3 phase ac system is the three alternating current of same frequency and voltage amplitude. It have three current carrying conductors which have 120 degree phase shift in the alternating current.
This type of arrangement in the 3 phase ac system generate constant power output.
3 phase ac system is most widely used in the generation of electricity, transmission of electricity and distribution of electricity.
It consists of three wire or four wire (three phase conductor and one neutral wire).