Compressor PWM Driving Circuit for Constant Input Power Under Overload
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Solution Overview
Problem
Conventional compressor driving devices face challenges in maintaining constant input power, especially during overloads, due to noise issues and inaccurate current detection, leading to complex configurations and potential shutdowns.
Innovation Solution
A compressor driving device with a power conversion circuit, drive circuit, voltage detector, current detector, and controller that uses inexpensive detection means to control input power by adjusting the duty ratio and conduction angle, ensuring constant input power and reducing harmonic components without additional components like reactors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional current detection methods are used, then noise reduction components like reactors are required, but this increases device complexity and cost
Solution Approach 1:
The invention extracts and eliminates the need for noise reduction components like reactors by using a novel current detection method that inherently filters noise through software processing rather than hardware components
Solution Approach 2:
The invention replaces mechanical/electrical noise filtering components (reactors) with a software-based detection and processing system that uses arithmetic operations to achieve noise reduction
2Ease of manufacture
If simple current detection is used, then cost is reduced, but measurement precision deteriorates due to noise and inaccurate detection
Solution Approach 1:
The invention uses feedback mechanisms where the detected current values are continuously processed, compared with expected values, and used to adjust control signals to maintain accurate measurement despite noise
Solution Approach 2:
The invention creates a mathematical model or reference copy of the expected current waveform and compares it with actual detected values to extract accurate measurement information from noisy signals
3Power
If duty ratio is increased to maintain power during overload, then input power is maintained, but noise and harmonic components increase
Solution Approach 1:
The invention dynamically adjusts control parameters based on real-time detection of current waveforms and noise levels, optimizing the balance between power delivery and noise generation
Solution Approach 2:
The invention changes control parameters such as PWM frequency, duty ratio modulation depth, and switching patterns to reduce harmonic components while maintaining required power levels
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
The solution enables safe operation of compressors without shutdowns, stabilizes motor rotation, and effectively regulates harmonics, enhancing reliability and reducing noise and vibration, while allowing for efficient use of inexpensive detection components.
Implementation Method 1
power conversion circuit that supplies power to the electric motor
Implementation Method 2
voltage detector that detects a voltage that is output to the electric motor
Implementation Method 3
current detector that detects a current that is output to the electric motor
Implementation Method 4
controller that controls the power conversion circuit based on a product of the detected voltage and the detected current so as to maintain constant input power
Data Source
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AI summary
A compressor driving device includes: a controller (23) that PWM drives a compressor; an inverter circuit unit (4) that supplies power to an electric motor included in the compressor; a drive circuit (5) that drives the inverter circuit unit (4) according to a control signal; a voltage detector (9) that detects a voltage that is output to the electric motor; and a current detector (10) that detects a current that is output to the electric motor. When a product of a detection value of the voltage detector (9) and a detection value of the current detector (10) is greater than a predetermined comparison value, a duty ratio of the control signal is reduced to cause the input power supplied to the electric motor by the inverter circuit unit (4) to have a predetermined input power level or less.