Star - Star Transformer

The Star – Star connection is applicable for low current, high voltage applications.


  • As the phase voltage is 1/ √ 3 to that of line voltage, number of turns per phase and amount of insulation is reduced that proportional.
  • No phase shift between primary voltage and secondary voltage.
  • It is possible to provide neutral connection to the primary winding as well as secondary winding.


  • The unbalance loading to the neutral causes neutral shift therefore the line to neutral voltage becomes unequal. This difficulty can be overcome by connecting star point of the primary to the star point of the alternator.
  • The primary of the transformer draws magnetizing current which consists of third and fifth harmonics. If the primary neutral is not connected to neutral of alternator, the third and fifth current flows which result in non – sinusoidal waveform. 
  • The primary neutral must be connected to the neutral of alternator in order to reduce distortion in the voltage waveform.

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