Welding Essentials: Questions and Answers

Chapter 13: Power Supplies & Electrical Safety

As scarce as the truth is, the supply has always been in excess of deman.

Josh Billings

Introduction

All electrically-based welding processes require a power supply. Their electrical characteristics must match the needs of each process. After reviewing the basics of electricity, we will look at the electrical components of a power supply and then study the difference between constant-voltage and constant-current power supplies. Next, we will follow the development of power supply designs from motor-generator sets to transformer-based supplies to inverters. Finally, we will look at the importance of equipment grounding and ground fault interrupters for personnel safety.

Electricity Fundamentals

What is an electric current?

When a group of electrons moves from one point to another, we say there has been flow of electric current or simply, a current.

What is an electric circuit?

It is a path along which an electric current can flow. Current flows through a circuit much like water flows through a pipe. The principal requirement of any circuit is to form a complete and unbroken path from one side of the voltage source (for example a battery or generator) to the other. Hence, current only flows when the switch is closed and completes the circuit path, Figure 13-1.


Figure 13-1: Electric circuit.

What makes current flow around a circuit?

A source provides the electric pressure, called voltage, which is measured in volts to push the current around the circuit. The abbreviation for volts is V. Voltage is also referred...

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