HVAC Fan Speed Feedback Control for Constant Duct Airflow
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Solution Overview
Problem
Air-conditioning devices struggle to accurately control fan rotation speed in response to fluctuations in static pressure due to variations in duct opening degrees, leading to potential errors in air flow rate calculation.
Innovation Solution
An air-conditioning apparatus equipped with a fan, fan motor, duct with multiple air outlets, a detection unit for airflow rate, dampers, and a fan motor control unit that adjusts the fan's rotation speed to maintain a constant airflow rate despite changes in damper opening degrees, using detected airflow rates and static pressure data to control the fan motor's frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If fan rotation speed is controlled based on external static pressure calculation without air flow detection, then device complexity is reduced, but measurement precision of air flow rate deteriorates
Solution Approach 1:
The patent implements a feedback mechanism where the air flow rate detection unit continuously monitors the actual air flow rate, and this detected value is fed back to the fan rotation speed control unit. The control unit adjusts the fan rotation speed based on the difference between the target air flow rate and the detected air flow rate, creating a closed-loop control system that improves measurement precision while maintaining manageable device complexity.
2Ease of operation
If fan rotation speed is calculated from external static pressure without detecting air flow variations, then ease of operation is improved, but reliability of air flow rate control deteriorates
Solution Approach 1:
The detection unit provides real-time feedback on actual air flow rate variations to the control unit, enabling the system to reliably adjust fan rotation speed in response to duct opening degree changes. This feedback mechanism ensures that the target air flow rate is maintained accurately despite static pressure fluctuations, improving reliability while keeping the operation simple through automated control.
Solution Approach 2:
The patent replaces manual calculation and mechanical control methods with electronic detection and control systems. The air flow rate detection unit uses electronic sensors to detect air flow variations, and the control unit uses electronic signals to adjust the fan motor rotation speed, substituting mechanical control with electronic systems that improve reliability.
3Adaptability or versatility
If fan rotation speed is adjusted in response to static pressure fluctuations without air flow detection, then adaptability to pressure changes is improved, but measurement precision of air flow rate deteriorates
Solution Approach 1:
The closed-loop feedback system allows the fan rotation speed to be adaptively adjusted in response to static pressure fluctuations while maintaining precise air flow rate measurement. The detection unit continuously monitors air flow rate and provides feedback to the control unit, which adjusts the fan speed to maintain the target air flow rate despite pressure changes, achieving both adaptability and measurement precision.
Data Source
AI summary
An air-conditioning apparatus includes a fan configured to send air to an air-conditioned space, a fan motor configured to drive the fan, a duct having a plurality of air outlets, the air sent by the fan flowing through the duct, a detection unit configured to detect an air flow rate of the fan, a damper provided to each of the plurality of air outlets, and a fan motor control unit configured to control a rotation speed of the fan motor such that the air flow rate assumes a constant value relative to variations in an opening degree of the damper of a plurality of dampers.