Most of the alternating current arc welding machines in use are of the single operator, static transformer type (fig. 5-19). For manual operation in industrial applications, machines having 200, 300, and 400 ampere ratings are the sizes in general use. Machines with 150 ampere ratings are sometimes used in light industrial, garage and job shop welding.

Alternating current arc welding machines . The transformers are generally equipped with arc stabilizing capacitors. Current control is provided in several ways. One such method is by means of an adjustable reactor in the output circuit of the transformer. In other types, internal reactions of the transformer are adjustable. A hand wheel, usually installed on the front or the top of the machine, makes continuous adjustment of the output current, without steps, possible.

The screws and bearings on arc welding machines with screw type adjustments should be lubricated every 3 months. The same lubrication schedule applies to chain drives. Contacts, switches, relays, and plug and jack connections should be inspected every 3 months and cleaned or replaced as required. The primary input current at no load should be measured and checked once a year to ensure the power factor connecting capacitors are working, and that input current is as specified on the nameplate or in the manufacturer’s instruction book.