Three-Phase Phase-Loss Detection Using XOR Time Counting

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Solution Overview

Problem

Conventional phase-loss detection methods for three-phase AC power sources are inefficient, requiring high hardware costs and long determination times, which do not meet the industry's demand for rapid response to power abnormalities.

Innovation Solution

A phase-loss detection apparatus using an analog-to-digital converter, exclusive OR operator, and signal operator to generate digital signals from two line voltages, accumulating time counts to determine phase-loss abnormalities, reducing circuit usage and improving response time.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional level type phase-loss detection structure is used with voltage sensors and comparison circuits, then the detection can identify phase-loss abnormalities, but the hardware cost is high and the determination time is too long

Engineering Contradiction:

Improvephase-loss detection accuracyVSAvoidhardware cost and circuit complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent extracts only the essential detection function by using a single-phase voltage sensor instead of three-phase sensors, and implements detection logic through software algorithms (counter accumulation) rather than complex hardware comparison circuits, thereby reducing hardware cost while maintaining detection accuracy

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent uses digital counter values to represent and accumulate voltage level information over time, creating a digital copy of the voltage presence/absence pattern that can be analyzed to detect phase-loss conditions without requiring continuous analog voltage comparison hardware

Inventive Principle:

Principle #26Copying

2Reliability

If conventional level type phase-loss detection structure is used with observation period, then the detection can filter false positives, but the response time is delayed and does not meet industry demand for rapid response

Engineering Contradiction:

Improvefalse positive filteringVSAvoiddetermination time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent pre-establishes the detection threshold (counter value threshold) based on expected normal operation patterns, allowing the system to immediately compare accumulated counter values against this predetermined threshold and make rapid determination without waiting for extended observation periods

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements dynamic detection by continuously accumulating counter values during operation and comparing against thresholds, allowing the system to adapt to varying operating conditions while maintaining rapid response capability through real-time evaluation rather than fixed observation periods

Inventive Principle:

Principle #15Dynamics

3Reliability

If three-phase AC voltage sensor is installed to read voltage values and compare with high and low voltage levels, then the detection can determine voltage abnormalities, but the hardware cost is high

Engineering Contradiction:

Improvevoltage abnormality detectionVSAvoidnumber of sensors and comparison circuits

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent makes the single-phase voltage sensor multi-functional by using it to detect both the presence/absence of voltage and the phase sequence information through timing relationships, eliminating the need for separate three-phase sensors and multiple comparison circuits

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent replaces the mechanical/analog comparison system (voltage sensors connected to comparison circuits with high/low voltage thresholds) with a digital counting system that uses a timer to accumulate presence/absence events, substituting continuous analog voltage comparison with discrete digital counting logic

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS11567112B2Phase-loss detection apparatus of three-phase AC power source and method of detecting phase loss

Publication Date: 2023.01.31 DELTA ELECTRONICS INC(CN)

AI summary

A method of detecting phase loss of a three-phase AC power source includes steps of: acquiring any two line voltages of the AC power source with a first cycle period, acquiring a first digital signal and a second digital signal, performing an exclusive OR operation between the first digital signal and the second digital signal to generate a level signal, accumulating a high-level time count value, or accumulating a low-level time count value, resetting the low-level time count value when the high-level time count value is accumulated, or resetting the high-level time count value when the low-level time count value is accumulated, and determining that the AC power source occurs a phase-loss abnormality when the high-level time count value is greater than or equal to ⅓ of the first cycle period or the low-level time count value is greater than or equal to ⅙ of the first cycle period.