| 摘要 |
1,188,326. Transformers. HIRST ELECTRIC INDUSTRIES Ltd. 12 July, 1968 [21 Aug., 1967], No. 38465/67. Heading H1T. A transformer, e.g. for electric arc welding, comprises primary 23 and secondary 24 windings on one leg 12 of a magnetic core 11, the secondary winding also embracing a movable core member 19 which abuts, in its lowered position, extended portions 16, 17 of the upper and lower yokes 14, 15 and which is movable to vary the air gap between itself and one of the yoke extensions (17). Member 18 and, correspondingly, the end of extension 16 are slightly tapered so that contact between the two is broken as soon as member 18 is raised slightly from its lowered position. The core is laminated and is constructed in two parts 11a 11b, which meet in V-shaped interfaces 21, 22 and are rigidly clamped in a frame. The yokes and the leg 13 are wider than leg 12 and member 18. The lower yoke extension 17 has a portion 26 of reduced width carrying a first bias coil 27 connected to either the primary or secondary winding to oppose the leakage flux at no load, and a second bias coil 28 connected in series with the secondary and suitably comprising a single turn to oppose the flux produced by coil 27 under load. For a three-phase transformer, Figs. 2, 3 (not shown), three transformers similar to Fig. 1 are disposed at 120 degrees to each other so as to form magnetically continuous starshaped yokes, legs 13 being omitted if desired. Means are provided to raise or lower all three movable members 18 together. Rectifier units (29) may be disposed within the outer periphery of the structure and a fan for forced ventilation may be mounted in the space (30) above the upper yoke. |
