GB1219217A - Constant voltage transformer - Google Patents

Abstract

1,219,217. Transformers. VARO Inc. 2 May, 1969 [21 June, 1968], No. 22584/69. Heading H1T. A constant voltage transformer comprises a primary 11 (Fig. 1), secondary 13 and resonant winding 15 having a capacitor 16 across it, the core having a shunt member 20, 21 with a non-magnetic gap 22, and the core construction being such that the flux capacity of the core portion encircled by the primary 11 is greater than that of the core portion encircled by the secondary and resonant windings 13, 15 which latter is greater than the flux capacity of the shunt core member at the position at which its capacity is a minimum. Dimension A is preferably 20-60% greater than dimension B. The air gap 22 may be stepped or sloped in various ways (Figs. 2-7, not shown). An alternative core construction has the windings 11, 13, 15 (Fig. 8) on a stepped centre limb and separated by shunt members 42, 43 which may be of unequal lengths or different magnetic materials, e.g. of laminated, solid or sandwich construction. The gaps may be at either or both ends of the shunts. A number of variations of the core shape of Fig. 8 are described (Figs. 9-13, not shown). Where grain oriented core laminations are used the core is designed so that saturation occurs, e.g. in the core part surrounded by the windings 13, 15 before it occurs where the flux travels across the grain, e.g. in the I laminations adjacent the gaps 35. Alternatively, parts of the outer laminations or of the I laminations can be narrowed to secure initial saturation there (Fig. 9, not shown). In the E laminations width ¢D having a cross-grain flux may be about ¢(A+25%). Instead of having various widths of different core portions the different flux capacities may be secured by omitting some laminations, e.g. in the centre leg (Fig. 12, not shown), or by making different core portions of different materials. The output voltage of the transformer can be varied by varying the non-magnetic gap(s) 35 by varying the number of shims (of epoxy glass, mica or paper) in the gaps and then clamping. For use at higher frequencies the core may be of moulded construction (Fig. 13, not shown). The transformer may be provided with compensating windings.