Spark Construction

Mob. : 09811172901 / 09999955565 / 09999955563

Servo Transformer Dimmer


Variable auto transformer is a Continuously variable voltage transformer, having a single layer winding on a toroidal core of high grade Steel. in an VARIAC 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. The basic Auto Transformer is meant for operation of a nominal voltage of 240 V A.C & can give output voltage anywhere between 0 270 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 0470V.


  • 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 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.
  • These auto transformers or dimmers are Suitable for indoor use on maximum ambient temperature of 45 C. Variable Auto Transformers are rated 240 volts Input and 0-270Volts output. Similarly, three 240-volt units are ganged in a star connection to result in a 470-volt line-to-line three-phase assembly. For 480-volt open delta applications, two 240-volt units are used in series in each of the two legs of the open delta assembly. In any of the above voltage applications, higher current requirements are met by paralleling two or more units in the ganged assembly.