameter of leg portions is varied based on their position within the slot and layer. By changing this geometric parameter, the current density distribution is optimized to achieve balanced temperature characteristics across all leg portions.
3Loss of energy
If larger radial extent is used in inner layer leg portions, then current carrying capacity increases, but AC copper losses increase due to proximity effect
Solution Approach 1:
The current carrying path in the inner layer is divided into multiple parallel first type leg portions with smaller individual radial extents. This segmentation reduces the proximity effect between adjacent conductor regions while maintaining the total current carrying capacity through the combined effect of multiple parallel paths.
Solution Approach 2:
The proximity effect, which normally causes increased AC copper losses, is counteracted by designing the first type leg portions with smaller radial extents. This design choice converts the potential harm of the proximity effect into a benefit by achieving more uniform current density distribution and reduced overall AC copper losses.
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 design reduces overheating and improves the efficiency and performance of the electric machine by balancing current density and increasing resistance in the inner layer leg portions.
Implementation Method 1
due to the proximity effect there will be a non-uniform current distribution in the leg portions extending within the inner layer
Implementation Method 2
the resistance of the two short-circuited first type leg portions can be increased in comparison to the afore-mentioned single leg portion
Implementation Method 3
a stator core comprising a longitudinal axis, an axial first face side and an axial second face side opposite to the first face side, the stator core providing an accommodation space for a rotor of the electric machine
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
Stator (1) for an electric machine (101), comprising: - a stator core (2) comprising a longitudinal axis (3), an axial first face side (4) and an axial second face side (5) opposite to the first face side (4), the stator core (2) providing an accommodation space (6) for a rotor (102) of the electric machine (101); - multiple hairpin conductors (9, 10) having first type leg portions (12, 15) and second type leg portions (15), the hairpin conductors (9, 10) being connected to each other so as to form a stator winding; and - a slot (7) formed within the stator core (2) and radially divided into an inner layer (18) located closest to the accommodation space (6) and into further layers (19a-d) being more distant to the accommodation space (6) than the inner layer (18); wherein two first type leg portions (12) extend within the inner layer, one second type leg portion (15) extends within each of the further layers (19a-d), in a cross-section perpendicular to the longitudinal axis (3), the radial extent of each of the first type leg portions (12) is smaller than the radial extent of each of the second type leg portions (15), and the first type leg portions (12) are electrically shortcircuited at the first face side (4).