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Auto Tansfermors or Dimmerstarts


We are manufacturer and exporter of continuously variable Auto Transformers, Variacs and Dimmer stat which operates on a nominal voltage of 240 V A.C & can give output voltage anywhere between 0 – 270 V, by a simple transformer action.

The basic Auto Transformer is meant for operation off a nominal voltage of 240 V A.C & can give output voltage anywhere between 0 – 240 V or up to 270 V, by a simple transformer action. Three such Variable Auto transformer when connected electrically in star & mechanically in tandem, became suitable for operations of 415 V 3 Phase A.C. supply & to give output of 0 – 415 V or up to 470 V.

Variacs or variable auto transformer is a continuously variable voltage transformer, having a single layer winding on a toroidal core of high grade Steel.

In an autotransformer portions of the same winding act as both the primary and secondary winding. the winding has at least three taps where electrical connections are made. One end of the winding is usually connected in common to both the voltage source and the electrical load. The other end of the source and load are connected to taps along the winding. Different taps on the winding correspond to different voltages, measured from the common end.

On one face of the copped winding, along the periphery, a special durable contact surface is made. A specially designed carbon brush slides smoothly on the surface. A contact arm holding the contact brush is fitted to the central shaft and as the control knob is rotated, the carbon brush slides over the winding and taps off a portion of voltage across the winding.

Any desired voltage within the maximum range can be obtained by adjusting the position of the brush. The calibrated dial reads approximately the output voltage at no-load, when the input is at its rated value. Rotation of the brush arm by manual of motor drive delivers an output voltage from zero to or above line voltage.

Variable Auto Transformer, manufactured by Purevolt 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. It is ideal controlling device for numerous applications in laboratories and in industrial & commercial fields.

Supply voltage adjustment, boosting of low lines and line voltage stabilization, either manually or automatically in automatic voltage stabilizers. Voltage and current control in development and experimental work.

Over and under voltage testing of electrical and electronic equipment.

Testing and calibration of voltmeters, ammeters, watt meters etc…

Built in as an integral control element in electrical, electronic and automatic control and process equipment.

Restaurants, photographic studios and darkrooms etc...

Motor speed control either direct or through suitable circuits.
Rated for 240V A.C. 50/60Hz. single phase supply and three phase model for 415V A.C. 50/60Hz three phase 4 wire supply

The output voltage of these Toroidal or variable transformer can be varied smoothly over two ranges:

Zero to full supply voltage

Zero to approx. 12% higher than the supply voltage

These auto transformers or dimmers are Suitable for indoor use on maximum ambient temperature of 45oC.