Stator Neutral Wire Current Density Reduction
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Solution Overview
Problem
In rotary electric machines, excessive current flowing through neutral wires can cause insulating coatings to melt, leading to insulation failure due to excessive temperature rise, as seen in conventional stator windings with three-phase connections where ends of partial windings are connected to neutral wires, resulting in twice the current flowing through these wires.
Innovation Solution
The stator design includes an annular stator core with slots arranged in a circumferential direction, featuring three-phase windings with partial windings electrically connected in parallel, and neutral wires connected to ends of all phase windings, ensuring current flows directly between partial windings without passing through neutral wires, dispersing current across both neutral wires, thus preventing excessive current flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If neutral wires are used to commonly connect ends of phase windings in star-connection, then the wiring structure is simplified and ease of manufacture is improved, but excessive current flows through the neutral wires causing temperature rise and insulation failure
Solution Approach 1:
The patent segments the neutral connection by dividing it into multiple separate neutral wires (first neutral wire and second neutral wire) instead of using a single common neutral wire. Each neutral wire connects to specific phase windings, which disperses the current flow and prevents excessive current concentration in one wire, thereby avoiding temperature rise and insulation failure while maintaining the simplified wiring structure.
2Ease of manufacture
If the same cross-sectional area wire is used for neutral wires as for partial windings, then manufacturing consistency is improved, but the neutral wires cannot handle twice the current flow without excessive temperature rise
Solution Approach 1:
The patent segments the current path by using multiple neutral wires with the same cross-sectional area as the partial windings. By distributing the current flow across multiple wires instead of forcing twice the current through a single wire of the same size, the temperature rise is prevented while maintaining manufacturing consistency in wire selection.
3Ease of operation
If ends of two partial windings of the same phase are connected to ends of neutral wires, then the star-connection structure is achieved, but twice as much current as each divided winding flows in the neutral wires
Solution Approach 1:
The patent segments the neutral connection function by introducing multiple neutral wires (first and second neutral wires) that separately connect to different phase windings. This segmentation distributes the current flow so that each neutral wire carries current from its connected phases rather than all currents converging in one wire, thereby reducing the quantity of current flowing through each individual neutral wire while maintaining the star-connection structure.
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 prevents excessive current from flowing through neutral wires, thereby avoiding insulation failure caused by abnormal temperature rises, ensuring reliable operation by reducing current density and preventing melting of insulating coatings.
Implementation Method 1
a stator winding formed by three phases of phase windings wound around the slots, and neutral wires for commonly connecting ends of the phase windings together in star-connection
Implementation Method 2
insulating coatings that surround the outer peripheral surfaces of the neutral wires
Data Source
AI summary
A stator of a rotary electric machine includes an annular stator core with a plurality of slots arranged in a circumferential direction, a stator winding formed by three phases of phase windings wound around the slots, and neutral wires for commonly connecting ends of the phase windings together in star-connection. Each of the phase windings has two partial windings that are electrically connected in parallel, ends of at least two sets of the partial windings formed by combining two partial windings among the total of six partial windings in different phases and the ends of the neutral wires are connected electrically, and the partial windings connected to both ends of each neutral wire include all the phases.