DE1904737

1,261,073. Transformers. LINCOLN ELECTRIC CO. 30 Jan., 1969 [2 Feb., 1968], No. 5132/69. Heading H1T. The output voltage from a transformer with a shell-type core is adjustable in small increments by taps on a secondary winding on the centre leg, the taps being disposed on the end turn at least one tap being spaced less than one half-turn from an end tap and at least one connection to a tap passing outwards through a hole in the core. There may be taps on the second turn of said winding including a tap X2 at its end which is insulated from the tap E2 at the beginning of the third turn, all the taps may be connected to appropriate contacts on two selector switches SW1, SW2, whereby setting of the switches adjusts the voltage output of the winding in small increments. There may be secondary windings 1, 3 on the other legs 11, 13 of the core T and there may be coarse tappings A, B, C, D, E at 1 turn intervals along all the secondary windings connected to a terminal board S. In the case of a three-phase transformer the terminals may be so disposed that a single shorting plate P may connect the three windings in star connection thereby varying the output voltage of each winding in coarse steps while ensuring that the voltage output difference between any two windings is less than the volts per turn of the winding. The transformer output taps may be connected to the input terminals of a full-wave rectifier R and inclusion of the selector switches SW1, SW2 and terminal board S provides a D.C. voltage supply, the output voltage being adjustable in small increments over a large range, such a supply being suitable for welding apparatus.