Compressor Standby Heating Using High-Frequency Inverter Control
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Solution Overview
Problem
Existing air-conditioning compressor heating methods using open-phase current and ON/OFF switching cycles face challenges in uniform heating, noise generation, and limited efficiency due to rotor-position-dependent inductance and low-frequency current inversion, which hinder efficient refrigerant heating and lead to mechanical vibration and noise issues.
Innovation Solution
An air-conditioning apparatus employing an inverter with dormant refrigerant detection, high-frequency AC voltage generation, and PWM signal generation to apply high-frequency AC voltage to the compressor motor, utilizing iron and copper losses for efficient heating, while minimizing mechanical vibration and noise by operating at frequencies above the compression frequency and incorporating phase and amplitude switching to optimize heating efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If open-phase current is used to heat the compressor, then the compressor can be warmed up to prevent liquid compression, but uniform heating cannot be achieved and coils may not receive current
Solution Approach 1:
The patent applies periodic current inversion to the stator coil, switching the current direction at predetermined intervals during a heating period. This periodic action ensures that all coils receive current over time, achieving uniform heating across the compressor while preventing liquid compression damage.
2Loss of energy
If current direction is inverted by ON/OFF switching of switching elements, then heating efficiency is improved through hysteresis loss, but the frequency cannot be raised to high levels limiting iron loss reduction
Solution Approach 1:
The patent dynamically adjusts the switching frequency of the inverter during the heating period, increasing it over time. This dynamic approach allows the system to initially generate heat through hysteresis loss at lower frequencies, then transition to higher frequencies to reduce iron loss and improve overall heating efficiency.
3Temperature
If low-frequency current inversion is used for heating, then the compressor can be warmed up, but mechanical vibration and noise are generated
Solution Approach 1:
The patent changes the frequency parameter of the applied current from low-frequency inversion to high-frequency operation. By operating at frequencies above the compression frequency (typically above 20 kHz), the system achieves effective heating while the high frequency pushes mechanical vibration and audible noise beyond human perception ranges.
4Loss of energy
If high-frequency AC voltage is applied to the motor, then iron and copper losses generate heat efficiently, but the frequency must be above compression frequency to reduce vibration and noise
Solution Approach 1:
The patent converts the typically harmful iron and copper losses into beneficial heating effect. By deliberately operating at high frequencies where these losses generate heat efficiently, the system uses what would normally be wasted energy to achieve the desired compressor warming, while simultaneously suppressing vibration and noise through frequency selection.
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 achieves high-efficiency heating of the compressor with reduced mechanical vibration and noise, preventing damage from refrigerant stagnation and compliance with environmental standards by leveraging iron and copper losses, and ensuring efficient refrigerant evaporation and reduced inverter losses.
Implementation Method 1
when the PWM signal generating means produces an output of the PWM signal to the inverter, the refrigerant in the compressor is heated by iron loss and copper loss in the motor
Implementation Method 2
when the PWM signal generating means produces an output of the PWM signal to the inverter, the refrigerant in the compressor is heated by iron loss and copper loss in the motor
Implementation Method 3
PWM signal generating means to cause the inverter to generate a high-frequency AC voltage by generating a PWM signal
Data Source
AI summary
A high efficiency refrigerant compressor standby heating method reduces vibrations and noise in a bearing of the compressor. The compressor comprises a motor, an inverter, an inverter controller, and a bus voltage detector to detect a bus voltage of the inverter. The inverter controller includes a dormant refrigerant detector to detect a dormant state of refrigerant in the compressor, a high-frequency AC voltage generator to output a high-frequency AC voltage command, which is out of a range of an operating frequency when the compressor is running, to a coil of the motor on the basis of an output of the dormant refrigerant detector, an amplitude, and a phase. A pulse width modulation signal generator to cause the inverter to generate a high-frequency AC voltage by generating a signal on the basis of the output of the high-frequency AC voltage generator and the output of the bus voltage detector.