Compressor Motor Wiring Switching for Stable Heat Pump Preheating
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Solution Overview
Problem
Existing heat pump devices face challenges in maintaining constant heat in compressors due to manufacturing and environmental variations, inefficiencies in high-frequency voltage application, and increased inverter losses from reduced winding resistance, leading to inadequate heating and reliability issues.
Innovation Solution
A heat pump device with a compressor, motor, wiring switching unit, and inverter that employs a heating operation mode using PWM signals and switching patterns to optimize impedance for efficient high-frequency or DC energization, ensuring consistent heat input and reduced noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If high-frequency single-phase AC power supply is used for compressor heating, then noise is reduced and vibration is suppressed, but heating efficiency degrades due to quick current decay during off-period
Solution Approach 1:
The patent applies periodic high-frequency AC voltage to the motor during compressor shutdown, utilizing the periodic on-off action to generate heat through copper loss while maintaining noise reduction benefits. The periodic energization creates repeated current cycles that accumulate thermal energy in the motor windings without causing continuous operation
Solution Approach 2:
The patent changes the frequency parameter of the applied voltage to high-frequency range, which shifts the operational characteristics to achieve both noise suppression and heating effect. By adjusting frequency as a key parameter, the system optimizes the balance between acoustic performance and thermal generation
2Quantity of substance
If high-frequency single-phase AC power supply is used, then current is reduced by inductance effect, but insufficient heat generation occurs with small motors having low iron loss
Solution Approach 1:
The patent modifies the frequency parameter to high-frequency range, which fundamentally changes the electrical characteristics of the motor. At high frequencies, the inductive reactance increases, limiting current while simultaneously generating heat through copper loss in the windings, compensating for low iron loss in efficient motors
3Temperature
If DC current is caused to flow in motor windings for preheating, then compressor heating is achieved, but inverter loss increases due to reduced winding resistance
Solution Approach 1:
The patent replaces the DC preheating method with high-frequency AC energization. This substitution eliminates the need for high current DC flow by utilizing high-frequency AC characteristics where inductive reactance naturally limits current while still generating sufficient heat through copper loss, thereby reducing inverter losses
4Temperature
If high-frequency voltage is applied to compressor motor, then heating effect is achieved, but manufacturing and environmental variations cause inconsistent heat output
Solution Approach 1:
The patent incorporates feedback control mechanisms that monitor the actual heating effect and adjust the high-frequency voltage parameters accordingly. By using feedback from temperature sensors or current measurements, the system compensates for manufacturing variations and environmental conditions to maintain consistent heat output
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 device achieves efficient heating of refrigerant in the compressor with high waveform output accuracy, maintaining constant electric power and preventing damage from insufficient heating, while reducing noise and inverter losses.
Implementation Method 1
a current having a frequency outside an audible frequency range (20 hertz to 20 kilohertz) is caused to flow to the motor (8), thereby heating the motor (8) by copper loss
Implementation Method 2
it is possible to not only increase the amount of heat generation because of the increase of iron loss
Implementation Method 3
an inverter 9 that applies a voltage to the motor 8; an inverter control unit 10 that generates a PWM signal for driving the inverter 9
Data Source
AI summary
A heat pump device includes: a compressor that compresses a refrigerant; a motor that drives the compressor; a wiring switching unit that switches a wiring structure of the motor; an inverter that applies a desired voltage to the motor; and an inverter control unit that generates a PWM signal for driving the inverter, that includes, as an operation mode, a heating operation mode in which a heating operation is performed on the compressor and a normal operation mode in which a refrigerant is compressed by performing a normal operation on the compressor, and that controls a switching operation of the wiring switching unit in accordance with an operation mode.