Direct and alternating currentAlternating current
Alternating current is characterised by its periodically changing polarity. In the European interconnected power system, the frequency is a uniform 50 Hz and the voltage varies depending on the voltage level. Alternating current has the great advantage that it can be raised or lowered to different voltages relatively easily by means of transformers. Alternating current is therefore most widely used in worldwide energy networks. In addition, alternating current can be produced relatively simply using synchronous or asynchronous machines.