Motor Control Device for Precise Airflow Maintenance
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Solution Overview
Problem
Conventional motor control systems for fans in air conditioners and ventilators fail to accurately maintain a predetermined airflow value due to variations in static pressure caused by factors like filter clogging or vent state, as they rely on controlling motor voltage rather than current, which is affected by armature circuit resistance changes due to heat and temperature.
Innovation Solution
A motor control device that includes input terminals for motor speed and torque parameters, a motor-speed target value unit to calculate necessary modifications at predetermined intervals, and an output terminal to control motor speed, using torque information to maintain precise airflow values unaffected by temperature changes, represented by equations (3) and (4).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If applied voltage V is controlled to maintain motor speed, then motor speed control is simplified, but airflow accuracy deteriorates due to resistance variations from heat generation and temperature changes
Solution Approach 1:
The patent changes the control parameter from applied voltage to motor current. By detecting and controlling motor current directly, the system compensates for resistance variations caused by heat generation and temperature changes, thereby maintaining accurate airflow control while preserving ease of operation through automated current adjustment.
2Device complexity
If total resistance R of armature circuit is used in control calculation, then control complexity is reduced, but control accuracy deteriorates due to resistance variations from heat generation and atmosphere temperature
Solution Approach 1:
The patent introduces feedback by detecting motor current and using this information to calculate the required applied voltage. The control device continuously monitors motor current and adjusts the applied voltage accordingly, creating a closed-loop system that compensates for resistance variations and maintains reliable airflow control.
3Measurement precision
If motor current I is controlled directly, then airflow precision is improved, but control complexity increases compared to voltage control
Solution Approach 1:
The patent uses motor current as an intermediary parameter between voltage control and airflow output. By detecting motor current and using it to calculate the appropriate applied voltage, the system achieves precise airflow control without requiring direct mechanical or complex electronic current control mechanisms, thus limiting the increase in device complexity.
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 enables precise maintenance of predetermined airflow values by accurately controlling motor speed based on torque information, reducing errors from heat and temperature variations, and ensuring consistent airflow even under changing static pressures.
Implementation Method 1
a motor that drives a fan
Implementation Method 2
total resistance R of the armature circuit and induced voltage E, based on a relationship of equation (2). V=E+I×R
Data Source
AI summary
A motor control device controls a fan motor, and controls a motor speed so as to maintain a predetermined airflow value. For this, the motor control device includes an input terminal for inputting a first operation parameter indicating the motor speed or a second operation parameter indicating a motor torque. Moreover, the motor control device includes a motor-speed target value arithmetically-operating unit that calculates, using a predetermined airflow value and the motor torque, a necessary modified value for the motor speed at the predetermined time intervals. Further, the motor control device includes an output terminal that outputs an instruction speed of the motor based on the necessary modified value.