Fan Motor Torque Feedback Under Changing Static Pressure
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Solution Overview
Problem
Conventional motor control systems for fans in air conditioners and ventilators fail to maintain a predetermined airflow value accurately due to variations in static pressure caused by factors like filter clogging or vent state changes, as they rely on controlling applied voltage rather than motor current, which is influenced by armature circuit resistance affected by heat generation and temperature.
Innovation Solution
A motor control device that includes input terminals for motor speed and torque parameters, a motor-speed target value calculator, and an output terminal to adjust motor speed based on calculated torque values, ensuring precise airflow control by using torque information to maintain the predetermined airflow value despite temperature changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If applied voltage V is controlled to maintain motor speed, then motor speed can be regulated, but airflow accuracy deteriorates due to armature circuit resistance variations from heat and temperature changes
Solution Approach 1:
The invention changes the control parameter from applied voltage to motor current. By controlling motor current directly instead of controlling voltage and indirectly affecting current through voltage, the system eliminates the influence of armature circuit resistance variations. The control unit calculates required motor current based on desired airflow and motor characteristics, then directly controls the inverter to output the calculated current, ensuring accurate airflow control regardless of temperature or resistance changes.
2Ease of operation
If voltage control method is used, then control simplicity is maintained, but control accuracy deteriorates due to inability to compensate for resistance changes
Solution Approach 1:
The invention implements a feedback control mechanism where the control unit continuously calculates the required motor current based on the desired airflow value and actual motor operating conditions. The inverter adjusts the motor current in real-time based on this calculation, creating a closed-loop control system that maintains accurate airflow control. This feedback approach automatically compensates for resistance variations without requiring manual intervention or complex external circuits.
3Device complexity
If armature circuit resistance variations are not compensated, then device complexity is reduced, but airflow control precision deteriorates
Solution Approach 1:
The invention replaces physical compensation mechanisms with computational compensation. Instead of using temperature sensors, resistance measurement circuits, or mechanical adjustment devices to compensate for armature circuit resistance variations, the system uses the controller's processing capability to calculate and directly control the motor current. This substitution of computational methods for physical compensation mechanisms maintains device simplicity while achieving high precision airflow control.
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 allows for precise maintenance of the predetermined airflow value without errors from motor heat or temperature changes, providing stable airflow control even under varying static pressures.
Implementation Method 1
a motor control device which controls a motor (4) that drives a fan (8)
Implementation Method 2
total resistance R of the armature circuit varies due to heat generation of the motor and atmosphere temperature
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.