Varivolt Transformer

“VARIVOLT“ is the most effective device meant for operation from a nominal input voltage of 240V 1Ph & can give output voltage anywhere between 0 to 240V or 0 to 270V 1Ph by simple transformer action. Three such “VARIVOLT“ connected electrically in star and mechanically in tandem, become suitable for operation from a nominal input voltage of 415V 3Ph and can give output anywhere between 0 to 415V or 0 to 470V 3Ph.

“VARIVOLT” AUTO TRANSFORMER is a continuously variable voltage auto transformer, having a movable carbon tip, fixed to brush arm sliding on a silver plated commutator. Rotation of the brush arm by either manual or motor drive, delivers an output voltage from zero to or above line voltage. “VARIVOLT” conforms to I.S. 5142.

Salient Features:

• Rugged Construction : “VARIVOLT” Auto transformers are designed for heavy duty trouble free operation. All components are designed to give maximum life to the unit under extreme operating conditions. Except for carbon tips, no other part needs any specific maintenance . Even carbon tips do not require to be changed frequently. This practically makes the “VARIVOLT” a maintenance free electrical equipment.
• Excellent Regulation : The drop in voltage from “no load to full load” is minimal in “VARIVOLT” Auto-transformers. (See fig…II for regulation characteristics)
• High Efficiency : Careful copper, core selection and design assures the user of low watt loss, as compared to other controllers. 
• No Wave form Distortion : “VARIVOLT” provides an output voltage wave-form, which is a distortionless replica of the input voltage wave-form.
• Silver Plated Commutator : A special silver plating technique is used on the commutator, enabling it to withstand high overloads and maintain constant contact drop. It also ensures smooth operation, long life and increased resistance to corrosion.
• Over-load Capacity : Because of its careful designing, “VARIVOLT” can withstand many over-loads, Fig…I gives an idea of the maximum overloading allowed with its relevant time limits. When repeated overloading takes place, care has to be exercised to provide sufficient off time to reduce the temperature build up.
• Low Operating Torque : A glass smooth commutator, special sintered bushings for the shaft and perfect assembling of coils results in low operating torque for all “VARIVOLT” Auto-transformers.
• Smooth and Linear Output : As voltage between turns is small and as the brush arm is in constant contact with more than one turn, harmful sparking is avoided and output voltage can be set to a fraction of a volt from zero onwards.
• Low Magnetizing Current : By using an adequate section of high quality grain oriented silicon steel, the iron losses in “VARIVOLT”, are controlled to the minimum. The no load current in all “VARIVOLT” transformers, is invariably less than 3% of the rated current.
• Negligible Maintenance and Trouble Free Long Life : “VARIVOLT” has been carefully designed. No special care has to be taken to maintain “VARIVOLT” auto transformers in normal working environments. The only components needing inspection and maintenance are the carbon tips and the commutator. Timely replacement of carbon tips and cleaning off foreign particles and accumulated dust, from the commutators surface, will ensure a considerably long, maintenance free, and uninterrupted life to the unit. Normally “VARIVOLT” auto transformers up to 28 Amps. are offered in air cooled or oil cooled construction. Models of 40 Amps. & above are offered in oil cooled construction. In very special cases “VARIVOLT”, above 40 Amps, can be offered in air cooled construction. This is possible due to the special paralleling techniques adopted by us.

Auto Transformers – Our Speciality :

“VARIVOLT”  is now available in high current ranges from 225 Amps. up to 2000 Amps. in single, two and three phase models. Special paralleling techniques designed by us, have made it possible to surpass the previous current limit of 200 Amps. for toroidal Auto Transformers.

The following are the salient features of High Current “VARIVOLT” Auto Transformers :-

• Special forced current paralleling techniques, result in current sharing of each coil ±2%.
• Flanged type pressed steel radiators, are supplied separately packed, making the units easy for transportation.
• Gear Driven High Torque A.C. Synchronous Motor drive.
• Terminals in the form of bus-bars.
• All other features of oil cooled auto transformers.