Outdoor Fan Power Detection for Air Conditioner Defrost Control
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Solution Overview
Problem
Existing air conditioner systems struggle to accurately detect frost formation on heat exchangers due to changes in fan rotational speed and torque constant control, which affect electric current measurements, making it difficult to infer frost formation and initiate defrosting operations effectively.
Innovation Solution
An air conditioner system that includes an outdoor heat exchanger, an outdoor fan, an outdoor fan motor, an outdoor fan inverter, and a control section that adjusts the fan motor's rotational speed based on current detection values to initiate defrosting operations, even under torque constant control conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the fan rotational speed is fixed to detect frost formation through electric current increase, then frost detection accuracy is improved, but energy consumption increases
Solution Approach 1:
The patent changes the detection parameter from electric current to electric power. By detecting electric power consumption of the fan motor, the system can identify frost formation while allowing fan speed to vary for energy saving. The control unit calculates electric power based on voltage and current measurements, enabling accurate frost detection without maintaining fixed fan rotational speed.
2Use of energy by moving object
If the fan rotational speed is reduced to save energy, then energy consumption decreases, but frost detection capability is lost
Solution Approach 1:
The patent transitions from using electric current as the detection parameter to using electric power. This parameter change allows the system to detect frost formation through power consumption patterns even when fan speed varies. The control unit monitors electric power and compares it against reference values to determine frost conditions, independent of fan rotational speed.
3Ease of operation
If constant torque control is applied to maintain current during speed reduction, then fan operation is optimized, but frost detection becomes impossible
Solution Approach 1:
The patent changes the detection approach from monitoring electric current to monitoring electric power. Under constant torque control, current remains relatively constant during speed reduction, but electric power changes due to the voltage-frequency relationship. By detecting electric power instead of current, the system can distinguish frost formation from normal speed variation caused by torque control.
Data Source
AI summary
The air conditioner has: an outdoor heat exchanger that exchanges heat between the air and a refrigerant flowing in the interior of this heat exchanger; an outdoor fan that blows air into the outdoor heat exchanger; an outdoor fan motor that rotationally drives the outdoor fan; an outdoor fan inverter that supplies a desired current to the outdoor fan motor; a current detector that detects the current flowing in the outdoor fan motor; and a control unit that controls the outdoor fan inverter such that the rotational frequency of the outdoor fan motor reaches a target rotational frequency. The control unit starts a defrosting operation of the outdoor heat exchanger on the basis of a detection value from the current detector during the heating operation.