Three-Phase Inverter Phase Switching for Uniform Compressor Preheating
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Solution Overview
Problem
Existing heat pump systems face challenges in uniformly heating the compressor due to uneven current distribution and limited high-frequency operation, leading to inefficiencies and noise generation, especially when using permanent magnet synchronous motors with saliency ratios.
Innovation Solution
A heat pump device with a three-phase inverter system that includes a voltage detection unit and an inverter control unit capable of generating high-frequency AC voltage by switching between phases θp and θn, synchronized with a carrier signal, to efficiently heat the refrigerant and maintain constant power application to the motor, thereby preventing compressor breakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If open-phase current is caused to flow to warm the motor winding, then the compressor is protected from liquid compression damage, but the heating is uneven and power efficiency is reduced
Solution Approach 1:
The patent applies periodic action by switching between different phase combinations (UV, VW, WU phases) in a cyclic manner during the preheating period. This periodic switching ensures that all motor windings are heated uniformly while protecting the compressor from liquid compression damage, and improves power efficiency by optimizing the current path through the windings.
2Productivity
If high-frequency voltage is applied to heat the compressor, then preheating efficiency is improved, but noise is generated and uniform heating is difficult to achieve
Solution Approach 1:
The patent employs periodic action by alternately switching between different phase combinations at high frequency during preheating. This periodic switching achieves efficient preheating while reducing noise compared to continuous high-frequency operation, as the alternating phases create a more balanced electromagnetic field that reduces vibration and noise generation.
Solution Approach 2:
The patent applies local quality by selectively applying high-frequency voltage to different phase combinations (UV, VW, WU) in a periodic manner. This ensures that each winding receives appropriate heating while maintaining uniform temperature distribution across the motor, preventing localized overheating and reducing noise from uneven thermal expansion.
3Productivity
If high-frequency voltage is applied to heat the compressor, then preheating efficiency is improved, but achieving uniform heating across all windings becomes difficult
Solution Approach 1:
The patent uses periodic action by cycling through different phase combinations (UV, VW, WU) during preheating. This ensures that all motor windings are heated uniformly over time, as each winding receives high-frequency voltage in turn, maintaining stable temperature distribution while achieving efficient preheating.
Solution Approach 2:
The patent applies local quality by selectively applying high-frequency voltage to different phase combinations in a periodic sequence. This ensures that each specific winding receives appropriate heating attention, achieving uniform temperature distribution across all windings while maintaining high preheating efficiency.
4Stability of the object's composition
If phase switching is performed to improve heating uniformity, then all windings are heated evenly, but the control complexity increases
Solution Approach 1:
The patent implements periodic phase switching between UV, VW, and WU phase combinations during preheating. This systematic periodic control achieves uniform heating across all windings while maintaining relatively simple control logic based on predetermined switching sequences, avoiding excessive control complexity.
Solution Approach 2:
The patent applies local quality by selectively controlling different phase combinations to ensure each winding receives appropriate heating. This targeted approach achieves uniform heating while using simple predetermined switching sequences rather than complex real-time control algorithms, keeping control complexity manageable.
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 reduced noise and improved power efficiency, ensuring uniform heating and preventing compressor failure due to liquid compression.
Implementation Method 1
controlling an on/off cycle of a switching element to periodically reverse a direction of a current flowing to a stator coil of a motor. With this technique, not only heat generation due to ohmic loss but also heat generation due to hysteresis loss is performed
Implementation Method 2
not only heat generation due to ohmic loss but also heat generation due to hysteresis loss is performed so that sufficient preheating can be performed
Data Source
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AI summary
An object of the present invention is to heat a refrigerant stayed in a compressor efficiently. A voltage-command correction-value computation unit 40 outputs a correction value Kv for correcting a voltage command value V* according to a bus voltage Vdc. A multiplier 41 calculates a voltage command value V*' acquired by correcting the voltage command value V* based on the correction value Kv. A voltage-command generation unit 25 generates and outputs three-phase voltage command values Vu*, Vv* and Vw* based on the corrected voltage command value V*' calculated by the multiplier 41 and a phase θ. A PWM generation unit 26 generates six drive signals corresponding to switching elements of an inverter 9 based on the three-phase voltage command values Vu*, Vv* and Vw* outputted by the voltage-command generation unit 25 and a carrier signal. The PWM generation unit 26 outputs the generated drive signals to the corresponding switching elements of the three-phase inverter, to cause the inerter to generate a high-frequency AC voltage.