Wound Rotor Cage Structure for Faster Assembly and Winding Retention

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Solution Overview

Problem

Wound rotors in synchronous electric machines are complex to manufacture and assemble, making them difficult to industrialize and increasing production costs and time.

Innovation Solution

A cage structure for the wound rotor comprising two parts with end crowns and circumferentially extending rods, where the rods are secured to form notch wedges and tie rods, allowing for simpler assembly and reduced production costs, with the option for welding and surface insulation treatment to eliminate the need for conventional insulating papers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a traditional wound rotor structure with multiple separate parts (rings, tie rods, notch shims) is used, then the rotor can maintain structural integrity and retain windings, but the manufacturing process becomes complex and assembly time increases

Engineering Contradiction:
Improvestructural integrityVSAvoidnumber of parts
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent combines multiple separate components (end rings, tie rods, and notch shims) into a single integrated cage structure. The cage comprises a body with notches that directly receive windings, eliminating the need for separate notch shims. The end rings are integrated with longitudinal rods that serve both as structural supports and as retention elements for coil heads, reducing the total number of parts while maintaining structural integrity.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The cage structure performs multiple functions simultaneously: it retains windings in notches, supports coil heads, provides structural rigidity, and enables cooling. The longitudinal rods serve both as structural supports and as pathways for cooling fluids, combining mechanical support and thermal management functions in a single component.

Inventive Principle:
Principle #6Universality (Multi-functionality)

2Reliability

If a traditional wound rotor structure with multiple separate parts is used, then the rotor can maintain structural integrity, but the assembly process becomes time-consuming and difficult to industrialize

Engineering Contradiction:
Improvestructural integrityVSAvoidassembly speed
Core Design Contradiction:
ReliabilityVSProductivity

Solution Approach 1:

The cage is divided into two separable halves that can be assembled around the rotor body and then joined together. This segmentation allows for easier manufacturing of each half and simplifies the assembly process, as the two halves can be positioned on opposite sides of the rotor and connected through the notches, reducing overall assembly time while maintaining structural integrity.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

By integrating multiple functions into the cage structure, the number of assembly steps is reduced. The cage body, end rings, and retention elements are combined into a single component that can be installed in one operation, eliminating the need for separate assembly steps for notch shims and tie rods.

Inventive Principle:
Principle #5Merging (Combining)

3Productivity

If a cage structure with two parts is used, then assembly is simplified and installation is faster, but additional joining operations (such as welding) are required

Engineering Contradiction:
Improveassembly speedVSAvoidjoining complexity
Core Design Contradiction:
ProductivityVSEase of manufacture

Solution Approach 1:

The cage is segmented into two halves that can be manufactured separately and then joined. The joining is facilitated by the notches in the rotor body, which provide alignment features and bonding surfaces. The two halves are connected through the notches using welding or other joining methods, which is simpler than assembling multiple separate components.

Inventive Principle:
Principle #1Segmentation

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 cage structure simplifies the assembly and robustness of the rotor, reduces production costs, and enables faster installation while providing electrical and thermal insulation, maintaining coil heads and windings effectively.

Implementation Method 1

the associated rods, joined together, are welded at their respective end portions

Methodology Applied
Scientific EffectWelding: Welding

Implementation Method 2

each part is made of an aluminum alloy, and these segments are treated to provide surface electrical insulation

Methodology Applied
Scientific EffectSurface insulation treatment: Anodising

Data Source

PatentEP3797468B1Cage for a wound rotor in a synchronous electric machine
Publication Date: 2023.11.01 RENAULT SA
  • EP3797468B1 patent drawingFigure 1~2
  • EP3797468B1 patent drawingFigure 3~4
  • EP3797468B1 patent drawingFigure 5

AI summary

The invention relates to a cage (20) for a wound rotor, comprising a first portion (201) and a second portion (202) intended to be rigidly connected to one another, each portion (201, 202) comprising an end ring (21) and a circumferential plurality of rods (22, 23) extending away from said end ring (21) parallel to the axis of revolution (X) of the end ring (21), each rod (22, 23) having a main portion (32) and an end portion (31), and for each rod (22) of said first portion (201), the end portion (31) of said rod (22) is shaped to be able to be rigidly connected to the end portion (31) of at least one complementary rod (23) of the second portion (202) when the two portions (201, 202) are each installed at a longitudinal end of the body (10) of the rotor (1), so that said two complementary rods (22, 23) rigidly connected form a slot wedge (24) extending between the two end rings (21, 22) of the two portions (201, 202) of the cage (20).