Induction Motor Rotor Teeth with Tapered Flange
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Solution Overview
Problem
In induction motors, increasing magnetic flux density to achieve miniaturization and high torque leads to increased spatial harmonic components, resulting in large harmonic secondary copper losses and degradation of motor characteristics.
Innovation Solution
The formation of a recessed surface on the flange of the rotor teeth, which is tapered in the rotating direction, reduces the influence of spatial harmonics on the rotor bar, thereby minimizing harmonic secondary copper loss without moving the rotor bar closer to the rotor core, and maintains motor efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If magnetic flux density in the gap is increased to achieve miniaturization and high torque, then motor size is reduced and torque is increased, but spatial harmonic component is increased leading to large harmonic secondary copper loss and degradation of motor characteristics
Solution Approach 1:
The invention applies local quality by creating a recessed portion at the distal end of the rotor tooth flange, specifically modifying only the outer circumferential surface geometry in the gap region. This localized structural change smooths the magnetic flux density distribution at the rotor bar surface without altering the overall motor design or global magnetic flux density, thereby reducing spatial harmonics and harmonic copper losses while maintaining motor size
Solution Approach 2:
The invention addresses the harmonic distortion problem by introducing a new geometric dimension - the recessed portion depth - to the rotor tooth flange structure. This dimensional modification changes the magnetic flux distribution pattern in the gap region, smoothing the flux density waveform and reducing spatial harmonic components that cause excessive copper losses
2Power
If magnetic flux density in the gap is increased to achieve miniaturization and high torque, then torque is increased, but spatial harmonic component is increased leading to large harmonic secondary copper loss and degradation of motor characteristics
Solution Approach 1:
The recessed portion is strategically positioned at the distal end of the rotor tooth flange where it interfaces with the stator core, creating a localized geometric feature that smooths magnetic flux transitions. This local modification reduces spatial harmonics and harmonic copper losses while preserving the overall high magnetic flux density required for high torque output
Solution Approach 2:
The invention converts the potentially harmful concentrated magnetic flux at the rotor tooth tip into a beneficial distributed flux pattern. The recessed portion acts as a flux distributor, transforming the sharp flux concentration that causes harmonics into a smoother flux distribution, thereby converting what would be a harmful effect into a beneficial one for reducing losses
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 reduces harmonic secondary copper loss, allowing for a smaller and more efficient induction motor with improved motor characteristics by smoothing the change in magnetic flux density and reducing leakage inductance.
Implementation Method 1
a stator coil (7) disposed in each stator slot (6). The rotor (3) has a rotor core (9) which is rotatably provided with respect to the stator (2)
Implementation Method 2
the rotor rotates by interaction between a magnetic field generated on the stator side and an induced current generated at the secondary conductor due to the magnetic field
Data Source
AI summary
According to one embodiment, an induction motor includes a stator and a rotor. The stator has a stator coil disposed at a stator core having a plurality of stator slots. The rotor has a rotor core rotatably provided with respect to the stator. The rotor core includes a plurality of rotor teeth and a rotor slot formed between the plurality of rotor teeth and having a rotor conductor disposed therein. The rotor teeth include a teeth main body and a flange. The teeth main body extends in a radial direction of the rotor core. The flange extends in a rotating direction of the rotor core from a distal end of the teeth main body. Then, a recessed surface is formed on at least part of an outer circumferential surface of a radial outer side in the flange.