Brushless Motor Efficiency via Reduced Electrical Resistance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Cordless electric power tools experience significant power loss due to internal impedance in batteries and electrical resistances in the motor, switch, and harness, leading to decreased overall electric efficiency during high-output operations.
Innovation Solution
Reducing electrical resistances by increasing the cross-sectional area of motor windings, limiting the on-resistance of motor controllers, and using semiconductor switches to eliminate contact and node resistances, while maintaining the nominal voltage of the battery within specific ranges to achieve improved overall electric efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the output (voltage) of the battery is increased to improve tool output, then the power loss in the battery decreases, but the device complexity and cost increase
Solution Approach 1:
The patent changes the electrical parameters of existing components (winding cross-sectional area, on-resistance values, contact resistance) rather than changing the battery voltage. By optimizing these parameters, the system achieves higher efficiency at the same battery output, resolving the contradiction between reducing energy loss and avoiding increased device complexity
Solution Approach 2:
The patent replaces mechanical contact switches with semiconductor switches (MOS-FETs) to eliminate contact resistance and node resistance. This substitution dramatically reduces electrical losses in the switching path without requiring higher battery voltage, thus resolving the contradiction
2Loss of energy
If the cross-sectional area of motor windings is increased to reduce winding resistance, then the overall electric efficiency improves, but the motor size and weight increase
Solution Approach 1:
The patent optimizes the winding cross-sectional area parameter to achieve the right balance between resistance reduction and motor weight. By carefully selecting this parameter along with other electrical parameters, the system improves efficiency without excessive weight gain
Solution Approach 2:
The patent substitutes semiconductor switches for mechanical contact switches, eliminating the need for heavy-duty contacts and associated wiring. This substitution reduces overall resistance losses without requiring proportionally larger motor components, thus resolving the weight-efficiency contradiction
3Loss of energy
If semiconductor switches are used to eliminate contact resistance, then the overall electric efficiency improves, but the device complexity increases
Solution Approach 1:
The patent replaces mechanical contact switches with semiconductor switches (MOS-FETs), which have no physical contacts and therefore zero contact resistance. Although semiconductor devices are more complex than simple contacts, their integration into the motor controller creates a unified electronic system that reduces overall complexity compared to managing multiple high-power mechanical contacts
Solution Approach 2:
The semiconductor switches serve multiple functions: they act as controllable switches, provide overcurrent protection, enable regenerative braking, and facilitate precise speed control. This multi-functionality consolidates what would otherwise require separate components, actually reducing overall system complexity while eliminating contact resistance 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
The overall electric efficiency of cordless electric power tools is enhanced to at least 70% during high-output operations, allowing for increased tool output without increasing battery output, resulting in improved performance and extended work capacity per charge.
Implementation Method 1
a motor that drives a tool
Implementation Method 2
a battery that supplies electric power to the motor
Implementation Method 3
a power loss occurs in the battery. This electric power loss is caused by internal impedance of the battery and becomes great according to the amount of current flowing to the battery
Data Source
AI summary
A cordless electric power tool comprises a motor that drives a tool, a battery that supply electric power to the motor and a motor drive circuit that is disposed between the motor and the battery. The motor is a three-phase brushless motor, and the battery has a nominal voltage of 18 volts. An overall electric efficiency of the cordless electric power tool becomes at least 70 percent when a value of current passing through the motor becomes at least 35 amperes but no more than 45 amperes and the cordless electric power tool outputs power of at least 450 watts but no more than 550 watts.