FOC Motor Braking Control for Power Tool Back-EMF Spikes
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing power tools with permanent-magnet synchronous motors experience voltage spikes and reverse bus currents during braking, potentially damaging components and disrupting power supplies, and current solutions require additional resistors and control circuits, increasing cost and space.
Innovation Solution
A power tool with a control circuit that includes a driver circuit, a controller, and a parameter detection module, utilizing field-oriented control (FOC) to adjust input parameters and control the motor's output power and torque for safe and fast braking without additional electronic elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional braking method with bleeder resistors is used, then braking safety is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts and eliminates the bleeder resistors and their control circuits from the system. Instead of using external resistive elements for braking, the invention utilizes the motor's own windings to consume the back electromotive force energy, thereby removing the need for additional braking components while maintaining braking safety.
Solution Approach 2:
The motor windings serve dual purposes: both as functional components for motor operation and as the braking mechanism itself. During braking, the motor windings automatically consume the back electromotive force energy without requiring external braking components,实现ing self-service braking functionality.
2Reliability
If traditional braking method with bleeder resistors is used, then braking safety is improved, but manufacturing cost increases
Solution Approach 1:
The patent removes the bleeder resistors and their control circuits from the system, thereby eliminating the manufacturing costs associated with these additional components. The braking function is achieved using existing motor windings, reducing overall manufacturing cost.
3Object-affected harmful factors
If traditional braking method with bleeder resistors is used, then voltage spike is suppressed, but space occupation increases
Solution Approach 1:
The patent extracts and eliminates the bleeder resistors and their control circuits from the system. Instead of using external resistive elements for braking, the invention utilizes the motor's own windings to consume the back electromotive force energy, thereby removing the need for additional braking components while maintaining braking safety.
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
Enables safe and rapid motor braking without additional components, consuming braking current within the motor windings to prevent reverse charge, thus protecting the power supply and reducing the risk of component damage.
Implementation Method 1
When a tool with a permanent-magnet synchronous motor brakes, the motor generally generates a relatively large voltage spike or a reverse bus current
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A power tool includes: a motor (11) including a rotor and multiple phases of stator windings (U, V, W); and a control circuit (110) configured to control the working state of the motor. The control circuit includes: a driver circuit including multiple switching elements (111); a controller (112) electrically connected to at least the driver circuit and capable of outputting a control signal to change the conducting states of the multiple switching elements in the driver circuit; and a parameter detection module (113) configured to detect a working parameter of the motor. In response to a braking signal, the controller sets an input parameter of the control circuit according to a preset parameter and the working parameter to control output power of the motor and/or output torque of the motor, thereby controlling the motor to brake.