Compressor Grid Fault Detection for Thermal Overload Prevention

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Compressors connected to electrical grids experience rapid current increases due to grid voltage drops, leading to potential stalling and thermal overload, causing grid instability and increased demand, which can result in repeated low voltage events.

Innovation Solution

A compressor monitoring system that includes current and voltage monitors, averaging modules, and a control module to detect grid faults by calculating ratios of average current and voltage values, generating a fault signal when thresholds are exceeded, and deactivating the motor to prevent overheating and stabilize the grid.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the compressor continues to operate during grid voltage drops, then the compressor can maintain cooling/heating function, but the current increases dramatically causing thermal overload and grid instability

Engineering Contradiction:

Improvecompressor operation continuityVSAvoidcurrent increase and thermal overload

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The system performs preliminary detection of grid voltage conditions and predicts potential current overload before it occurs. By calculating the ratio of average current to average voltage and comparing against thresholds, the system identifies at-risk conditions and shuts down the compressor proactively, preventing thermal overload and grid instability while maintaining operational reliability through early intervention

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system continuously monitors grid voltage and compressor current, calculating their ratios and comparing against predetermined thresholds. This feedback mechanism detects when voltage drops cause current to rise to dangerous levels, automatically triggering compressor shutdown to prevent thermal overload and grid instability, thus resolving the contradiction between continuous operation and preventing harmful current increases

Inventive Principle:

Principle #23Feedback

2Object-affected harmful factors

If the compressor is shut down during grid faults, then thermal overload and grid instability are prevented, but the cooling/heating function is interrupted

Engineering Contradiction:

Improvethermal overload preventionVSAvoidcooling/heating function availability

Core Design Contradiction:

Object-affected harmful factorsVSProductivity

Solution Approach 1:

The system uses continuous feedback monitoring of voltage-current ratios to detect grid fault conditions. When the ratio exceeds thresholds indicating dangerous current levels, the system automatically shuts down the compressor to prevent thermal overload and maintain grid stability. The system only restarts when grid conditions return to normal, ensuring productivity is restored safely while preventing harmful effects during vulnerable periods

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system converts the harmful effect of grid voltage drops into a beneficial protective mechanism. By detecting voltage-current ratio anomalies, the system triggers compressor shutdown that prevents thermal overload and grid instability. This protective shutdown, while interrupting cooling/heating function, ultimately benefits the overall system by preventing more severe failures and enabling safer restart conditions

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Device complexity

If simple current threshold monitoring is used, then the device complexity is low, but it cannot distinguish between startup current and fault current

Engineering Contradiction:

Improvemonitoring system simplicityVSAvoidcurrent anomaly detection accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The system changes the monitoring parameter from simple current magnitude to the ratio of average current to average voltage. This parameter transformation enables the system to distinguish between normal startup conditions (where both current and voltage are stable) and fault conditions (where voltage drops cause current to rise disproportionately). The ratio metric provides precise fault detection while maintaining relatively simple device complexity through straightforward calculations and threshold comparisons

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS9941688B2Compressor protection and grid fault detection device

Publication Date: 2018.04.10 COPELAND LP

AI summary

A method of operating a refrigeration system that receives power from an electrical grid includes selectively operating at least one component of the refrigeration system in a first state. The method includes selectively detecting a fault event of the electrical grid in response to a concurrent (i) increase in amount of current drawn by the component and (ii) decrease in voltage of power received by the component. The method includes, in response to detecting the fault event, switching the component from the first state to a second state. The component consumes less power in the second state than in the first state. The method includes determining a first delay period. The method includes identifying a conclusion of the fault event. The method includes, in response to the conclusion of the fault event, waiting for the first delay period before switching the component back to the first state.