Electrical engineering for welding

Topic overview

The arc has negative dynamic behaviour and changes with length, temperature, ionisation, metal transfer, short circuits, wire feed, polarity and resistance of the entire secondary circuit. IWE/IWT personnel must therefore understand not only the current value, but also how the source generates, rectifies, smooths, measures and regulates current .

This module breaks the source down as a technical system: input stage, transformation, rectification, power switches, DC link, secondary rectifier, inductor, current measurement, feedback, protections and their manifestation in current/voltage graphs.

The objective is not to repair the source at service-technician level. It is to distinguish whether a quality problem originates in the WPS, torch, return connection, wire feeding, source dynamics, inductance/pulse settings or an unsuitable source type for the process.

Static characteristic describes how voltage and current change during slow shifts of the operating point. Dynamic characteristic describes how quickly the source responds during ignition, droplet formation, short circuit, droplet detachment or pulsed welding.

What the module covers

• A welding power source is not a ‘box of amps’. It is a fast control system that regulates an unstable plasma load.
• What the welding coordinator must know
• Static vs dynamic behaviour
• Why ‘220 A’ is insufficient
• Welding power-source architecture
• Main components and their functions in a welding power source
• Rectifier: circuit and graph response
• Inductor L: its function in the arc