Welding Power Supply Single Phase Detection via DC Ripple

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Solution Overview

Problem

Conventional welding-type power sources lack a cost-effective method to detect single phase AC input power, which can cause thermal stress and damage when equipment designed for three-phase operation is used with single phase power, as they do not typically measure phase-to-phase voltages or currents.

Innovation Solution

The system detects single phase AC input by monitoring the ripple voltage on the DC power bus synchronously with the AC input and comparing voltage samples using a processor, without requiring additional circuitry, and can power down or limit output to prevent damage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If phase-to-phase voltages or currents are measured to detect single phase operation, then detection accuracy is improved, but device complexity and cost increase due to additional circuitry

Engineering Contradiction:

Improvesingle phase detection accuracyVSAvoidcircuitry complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The system uses existing circuitry components (rectifier, DC power bus, processor) to detect single phase operation without requiring additional measurement circuitry. The processor leverages voltage samples already being taken for other control functions to determine input phase configuration, making the existing system serve the detection function as well.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The voltage sampling circuitry originally designed for power control and regulation is made multi-functional by also using it to detect single phase operation. The same processor that controls the rectifier and monitors DC bus voltage now also analyzes these voltage samples to identify single phase input conditions, eliminating the need for dedicated detection circuitry.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Device complexity

If single phase operation is not detected, then device complexity remains low, but thermal stress and equipment damage occur

Engineering Contradiction:

Improvedetection system complexityVSAvoidthermal stress

Core Design Contradiction:

Device complexityVSObject-affected harmful factors

Solution Approach 1:

The processor continuously monitors DC power bus voltage samples and uses this feedback to identify single phase operation conditions. When single phase operation is detected, the system provides feedback by triggering protective actions such as alarm signals or shutdown commands to prevent thermal stress and equipment damage.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system performs preliminary detection of single phase operation before thermal damage can occur. By analyzing voltage samples in real-time and identifying single phase conditions early, the system can take preventive protective actions before excessive thermal stress develops in the power source components.

Inventive Principle:

Principle #10Preliminary action

3Adaptability or versatility

If additional circuitry is added to detect single phase input, then detection capability is improved, but manufacturing cost increases

Engineering Contradiction:

Improveinput phase detection capabilityVSAvoidmanufacturing cost

Core Design Contradiction:

Adaptability or versatilityVSEase of manufacture

Solution Approach 1:

Inventive Principle:

Principle #25Self-service

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 method effectively differentiates between single and three-phase AC inputs without additional cost or circuitry, protecting the equipment from thermal stress and potential damage by accurately identifying single phase operation and responding accordingly.

Implementation Method 1

converting, via a rectifier circuit, the AC input power to direct current (DC) power

Methodology Applied

Scientific EffectRectification:

Implementation Method 2

detecting whether single-phase AC power is coupled to the input by monitoring voltage samples of the DC power using a voltage sampling timing based on a frequency and voltage of AC power connected to the input

Methodology Applied

Scientific EffectVoltage sampling and comparison:

Data Source

PatentUS20230226633A1Single phase input detection and power source protection

Publication Date: 2023.07.20 ILLINOIS TOOL WORKS INC

AI summary

A welding-type power supply that receives alternating current (AC) input power and converts the AC input power to direct current (DC) power to provide power for welding tools. The welding-type power supply is configured to detect whether single phase AC power or three-phase AC power is connected to the input of welding-type power supply. Single phase input power may be detected by sampling ripple voltage of the DC power, either synchronously with the AC input power or synchronously with a signal generated by an output of the welding-type power supply.