Outer Rotor Motor Inverter Control for Current Ripple Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Low inductance outer rotor motors in power tools experience high current ripple, leading to significant thermal losses and reduced efficiency due to faster current rise times and increased heat dissipation.
Innovation Solution
Implementing a high switching frequency of approximately 20 kHz to 100 kHz in power tools, particularly in outer rotor motors, using synchronous rectification and hybrid polymer capacitors to reduce current ripple and thermal losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If low inductance outer rotor motors are used, then motor size and weight are reduced, but current ripple increases causing high thermal losses
Solution Approach 1:
The patent increases the switching frequency from traditional 8 kHz to 20-100 kHz, which fundamentally changes the operational parameters of the motor control system. This parameter change reduces the time available for current ripple to develop, thereby reducing thermal losses while maintaining the benefits of low inductance motors
2Speed
If low inductance outer rotor motors are used, then motor response time is improved, but current ripple increases causing heat dissipation issues
Solution Approach 1:
By changing the switching frequency parameter to 20-100 kHz, the system maintains fast motor response characteristics while reducing the amplitude and duration of current ripple, thereby minimizing heat generation during high-speed operation
3Device complexity
If traditional switching frequency is used, then device complexity is low, but current ripple causes reduced speed linearity
Solution Approach 1:
The patent implements a higher switching frequency (20-100 kHz) which, while increasing control complexity, significantly improves speed linearity by reducing current saturation effects. The benefit of improved motor control performance justifies the increased complexity in the control system
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 high switching frequency reduces thermal losses, improves speed linearity, and enhances motor efficiency by minimizing current saturation and heat dissipation, resulting in smoother operation and improved performance.
Implementation Method 1
Power tools include motors that are typically powered by an electrical source, such as a DC battery or a conventional AC source
Data Source
AI summary
Power tools and methods of operating the same. One power tool includes a housing, a battery pack receptacle coupled to the housing and configured to receive a power tool battery pack, and a motor supported within the housing, wherein the motor is configured to be powered by the power tool battery pack. The power tool further includes an inverter electrically connected to the motor, wherein the inverter includes a plurality of switching elements. The power tool further includes a controller including an electronic processor configured to generate a control signal to operate the plurality of switching elements of the inverter at a switching frequency between approximately 20 kHz and approximately 100 kHz to provide power from the power tool battery pack to drive the motor.