Variable Auto Transformers

CVVAT is the most useful and effective device for step less, break less and continuous control of a.c. voltage and, therefore, for control of various other parameters, dependent on a.c. voltage. This product is an ideal controlling device for numerous applications in laboratories and in industrial & commercial fields.

The continuously variable voltage auto-transformer is meant for operation off a nominal voltage of 240V A.C. and can give output voltage anywhere between 0 to 240V, or up to 270V, by a simple transformer action.  Three such units when connected electrically in star, and mechanically in tandem, become suitable for operation off 415V 3 phase A.C. supply and to give output from zero to 415V, or up to 470V.


CVVAT is probably the best device to obtain a continuously variable output voltage from a fixed a.c. voltage source. This is clearly evident from various special features and operating advantages, given below:

  • Simple & rugged in construction - Therefore has long life, is relatively cheaper, noiseless in operation, compact and easy to understand, maintain and repair.
  • Good Regulation - Voltage drop on load is low, due to low resistance of conductor and low leakage flux of toroidal core.
  • Output voltage variation on no-load and even on load is effortless, smooth, continuous, break less and linearly proportional to angular rotation.
  • High Efficiency - No load losses and load losses are low.
  • Negligible waveform and power factor distortion due to simple transformer action.
  • Excellent short time overloads capacity.
  • Easy for remote operation with the help of motor drive.
  • Wide range of models.


Typical Applications:
CVVAT, because of its unique characteristics and features find a very wide field of applications. A few of them are:

  • Light control in auditoriums, hotel, restaurants, theatre stages, photo-studios, verandahs, lobbies, conference halls, cinema houses and even in homes.
  • Voltage and current control in experimental and development work in laboratories and R&D Depts.
  • Testing and calibration of indicating instruments.
  • Current control for testing relays, current transformers, circuit breakers, etc.
  • Temperature control in ovens, furnaces, moldings processes, etc.
  • Testing of electrical and electronic equipment for under voltage and overvoltage performance.
  • Breakdown testing of insulation.
  • Control of D.C. voltage in electrochemical processes, such as electroplating, battery plate forming, anodizing, metal refining, hydrogenation, catholic protection, etc.
  • Starting of A.C. motors.
  • Speed control of D.C. motors in textile, plastic and paper industries and other extrusion processes.
  • Manual or servo controlled A.C. voltage stabilizers and D.C. Power Supply Equipment.
  • Phase shifting transformers.

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