Motor Cogging Torque Reduction via Salient Pole Asymmetry
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Solution Overview
Problem
Motors with a consequent-pole structure experience magnetic imbalance leading to increased vibration and rotational performance deterioration due to cogging torque, which existing designs fail to adequately address.
Innovation Solution
The motor design incorporates a rotor with magnets and salient poles arranged at specific intervals, along with a stator featuring teeth and coils, where the opening angles of the salient poles are set to differ and satisfy specific angular relationships, effectively canceling out cogging torque and improving rotational performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a consequent-pole structure with magnets and salient poles is used, then the number of magnets is reduced by half, but magnetic imbalance occurs leading to increased vibration and cogging torque
Solution Approach 1:
The patent applies asymmetry by setting different opening angles for different salient poles. Specifically, first salient poles have a first opening angle and second salient poles have a second opening angle that is different from the first. This asymmetric design creates intentional magnetic imbalance compensation, where the cogging torque generated by salient poles with larger opening angles counteracts the cogging torque from salient poles with smaller opening angles, thereby reducing overall vibration and cogging torque in the motor
2Device complexity
If salient poles are arranged between magnets at equal intervals, then the rotor structure is simplified, but magnetic imbalance causes deterioration of rotational performance
Solution Approach 1:
The patent applies local quality by making each salient pole have different local characteristics through varying opening angles. While all salient poles are arranged at equal intervals maintaining structural simplicity, individual salient poles have different opening angles (first opening angle for odd-numbered salient poles, second opening angle for even-numbered salient poles). This local variation in geometry allows each salient pole to generate different cogging torque characteristics, and the cumulative effect of these local differences results in overall cogging torque reduction while preserving the simple equal-interval arrangement
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 significantly reduces cogging torque, enhancing the motor's rotational performance and reducing vibration by ensuring the phases of cogging torques generated at different salient poles are out of phase, thereby improving overall motor efficiency.
Implementation Method 1
a magnet having a force (induction) of magnetic flux and a salient pole having no force of magnetic flux are mixed
Implementation Method 2
multi-phase coils attached to the teeth
Data Source
AI summary
There is provided a motor including a rotor and a stator arranged outside the rotor in the radial direction. The rotor includes a rotor core, a plurality of magnets arranged at equal intervals in the circumferential direction of the rotor core and functioning as one magnetic pole, and salient poles integrated with the rotor core, each arranged between adjacent magnets and at a distance from the magnets. The salient poles function as the other magnetic pole. A stator has a stator core having a plurality of teeth extending in the radial direction of the stator and arranged at equal intervals in the circumferential direction, and multi-phase coils attached to the teeth.