Varivolt-continuously variable voltage auto transformers-are manufactured as per IS 5142-1969 by using low loss CRGO torroidal cores.They are of rugged construction. Excellent regulation and efficiency are assured by careful selection of core section and copper conductor. A silver plated commutator ensures smooth operation, long life and increased resistance to corrosion. Linear output is smooth as the voltage between turns is small, thereby avoiding any harmful sparking as also enabling very precise selection of output voltage. No elaborate maintenance needs to be done on the unit except inspection and replacement of worn-out carbon contact tips and cleaning of commutator. It has further features such as low magnetising current, low operating torque and no wave form distortion. High current auto transformers are also available from 225 to 1,000 amps in single and three phase models. The firm has used special paralleling techniques to ensure that the current sharing in the coils does not vary more than 2%. Two phase models also available on request.