Compressor Motor Wiring Switching for Heat Pump Preheating
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Solution Overview
Problem
Existing heat pump devices face challenges in maintaining constant compressor heat levels due to manufacturing and environmental variations, inefficiencies in high-frequency AC power supply, increased inverter losses with DC preheating, and voltage imbalance issues with PWM modulation, leading to reduced heating efficiency and reliability.
Innovation Solution
A heat pump device that employs a configuration with a wiring switching unit to optimize impedance for heating mode, using either DC or high-frequency energization based on the necessary heat amount, and an inverter control unit to manage voltage and phase commands for efficient refrigerant heating while minimizing noise and inverter losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If high-frequency AC voltage is applied to the motor during compressor shutdown, then noise is reduced and vibrations are suppressed, but the heating efficiency of the compressor degrades due to quick current decay during off-periods
Solution Approach 1:
The patent changes the voltage frequency parameter to a high frequency (20-100 kHz) that is above the audible range, thereby reducing noise and vibrations. This parameter change simultaneously causes the current to decay quickly during off-periods, reducing heating efficiency, which is why the patent also employs locked rotor control to maintain heating effectiveness.
Solution Approach 2:
The patent uses periodic high-frequency voltage application with specific on-off timing to achieve both noise reduction and heating. By controlling the duty cycle and timing of the high-frequency voltage application, the system maintains heating effectiveness while keeping the compressor rotor locked and noise below audible levels.
2Temperature
If DC current is caused to flow in the motor windings for preheating, then the compressor can be heated, but the current must be increased to compensate for reduced winding resistance, leading to increased inverter losses
Solution Approach 1:
The patent changes from DC current to high-frequency AC voltage, fundamentally changing the electrical parameter. This allows heating through iron loss in the motor core rather than relying solely on copper loss in the windings, thereby avoiding the need to increase current and the associated inverter losses.
Solution Approach 2:
The patent substitutes the heating mechanism from resistive heating (copper loss) to electromagnetic heating (iron loss) by applying high-frequency AC voltage. This substitution enables effective heating at lower current levels, reducing inverter losses while maintaining compressor temperature.
3Object-affected harmful factors
If high-frequency single-phase AC power supply is used, then noise is reduced and vibrations are suppressed, but a fully-off period is generated for a relatively long period of time causing high-frequency current to decay quickly
Solution Approach 1:
The patent changes the voltage frequency to a high value (20-100 kHz) and adjusts the duty cycle to ensure that the on-period is sufficient for current buildup while the off-period remains brief enough to prevent complete current decay. This parameter optimization allows the system to achieve noise reduction while maintaining continuous heating effectiveness.
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 efficient heating of refrigerant in the compressor with high waveform output accuracy, maintaining constant electric power input, reducing noise, and preventing compressor damage from insufficient heating, while optimizing heat generation and reducing inverter losses.
Implementation Method 1
a high-frequency current is caused to flow to a motor 8 and the refrigerant stagnated in the compressor 1 is heated
Implementation Method 2
PWM signal generating means to cause the inverter to generate a high-frequency AC voltage by generating a PWM signal
Data Source
Figure 1
Figure 2~3
Figure 4-1~4-3
AI summary
A heat pump device includes: a compressor (1) that compresses a refrigerant; a motor (8) that drives the compressor; a wiring switching unit (33) that switches a wiring structure of the motor (8); an inverter (9) that applies a desired voltage to the motor (8); and an inverter control unit (10) that generates a PWM signal for driving the inverter (9), that includes, as an operation mode, a heating operation mode in which a heating operation is performed on the compressor (1) and a normal operation mode in which a refrigerant is compressed by performing a normal operation on the compressor (1), and that controls a switching operation of the wiring switching unit (33) in accordance with an operation mode.