Soft Starter Star-Point Circuit for Component Fault Detection

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Solution Overview

Problem

Existing motor arrangements in automation technology require multiple hardware components and complex assembly to achieve high safety integrity levels, which increases cost and complexity, and there is a need for a more efficient method to diagnose defective components in soft starters.

Innovation Solution

A soft starter system with semiconductor switching elements and electromechanical switches in each phase, connected in a star-point circuit with passive components, allows for detection of defective components through reduced voltage drops, using a voltage measuring device and control unit to identify defects without additional hardware, thereby achieving Safety Integrity Level 1 without contactors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If multiple hardware components (contactors, safety switching devices) are used to achieve high safety integrity levels, then safety integrity level is improved, but device complexity and cost increase

Engineering Contradiction:

Improvesafety integrity levelVSAvoidhardware components

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The soft starter performs self-diagnosis by monitoring its own semiconductor switching elements and electromechanical switches. The control unit continuously checks the operational status of these components and can autonomously detect defects without requiring external monitoring devices or additional safety components.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The control unit serves multiple functions: it controls the semiconductor switching elements for soft starting, monitors the operational status of all switching components, detects defects through voltage measurements, and manages safety functions. This multi-functionality eliminates the need for separate safety switching devices and contactors.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If multiple hardware components are used to achieve high safety integrity levels, then safety integrity level is improved, but cost increases

Engineering Contradiction:

Improvesafety integrity levelVSAvoidcost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The control unit combines multiple functions into a single device: soft starting control, operational status monitoring, defect detection through voltage measurements, and safety management. This consolidation eliminates the need for separate safety switching devices and contactors, reducing component count and cost.

Inventive Principle:

Principle #5Merging (Combining)

3Difficulty of detecting and measuring

If voltage drop detection method is used to identify defective components, then diagnostic capability is improved, but measurement precision requirements increase

Engineering Contradiction:

Improvediagnostic capabilityVSAvoidvoltage drop detection

Core Design Contradiction:

Difficulty of detecting and measuringVSMeasurement precision

Solution Approach 1:

The circuit lines forming a star point serve as intermediary elements that facilitate voltage measurements. By measuring voltage drops across these star-point connected lines, the system can indirectly detect the operational status of semiconductor switching elements and electromechanical switches without requiring direct contact with the switching components themselves.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces complex mechanical diagnostic systems with electrical voltage measurements. Instead of using mechanical test equipment or physical inspection methods, the control unit uses electrical voltage drop measurements across the star-point circuit lines to detect defective switching components, simplifying the diagnostic approach.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 solution enables quick and cost-effective detection of defective components, reducing hardware requirements and ensuring high safety integrity with minimal components, allowing for simplified and economical motor arrangements, and supports both SIL 1 and SIL 3 levels with reduced complexity.

Implementation Method 1

a voltage measuring device, which is arranged in parallel to a semiconductor switching element in the first phase... a reduced voltage drop occurs in the semiconductor switching element of the first phase due to the circuit forming a star point. The reduced voltage drop due to the circuit forming a star point can be detected by way of a voltage measuring device

Methodology Applied

Scientific EffectVoltage drop detection: Ohm's Law

Data Source

PatentUS11374527B2Diagnosable soft starter, diagnostic method, and motor arrangement

Publication Date: 2022.06.28 SIEMENS AG

AI summary

A soft starter includes a plurality of live phases, wherein a semiconductor switching element and an electromechanical switch parallel-connected thereto are arranged in each phase. In the soft starter, on a load-facing side of the semiconductor switching elements and of the electromechanical switches, the plurality of phases are connected in a circuit forming a star point. The star point circuit includes at least one passive component and is configured for detecting a reduced voltage drop in a defective state of a semiconductor switching element and/or of an electromechanical switch.