Auto Transformer

An auto transformer  is an electrical transformer with only one winding.  In an auto transformer, portions of the same winding act as both the primary and secondary sides of the transformer.


  • A range of step-up/step- down auto-transformers 0-110- 220-230- 240V, 50/60Hz.
  • Power ratings 100 ~ 5000VA
  • Connection made by insulated terminal block
  • Windings are covered with metal shrouds
  • Insulating rating: Class B


  • Used in both Synchronous motors and induction motors.
  • Used in electrical apparatus testing labs since the voltage can be smoothly and continuously varied.
  • They find application as boosters in AC feeders to increase the voltage levels.
    • Power transmission and distribution
    • Audio system
    • Railways