Advantages and disadvantages of three phase system over single phase System
A) In a single phase circuit the power delivered is pulsating. In three phase system the total power delivered is stable if the loads are balanced by the power of any one phase or circuit might be negative. So three - phase system is highly desirable mainly for power loads.
B) The rating of a given machine enhances with enhance in number of phases. For example the output of a three phase motor is 1.5 times the output of one phase motor of the similar size.
c) Single -phase induction motors, have no initial torque and so it is essential to give these motors with an auxiliary means of starting, but in case of three phase motors except synchronous motors there is no requirement of providing an auxiliary means for starting.
D) Power factor of single phase motor is lower than that of three phase motor of the similar rating (output & speed).