Three phase system is universally employed for a generation, transmission and distribution of electric power. There are several reasons for why three-phase systems are more commonly used over higher phase (four phase or six phase) systems. Simply we can say that a three phase system is more efficient over other phase systems.
The Increase in efficiency means increase in output power of a machine. The power output of machine increases with increase the number of phases of the system. So the output power of two-phase is more than that of single-phase system. Three phase power output is much higher than two phase. Also power output of four phase and higher than previous ones. Now one question comes to our mind ‘Why three phase system is used over more efficient four or five phase systems?’.
The reason for choosing three phase is dependent on the percentage of increase of output power on increasing the number of phases. Let us check how much the power increase.
- If a two-phase system is employed in a machine the output of the machine increase by 41.4% over the single phase system.
- If a there phase system is used, 50% increase is observed in the output of the machine.
- If the number of phases in increased from three to a large number, the increase in output is only 7%. And it will cause complication.
- Considering the power output, three phase system is more economical over higher phase systems.
- Two phase supply and six-phase supply, when required, is obtained from 3 phase supply.
Hence, three phase systems are most commonly used over higher phase systems.