Rotor Core Interpole Bridge Layout for Lower Q-Axis Inductance
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Solution Overview
Problem
The existing rotating electrical machines with arc-shaped outer circumferential surfaces between poles experience increased q-axis inductance at high speeds, leading to reduced operable range and torque output, particularly in applications like electric power steering devices that require high torque at high rotation speeds.
Innovation Solution
A rotating electrical machine design featuring a rotor core with petal-shaped outer circumferential portions and interpole bridges having flat surfaces facing the magnetic gap, which increases magnetic resistance and reduces q-axis inductance, thereby improving high-speed rotation characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the outer circumferential surface between the poles of the rotor core is formed in an arc shape, then the magnetic force and torque are improved, but the q-axis inductance increases
Solution Approach 1:
The invention applies different surface geometries to different regions of the rotor core: arc-shaped surfaces at the magnetic poles for high magnetic force, and flat surfaces at the interpole bridges for low inductance. This local differentiation resolves the contradiction by optimizing each region for its specific function.
Solution Approach 2:
The outer circumferential surface of the rotor core is segmented into distinct regions: arc-shaped portions corresponding to magnetic poles and flat portions corresponding to interpole bridges. This segmentation allows independent optimization of torque generation and inductance control in different areas.
2Power
If the outer circumferential surface between the poles of the rotor core is formed in an arc shape, then the magnetic force is increased, but the operable range is reduced
Solution Approach 1:
Different surface geometries are applied to different regions: arc-shaped surfaces enhance magnetic force at poles, while flat surfaces reduce q-axis inductance at interpole bridges, preserving operable range. This local quality differentiation resolves the contradiction between magnetic force and operable range.
Solution Approach 2:
The rotor core surface is segmented into pole regions and interpole bridge regions with different geometries, allowing the system to simultaneously achieve high magnetic force and wide operable range by optimizing each segment for its specific function.
3Force
If the outer circumferential surface between the poles of the rotor core is formed in an arc shape, then the torque output is improved, but the high-speed rotation characteristics are deteriorated
Solution Approach 1:
The invention uses arc-shaped surfaces at magnetic poles to maximize torque output while using flat surfaces at interpole bridges to minimize q-axis inductance, preventing terminal voltage increase at high speeds. This local differentiation resolves the contradiction between torque output and high-speed characteristics.
Solution Approach 2:
The rotor core is segmented into torque-generating regions (arc-shaped pole surfaces) and inductance-control regions (flat interpole bridge surfaces), enabling simultaneous optimization of torque output and high-speed rotation characteristics.
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 design enhances the operable range and torque output by reducing q-axis inductance and torque pulsation, allowing for a wider range of rotation speed-torque characteristics, especially beneficial for electric power steering devices.
Implementation Method 1
the path of a magnetic flux passing through the magnetic gap becomes short, so that the magnetic resistance between the portion between the poles and the stator is decreased
Implementation Method 2
the magnetic resistance between the portion between the poles and the stator is decreased
Implementation Method 3
three-phase currents are applied from an inverter to coils wound around a plurality of tooth portions formed in a stator core
Implementation Method 4
permanent magnets for forming magnetic poles are embedded in the rotor core
Data Source
AI summary
A rotor core of a rotating electrical machine has interpole bridges each disposed on an outer circumferential side with respect to a permanent magnet in a non-magnetic portion between the poles, and interpole diameter bridges each surrounded by two permanent magnets and an interpole bridge. The outer circumferential surface of each interpole bridge is formed by a first flat surface. Thus, a path of a magnetic flux passing through a magnetic gap is lengthened, so that a q-axis inductance is reduced. In addition, a width in a radial direction of each interpole bridge and a width in a circumferential direction of each interpole diameter bridge are constant, and each interpole bridge and each interpole diameter bridge are disposed so as to be perpendicular to each other to form a T shape. Thus, the concentration of stress during press-fitting of the permanent magnet into a magnet hole can be reduced.