Electrical technology

Sources of electrical power

The principle sources of electrical power of interest to the welder are (1) batteries and accumulators, (2) generators.

Batteries generate electrical energy by chemical action. Primary batteries, such as the Leclanché (used for flash lamps and transistor radios), continue giving out an electric current until the chemicals in them have undergone a change, and then no further current can be given out.

Secondary batteries or accumulators are of two types: (1) the lead–acid, and (2) the nickel–iron alkaline. In the former, for example, there are two sets of plates, one set of lead peroxide and the other set of lead, immersed in dilute sulphuric acid (specific gravity 1.250, i.e. 4 parts of distilled water to 1 part of sulphuric acid). Chemical action enables this combination to supply an electric current, and when a current flows from the battery both the lead peroxide plates and the lead plates are changed into lead sulphate, and when this change is complete the battery can give out no more current. By connecting the battery to a source of electric power, however, and passing a current through the battery in the opposite direction from that in which the cell gives out a current, the lead sulphate is changed back to lead peroxide on one set of plates and to lead on the other set. The battery is then said to be ‘charged’ and is ready to supply current once again.