Nested Rotor Permanent-Magnet Machine for Lower Copper Loss
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Solution Overview
Problem
Conventional rotating field machines suffer from high copper losses and inefficient utilization of the rotor, leading to reduced efficiency and power density.
Innovation Solution
A three-phase rotating field machine design featuring a nested stator and rotor configuration with two concentric rotor elements and a second air gap, where windings transition within the winding head region, reducing inactive areas and increasing the proportion of active windings for torque generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional single-rotor design with diametrically opposite winding routing is used, then machine structure is simple, but copper losses increase due to excessive winding overhangs
Solution Approach 1:
The patent employs a nested rotor configuration where an inner rotor element with permanent magnets is positioned within the bore of an outer rotor element. This nested arrangement allows the stator windings to transition from one air gap to another through the winding overhang area, significantly reducing the length of inactive winding sections and thereby reducing copper losses without substantially increasing overall machine complexity
Solution Approach 2:
The invention transitions from a conventional single-plane winding arrangement to a three-dimensional configuration where windings extend through multiple air gaps (inner and outer). By utilizing the axial dimension and creating radial transitions through the winding overhang area, the patent reduces the circumferential path length of windings, minimizing inactive winding sections and copper losses
2Power
If larger air gap is used to accommodate higher power, then power capacity increases, but rotor underutilization occurs and efficiency decreases
Solution Approach 1:
The nested rotor design with two concentric rotor elements creates two distinct air gaps (inner and outer) that both contribute to torque generation. This configuration allows the rotor to effectively utilize the available space and magnetic flux in both air gaps, improving power density while maintaining efficiency by maximizing the active torque-generating area without excessive air gap lengths
Solution Approach 2:
The patent ensures continuous useful action by configuring the windings so that both sections (in the inner and outer air gaps) actively contribute to torque generation. The nested rotor structure maintains magnetic field continuity across both air gaps, ensuring that the rotor elements are continuously and effectively utilized for electromagnetic torque production, thereby improving efficiency and power density
3Loss of energy
If winding turns extend diametrically across the stator, then electrical connections are established, but inactive winding sections increase and copper losses rise
Solution Approach 1:
The patent reconfigures the winding arrangement from a conventional diametrically opposite single-plane configuration to a three-dimensional arrangement where windings transition radially through the winding overhang area between inner and outer air gaps. This dimensional change reduces the circumferential extent of inactive winding sections, minimizing copper losses while maintaining proper electrical connections
Solution Approach 2:
The winding overhang area serves as an intermediary region that facilitates the transition of winding turns from the inner air gap to the outer air gap. This intermediate zone allows the windings to change direction and plane, enabling compact routing that reduces inactive winding sections and copper losses while maintaining electrical connectivity
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 significantly reduces copper losses and enhances efficiency and power density while maintaining machine dimensions, utilizing both air gaps for torque generation and minimizing remagnetization losses.
Implementation Method 1
a three-phase induction machine (1) with a rotor (2), which has a first ring-shaped, in particular cylindrical, rotor element (5) with permanent magnets (7a), and with a stator (3) with individual windings (11, 12, 13)
Implementation Method 2
both of which contribute to the generation of torque, while only one air gap is usual in the prior art and the magnetic field lines extend via the magnetically passive, return ring (yoke) shut down
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
The invention relates to a three-phase rotating field machine (1) with a rotor (2) comprising a first annular rotor element (5) with permanent magnets (7a), and with a stator (3) comprising individual windings (11, 12, 13), each of which is assigned to one of three phases of a three-phase system and which repeat cyclically in the circumferential direction of the stator (3), wherein a first radial air gap (8) exists between the stator (3) and the first rotor element (5). The rotor (2) has a second annular rotor element (6) with permanent magnets (7b) located concentrically and radially further outwards than the first rotor element (5), which is rotationally fixed to the first rotor element (5) and from which the stator (3) is spaced, forming a second radial air gap (9).A first section (13a) of a turn of the windings (11, 12, 13) extends axially in the first air gap (8) and transitions into a second section (13b) of the turn at the end face of the stator (3), which extends in the opposite axial direction in the second air gap (9). With this novel, nested stator and rotor design, the lengths of the end-face winding sections in the so-called winding head are reduced to a minimum, thus minimizing the losses caused by these winding sections. This increases the efficiency of the rotating field machine.