Power Failure Detection Circuit for VRF System Fan and Valve Shutdown
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Solution Overview
Problem
In a variable refrigerant flow VRF system, power failures can cause the fan motor to stop, leading to refrigerant flow without effective energy exchange, resulting in condensation and potential safety hazards, especially with flammable refrigerants.
Innovation Solution
A power failure detection circuit that includes a rectifying circuit, switching circuit, and judgment circuit to detect power failures by converting AC voltage to a periodic pulse and triggering a fan and electronic expansion valve control when no pulse is received within a preset time period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the fan motor stops rotating due to power failure, then the system saves energy by stopping operation, but refrigerant continues to flow without effective energy exchange causing condensation and safety hazards
Solution Approach 1:
The patent applies preliminary action by closing the electronic expansion valve before the fan motor stops rotating during power failure. The control circuit detects power failure and proactively closes the expansion valve to stop refrigerant flow, preventing condensation and safety hazards before they occur. This anticipatory measure ensures that the refrigerant flow is halted in advance, avoiding the harmful effects that would result from continued flow without fan operation.
2Quantity of substance
If the electronic expansion valve remains open during power failure, then refrigerant flow continues, but without fan operation the refrigerant cannot be effectively evaporated or cooled causing system malfunctions
Solution Approach 1:
The control circuit performs preliminary action by detecting power failure and closing the electronic expansion valve before refrigerant flow can cause system malfunctions. This ensures that the refrigerant quantity is reduced proactively, preventing the condition where refrigerant accumulates without proper evaporation or cooling, thereby maintaining system reliability.
3Device complexity
If a simple power failure detection method is used, then the device complexity is reduced, but the detection precision and reliability of power failure detection may be insufficient
Solution Approach 1:
The patent uses an intermediary approach by introducing a control circuit that includes a rectifying circuit, switching circuit, and judgment circuit. This intermediary detection system converts AC voltage to periodic pulses and monitors their presence to reliably detect power failure. The intermediary circuits provide reliable detection without requiring overly complex systems, achieving a balance between detection reliability and device complexity.
4Object-affected harmful factors
If the fan continues to operate during power failure, then air supply prevents condensation, but energy is wasted and the system operates inefficiently
Solution Approach 1:
The control circuit applies preliminary action by closing the electronic expansion valve immediately upon detecting power failure, stopping refrigerant flow before condensation can occur. This eliminates the need for the fan to continue operating to prevent condensation, thereby avoiding energy wastage while still preventing harmful condensation effects.
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
Timely closure of the fan and electronic expansion valve prevents energy wastage and safety hazards by ensuring the system shuts down properly during power outages.
Implementation Method 1
a rectifying circuit for full-wave rectifying an alternating current voltage so as to obtain a first voltage
Implementation Method 2
a switching circuit for converting the first voltage into a periodic voltage pulse; and a judgment circuit for providing an output signal when the periodic voltage pulse is not received within a preset time period
Data Source
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AI summary
The present application relates to a power failure detection circuit (1000), the circuit comprises: a rectifying circuit (110) for full-wave rectifying an alternating current voltage so as to obtain a first voltage; a switching circuit (120) for converting the first voltage into a periodic voltage pulse; and a judgment circuit (130) for providing an output signal to a fan control circuit (140) for closing a fan when the periodic voltage pulse is not received within a preset time period, and providing the output signal to a micro-control unit (150) for closing an electronic expansion valve. The present application also relates to a control circuit for a variable refrigerant flow VRF system.