Three-Phase Alternator Failure Detection via Voltage Difference

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Solution Overview

Problem

Existing methods for detecting failures in three-phase alternators, such as open circuits and short-circuits to ground, are inadequate as they fail to differentiate between normal and failure conditions under varying loads and are influenced by protective components and long wiring lengths, and rely on costly microprocessors for phase shift measurements.

Innovation Solution

A method and device that rectify voltages from three phases, calculate a voltage difference by summing and subtracting rectified voltages, and compare this difference to thresholds to detect failures, using analog or software components, thereby overcoming the limitations of phase shift measurement methods.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If phase shift measurement method is used to detect failures, then failure detection capability is provided, but the method cannot differentiate between normal and failure conditions under varying loads due to residual voltage from protective capacitors

Engineering Contradiction:

Improvefailure detection capabilityVSAvoidphase shift measurement accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The invention changes the measurement parameter from phase shift to voltage difference between phases. By measuring the absolute voltage difference rather than phase relationships, the system becomes insensitive to residual voltages from capacitors and can reliably detect failures under all load conditions.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention extracts only the necessary information for failure detection by comparing voltage differences between phases rather than measuring complete phase relationships. This extraction approach eliminates the influence of protective capacitors while maintaining failure detection capability.

Inventive Principle:

Principle #2Taking out (Extraction)

2Reliability

If phase shift measurement is performed using microprocessors or programmable logic circuits, then failure detection is achieved, but the cost of components and certifications increases

Engineering Contradiction:

Improvefailure detectionVSAvoidmicroprocessor and certification requirements

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The invention replaces expensive microprocessors and programmable logic circuits with simple, inexpensive analog components such as operational amplifiers, resistors, and capacitors. These basic components perform the voltage difference calculation and threshold comparison without requiring costly certifications.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The invention substitutes digital processing (microprocessor-based phase shift measurement) with an analog electrical system that directly computes voltage differences and compares them to thresholds using operational amplifiers and comparators, eliminating the need for complex digital processing and certifications.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Adaptability or versatility

If long wiring is used between alternator and load, then system flexibility is improved, but voltage drop from common mode current disrupts phase shift measurement

Engineering Contradiction:

Improvewiring flexibilityVSAvoidphase shift measurement accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The invention changes the measurement parameter from phase shift (which is sensitive to voltage drops) to voltage difference between phases. This parameter change makes the measurement immune to common mode voltage drops caused by long wiring, as both phases experience similar drops that cancel out in the differential measurement.

Inventive Principle:

Principle #35Parameter changes

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 effectively detects open circuits and short-circuits to ground regardless of load conditions and wiring length, reducing reliance on expensive microprocessors and ensuring reliable failure detection in three-phase alternator systems.

Implementation Method 1

rectification of the voltages generated by the three-phase alternator in a first phase, a second phase, and a third phase

Methodology Applied

Scientific EffectRectification: Diode

Data Source

PatentUS9500709B2Method for detecting a failure in a three-phase alternator, device for detecting failures and associated computer programme

Publication Date: 2016.11.22 SAFRAN ELECTRONICS & DEFENSE (FR)

AI summary

The invention concerns a method for detecting a failure in a three-phase alternator connected to a three-phase rectifier bridge. The method comprises the following steps — rectifying (70) the voltages generated by the three-phase alternator; — adding (76) the rectified voltages taken at the first and second phases in order to obtain a voltage sum; — subtracting (78), from said voltage sum, twice the rectified voltage taken at the third phase, in order to obtain a voltage difference; — comparing (80) the voltage difference to a high threshold and a low threshold; — detecting (82) a failure when the voltage difference is less than said low threshold or when the voltage difference is greater than said high threshold. The invention also concerns a device for detecting failures and an associated computer programme.