Rotating Electric Machine Rotor Pole Axial Cuts Torque Ripple
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Solution Overview
Problem
Field coil type rotating electric machines experience increased torque ripple due to variations in magnetic flux, leading to degraded NV (Noise and Vibration) characteristics, as the main-pole end portions of the rotor interrupt and re-establish magnetic flux with the stator teeth, causing fluctuations in torque.
Innovation Solution
The introduction of axial cuts on the main-pole end portions of the rotor, which offset the timing of magnetic flux interruptions, allowing for the cancellation of first and second torque ripples generated by cut and non-cut portions respectively, thereby reducing overall torque ripple.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the main-pole end portions of the rotor are designed to radially face the stator teeth, then magnetic flux can be effectively generated, but torque ripple increases due to interruptions and re-establishment of magnetic flux
Solution Approach 1:
The main-pole end portion is segmented into a first main-pole end portion and a second main-pole end portion, which are positioned at different radial distances from the rotor axis. This segmentation allows the first portion to face stator teeth while the second portion faces stator slots, thereby interrupting the continuous magnetic flux path and reducing torque ripple through phased cancellation of magnetic fluctuations.
2Reliability
If the main-pole end portions continuously face the stator teeth, then magnetic flux is maintained, but NV characteristics degrade due to torque fluctuations
Solution Approach 1:
The rotor design creates a periodic interruption of magnetic flux as the segmented main-pole end portions rotate past the stator teeth. The first and second main-pole end portions alternately face the stator teeth and slots, creating a periodic modulation of magnetic flux that cancels out torque ripple and improves NV 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
This configuration effectively reduces torque ripple, improving the NV characteristics of the rotating electric machine by synchronizing the phases of torque fluctuations, resulting in a more stable operational performance.
Implementation Method 1
field current flows through the field coil, causing the field coil to be excited and thereby generating magnetic flux. The generated magnetic flux flows through a magnetic circuit which includes the rotor core, the main poles, the stator teeth and the stator core. Consequently, torque is generated with the magnetic flux flowing through the magnetic circuit and electric current flowing through the stator coil.
Data Source
AI summary
A field coil type rotating electric machine includes a stator and a rotor. The stator includes a stator core, stator teeth arranged in a circumferential direction and each radially protruding from the stator core, and a stator coil wound on the stator teeth. The rotor includes a rotor core, main poles arranged in the circumferential direction and each radially protruding from the rotor core, and a field coil wound on the main poles. Each of the stator teeth and the main poles extends in an axial direction. Each of the main poles has a pair of main-pole end portions located respectively at circumferential ends of the main pole and both radially facing the stator. For each of the main poles, in at least one of the main-pole end portions of the main pole, there is formed at least one cut for part of an axial length of the main pole.