Single-Phase EC Motor Stator for Defined Start Direction
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Solution Overview
Problem
Single-phase electronically commutated motors face challenges in defining the rotational start direction of the motor rotor without significantly reducing motor efficiency, primarily due to the large average air gap caused by asymmetric rotor-facing pole shoe edges, which decreases efficiency.
Innovation Solution
The motor design incorporates a laminated stator body with ferromagnetic lamination sheets connected by axial punch protrusions, featuring asymmetrically shaped pole teeth with stator coils coiled in opposite directions and radially arranged punch protrusions near the rotor-facing pole shoe edge, enhancing magnetic field asymmetry to define a preferred rotational direction while minimizing mechanical deformations and maintaining efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If asymmetric rotor-facing pole shoe edges are used to define rotational start direction, then the preferred rotational start direction is achieved, but the average air gap increases and motor efficiency decreases
Solution Approach 1:
The invention applies local quality by positioning punch protrusions specifically near the rotor-facing pole shoe edge of each pole tooth, creating localized magnetic resistance enhancement only where needed. This localized modification asymmetrically influences the magnetic field distribution to define rotational start direction without requiring overall asymmetric pole shoe geometry, thereby maintaining a smaller average air gap and preserving motor efficiency.
Solution Approach 2:
The invention changes the magnetic resistance parameter locally by introducing punch protrusions that mechanically deform the lamination sheets. This deformation alters the magnetic conductivity in specific regions, creating asymmetric magnetic field characteristics during startup without changing the overall geometric symmetry of the pole shoes, thus avoiding the efficiency penalty associated with larger air gaps.
2Ease of operation
If asymmetric pole shoe geometry is used to achieve preferred rotational direction, then rotational start direction is defined, but the air gap between stator and rotor increases
Solution Approach 1:
The punch protrusions create localized modifications near the rotor-facing pole shoe edge, affecting only specific regions of the magnetic circuit. This localized approach achieves the necessary magnetic field asymmetry for directional control without requiring overall asymmetric pole shoe geometry, thereby maintaining a smaller average air gap distance between stator and rotor.
Solution Approach 2:
Instead of achieving asymmetry through geometric dimensioning of the pole shoe edges, the invention introduces a new dimension of control by modifying the magnetic resistance property through punch protrusions. This dimensional shift from geometric asymmetry to material property modification allows directional control with symmetric or near-symmetric pole shoe geometry, reducing the air gap.
3Ease of operation
If punch protrusions are positioned near the rotor-facing pole shoe edge, then magnetic field asymmetry is enhanced and rotational direction is defined, but mechanical deformation of lamination sheets occurs
Solution Approach 1:
The punch protrusions are positioned at specific locations near the rotor-facing pole shoe edge of each pole tooth, creating localized magnetic resistance enhancement. By concentrating the deformation in small, controlled areas rather than applying asymmetric geometry across entire pole shoes, the invention achieves magnetic field asymmetry while minimizing overall lamination sheet misalignment and maintaining manufacturing precision.
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 ensures a preferred rotational start direction for the motor rotor while reducing the average air gap and enhancing motor efficiency by optimizing the stator magnetic field asymmetry without compromising mechanical stability.
Implementation Method 1
The laminated stator body allows avoiding, or at least significantly suppressing, eddy currents within the stator
Implementation Method 2
The punch process mechanically deforms the lamination sheet, so that the microstructure and, as a result, the magnetic conductivity of the lamination sheet is changed within the punch protrusion and in its direct vicinity
Implementation Method 3
The rotor-facing pole shoe edge defines a non-constant air gap between the motor stator and the motor rotor with respect to a circumferential direction of the motor rotor generating a not-homogeneous magnet field
Data Source
Figure 1~2
Figure 3
AI summary
A single-phase electronically commutated motor (10) with a motor rotor (15) and with a laminated stator body (21) comprising at least one set (231-236) of ferromagnetic lamination sheets (28) positively connected to each other by axial punch protrusions (37, 38) wherein the lamination sheet set (231-236) defines a plurality of pole teeth (241-246) with pole shoes (30), the pole teeth (241-246) being provided with a plurality of stator coils (22), wherein the rotor-facing pole shoe edge (33) is shaped asymmetrically with respect to a radial pole tooth centerline (M), so that the rotor-facing pole shoe edge (33) defines a non-constant air gap (36) between the stator pole shoe (30) and the motor rotor (15), wherein each stator pole tooth (241-246) comprises an axial punch protrusion (38) radially arranged close to the rotor-facing pole shoe edge (33) so that the distance between the punch protrusion edge and the rotor-facing pole shoe edge (D1) is less than the distance between the punch protrusion edge and any other lamination sheet edge (D2).