Power Tool Motor Winding Layout for Lower Loss and Better Cooling
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Solution Overview
Problem
Conventional electric motors in cordless power tools suffer from high power losses, inefficient cooling, and a large 'empty stator area' due to small wire cross sections and suboptimal winding practices, leading to reduced efficiency and heat dissipation issues.
Innovation Solution
The electric motor design features a stator with a series of pole teeth wound with a winding that has a reference diameter, where the ratio of the reference diameter to the stator inner diameter multiplied by the number of pole teeth is greater than 0.3, optimizing the filling ratio and reducing empty stator areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If small cross section metal wire is used for winding coils, then the wire can be guided through slits during winding, but power losses increase and efficiency deteriorates
Solution Approach 1:
The patent changes the cross-sectional parameters of the metal wire from small to large (e.g., from 0.5mm to 2mm or more), which reduces electrical resistance and power losses while maintaining manufacturability through optimized winding processes
Solution Approach 2:
Instead of guiding thin wire through slits, the patent inverts the approach by using thicker wire that can be directly placed or pressed into the grooves, eliminating the need for complex guidance through narrow slits
2Ease of manufacture
If small cross section metal wire is used for winding coils, then winding can be performed, but empty stator area increases and total winding area is not optimally used
Solution Approach 1:
The patent changes the cross-sectional area parameter of the winding conductor from small to large, which increases the filling ratio in the stator grooves and reduces empty stator area, thereby optimizing the use of total winding area
Solution Approach 2:
The patent uses solid block-like conductors that can be directly pressed into grooves, copying the final desired shape rather than forming it through winding thin wire, which achieves better space utilization
3Ease of manufacture
If conventional winding with small wire cross section is used, then coils can be formed, but heat dissipation becomes insufficient and cooling efficiency is reduced
Solution Approach 1:
The patent changes the thermal parameters by using larger cross-section conductors with better thermal conductivity and increased surface area, which enhances heat dissipation capability while maintaining coil functionality
Solution Approach 2:
The patent employs composite conductor structures combining highly conductive metal materials with optimized geometric shapes, creating a composite solution that simultaneously improves electrical and thermal performance
4Loss of energy
If larger wire cross section is used, then power losses are reduced and efficiency improves, but the wire cannot be guided through existing slits during winding
Solution Approach 1:
The patent inverts the traditional winding approach by not guiding wire through slits at all, instead using direct placement or pressing of solid conductors into grooves, which accommodates large cross-sections that would be impossible to guide through narrow slits
Solution Approach 2:
The patent segments the stator structure into distinct grooves that can independently receive large conductors, allowing each segment to be filled with optimally sized wire without constriction from narrow guiding slits
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 enhances both the drive and heat dissipation efficiency of the electric motor, allowing for better cooling and reduced power losses, while also achieving a high power density and compact motor design.
Implementation Method 1
the corresponding rotary movement being based on the forces of attraction and repulsion of magnetic fields that are generated in the area of the electric motor
Implementation Method 2
An electric motor is designed to convert electrical power into mechanical power. Electric motors usually generate rotating movements, the corresponding rotary movement being based on the forces of attraction and repulsion of magnetic fields
Data Source
AI summary
An electric motor, in particular for a power tool, the electric motor having a stator with an inner opening for receiving a rotor. The inner opening has a diameter corresponding to an inner diameter of a stator, the stator having a series of pole teeth, which are each wound with a winding to form a coil. The winding is characterized by a reference diameter, a ratio of the reference diameter to the stator inner diameter multiplied by a number of pole teeth being greater than 0.3. Taking into account the internal resistance of an energy storage cell of an energy supply device of a maximum of 10 milliohms, the ratio of the diameters may be greater than 0.03 (milliohms)−1. Also provided is an electric motor, in particular for a power tool, a ratio being formed from a sum of total winding conductor cross sections and a free winding cross section, the ratio being multiplied by a number of pole teeth and the product being greater than 2.2. Taking into account the internal resistance of an energy storage cell of the energy supply device of a maximum of 10 milliohms, the ratio of the areas of the cross sections may be greater than 0.22 (milliohms)−1. Also provided is a power tool with one of the electric motors, and a system including a power tool and an energy supply device.