DC Motor Asymmetrical Magnetic Field Dual Speed Operation
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Solution Overview
Problem
Existing direct current motors with permanent magnet stators and four stator poles lack the ability to operate at multiple speeds without external dissipative elements, making them inefficient for applications requiring varied speeds with limited design changes and maintaining power at maximum speed.
Innovation Solution
The motor employs asymmetrical magnetic fields by using high-power neodymium-iron-boron magnets and lower-power ferrite magnets, along with a ferromagnetic yoke structure and selective brush connections to achieve two distinct operating speeds without external dissipative elements, allowing for design modifications that maintain overall dimensions and power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If external dissipative elements are used to adjust motor speed, then speed adjustment capability is improved, but device complexity and energy loss increase
Solution Approach 1:
The patent applies asymmetry by using permanent magnets of different magnetic moments arranged asymmetrically around the stator circumference. Specifically, at least one permanent magnet has a magnetic moment different from the others, creating an asymmetric magnetic field distribution. This asymmetric configuration enables the motor to operate at multiple distinct speeds (first speed and second speed) by selectively energizing different brush combinations, eliminating the need for external dissipative elements and achieving speed adjustment without increasing device complexity
Solution Approach 2:
The patent implements local quality by assigning different magnetic moments to different permanent magnets at specific stator positions. Each permanent magnet is localized with specific magnetic properties (different magnetic moments) to create regions of varying magnetic strength around the stator. This local differentiation in magnetic quality allows the motor to produce different torque characteristics and operate at multiple speeds through selective brush connections, avoiding the need for external speed control components
2Adaptability or versatility
If external dissipative elements are used for speed adjustment, then multiple speed operation is achieved, but energy efficiency deteriorates
Solution Approach 1:
The asymmetric arrangement of permanent magnets with different magnetic moments creates inherently different magnetic field strengths in different stator regions. This asymmetry allows the motor to operate at multiple speeds by selectively connecting different brush combinations to the rotor windings, thereby activating different magnetic circuit paths. This eliminates the need for external dissipative elements that would waste energy, achieving multiple speed operation with improved energy efficiency
Solution Approach 2:
The patent extracts and eliminates external dissipative elements from the speed control system. By incorporating the speed adjustment capability directly into the motor's magnetic structure through asymmetric permanent magnet arrangement and selective brush connections, the harmful external components are removed, thereby improving energy efficiency while maintaining multiple speed operation capability
3Loss of energy
If asymmetric magnetic fields are used to achieve multiple speeds, then external dissipative elements are eliminated, but manufacturing complexity increases
Solution Approach 1:
While the asymmetric permanent magnet arrangement does increase manufacturing complexity compared to symmetric designs, the patent mitigates this by using standard permanent magnet materials and simple assembly procedures. The asymmetric configuration is achieved by positioning permanent magnets with different magnetic moments at specific stator locations, which can be done during standard motor assembly without requiring complex manufacturing processes or specialized equipment
Solution Approach 2:
The patent achieves multiple speed operation by changing the magnetic moment parameter of permanent magnets at different stator positions. This parameter variation (different magnetic moments) is implemented using commercially available permanent magnets with different ratings, which can be selected and positioned during assembly. This approach to parameter change avoids the need for complex manufacturing processes while enabling the asymmetric magnetic field configuration necessary for multiple speed operation
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
The motor effectively operates at two selectable speeds with sufficient difference, reducing the need for external dissipative elements and allowing for cost-effective production, while maintaining power and dimensions similar to existing motors.
Implementation Method 1
a rotor (3) with an overlapping winding (4) and four stator poles (5, 6, 7, 8)... two positively polarized brushes (11, 12), two negatively polarized brushes (13, 14)... five commutator segments (10a, 10b, 10c, 10d, 10e)
Implementation Method 2
asymmetrical magnetic fields by using high-power neodymium-iron-boron magnets and lower-power ferrite magnets
Implementation Method 3
The pole (5) comprises a high-power permanent magnet, made for example of neodymium-iron-boron, while the poles (6, 7 and 8) comprise respective relatively low-power permanent magnets, in particular of ferrite
Implementation Method 4
a ferromagnetic yoke structure... The yoke structure (9) is fitted outside the casing (2) and bears against the latter's lateral surface
Data Source
Figure 1~2
Figure 3~5
AI summary
Described is a direct current motor (1) with permanent magnet stator, having at least four stator poles (5, 6, 7, 8) which are spaced at equal angular intervals about the rotation axis (A) of the rotor (3) and which generate a magnetic field that is asymmetrical about the rotation axis (A) of the rotor (3) and where the rotor winding (4) can be powered partially and selectively at least at two fixed, explementary angular sectors.