Multi-gap Rotary Machine with Dual Stators and Salient Poles
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Solution Overview
Problem
Conventional double-stator IPM motors face limitations in increasing power density due to short-pitch stator winding, concaved salient poles, increased magnetic resistance, and magnetic saturation, which hinder the full utilization of reluctance and magnet torque.
Innovation Solution
A multi-gap type rotary electric machine design with an annular rotor and stators featuring full-pitch windings, where inner and outer magnets are embedded at equal pitches, and salient poles are formed between adjacent magnets, ensuring the pole pitch of the rotor matches the magnetic field generated by the stators, thus optimizing both reluctance and magnet torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the outer-salient-pole width is increased to ensure high reluctance torque rate in the outer magnetic circuit, then the reluctance torque rate in the outer magnetic circuit is improved, but the magnetic path length increases causing increased magnetic resistance and decreased reluctance torque, and the magnet width decreases causing decreased magnet torque
Solution Approach 1:
The invention divides the motor into two separate magnetic circuits (inner and outer) with independent stators and rotors. This segmentation allows each magnetic circuit to be optimized independently, so the outer magnetic circuit can have increased salient-pole width for high reluctance torque rate without negatively impacting the inner magnetic circuit's performance.
Solution Approach 2:
The invention transitions from a single magnetic circuit to a dual magnetic circuit configuration by adding the inner stator and rotor. This dimensional change in the magnetic circuit architecture allows simultaneous optimization of both reluctance torque rate and magnetic path length by distributing functions across two independent circuits.
2Device complexity
If short-pitch winding is used in the stator, then the device complexity is reduced, but the pole pitch of the rotor does not coincide with the pole pitch of the magnetic field generated by the stator windings causing reluctance torque not to be fully used
Solution Approach 1:
The invention segments the stator into inner and outer stators, each with independent windings. This allows each stator to use full-pitch winding configuration optimized for its corresponding rotor's pole pitch, maximizing reluctance torque utilization in both magnetic circuits without increasing overall device complexity significantly.
Solution Approach 2:
The invention changes the winding pitch parameter from short-pitch to full-pitch in both inner and outer stators. This parameter change ensures that the pole pitch of each rotor coincides with the pole pitch of the magnetic field generated by its corresponding stator, enabling full utilization of reluctance torque while maintaining manageable device complexity.
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 enhances output torque, reduces size, and increases power density by fully utilizing reluctance and magnet torque, preventing magnetic saturation in the rotor yoke and allowing for efficient magnetic flux distribution.
Implementation Method 1
a plurality of inner magnets, each composed of a permanent magnet, embedded in radially inner portions of the rotor core
Implementation Method 2
The IPM motors can use reluctance torque that is a core attractive force, in addition to magnet torque that is generated by magnets
Implementation Method 3
the rotor yoke, in which the magnetic path is shared between the outer and inner magnetic circuits
Data Source
AI summary
A multi-gap type rotary electric machine is provided, where the machine is provided a shaft supported rotatably by a baring secured to a housing. An annular rotor is secured to the shaft and configured to rotate together with the shaft. Double stators are secured to the housing and configured to have gaps between the stators and the rotor. Relationships of: 3.5<P13/P6 (1) and P7/P6>0.5 (2) are met, where P6 denotes a circumferential width of each of outer salient poles, P7 denotes a circumferential width of each of inner salient poles, and P13 denotes a circumferential width of each of the outer magnets.