Three Phase System Advantages over Single Phase System

Three Phase System Advantages 

In polyphase AC system it is possible to use two , three or more individual circuits, operate at same frequency, their voltages and currents are out of phase from one another.

Single phase system has its own limitations and has been replaced by three-phase system.

Advantages of three-phase system over single phase systems

The advantages of polyphase system over single phase systems are given below:

  1. Power delivered is constant. In single phase circuit the power delivered is pulsating and objectionable for many applications.
  2. For a given frame size a polyphase machine gives a higher output than a single phase machine.
  3. Polyphase induction motors are self starting and are more efficient. Single phase motor has no starting torque and requires an auxiliary means for starting.
  4. Comparing with single phase motor, three phase induction motor has higher power factor and efficiency.
    Three phase motors are very robust, relatively cheap, generally smaller, have self-starting properties, provide a steadier output and require little maintenance compared with single phase motors.
  5. For transmitting the same amount of power at the same voltage, a three phase transmission line requires less conductor material than a single phase line. The  three phase transmission system is so cheaper.
    For a given amount of power transmitted through a system, the three phase system requires conductors with a smaller cross-sectional area.
    This means a saving of copper and thus the original installation costs are less.
  6. Polyphase motors have uniform torque whereas most of the single phase motors have pulsating torque.
  7. Parallel operation of three-phase generators is simpler then that of single phase generator.
  8. Polyphase system can set up rotating magnetic field in stationary windings.

What are the advantages of three phase supply over single phase supply?

The comparison between single phase supply system and three phase supply system is summarized in the below table.

Single Phase Supply Three Phase supply
power delivered is pulsating Power delivered is constant
Single Phase induction motors are not self starting as it does not have starting torque. Three phase induction motors are self starting.
Parallel operation is not easy. Parallel Operation is easy.
Efficiency of single phase motor is lesser. High efficiency.
Single phase motors have pulsating torque. Three phase motors have uniform torque.
Single phase motors have lower power factor. Three phase motors have higher power factor.

Thanks for reading about three phase system Advantages…

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1 Response

  1. Shashi says:

    How much amount (% saving) of cu saving in case of 3 phase system as compare to 1 phase system

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