Outdoor Fan Control for Sensorless Heat Exchanger Defrost
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Solution Overview
Problem
Existing air conditioner systems require a current detecting sensor to detect frost formation on outdoor heat exchangers during heating operations, leading to increased costs for defrost operations.
Innovation Solution
The system employs a control unit that generates a rotation-speed command voltage to control the outdoor fan motor's speed, allowing for frost detection and defrost initiation without the need for a current detecting sensor, using a duty ratio or actual rotation number feedback to determine when to start the defrost operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a current detecting sensor is provided to detect fan current for frost detection, then frost formation detection accuracy is improved, but device cost increases
Solution Approach 1:
The control unit utilizes its own existing duty ratio data and rotation-speed command voltage information to detect frost formation, eliminating the need for external current detecting sensors. The system serves itself by repurposing control signals already present in the system for the dual function of fan control and frost detection.
Solution Approach 2:
The control unit performs multiple functions: it generates rotation-speed command voltage for fan control and simultaneously uses the duty ratio information from this same signal to detect frost formation. This multi-functionality allows the system to achieve accurate frost detection without adding separate sensing components.
2Reliability
If a current detecting sensor is provided to detect fan current, then defrost operation reliability is improved, but device complexity increases
Solution Approach 1:
The control unit independently determines frost formation conditions by analyzing its own duty ratio data, eliminating dependence on separate current sensing components. This self-service approach ensures reliable defrost operation while reducing system complexity.
Solution Approach 2:
The control unit continuously monitors the duty ratio information from the rotation-speed command voltage and uses this feedback to detect changes in fan motor characteristics that indicate frost formation. This feedback mechanism ensures reliable defrost timing without requiring additional sensors.
3Device complexity
If duty ratio information is used for frost detection instead of current sensing, then device cost is reduced, but measurement precision may decrease
Solution Approach 1:
The patent replaces physical current sensing (electrical measurement) with electrical signal analysis (duty ratio monitoring). By analyzing the duty ratio information already present in the rotation-speed command voltage, the system achieves frost detection functionality without mechanical or electrical current sensors, reducing cost while maintaining adequate precision.
Solution Approach 2:
The control unit combines multiple pieces of information (rotation-speed command voltage, duty ratio data, and fan motor characteristics) to create a composite detection mechanism that compensates for the lack of direct current sensing, maintaining detection accuracy through information integration.
Data Source
AI summary
An air conditioner 1 includes: an outdoor heat exchanger 14; an outdoor fan 12 for blowing air to the outdoor heat exchanger; an outdoor fan motor 20 that drives the outdoor fan; an outdoor fan inverter 21 that drives the outdoor fan motor; and a control unit 31 that generates a rotation-speed command voltage for controlling the rotation number of the outdoor fan motor. In addition, the control unit starts a defrost operation of the outdoor heat exchanger, based on the rotation-speed command voltage. In this manner, it is possible to achieve an outdoor device of an air conditioner in which there is no need to provide a current detecting sensor, and it is possible to detect frost formation over the heat exchanger during a heating operation and to perform a defrost operation at low costs.