Motor Braking Circuit With Selective Resistive Loads for Heat Control
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Solution Overview
Problem
Existing power tools with large braking resistors face high manufacturing costs due to excess heat concentration and the need for costly heat dissipation components, which also occupy valuable space.
Innovation Solution
A motor braking circuit with selectively connectable resistive loads and field effect transistors (FETs) that distribute braking current across multiple paths, reducing the size and cost of resistors and dissipating heat over a larger area, while using a straight connect power interface without mechanical switches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large braking resistor is used to absorb excess current during motor braking, then the motor can be stopped within the prescribed time period, but excess heat is concentrated at one location and costly heat dissipation components are required
Solution Approach 1:
The patent divides the braking function into two segments: regenerative braking (returning energy to power source) and resistive braking (dissipating energy as heat). The motor controller selectively activates these braking modes based on system impedance conditions, avoiding the need for a single large braking resistor that concentrates heat.
Solution Approach 2:
The patent changes the operating parameters of the braking system by monitoring system impedance and dynamically selecting between regenerative and resistive braking modes. This parameter-based control allows the system to achieve effective braking without consistently using high-power resistive braking that generates excessive heat.
2Reliability
If a large braking resistor is used to absorb excess current during motor braking, then the motor can be stopped within the prescribed time period, but the cost of manufacturing the power tool increases due to the resistor and heat dissipation components
Solution Approach 1:
The patent implements a dynamic braking control system that adjusts the braking method based on real-time system conditions. The motor controller monitors system impedance and selectively switches between regenerative and resistive braking modes, allowing the use of smaller, less expensive braking components compared to a fixed large braking resistor design.
Solution Approach 2:
The patent changes the operating parameters of the braking system by monitoring system impedance and dynamically selecting between regenerative and resistive braking modes. This parameter-based control allows the system to achieve effective braking without consistently using high-power resistive braking that generates excessive heat.
3Reliability
If a large braking resistor is used to absorb excess current during motor braking, then the motor can be stopped within the prescribed time period, but valuable space is occupied by the resistor and heat dissipation components
Solution Approach 1:
The patent divides the braking function into two segments: regenerative braking (returning energy to power source) and resistive braking (dissipating energy as heat). The motor controller selectively activates these braking modes based on system impedance conditions, avoiding the need for a single large braking resistor that occupies significant space.
Solution Approach 2:
The patent implements a dynamic braking control system that adjusts the braking method based on real-time system conditions. The motor controller monitors system impedance and selectively switches between regenerative and resistive braking modes, allowing the use of smaller, space-efficient braking components compared to a fixed large braking resistor design.
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 approach reduces manufacturing costs, improves heat management, and provides space-saving options by using smaller resistors and transistors, effectively braking the motor within prescribed time limits.
Implementation Method 1
A motor braking circuit with selectively connectable resistive loads and field effect transistors (FETs) that distribute braking current across multiple paths
Implementation Method 2
distribute braking current across multiple paths, reducing the size and cost of resistors and dissipating heat over a larger area
Data Source
AI summary
Apparatus and method for motor braking using selectively connectable resistance. The method includes controlling, using a motor controller of the power tool, a power switching network to drive a motor of the power tool in response to actuation of a user input and determining, using the motor controller, a variable tool characteristic. The method further includes determining, using the motor controller, that the user input is de-actuated. The method also includes controlling, using the motor controller, the power switching network to brake the motor when the variable tool characteristic satisfies the tool characteristic threshold and controlling, using the motor controller, a braking circuit to brake the motor when the variable tool characteristic does not satisfy the tool characteristic threshold. The braking circuit includes one or more resistive loads and is selectively coupled to the motor terminals of the motor.