Rotor Cavities Suppress Harmonics in Synchronous Machines
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Solution Overview
Problem
Three-phase permanent-magnet-excited synchronous machines experience significant thermal losses due to circular currents induced by third and ninth harmonics in delta circuits, which are not effectively addressed by existing technologies.
Innovation Solution
The rotor design incorporates slot-like recesses or cavities that extend along the axial extent of the pole pitch and are positioned at the maximum values of third, ninth, and other harmonics, reducing magnetic conductivity and thereby attenuating these harmonics, while preserving the sinusoidal basic function for torque formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the rotor uses a conventional design with uniform magnetic field distribution, then the machine structure is simple, but third and ninth harmonics are large causing significant circular currents and thermal losses in delta circuits
Solution Approach 1:
The rotor employs local quality modification by introducing slot-like recesses at specific circumferential positions where third and ninth harmonics are maximum, while maintaining uniform structure in other regions. This localized modification reduces harmonics and circular currents without requiring complete structural redesign, thereby reducing thermal losses while keeping the overall rotor structure relatively simple.
Solution Approach 2:
The invention changes the magnetic conductivity parameter locally by creating slot-like recesses in the rotor at specific positions. These recesses modify the magnetic field distribution by reducing magnetic conductivity in targeted areas, which attenuates third and ninth harmonics and reduces circular currents in delta circuits, thereby reducing thermal losses without significantly complicating the overall rotor design.
2Loss of energy
If the rotor is designed to minimize harmonics through complex sinusoidal configurations, then thermal losses are reduced, but manufacturing complexity and cost increase significantly
Solution Approach 1:
Instead of implementing a completely complex sinusoidal rotor configuration, the invention applies local quality modification by introducing simple slot-like recesses at specific circumferential positions. These recesses are easier to manufacture than full sinusoidal configurations while still effectively reducing third and ninth harmonics and thermal losses, thus improving ease of manufacture while maintaining energy efficiency.
Solution Approach 2:
The rotor design segments the harmonic reduction function into specific localized slot-like recesses rather than requiring a completely complex sinusoidal configuration throughout. This segmentation allows for simpler manufacturing of individual recesses while achieving the overall goal of harmonic reduction and thermal loss minimization.
3Object-generated harmful factors
If slot-like recesses are positioned at maximum values of third and ninth harmonics, then circular currents are suppressed, but the rotor structure becomes more complex
Solution Approach 1:
The invention applies local quality modification by introducing slot-like recesses at specific circumferential positions where third and ninth harmonics are maximum, while maintaining uniform structure in other regions. This localized modification suppresses circular currents in delta circuits without requiring complete structural redesign, thereby reducing harmful effects while keeping the overall rotor structure relatively simple.
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 suppresses disruptive harmonics, reducing circular currents and thermal losses, thereby improving efficiency and energy utilization, especially in delta circuits, and is simpler and cost-effective to manufacture compared to sinusoidal configurations.
Implementation Method 1
slot-like recesses or cavities that extend along the axial extent of the pole pitch and are positioned at the maximum values of third, ninth, and other harmonics, reducing magnetic conductivity and thereby attenuating these harmonics
Implementation Method 2
a voltage can be induced by means of a magnetic field which is generated by magnetic poles of the rotor
Implementation Method 3
magnetic fields of permanent magnets used therein
Data Source
AI summary
Circulating currents are suppressed and thermal losses are reduced in a three-phase permanent-magnet-excited synchronous machine in a delta circuit. The machine has a stator in which, during operation, a voltage is induced by way of a magnetic field generated by magnetic poles of a rotor. A field strength of the magnetic field has, along a circumferential coordinate of the rotor, a profile formed from superimposition of a sinusoidal basic function and of sinusoidal harmonics of the basic function. Groove recesses and/or cavities are located in and/or under a circumferential face of the rotor that face the stator and follow an axial extent of the pole pitch of the rotor in their longitudinal extent and extend transversely with respect to the longitudinal extent along the circumferential coordinate in the region of the maximum values of at least the third harmonic and outside the maximum values of the basic function.