Electrodynamic Braking for Universal Motors Reducing Brush Wear
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Solution Overview
Problem
Existing electrodynamic braking devices for universal motors are not suitable for applications with dangerous tools, as they cause significant brush wear and sparking, leading to maintenance issues and reduced operational reliability.
Innovation Solution
An electrodynamic braking device with a specific circuit arrangement that shortens the armature during braking and excites the field winding from a power supply system using control electronics, reducing brush sparking and wear, and ensuring operational reliability through monitoring and phase gating control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrodynamic braking devices are used for universal motors, then braking function is achieved, but brush wear and sparking increase significantly
Solution Approach 1:
The patent replaces conventional mechanical braking systems with an electrodynamic braking system that uses electromagnetic fields to generate braking torque. The motor operates as a generator during braking, converting mechanical energy to electrical energy, which is then dissipated through resistors. This substitution eliminates direct mechanical contact, thereby reducing brush sparking and wear while maintaining operational reliability.
Solution Approach 2:
The patent introduces control electronics as an intermediary between the motor and the braking resistors. This control system manages the switching between motor and braking modes, controls the braking torque by regulating current flow through the armature, and ensures smooth transition to prevent arcing. The intermediary control system optimizes the braking process to minimize harmful effects on brushes.
2Productivity
If braking torque is increased for rapid stopping, then braking performance improves, but brush wear and sparking worsen
Solution Approach 1:
The patent employs dynamic control of the braking process through electronic regulation. The control electronics continuously adjust the braking torque based on the motor's rotational speed, ensuring optimal braking force at each moment. This dynamic adjustment allows rapid stopping while preventing excessive current surges that would cause brush arcing and wear. The system adapts the braking characteristics in real-time to balance performance and component protection.
Solution Approach 2:
The patent utilizes the periodic nature of AC power supply to synchronize the braking operation. The control system switches the braking resistors into the circuit in synchronization with the AC cycle, ensuring that switching occurs at appropriate moments to minimize arcing. This periodic action allows the system to achieve rapid braking while reducing the harmful effects of brush contact during switching transitions.
3Reliability
If field winding is continuously excited during braking, then braking torque is maintained, but energy consumption increases
Solution Approach 1:
The patent applies partial excitation of the field winding during braking operation. Rather than maintaining full field excitation throughout the entire braking process, the control system adjusts the field current to the minimum level required to generate sufficient braking torque at each moment. This partial action approach maintains adequate braking performance while significantly reducing energy consumption compared to continuous full excitation.
Solution Approach 2:
The patent dynamically changes the excitation parameters of the field winding during braking. The control electronics adjust both the magnitude and timing of field current based on the motor's speed and loading conditions. By optimizing these parameters in real-time, the system maintains reliable braking performance across varying operating conditions while minimizing energy consumption through efficient use of the field winding.
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 achieves smooth, rapid braking with extended brush life and reduced maintenance, while minimizing brush sparking and wear, ensuring safe and reliable operation for tools like handheld circular saws and angle grinders.
Implementation Method 1
a field winding (2) which is connected to a power supply system (L, N)
Implementation Method 2
an armature winding (1) which is connected to a shorting switch (S2)
Data Source
AI summary
An electrodynamic braking device for a universal motor is proposed, wherein during a braking operation a field winding is supplied from a network, and an armature is directly short-circuited, and a braking operation is carried out using a program of a controller of a control electronics system, whereby good braking is achieved with relatively low brush wear. Such an electrodynamic braking device is advantageously applied in a power tool equipped with a dangerous tool.