| 摘要 |
Single phase or three phase welding transformers having a primary coil wound on one limb of a rectangular core, a secondary coil wound around both said one limb and a movable core member so as to enclose said primary coil. The limbs of said rectangular core adjacent said one limb are formed with upper and lower extensions respectively which abut the upper and lower ends respectively of said movable core member when in its lowered position. The movable core member is movable in a direction substantially parallel to the longitudinal axis of said secondary coil such that an air gap of variable width is formed between the lower extension and the lower end of the movable core member. Non-magnetic guides fixed to the movable core member are spring urged against a bearing surface provided on a casting fixed to the rectangular core. The reaction to the spring force is also provided by the casting. Gaps may be maintained at all times between the rectangular core and the movable core member and/or bias coils provided to maintain high open circuit secondary voltage.
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