Auto transformer is a kind of dry type transformer where primary and secondary shares same common single winding.  There is no isolation between the input and output circuits.  Auto transformer has only one winding per phase.  Auto transformers are economical compared to Isolation Transformers because they are smaller in size.  Auto transformers can be installed in indoor or outdoor depending on enclosures.  Single phase and three phase units are available in 60HZ or 50HZ designs.

Advantage of Auto Transformers:

  1. Lower cost:  The advantage of the auto transformer is size, weight and cost, depending on how close the input and output voltages are.
  2. Less copper is used in its design and construction.
  3. Lower losses and lower excitation current.


  • Used in both Synchronous motors and induction motors.
  • Used in electrical apparatus testing labs.
  • Used in electric heating, air conditioners, Industrial machinery etc.


  • Less noise.
  • Can be used in either step-up or step-down.
  • CSA Certified, File No. 0900242_0_000
  • UL Listed, File No. 20121218-E38760
  • Nema-1 enclosure suitable for indoor application. Nema-3R suitable for outdoor application.
  • Taps are available upon customer request.
  • Open type or enclosed type as per customer preference.
  • Custom auto transformers can be built when special voltage combination is required.


Please call factory for current updated shop drawings or email