AC Brushless Power Tool Startup With Reduced DC Bus Pulsation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Alternating current power tools face high probabilities of startup failure due to large electrolytic capacitors, which generate heat and affect heat dissipation, and without them, voltage input to the motor produces significant pulsation.
Innovation Solution
A power tool design incorporating a small electrolytic capacitor or a thin film capacitor in series with a rectifier circuit to filter pulsating direct current, combined with a controller that outputs PWM signals based on alternating current detection and rotor position calculations to manage motor startup effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a large electrolytic capacitor is used to stabilize input voltage, then voltage stability is improved, but device size increases and heat generation worsens
Solution Approach 1:
The patent changes the capacitance parameter from large to small by using a small electrolytic capacitor combined with a thin film capacitor. This parameter change allows the system to maintain voltage stability during motor startup while significantly reducing the overall capacitor volume and associated heat generation.
Solution Approach 2:
The patent employs a composite capacitor configuration by combining a small electrolytic capacitor with a thin film capacitor in parallel. This composite structure leverages the high capacitance density of electrolytic capacitors for bulk energy storage and the low ESR (equivalent series resistance) of thin film capacitors for high-frequency ripple filtering, achieving effective voltage stabilization with reduced size and heat generation.
2Stability of the object's composition
If a large electrolytic capacitor is used to stabilize input voltage, then voltage stability is improved, but heat generation increases and component lifespan decreases
Solution Approach 1:
The patent changes the capacitance parameter from large to small by using a small electrolytic capacitor combined with a thin film capacitor. This parameter change allows the system to maintain voltage stability during motor startup while significantly reducing the overall capacitor volume and associated heat generation.
Solution Approach 2:
The patent employs a composite capacitor configuration by combining a small electrolytic capacitor with a thin film capacitor in parallel. This composite structure leverages the high capacitance density of electrolytic capacitors for bulk energy storage and the low ESR (equivalent series resistance) of thin film capacitors for high-frequency ripple filtering, achieving effective voltage stabilization with reduced size and heat generation.
3Volume of stationary object
If no large electrolytic capacitor is used, then device size is reduced and heat dissipation is improved, but voltage pulsation increases and startup reliability decreases
Solution Approach 1:
The patent changes the capacitance parameter from large to small by using a small electrolytic capacitor combined with a thin film capacitor. This parameter change allows the system to maintain voltage stability during motor startup while significantly reducing the overall capacitor volume and associated heat generation.
Solution Approach 2:
The patent employs a composite capacitor configuration by combining a small electrolytic capacitor with a thin film capacitor in parallel. This composite structure leverages the high capacitance density of electrolytic capacitors for bulk energy storage and the low ESR (equivalent series resistance) of thin film capacitors for high-frequency ripple filtering, achieving effective voltage stabilization with reduced size and heat generation.
4Temperature
If no large electrolytic capacitor is used, then heat dissipation performance is improved, but voltage pulsation increases and startup reliability decreases
Solution Approach 1:
The patent changes the capacitance parameter from large to small by using a small electrolytic capacitor combined with a thin film capacitor. This parameter change allows the system to maintain voltage stability during motor startup while significantly reducing the overall capacitor volume and associated heat generation.
Solution Approach 2:
The patent employs a composite capacitor configuration by combining a small electrolytic capacitor with a thin film capacitor in parallel. This composite structure leverages the high capacitance density of electrolytic capacitors for bulk energy storage and the low ESR (equivalent series resistance) of thin film capacitors for high-frequency ripple filtering, achieving effective voltage stabilization with reduced size and heat generation.
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 reduces the probability of startup failure by stabilizing voltage input and minimizing heat generation, ensuring accurate rotor position calculation and continuous torque generation, thus enhancing the power tool's reliability and lifespan.
Implementation Method 1
A power tool design incorporating a small electrolytic capacitor or a thin film capacitor in series with a rectifier circuit to filter pulsating direct current
Implementation Method 2
a rectifier circuit to filter pulsating direct current
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
Provided is an alternating current power tool. The alternating current power tool includes a brushless motor, a power module, a voltage conversion module, a drive circuit, and a controller. The power module is configured to receive an alternating current to supply power to the stator winding. The voltage conversion module is configured to receive the alternating current received by the power module and operatively output a direct current bus voltage. The drive circuit is electrically connected to the power conversion module and configured to drive the brushless motor. The controller is configured to start timing when the alternating current received by the power module crosses through a point of zero. In a preset time interval [T1, T2] of each half cycle, a first control signal is outputted to the drive circuit to power on the stator winding. The starting time of the preset time interval is T1, and the cut-off time of the preset time interval is T2.