Field Winding Interlayer Short-Circuit Detection

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Solution Overview

Problem

Existing methods for detecting interlayer short-circuits in field windings of rotating electrical machines face challenges in distinguishing between temperature changes and actual short-circuits, especially under varying operating conditions, due to insufficient temperature monitoring and small current fluctuations caused by short-circuits.

Innovation Solution

A field winding interlayer short-circuit detection apparatus that calculates a field winding resistance value from current and voltage measurements and compares it to a reference value, using determination condition expressions to differentiate between normal and abnormal resistance changes, thereby determining the presence of an interlayer short-circuit.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If field winding resistance is monitored to detect interlayer short-circuit, then short-circuit detection capability is improved, but temperature change interference makes it difficult to distinguish between temperature-induced resistance changes and short-circuit resistance changes

Engineering Contradiction:

Improveshort-circuit detection accuracyVSAvoidinability to distinguish temperature effect from short-circuit effect

Core Design Contradiction:

Measurement precisionVSLoss of information

Solution Approach 1:

The patent segments the resistance change analysis into two independent components: temperature-induced resistance changes and short-circuit-induced resistance changes. By separately monitoring temperature and calculating resistance, the system can isolate and identify the specific cause of resistance changes, resolving the ambiguity between temperature effects and short-circuit effects.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces temperature monitoring as an intermediary parameter to mediate the relationship between resistance measurement and short-circuit detection. By using temperature as a reference variable, the system can compensate for temperature-induced resistance changes and accurately detect true short-circuit conditions.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of operation

If current fluctuation is used to detect short-circuit, then detection method is simple, but the small current fluctuation (less than 1%) is smaller than normal operation fluctuation (2-3%), making it difficult to determine short-circuit

Engineering Contradiction:

Improvedetection method simplicityVSAvoidshort-circuit detection reliability

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent introduces resistance calculation as an intermediary measurement that amplifies the short-circuit signal. Instead of directly measuring the small current fluctuation (less than 1%), the system calculates resistance which provides a more sensitive and reliable indicator of short-circuit conditions, while still maintaining operational simplicity.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the measurement parameter from current to resistance. This parameter transformation converts the difficult-to-detect small current fluctuation into a more detectable resistance change, improving measurement precision while maintaining the simplicity of the detection approach.

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If temperature measurement points are increased to grasp temperature distribution, then temperature monitoring accuracy is improved, but device complexity and cost increase

Engineering Contradiction:

Improvetemperature distribution measurement accuracyVSAvoidnumber of temperature sensors

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent makes the field winding resistance measurement serve multiple functions: it simultaneously monitors both temperature effects and short-circuit conditions. This multi-functionality eliminates the need for additional dedicated temperature sensors, reducing device complexity while maintaining measurement precision through the dual-use of resistance data.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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

Enables early detection of interlayer short-circuits in rotating electrical machines with varying operating conditions, improving the reliability of performance maintenance by accurately distinguishing between temperature-induced and short-circuit-related resistance changes.

Implementation Method 1

a field winding resistance calculator to calculate, for a field winding of a rotating electrical machine, a field winding resistance calculated value from a detected value of a field winding current and a detected value of a field winding voltage

Methodology Applied

Scientific EffectOhm's Law: Ohm's Law

Data Source

PatentUS11320489B2Field winding interlayer short-circuit detection apparatus and field winding interlayer short-circuit detection method

Publication Date: 2022.05.03 KK TOSHIBA

AI summary

According to the embodiment, a field winding interlayer short-circuit detection apparatus comprises: a field winding resistance calculator to calculate, for a field winding of a rotating electrical machine, a field winding resistance calculated value from a detected value of a field winding current and a detected value of a field winding voltage; a determiner to determine presence or absence of an interlayer short-circuit in the field winding by using a comparison result between the field winding resistance calculated value and the reference resistance value.