Brushless Motor Stator Bus Bar Layout for Shorter Power Tools
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional brushed motors in cordless power tools are less durable and less efficient due to brush wear and tear, and their compact design is hindered by the length of the stator assembly in brushless motors.
Innovation Solution
A stator assembly for a brushless DC motor with a lamination stack, field windings, and a bus bar system that includes conductive terminals and end insulators to reduce the overall length, allowing for efficient power transmission and improved durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a brushless DC motor is used to improve durability and energy efficiency, then the motor length increases due to the stator assembly structure
Solution Approach 1:
The bus bar is nested within the stator assembly structure, with conductive terminals integrated into the end insulators. This nesting arrangement allows the bus bar to be accommodated within the existing stator volume without increasing the overall motor length, while still providing the necessary electrical connections for the brushless DC motor windings.
Solution Approach 2:
The bus bar is positioned in a radial direction relative to the stator assembly, utilizing the radial dimension rather than extending axially. This dimensional change allows electrical connections to be made without increasing the motor's axial length, effectively resolving the contradiction between durability improvement and length increase.
2Length of moving object
If the stator assembly length is reduced for compact design, then the electrical connection complexity increases
Solution Approach 1:
The conductive terminals are merged with the end insulators to form an integrated component. This combination eliminates the need for separate terminal components and simplifies the electrical connection structure, allowing compact stator assembly design without increasing connection complexity.
Solution Approach 2:
The end insulators serve multiple functions: providing electrical insulation between the bus bar and stator core, and housing the conductive terminals for electrical connections. This multi-functionality reduces the number of separate components needed, enabling compact design while maintaining simple electrical connections.
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 solution enhances the energy efficiency and durability of the motor, reducing the motor's length for compact handheld power tools while maintaining performance, thus extending operation time and improving reliability.
Implementation Method 1
A set of sense magnets coupled to the PMs in the rotor assembly are sensed by a sensor, such as a Hall Effect sensor, to identify the current position of the rotor assembly.
Implementation Method 2
When power is applied to a winding, the resulting current in the winding generates a magnetic field that couples to the rotor. The magnetic field associated with the PM in the rotor assembly attempts to align itself with the stator generated magnetic field resulting in rotational movement of the rotor.
Data Source
AI summary
A stator assembly for a brushless DC motor includes a stator core including stator poles and an outer surface, at least one magnet wire wound on the poles forming stator windings, and a bus bar including a non-conductive mount arranged on the outer surface and conductive terminals. Each conductive terminal includes: a main portion mounted on the non-conductive mount substantially parallel to the longitudinal axis of the motor, a tang portion folded over the main portion from a first longitudinal end of the main portion, and a connection tab at a second longitudinal end of the main portion. At least a contact portion of the at least one magnet wire is wrapped around the tang portion and fused to make an electric connection to the conductive terminal, and the connection tab makes electric contact with a wire supplying electric power to the motor.