Motor Protect-Control Device for Silent Switchover via Fixed PWM
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Solution Overview
Problem
Conventional motor control systems using PWM signals to regulate cooling fan motor speeds result in noise during switchover due to variable frequency and duty cycle, leading to current limitations that disrupt rotational speed control and generate noise perceived by humans.
Innovation Solution
A protect-control device comprising a motor coil set, a driving unit, a sensing unit, and a control unit that adjusts the driving level based on a preset reference level to maintain a stable duty cycle and frequency above 25 KHZ, reducing noise by limiting current and protecting against frequency drops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If PWM signal duty cycle and frequency are varied to control motor rotational speed, then motor speed control flexibility is improved, but noise is generated during switchover that is perceivable by humans
Solution Approach 1:
The patent changes the frequency parameter of the PWM signal from variable to fixed above 25 KHZ, and changes the duty cycle parameter to maintain a basic constant value. This parameter transformation eliminates the noise issue while preserving motor speed control flexibility through other means.
Solution Approach 2:
Instead of controlling motor speed by varying duty cycle and frequency as in conventional PWM control, this patent inverts the approach by maintaining fixed frequency and duty cycle parameters, and controlling speed through alternative methods that do not generate audible noise during switchover.
2Reliability
If current limiting is applied to protect the motor during switchover, then motor protection is improved, but rotational speed control is disrupted and noise is generated
Solution Approach 1:
The patent implements current limiting protection in advance by setting fixed PWM parameters (frequency above 25 KHZ and basic duty cycle) before switchover occurs. This preliminary configuration prevents noise generation during the actual switchover event while maintaining motor protection capabilities.
Solution Approach 2:
The patent converts the potential harm of current fluctuations during switchover into a benefit by using fixed high-frequency PWM parameters. The current limiting function is maintained but operates in a way that prevents noise generation, turning a protective measure that could cause noise into a silent protection mechanism.
3Ease of operation
If PWM frequency is reduced below 25 KHZ during current limiting, then current control is simplified, but noise becomes perceivable by humans
Solution Approach 1:
The patent maintains the PWM frequency parameter fixed above 25 KHZ throughout operation, including during current limiting conditions. This parameter setting simplifies current control while ensuring the frequency remains in the ultrasonic range where it is not perceivable by humans.
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 device effectively reduces noise during motor switchover by maintaining a stable rotational speed range and duty cycle, ensuring the frequency remains above 25 KHZ, which is not perceivable by humans, while providing current protection and limiting functions.
Implementation Method 1
the Hall component 102 of the driving circuit 10 detects the magnetic pole change of the rotor to produce positive voltage H+ and negative voltage H− outputting to the driving component 103
Data Source
AI summary
A protect-control device capable of limiting current for reducing noise resulting from switchover of a motor includes a motor coil set, a driving unit, a sensing unit and a control unit. The motor coil set constitutes a motor. The driving unit is electrically connected to the motor coil and provides a driving level to pass through the motor coil for driving the motor. The sensing unit is electrically connected to the motor coil set, provides a preset reference level, detects the driving level, compares the driving level to the preset reference level and outputs identifying signal. The control signal is electrically connected to the driving unit, the sensing unit and a Hall component, adjusts the driving level based on the identifying signal for driving unit output maintaining a basic duty cycle.