Scroll compressor differential pressure control during compressor startup transitions

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Solution Overview

Problem

Existing cooling systems face inefficiencies due to undirected unloading of scroll compressors, which reduces cooling capacity and stability, particularly at varying ambient temperatures and pressure differences.

Innovation Solution

Implementing a method that dynamically adjusts compressor parameters and fan speeds using proportional integral derivative (PID) control and hysteresis-based adjustments to maintain pressure differences above a predetermined level, preventing undirected unloading by activating lead and lag compressors and controlling condenser fan speeds.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If the pressure difference is reduced to increase operating efficiency, then energy consumption is minimized, but the stationary scrolls separate from orbiting scrolls causing undirected unloading and reducing cooling capacity

Engineering Contradiction:

Improveenergy consumptionVSAvoidcooling capacity

Core Design Contradiction:

Use of energy by moving objectVSProductivity

Solution Approach 1:

The control system performs preliminary action by detecting the pressure difference before undirected unloading occurs and proactively adjusting the condenser fan speed to maintain pressure difference above the minimum threshold, preventing compressor unloading and maintaining cooling capacity while optimizing energy consumption

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system implements feedback control by continuously monitoring the pressure difference across the compressor and using this information to dynamically adjust the condenser fan speed, ensuring the pressure difference remains within the optimal range to prevent unloading while minimizing energy consumption

Inventive Principle:

Principle #23Feedback

2Reliability

If the condenser fan speed is increased to maintain pressure difference, then compressor unloading is prevented, but energy consumption increases

Engineering Contradiction:

Improvecompressor operation stabilityVSAvoidenergy consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The system applies dynamics by making the condenser fan speed adjustable and variable rather than fixed, allowing the fan speed to be dynamically optimized based on real-time pressure difference conditions, thereby maintaining compressor stability only when necessary and reducing energy consumption when pressure difference is sufficient

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The control system changes the operational parameters by adjusting the condenser fan speed based on the measured pressure difference, modifying the system's operating state to maintain reliability only when pressure difference falls below the minimum threshold, thereby optimizing energy consumption across varying operating conditions

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If PID control is used to control condenser fan speed, then pressure control precision is improved, but during compressor startup the pressure difference drops below minimum level causing unloading

Engineering Contradiction:

Improvepressure control precisionVSAvoidcompressor operation stability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The system performs preliminary action by detecting compressor startup conditions and temporarily overriding PID control with alternative control logic that maintains higher condenser fan speed during startup, preventing pressure difference from dropping below minimum level and avoiding compressor unloading during the critical startup phase

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The control system introduces an intermediary control mechanism that acts as a mediator between PID control and compressor operation, temporarily switching to a different control strategy during compressor startup to bridge the gap between precision control requirements and the need to maintain sufficient pressure difference during transient conditions

Inventive Principle:

Principle #24Intermediary (Mediator)

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 ensures stable compressor operation and maintains cooling capacity by preventing undirected unloading, enhancing energy efficiency and temperature control across varying conditions.

Implementation Method 1

controlling a speed of the condenser fan using a proportional integral derivative (PID) method

Methodology Applied

Scientific EffectProportional integral derivative (PID) control: Feedback

Implementation Method 2

hysteresis-based adjustments to maintain pressure differences above a predetermined level

Methodology Applied

Scientific EffectHysteresis: Hysteresis

Data Source

PatentUS9829233B2Scroll compressor differential pressure control during compressor startup transitions

Publication Date: 2017.11.28 VERTIV CORP

AI summary

A method including: determining a cooling value; and comparing the cooling value to an activation point of a lead compressor. The lead compressor is in a tandem set of scroll compressors of a cooling system. The tandem set of compressors comprises a lag compressor. The method further includes: activating the lead compressor when the cooling value is greater than the activation point; activating the lag compressor subsequent to activating the lead compressor; and determining whether conditions exist including: an alarm associated with the lag compressor being generated, and the lead compressor being deactivated. The method further includes deactivating the lag compressor when at least one of the conditions exists in the cooling system.