TDJA /TSJA series oil cooling type variable transformer/VARIAC is similar to the conventional vertical wound rotor asynchronous motor. When the relative position of stat-or is changed, the inductive potential phase (three phase) of stat or winding will be changed, also the inductive potential amplitude (single phase), which ensures output voltage in a certain range. When the output voltage is beyond the range of rating accuracy, directly or indirectly take the output signal voltage of voltage regulator, by comparison with the reference voltage of voltage stabilizing controller, after amplification, the servo motor of voltage regulator drives reversible operation so that the output voltage can reach the rated value automatically in a certain accuracy range. Widely used in plumbing, sanitary ware, car spares, valves, iron cast lines, etc.