BLDC Motor Circuit and Winding Layout for Compact Power Tools
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Solution Overview
Problem
Conventional brushless direct-current (BLDC) motors for rotary tools face challenges in achieving high power density within a compact size, limiting their maximum power output and efficiency.
Innovation Solution
The design incorporates a rotor assembly with embedded or surface-mount magnets, a stator assembly with optimized winding configurations, and a circuit board for connecting stator windings in series and parallel configurations, maximizing wire density and reducing electrical resistance, while maintaining a compact size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional BLDC motor designs are used, then the motor structure is simple and easy to manufacture, but the power density and maximum power output are limited
Solution Approach 1:
The motor is divided into distinct functional modules: rotor assembly with magnets, stator assembly with windings, and circuit board with conductive traces. This segmentation allows optimization of each component for high power density while maintaining manufacturing simplicity through modular assembly procedures.
Solution Approach 2:
The patent achieves high power density by optimizing the three-dimensional arrangement of components within the motor envelope. The rotor magnets are positioned radially, stator windings are wound tightly around stator teeth, and the circuit board is integrated adjacent to the stator, maximizing space utilization in all spatial dimensions.
2Power
If the motor size is reduced for compact tools, then the tool portability improves, but the maximum power output decreases
Solution Approach 1:
The patent achieves high power output in a compact size by optimizing critical parameters: the motor constant Km is maximized through careful selection of magnet strength, winding turns, and core material properties. The ratio of motor size constant to magnetic envelope exceeds 900 (N·m/√W)/m³, indicating superior power density achieved through parameter optimization rather than simply scaling up motor dimensions.
3Power
If stator windings are configured for high power output, then the power density increases, but the electrical resistance and thermal losses increase
Solution Approach 1:
The circuit board is positioned adjacent to the stator assembly with conductive traces strategically routed to minimize current path length. This local optimization of electrical connections reduces resistive losses in the high-current paths between stator windings and power electronics, allowing higher power output with reduced thermal 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 enhances power output density, increasing the motor constant and maximum power output to at least 1840 watts, with improved thermal efficiency and reduced size, surpassing conventional BLDC motors in terms of power and efficiency.
Implementation Method 1
a stator assembly including a stator comprising a stator core and stator teeth radially extending from the stator core and defining slots therebetween, and stator windings wound on the stator teeth
Implementation Method 2
a rotor assembly including rotor shaft extending along a longitudinal axis and a rotor supporting magnets mounted on the rotor shaft
Data Source
AI summary
A brushless direct-current (BLDC) motor for a power tool includes a rotor assembly and a stator assembly including stator windings. A ratio of a motor size (Km) constant of the motor to an electrical envelope of the motor including electrical parts of the motor is greater than approximately 850 (N·m/√W)/m{circumflex over ( )}3. A ratio of a motor size (Km) constant of the motor to a magnetic envelope of the motor including stator core and windings is greater than approximately 980 (N·m/√W)/m{circumflex over ( )}3.