Compressor Preheating Control Using Rotor Position and High-Frequency Voltage
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Solution Overview
Problem
Existing heat pump devices face inefficiencies in heating the compressor, particularly due to the regeneration of high-frequency current during fully-off periods and increased inverter losses with modern motors having lower winding resistance, leading to inadequate heat generation and reliability issues.
Innovation Solution
A heat pump device that includes a compressor, motor, heat exchanger, and an inverter control unit with a magnetic-pole-position estimation unit and amplitude and phase determination unit, which generates drive signals to apply a high-frequency voltage that stabilizes compressor heating regardless of the rotor's stop position, optimizing heat output and reducing energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a high-frequency single-phase AC power supply is used to heat the compressor, then noise is reduced and vibration is suppressed, but the heating efficiency degrades due to fast current decay during fully-off periods
Solution Approach 1:
The patent applies different voltage strategies to different operational phases: during active periods, high-frequency voltage is applied for noise reduction, while during fully-off periods, voltage is maintained to prevent current decay and ensure continuous heating efficiency. This localized quality adjustment resolves the contradiction between noise reduction and heating efficiency.
Solution Approach 2:
The patent employs periodic voltage application with controlled fully-off periods, where the inverter switches between high-frequency voltage application and brief interruption phases. This periodic action maintains heating efficiency by preventing current decay while still achieving noise reduction during the active high-frequency phases.
2Stability of the object's composition
If a DC current is caused to flow in the motor winding for preheating, then the rotor does not rotate, but the inverter loss increases due to decreased winding resistance in modern motors
Solution Approach 1:
The patent changes the electrical parameters by applying high-frequency AC voltage instead of DC current for preheating. This parameter change allows the system to achieve rotor stabilization while reducing inverter losses, as the high-frequency AC current interacts with the motor's inductance rather than relying solely on resistive heating, which is less effective in modern low-resistance motors.
Solution Approach 2:
The patent utilizes mechanical vibration through high-frequency current application to the motor windings. This vibration prevents rotor rotation during preheating while being more energy-efficient than DC current, as it leverages the motor's electromagnetic characteristics rather than overcoming low winding resistance through high current.
3Temperature
If a high-frequency voltage is applied to the motor to heat the compressor, then the compressor temperature increases, but the heat generation is insufficient when the rotor is in certain stop positions
Solution Approach 1:
The patent implements feedback control by monitoring the rotor position and adjusting the inverter's voltage application accordingly. When the rotor is in positions that result in low heat generation, the system detects this and modifies the voltage waveform or frequency to ensure adequate heating, thereby maintaining reliable compressor temperature increase regardless of rotor position.
Solution Approach 2:
The patent employs dynamic voltage control where the inverter adjusts its output characteristics based on real-time rotor position. This dynamic adjustment ensures that the high-frequency voltage application remains effective for heating across all rotor stop positions, preventing insufficient heat generation that would compromise heating reliability.
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 effectively prevents refrigerant retention and enhances energy efficiency by stabilizing compressor heating and reducing energy consumption, while minimizing noise and increasing the reliability of the heat pump device.
Implementation Method 1
a heating-operation-mode control unit that controls the drive-signal generation unit when the compressor is heated by applying, to the motor, a high-frequency voltage with which the motor is not capable of being rotationally driven
Implementation Method 2
a magnetic-pole-position estimation unit that estimates a magnetic pole position, which indicates a stop position of a rotor of the motor, on a basis of an induced voltage of the motor
Data Source
AI summary
A heat pump device includes a compressor including a motor, a heat exchanger, an inverter, and an inverter control unit. The inverter control unit generates a drive signal for the inverter. When the compressor is heated, the inverter control unit applies, to the motor, a high-frequency voltage with which the motor cannot be rotationally driven; estimates a magnetic pole position indicating a stop position of a rotor of the motor; determines an amplitude and a phase of a voltage command based on an estimation result of the magnetic pole position and a necessary amount of heat, and generates a drive signal.