Variable-Frequency Compressor Startup for Noise and Lubrication Control

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Solution Overview

Problem

Conventional refrigerant compressors using hydrocarbon refrigerants like R600a experience abnormal noise and lubrication issues due to rapid refrigerant evaporation and bubble formation at low ambient temperatures, leading to lubricant discharge and lack of lubrication, especially during initial startup and defrosting operations.

Innovation Solution

The compressor operates at a high frequency for a short period to evaporate refrigerant dissolved in lubricant, then transitions to a lower frequency for a longer period to prevent bubble formation and maintain adequate lubrication, employing a variable frequency control method to manage refrigerant evaporation and lubricant supply.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If the compressor operates at high frequency at low ambient temperature, then refrigerant evaporation is accelerated, but bubbles are intensely produced and lubricant is discharged

Engineering Contradiction:

Improvecompressor rotation frequencyVSAvoidlubrication stability

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The controller performs preliminary action by detecting low ambient temperature conditions before compressor startup and pre-positioning the compressor at a moderate frequency (30 Hz) for a predetermined period. This preliminary moderate-frequency operation allows refrigerant to evaporate gradually without intense bubble formation, preventing lubricant discharge before the compressor enters high-frequency operation.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system dynamically adjusts compressor frequency based on ambient temperature conditions. At low ambient temperatures, the compressor operates at moderate frequency initially, then transitions to high frequency after the predetermined period. This dynamic frequency adjustment resolves the contradiction between needing high speed for performance and maintaining lubrication stability.

Inventive Principle:

Principle #15Dynamics

2Reliability

If the compressor operates at low frequency at low ambient temperature, then bubble formation is reduced, but refrigerant dissolving in lubricant evaporates little and lubrication remains insufficient

Engineering Contradiction:

Improvelubrication stabilityVSAvoidrefrigerant evaporation efficiency

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The controller implements periodic action by operating the compressor at moderate frequency for a predetermined period immediately after startup, then transitioning to high frequency for ordinary operation. This time-based periodic operation ensures refrigerant evaporates sufficiently during the moderate-frequency phase while maintaining lubrication stability, then achieves high productivity during the high-frequency phase.

Inventive Principle:

Principle #19Periodic action

3Productivity

If the compressor starts at high frequency, then refrigerant compression efficiency is improved, but abnormal noise is generated due to intense bubble formation

Engineering Contradiction:

Improverefrigerant compression efficiencyVSAvoidabnormal noise

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The controller performs preliminary action by detecting low ambient temperature conditions and pre-positioning the compressor at moderate frequency before ordinary high-frequency operation. This preliminary moderate-frequency operation allows refrigerant to evaporate gradually without intense bubble formation, preventing abnormal noise before high-frequency compression begins.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system dynamically adjusts compressor frequency based on operating conditions and time. At startup under low ambient temperature, the compressor operates at moderate frequency, then transitions to high frequency after a predetermined period. This dynamic adjustment eliminates abnormal noise during startup while maintaining high compression efficiency during ordinary operation.

Inventive Principle:

Principle #15Dynamics

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

This approach prevents abnormal noise and lubrication obstructions by controlling refrigerant evaporation and lubricant distribution, ensuring consistent lubrication and reducing bubble formation, thereby enhancing compressor performance and reliability.

Implementation Method 1

the compressor operates at a first frequency for a first period of time... the compressor operates at a second frequency lower than the first frequency... refrigerant dissolving in the lubricant to evaporate gradually

Methodology Applied

Scientific EffectEvaporation: Evaporation

Implementation Method 2

Compressor 10 includes a lubricating mechanism (not shown) formed of a centrifugal pump therein

Methodology Applied

Scientific EffectCentrifugal force: Centrifugal Force

Data Source

PatentUS7451609B2Method of controlling compressor and controller

Publication Date: 2008.11.18 PANASONIC HOLDINGS CORP

AI summary

A compressor is operable to compress refrigerant at a variable operation frequency. According to a method of controlling the compressor, the compressor starts operating, and just after that, the compressor operates at a first frequency for a first period of time. Just after that, the compressor operates at a second frequency lower than the first frequency for a second period of time longer than the first period, and after that, the compressor operates at an ordinary operation. This method does not cause the compressor to generate an abnormal noise or obstruction to lubrication.