Introduction

In the preceding modules, the fundamental physical principles and the basic components have been discussed. Furthermore, the essential technical behaviours in direct-current (DC) networks were clarified. In DC networks, electrical circuits are supplied with direct current, whereas alternating-current (AC) networks operate with alternating current. DC flows continuously in one direction, while AC periodically reverses its direction. The regularity of this reversal follows a specific frequency. For example, an ideal electrical resistor is not frequency-dependent. In contrast, components such as capacitors and inductors exhibit different complex impedances at different frequencies. To analyse these periodic quantities, the following topics are addressed:

• Pointer diagram
• Complex AC circuit analysis
• Effective value
• Apparent power, active power and reactive power
• Three-phase current
• Co-system, counter-system and zero system