PWM AC Blind Drive With Hysteresis Brake for Quiet Speed Control
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Solution Overview
Problem
Existing shading systems face issues with fixed speed operation due to induction motors, inefficiency, noise generation from phase-angle control, and dependency on mains frequency, leading to user discomfort and operational limitations.
Innovation Solution
Employing an AC motor controlled by pulse-width modulation (PWM) with a braking unit, specifically a magnetic hysteresis brake, to achieve high-frequency control, reduce noise, and optimize energy use, allowing independent operation from mains voltage fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If phase-angle control is used to control the electric drive, then speed adjustment is possible, but noise is generated and efficiency is reduced
Solution Approach 1:
The patent replaces phase-angle control with pulse-width modulation (PWM) technology. PWM controls the electric drive by switching the power supply on and off at high frequency, rather than using phase-angle control which causes audible humming noise. This substitution eliminates the noise problem while maintaining speed adjustment capability, as PWM operates at frequencies above the human audible range.
Solution Approach 2:
The patent changes the control parameter from phase-angle control to pulse-width modulation with switching frequencies in the kHz range (15-20 kHz). This parameter change moves the operating frequency above the human audible range, eliminating the annoying humming noise while enabling precise speed control through duty cycle adjustment.
2Speed
If phase-angle control is used to control the electric drive, then speed adjustment is possible, but efficiency is reduced and heating increases
Solution Approach 1:
The patent replaces phase-angle control with pulse-width modulation (PWM) technology. PWM controls the electric drive by switching the power supply on and off at high frequency, rather than using phase-angle control which causes audible humming noise. This substitution eliminates the noise problem while maintaining speed adjustment capability, as PWM operates at frequencies above the human audible range.
Solution Approach 2:
The patent changes the control parameter from phase-angle control to pulse-width modulation with switching frequencies in the kHz range (15-20 kHz). This parameter change moves the operating frequency above the human audible range, eliminating the annoying humming noise while enabling precise speed control through duty cycle adjustment.
3Device complexity
If induction motors are used, then the electric drive is simple, but speed is fixed and dependent on mains frequency
Solution Approach 1:
The patent applies pulse-width modulation to the induction motor control, making the speed dynamic rather than fixed. By varying the duty cycle of the PWM signal, the effective voltage and frequency supplied to the motor can be adjusted, enabling continuous speed variation while maintaining the simple induction motor structure. The braking unit also provides dynamic speed control during downward movement.
Solution Approach 2:
The patent changes the control parameter from phase-angle control to pulse-width modulation with switching frequencies in the kHz range (15-20 kHz). This parameter change moves the operating frequency above the human audible range, eliminating the annoying humming noise while enabling precise speed control through duty cycle adjustment.
4Area of stationary object
If multiple shading systems are used, then coverage is improved, but synchronous operation is difficult to achieve
Solution Approach 1:
The patent employs PWM control with high-frequency switching (15-20 kHz) that enables precise timing control of multiple shading systems. The high-frequency operation allows for synchronized operation of multiple blinds by providing precise control signals to each system, ensuring they operate in unison when controlled from a central location.
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 smooth, quiet, and energy-efficient operation of shading systems with precise control, eliminating audible noise and heat generation, and ensuring synchronized operation across multiple blinds.
Implementation Method 1
The brake unit (6) is designed in the form of a magnetic hysteresis brake
Implementation Method 2
A control unit (7) is provided which controls the AC motor (5) with pulse-width modulation
Data Source
Figure 1
Figure 2~3
Figure 4(a)~4(c)
AI summary
The invention relates to a shading system (1) with a blind (2) which can be moved upwards or downwards by means of an electric drive. The electric drive is designed as an AC motor (5). A control unit (7) is provided, which controls the AC motor (5) with pulse-width modulation. A brake unit (6) is associated with the AC motor (5).