Drain Pump Motor Speed Control Using Current-Based Ripple Detection
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Solution Overview
Problem
Laundry treatment machines generate noise during drainage due to the constant speed operation of drain pumps, which is not optimized for varying water levels, leading to inefficient drainage and increased noise.
Innovation Solution
A drain pump driving apparatus that includes a motor, an inverter to convert DC power to AC power, an output current detector, and a controller to calculate speed ripple and adjust the motor speed based on the detected current, allowing for variable speed operation to reduce noise and improve drainage efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the drain pump operates at constant speed, then the structure is simple and reliable, but noise increases and drainage efficiency decreases due to inability to adapt to varying water levels
Solution Approach 1:
The motor speed control system transitions from constant speed operation to variable speed operation, dynamically adjusting the motor speed based on detected output current and calculated speed ripple. This allows the drain pump to adapt to varying water levels and drainage conditions, improving drainage efficiency while managing noise levels through controlled speed variation.
Solution Approach 2:
The system changes the operating parameter of motor speed from a fixed constant value to a variable parameter that is continuously adjusted based on output current detection and speed ripple calculation. This parameter change enables the motor to operate at optimal speeds for different drainage conditions, resolving the contradiction between simplicity and efficiency.
2Productivity
If the motor speed is increased to improve drainage speed, then productivity increases, but noise and energy consumption increase
Solution Approach 1:
The motor speed is dynamically adjusted based on real-time detection of output current and calculation of speed ripple. During phases when high drainage speed is needed, the motor operates at higher speeds to maximize productivity. When water levels decrease or drainage is complete, the speed is reduced to minimize noise, thus resolving the contradiction between productivity and noise generation.
Solution Approach 2:
The motor operates in periodic cycles of high-speed drainage and low-speed idle operation. The controller periodically detects output current and calculates speed ripple to determine when to switch between high-speed and low-speed modes, enabling the system to achieve high productivity during active drainage while minimizing noise during idle or low-flow periods.
3Ease of operation
If additional sensors are added to optimize motor speed control, then drainage efficiency improves, but device complexity and cost increase
Solution Approach 1:
The motor control system uses the motor's own output current as the sensing parameter to detect operating conditions and calculate speed ripple. This self-service approach eliminates the need for external water level sensors or flow sensors, as the motor's electrical characteristics provide sufficient information for optimal speed control, resolving the contradiction between optimization capability and system complexity.
Solution Approach 2:
The output current detector serves multiple functions: it monitors motor operation status, detects water level conditions through current characteristics, and provides data for speed ripple calculation. This multi-functionality eliminates the need for separate sensors, allowing the system to achieve optimized drainage efficiency without increasing device complexity through additional sensing components.
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 noise and enhances drainage performance by gradually or stepwise decreasing motor speed as the speed ripple increases, ensuring smooth operation and reduced power consumption without the need for additional sensors.
Implementation Method 1
an inverter to convert a direct current (DC) power to an alternating current (AC) power by a switching operation
Data Source
AI summary
Disclosed herein is a drain pump driving apparatus and a laundry treatment machine including the same. The drain pump driving apparatus and the laundry treatment machine including the same according to an embodiment of the present invention include a motor to operate the drain pump, an inverter to convert a direct current (DC) power to an alternating current (AC) power by a switching operation and output the converted AC power to the motor, an output current detector to detect an output current flowing to the motor, and a controller to control the inverter, wherein the controller may calculate a speed ripple of the motor based on the output current and performs a control operation based on the calculated speed ripple of the motor to change a speed of the motor.