Sensorless Motor with Asymmetric Consequent Pole Rotor
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Solution Overview
Problem
Motors using consequent pole type rotors with embedded magnets face challenges in achieving stable induced voltage and irregular waveforms, making it difficult to employ sensorless driving techniques due to higher distortion rates and asymmetrical peak intervals, which hinder efficient control and rotation.
Innovation Solution
A motor design with a stator having 3×n teeth and a rotor core featuring n magnets and salient poles, where the electrical angle between magnet ends is set to be smaller than that between salient pole ends, ensuring stable and regular induced voltage waveforms by concentrating magnetic attraction and optimizing rotor position detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a consequent pole type rotor with embedded magnets is used, then the motor achieves higher output with smaller and lighter structure, but the induced voltage waveform becomes irregular with high distortion rate
Solution Approach 1:
The patent applies asymmetry by making the electrical angle between magnet ends smaller than the electrical angle between salient pole ends. This asymmetric angular configuration creates a specific magnetic field distribution that generates a regular sinusoidal induced voltage waveform, resolving the waveform irregularity problem while maintaining the consequent pole structure's high output density.
2Device complexity
If a consequent pole type rotor is used, then the motor structure is simplified and costs are reduced, but sensorless driving technique cannot be employed due to irregular induced voltage waveform
Solution Approach 1:
The asymmetric electrical angle configuration between magnets and salient poles generates a clean sinusoidal induced voltage waveform, which provides the necessary signal quality for sensorless control algorithms to accurately detect rotor position and speed, thereby enabling sensorless driving in simplified consequent pole motors.
3Device complexity
If magnets and salient poles are arranged with equal electrical angles, then the rotor structure is symmetric and simple, but the induced voltage waveform shows peak deviation and asymmetry
Solution Approach 1:
The patent deliberately introduces asymmetry in the electrical angles between magnet ends and salient pole ends to correct the waveform distortion caused by symmetric arrangement. This controlled asymmetric design ensures that the induced voltage waveform maintains proper peak positioning and symmetry, achieving precise waveform control through asymmetric geometric configuration.
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 allows for stable and rapid induction of voltage, enabling effective sensorless driving techniques with reduced distortion, similar to normal motors, thus facilitating efficient rotation control and miniaturization of electric pumps.
Implementation Method 1
a waveform of an induced voltage between phases
Data Source
AI summary
A motor in which drive current supplied to a winding is controlled in accordance with a rotational position of a rotor detected from a waveform of an induced voltage between phases. The motor is provided with a stator including 3×n teeth and windings for three phases. A rotor includes a rotor core, an n number of magnets, and an n number of salient poles. The magnets function as one of the magnetic poles, the salient poles function as the other one of the magnetic poles. Each salient pole is spaced apart by a gap from the adjacent ones of the magnets in the circumferential direction. The magnets and gap are arranged inward in the radial direction from the rotor core. An electrical angle between two ends of each magnet is set to be smaller than an electrical angle between two ends of each salient pole.