Heat Pump Compressor Preheating Using High-Frequency Inverter Control
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Solution Overview
Problem
Existing heat pump devices face inefficiencies in heating refrigerant during standby and generating the necessary heat output, leading to increased vibration and noise in compressors due to high-frequency single-phase alternating-current power supply and reduced winding resistance in modern motors, which results in inadequate heat generation and increased inverter losses.
Innovation Solution
A heat pump device with an inverter control unit that switches between normal and heating operation modes, applying high-frequency voltage to the compressor motor without rotation to efficiently heat the refrigerant and reduce vibration and noise, using a converter to manage voltage and current effectively, and employing wide bandgap semiconductor devices like SiC to enhance efficiency and reduce losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If high-frequency single-phase alternating-current power supply is applied to the compressor motor, then the compressor can be heated during standby, but the heating efficiency deteriorates due to fast current decay during off-periods and the compressor generates vibration and noise
Solution Approach 1:
The patent changes the electrical parameters by applying three-phase power supply instead of single-phase, and controls the switching elements to generate specific voltage patterns. This transforms the heating mechanism from relying on resistive heating during off-periods to utilizing iron loss and copper loss during active switching periods, thereby improving heating efficiency while reducing vibration and noise.
Solution Approach 2:
The patent employs periodic switching of the three-phase power supply to the compressor motor during standby. The switching elements are turned on and off in a controlled periodic manner to generate high-frequency voltage that produces necessary iron loss and copper loss for heating, while the periodic nature allows optimization of the heating effect without continuous high-current flow that causes vibration and noise.
2Use of energy by moving object
If modern high-efficiency motors with reduced winding resistance are used, then motor efficiency improves, but heat generation during preheating decreases because heat generation is proportional to the product of winding resistance and square of electric current
Solution Approach 1:
The patent replaces the traditional direct-current preheating method with a three-phase AC power supply method. Instead of relying on resistive heating from DC current flow, the system uses controlled three-phase voltage application that generates heat through iron loss in the motor core and copper loss in the windings, which is more effective for modern low-resistance motors while maintaining high motor efficiency during normal operation.
Solution Approach 2:
The patent changes the electrical supply parameters from DC to three-phase AC with controlled frequency and voltage. By adjusting the switching timing and duration of the three-phase power supply, the system optimizes the balance between generating sufficient heat for preheating and maintaining low inverter losses, effectively addressing the reduced heat generation in modern high-efficiency motors.
3Temperature
If direct current is applied to motor winding for preheating, then the compressor can be heated, but inverter losses increase due to the need to supply high current to compensate for reduced winding resistance
Solution Approach 1:
The patent changes the preheating method from DC current application to controlled three-phase AC voltage application. By adjusting the frequency, voltage amplitude, and switching timing of the three-phase power supply, the system achieves effective compressor heating while minimizing the current magnitude required, thereby reducing inverter losses compared to traditional DC preheating methods.
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 stable and efficient heating of refrigerant on standby, reduces compressor vibration and noise, and improves the overall efficiency and reliability of the heat pump device while minimizing costs associated with heat dissipation structures.
Implementation Method 1
applying high-frequency voltage to the compressor motor without rotation to efficiently heat the refrigerant
Implementation Method 2
applying high-frequency voltage to the compressor motor without rotation to efficiently heat the refrigerant
Implementation Method 3
using a converter to manage voltage and current effectively
Data Source
AI summary
A heat pump device includes a compressor including a compression mechanism that compresses a refrigerant and a motor that drives the compression mechanism, an inverter that applies a voltage for driving the motor, a converter that applies a voltage to the inverter, an inverter control unit that generates a driving signal for driving the inverter, and a converter control unit that generates a driving signal for driving the converter. The inverter control unit includes a heating-operation-mode control unit that controls a driving-signal generating unit such that the driving-signal generating unit outputs, as inverter driving signals, PWM signals for heating the compressor without rotationally driving the motor by feeding a high-frequency current that the motor cannot follow in a heating operation mode.