Three-Phase Inverter Control for Uniform Compressor Refrigerant Heating
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Solution Overview
Problem
Existing heat pump compressor heating methods using open-phase current and switching element control fail to achieve uniform heating and are limited by noise and efficiency, particularly in permanent magnet synchronous motors with varying rotor positions.
Innovation Solution
A heat pump device with a three-phase inverter and an inverter control unit that generates high-frequency AC voltage by switching phases θ1 and θ2 by 180 degrees and adding a phase θ3, synchronized with a reference signal, to produce drive signals for efficient refrigerant heating while minimizing noise and rotor position dependency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If open-phase current is caused to flow to warm the motor winding, then the refrigerant can be heated, but the heating is not uniform and the current may not flow to all phases according to rotor position
Solution Approach 1:
The patent applies periodic action by cyclically reversing the direction of current flowing to the stator coil through controlled on/off cycling of switching elements. This periodic current reversal ensures that all phases receive heating over time cycles, achieving uniform heating regardless of instantaneous rotor position, thereby resolving the non-uniform heating problem of open-phase current methods.
2Loss of energy
If switching elements are repeatedly turned on and off to generate heat, then power efficiency can be improved, but the current frequency cannot be high frequency and noise may be generated
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the on/off cycle duration and switching frequency of the inverter switching elements. By optimizing these temporal parameters, the system generates sufficient heat through ohmic and hysteresis losses while maintaining switching frequencies that minimize audible noise, thus resolving the contradiction between heating efficiency and noise generation.
3Use of energy by moving object
If open-phase current is used for heating, then current consumption can be reduced, but the compressor cannot be heated uniformly and heating efficiency is limited
Solution Approach 1:
The patent applies universality by designing a three-phase inverter system where all three phases are simultaneously activated with controlled current flow. This multi-phase approach ensures that heating is applied uniformly across all motor windings regardless of rotor position, achieving both low current consumption and high heating efficiency through coordinated multi-functional operation of all inverter phases.
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, suppressing noise and motor vibrations, and ensuring consistent heating regardless of rotor position, thereby improving heating efficiency and reducing power consumption.
Implementation Method 1
heat generation by an ohmic loss
Implementation Method 2
heat generation by an hysteresis loss
Data Source
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AI summary
An object of the present invention is to heat a refrigerant accumulated in a compressor efficiently. A phase switching unit 19 switches a phase θ1 and a phase θ2 different from the phase θ1 substantially by 180 degrees and outputs the phase, synchronously with a carrier signal. An adder 20 adds a phase θplus, which is n times a size of 60 degrees, to the phase output from the phase switching unit 19 and outputs the phase as a voltage command phase θ. A high-frequency AC voltage generation unit 13 generates three-phase voltage command values Vu*, Vv*, and Vw* based on the voltage command phase output by the adder 20 and outputs these command values. A PWM-signal generation unit 17 compares the three-phase voltage command values Vu*, Vv*, and Vw* output from the high-frequency AC-voltage generation unit 13 with the carrier signal to generate six drive signals corresponding to respective switching elements 18a to 18f of an inverter 9, and outputs respective generated drive signals to the corresponding switching elements of the three-phase inverter, and generates a high-frequency AC voltage in the inverter 9.