Compressor Preheating PWM Control to Eliminate AC Vibration Noise
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Solution Overview
Problem
Conventional air-conditioning apparatuses experience vibrations and noise during preheating due to the generation of differential component frequencies from the interference between output voltage frequency and PWM carrier frequency, leading to degradation in performance and potential compressor malfunction.
Innovation Solution
The apparatus employs a control unit with a second PWM signal generating unit that uses synchronous PWM with a high-frequency voltage command to preheat the coolant without generating low-frequency components, ensuring efficient heating without vibrations or noise, and optionally uses an interior permanent magnet type synchronous electric motor to stabilize the heating process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If asynchronous PWM is used for variable speed control of the compressor, then the compressor can operate at variable speeds, but differential component frequencies are generated causing vibrations and noise during preheating operation
Solution Approach 1:
The patent applies dynamics by making the PWM control method adjustable based on operating conditions. The control unit dynamically switches between asynchronous PWM (for normal variable speed operation) and synchronous PWM (for preheating operation), allowing the system to adapt its control strategy to eliminate vibrations and noise during preheating while maintaining variable speed capability during normal operation
Solution Approach 2:
The patent changes the PWM control parameters by switching from asynchronous PWM to synchronous PWM during preheating operation. This parameter change eliminates the generation of differential component frequencies that cause vibrations and noise, while the system retains the ability to use asynchronous PWM for variable speed control during normal operation
2Reliability
If high-frequency open-phase current is passed to warm the motor winding for preheating, then liquid compression is prevented, but differential component frequencies cause prominent vibrations and noise when the motor is not running
Solution Approach 1:
The patent changes the PWM control parameters by switching to synchronous PWM with a high-frequency voltage command during preheating operation. This generates high-frequency current that warms the motor winding to prevent liquid compression, while the synchronous PWM method eliminates the differential component frequencies that cause vibrations and noise
Solution Approach 2:
The patent uses periodic high-frequency voltage commands in synchronous PWM to generate high-frequency current in the motor winding during preheating. This periodic action effectively warms the winding to prevent liquid compression while avoiding the low-frequency vibrations and noise associated with asynchronous PWM
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
This solution allows for effective preheating of the coolant without causing vibrations or noise, ensuring efficient and stable operation of the compressor, reducing the risk of malfunction and improving overall performance.
Implementation Method 1
a control unit that receives the output signal passes a high-frequency open-phase current of low intensity to a motor winding so that the motor winding is warmed
Implementation Method 2
the apparatus employs a control unit with a second PWM signal generating unit that uses synchronous PWM with a high-frequency voltage command to preheat the coolant without generating low-frequency components
Data Source
Figure 1~2
Figure 3~4(b)
Figure 5~6
AI summary
An object is to provide an air-conditioning apparatus in which the coolant can be preheated without causing vibrations or noise. The air-conditioning apparatus includes a coolant circuit configured by sequentially connecting a compressor 1, an indoor heat exchanger 5, an expansion valve 4, and an outdoor heat exchanger 3; a motor 12 that operates a compressor mechanism 11 disposed inside the compressor 1; an inverter 6 for driving the motor 12; and a control unit 7 that controls the inverter 6. The control unit 7 includes a liquefaction detecting unit 74 that detects coolant liquefaction in the compressor 1; includes a first PWM signal generating unit 72 that generates an inverter control signal for driving the motor 12; includes a second PWM signal generating unit 73 that generates an inverter control signal for making the motor 12 perform a preheating operation; and includes a switching unit 71 that performs switching in such a way that the first PWM signal generating unit 72 or the second PWM signal generating unit 73 outputs the corresponding inverter control signal to the inverter 6.