Heat pump device, heat pump system, and control method for three-phase inverter in a heat pump device
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Solution Overview
Problem
Existing heating techniques for compressors in heat pump devices, such as those described in Patent Literature 1 and 2, face inefficiencies due to the use of high-frequency low voltage, leading to quick attenuation of current and poor heating efficiency, especially during the full-off section where high-frequency current is regenerated back to the DC power supply without being refluxed to the motor.
Innovation Solution
A heat pump device utilizing a three-phase inverter with a control method that ensures two or more switching elements on the positive voltage side are not simultaneously turned off, allowing efficient current flow to the motor, thereby efficiently heating the refrigerant through iron and copper losses, and applying high-frequency voltage to the motor to prevent rotation and vibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a high-frequency single-phase AC power is applied to the compressor, then the compressor can be heated to facilitate lubrication action, but the current attenuates quickly during the full-off section, deteriorating the heating efficiency
Solution Approach 1:
The patent applies periodic high-frequency AC voltage to the compressor motor windings in a controlled manner, using specific PWM patterns that periodically switch between different voltage states. This periodic action ensures continuous heating effect while minimizing energy loss by preventing full-off sections where current would attenuate.
Solution Approach 2:
The patent changes the voltage application parameters by using three-phase AC power instead of single-phase, and by controlling the switching elements to maintain continuous current flow. This parameter change from single-phase to three-phase power fundamentally alters the current characteristics, preventing quick attenuation and improving heating efficiency.
2Temperature
If high-frequency voltage is applied to the motor, then the refrigerant can be heated through iron loss and copper loss, but switching elements may be simultaneously turned off causing current attenuation
Solution Approach 1:
The patent dynamically controls the switching elements in the three-phase inverter, ensuring that at least one switching element remains on in each phase leg during high-frequency operation. This dynamic switching control prevents simultaneous turn-off of all switching elements, maintaining continuous current flow and minimizing energy loss while achieving effective heating.
Solution Approach 2:
The patent ensures continuous current flow through the motor windings by preventing full-off sections in the switching pattern. By maintaining at least one conducting path at all times during high-frequency voltage application, the useful heating action continues without interruption and energy loss is minimized.
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 approach efficiently heats the refrigerant in the compressor by minimizing current attenuation and optimizing voltage application, reducing noise and inverter losses, while preventing refrigerant stagnation and promoting efficient heating.
Implementation Method 1
a high-frequency voltage is applied to a three-phase inverter, a refrigerant retained in a compressor can be efficiently heated by iron loss of a motor and copper loss generated by a current flowing in a winding
Implementation Method 2
a high-frequency voltage is applied to a three-phase inverter, a refrigerant retained in a compressor can be efficiently heated by iron loss of a motor and copper loss generated by a current flowing in a winding
Implementation Method 3
applying high-frequency voltage to the motor to prevent rotation and vibration
Data Source
Figure 1
Figure 2
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AI summary
An object of the present invention is to efficiently heat a refrigerant retained in a compressor. An inverter control unit 12 generates six drive signals corresponding to the respective switching elements 16a to 16f of the inverter 9, and outputs the generated drive signals to the corresponding switching elements 16a to 16f of the inverter 9 to cause the inverter 9 to generate a high-frequency AC voltage. Particularly, the inverter control unit 12 generates a drive signal having a switching pattern A for turning on all the three switching elements 16a-16c or 16d-16f on a positive voltage side or a negative voltage side of the inverter 9, and subsequent thereto, generates a drive signal having a switching pattern B for turning on two switching elements of the three switching elements 16a-16c or 16d-16f and turning off one switching element thereof.