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���Branch : Electrical Engineering�Semester : 4th �Subject : energy conversion – i �

Chapter : 04�Topic : Single Phase Auto-Transformer�Faculty : Dr. Mrutyunjay Das

Mayurbhanj School Of Engineering, Baripada

AY-2021-2022

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contents

  • Construction
  • Working Principle
  • Comparison of Auto-transformer with Two-winding Transformer
  • Uses
  • On load tap changer
  • Off load Tap changer

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Construction

  • An auto transformer has only one winding which is shared by both primary and secondary circuit.
  • Number of turns shared by secondary are variable.
  • EMF induced in the winding is proportional to the number of turns.
  • Therefore, the secondary voltage can be varied by just varying secondary number of turns.

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Working Principle

  • The supply voltage is applied across AB, and the load is connected across CB.
  • When an AC voltage V1 is applied across AB, an alternating flux is set up in the core, as a result, an emf E1 is induced in the winding AB.
  • A part of this induced emf is taken in the secondary circuit.

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Comparison of Auto-transformer with Two-winding Transformer

Weight of cu. in section AC

Weight of cu. in section BC

Total weight of cu.in auto-transformer

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Tap changing transformer

  • Off – load Tap changing Transformer:

The transformer is disconnected from the main supply when the tap changing is usually done manually.

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Tap changing transformer

  • On load tap changing transformer:

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