Most electric systems use three-phase AC circuits for power generation, transmission, and distribution. The main advantages of 3-phase systems over single-phase systems are:
- Higher power density (power per unit volume)
- Higher specific power (power per unit mass)
In a single-phase system, the instantaneous power fluctuates with an average value. On the other hand, the instantaneous power of a 3-phase system is constant. Furthermore, three-phase induction motors are self-starting whereas single-phase induction motors need auxiliary tools to start them.