Brushless Motor Parallel Stator Coils Reduce Resistance
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Solution Overview
Problem
Brushless motors in electric tools face limitations in output due to high resistance in stator coils connected in series, which restricts the increase in line diameter and thus output.
Innovation Solution
The implementation of parallel-connected stator coils with crossover wires that electrically connect each phase, reducing resistance and enhancing output by configuring a neutral point and simplifying wire connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If stator coils are connected in series, then the motor structure is simpler, but the resistance increases which reduces output
Solution Approach 1:
The patent divides the three-phase windings into multiple independent coil groups within each phase. Instead of a single series-connected coil per phase, multiple coils are arranged in parallel, segmenting the current path to reduce resistance while maintaining the three-phase structure. This segmentation allows multiple coils to carry current simultaneously, increasing power output without significantly increasing structural complexity.
Solution Approach 2:
The patent transitions from a single-dimensional series connection to a multi-dimensional parallel connection arrangement. By organizing coils in parallel within each phase and using crossover wires to connect them, the system adds a dimensional aspect to the electrical connection topology. This dimensional change in connection architecture reduces resistance and enables higher current flow, thereby increasing motor output.
2Loss of energy
If line diameter of stator coil is increased, then resistance decreases, but winding slot width limits the increase
Solution Approach 1:
Instead of using a single thick wire that would exceed slot width limits, the patent segments the winding into multiple thinner coils connected in parallel. Each coil can be accommodated within the slot width constraints, while the parallel arrangement of multiple coils provides the equivalent of a thicker wire by distributing current across multiple paths, thereby reducing overall resistance and copper loss.
Solution Approach 2:
The patent creates multiple copies of smaller coil units rather than one large coil. Each coil unit is designed to fit within the winding slot dimensions, and multiple identical or similar coil units are arranged in parallel. This copying approach allows the system to achieve the electrical equivalent of a larger conductor while respecting the physical constraints of the winding slot geometry.
3Power
If parallel-connected stator coils are implemented, then output increases, but the number of wire connections increases
Solution Approach 1:
The patent merges the connection functions of multiple coils within each phase by using a common parallel connection architecture. Crossover wires are used to combine multiple coil ends at shared connection points, reducing the total number of discrete connections compared to individual series connections. The merging of connection paths in a systematic parallel arrangement simplifies the overall wiring complexity while maintaining the power benefits of parallel coils.
Solution Approach 2:
The crossover wires serve multiple functions simultaneously: they connect coils within a phase in parallel, provide mechanical support, and establish electrical continuity across multiple connection points. This multi-functionality reduces the need for separate dedicated connection elements for each coil, thereby reducing the overall number of wire connections required while achieving the desired parallel configuration for increased output.
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 reduces resistance, improves operability, and increases the output of the brushless motor while maintaining a compact design by reducing the number of wire connections and processes involved.
Implementation Method 1
By a magnetic field generated by the stator coils, a rotor having a magnet is rotated.
Data Source
AI summary
An electric tool includes a brushless motor having a plurality of phases, the brushless motor. The brushless motor includes a plurality of stator coils connected in parallel with each of the plurality of phases, and a plurality of crossover wires, each of the crossover wires being configured to electrically connect the plurality of stator coils for each of the plurality of phases to each other. The plurality of crossover wires for the plurality of phases are electrically connected to each other.