Current detecting device, air conditioning apparatus, correction constant calculating system and correction constant calculating method
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Solution Overview
Problem
In air conditioning apparatus where the motor and driver are integrated, accurately detecting motor current is challenging due to the combination of motor and drive currents flowing through the same wire, leading to difficulties in separate current measurement and control.
Innovation Solution
A current detecting device with a current leveling unit, comprising a resistor and capacitor filter circuit, levels the drive current, allowing for accurate determination of motor current by subtracting the leveled drive current from the total current detected, and a correction constant is calculated and stored to further refine the motor current calculation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the motor and driver are integrated into a single device, then the device complexity is reduced and space is saved, but the accuracy of motor current detection deteriorates because motor current and drive current flow through the same wire
Solution Approach 1:
The patent segments the total current into motor current and drive current components by introducing a current leveling unit that processes the drive current separately. The current detecting unit detects the combined current, while the current leveling unit (using RC circuit) levels the drive current portion, allowing the control unit to subtract the leveled drive current from the total current to obtain accurate motor current. This segmentation resolves the measurement accuracy issue while maintaining integration.
Solution Approach 2:
The patent introduces a current leveling unit as an intermediary component between the driver and the current detecting unit. This intermediary processes the drive current by leveling it (using resistor and capacitor), enabling the control unit to accurately extract motor current from the combined current signal. The intermediary element facilitates accurate measurement without requiring physical separation of the currents.
2Ease of manufacture
If a shunt resistor is used to detect motor current, then the current detection method is simple and cost-effective, but the detection accuracy deteriorates when drive current is also present on the same wire
Solution Approach 1:
The patent maintains the simple shunt resistor-based detection method but segments the current measurement process by adding a current leveling unit. The shunt resistor detects total current, while the current leveling unit separately processes drive current, allowing accurate extraction of motor current through subtraction in the control unit. This preserves manufacturing simplicity while improving detection accuracy.
Solution Approach 2:
The current leveling unit acts as an intermediary that processes the drive current component of the total current detected by the shunt resistor. By leveling the drive current portion and enabling its subtraction from the total current, the intermediary element allows the simple shunt resistor method to achieve accurate motor current detection despite the presence of drive current.
3Device complexity
If the drive current is not leveled, then the current detection system is simpler, but the motor current determination accuracy deteriorates due to drive current fluctuations
Solution Approach 1:
The patent segments the current processing into two parallel paths: one detecting total current via shunt resistor, and another leveling the drive current via RC circuit. This segmentation allows the system to handle drive current fluctuations separately, improving motor current determination accuracy while adding minimal complexity compared to a completely integrated approach.
Solution Approach 2:
The current leveling unit changes the parameter of drive current by applying RC filtering, transforming the fluctuating drive current into a leveled version. This parameter change enables accurate extraction of motor current from the combined current signal, improving measurement precision with a relatively simple filtering approach.
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
Enables accurate motor current determination and control, ensuring consistent air volume delivery and accounting for variations in the motor and detection unit, thereby improving motor speed control and air conditioning performance.
Implementation Method 1
a current leveling unit (93) which levels the drive current (Id), wherein the current leveling unit (93) comprises a capacitor (C1) and a resistor (R1)
Implementation Method 2
The resistor R1 and the capacitor C1 form a filter circuit for leveling the drive current
Data Source
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AI summary
This invention provides a current detecting device with which an accurate motor current can be obtained and an air conditioning apparatus equipped therewith. This invention also provides a correction constant calculating system equipped with the current detecting device and a correction constant calculating method. A current detecting device (9) is equipped with a current leveling unit (93), a GND wire (94), and a current detecting unit (95). The current leveling unit (93) levels a drive current (Id) that is passed through a second motor driver (82) for driving a second fan motor (81). On the GND wire (94), a motor current (Im) that has been passed through the second fan motor (81) and the drive current (Id) that has been leveled by the current leveling unit (93) flow. The current detecting unit (95) detects the sum of the motor current (Im) and the drive current (Id) that has been leveled flowing on the GND wire (94).