Patent GB-190606316-A (GB)
Title: Improvements in and relating to Electrical Transformers.
Filed: 1906-03-15
Granted: 1907-01-03
Abstract: 6316. British Thomson-Houston Co., [General Electric Co.]. March 15. Distributing; regulating; transformers.-A variable-voltage transformer, which is an improvement on that described in Specification No. 17,388, A.D. 1902, is provided with means for magnetically shunting and means for varying the reluctance of the magnetic circuit passing through one of the coils. The transformer may be applied wherever a wide range of voltage is required, e.g, in thawing water-pipes or for testing purposes. Owing to the even variation obtained, there is no danger of suddenly striking resonant conditions, as in step-bystep control, when the transformer is used in testing cables or other devices possessing capacity. In the form shown in Figs. 1 and 3, the primary P and secondary S are mounted on the middle leg of a laminated core A. Two magnetic members B, C are mounted on opposite sides of the secondary S, and may be moved vertically by means of a shaft D, the arrangement being such that one member is moved down as the other is moved up. The members are approximately balanced magnetically so that little effort is required for operation. The member B by its movement varies the reluctance of the magnetic circuit of the primary, shunting the secondary as described in the above-mentioned Specification. The member C varies the reluctance of the magnetic circuit passing through both coils P, S. The relative position of the members B, C gives a voltage variation from maximum almost to zero. In the form shown in Fig. 5, the member C<3>, which varies the reluctance of the magnetic circuit passing through both coils, is pivoted at e to the frame and connected by a link C<4> to the member B. A considerable movement of the member C<3> is made before the member B has moved far down, and a somewhat more even variation of the secondary voltage is obtained. In some cases, either or both of the members B, C are made in halves which may be separated by right and lefthanded screws, and, in this case, the laminations of the members may be at right-angles to the main core A. In the form shown in Fig. 8, which is particularly adapted for controlling the voltage of an alternating-current load circuit, there are two secondaries S', S<2> provided with movable members F<1>, F<2>, so that, when the flux of the primary P is diverted from, one secondary, it is passed through the other. The coils may, as shown in Fig. 10, be connected in series with each other and with the load circuit, but in opposition to each other with respect to their induced voltages. By altering the position of the members F<1>, F<2>, the voltage supplied to the line may be controlled both in amount and direction. The two coils S<1>, S<2> may be used as primaries, and the coil P as secondary, in which case the primaries are connected in series and in opposition with respect to induced voltage, the secondary being in series with the line. In order to balance the horizontal pulls on the members F<1>, F<2>, the form shown in Fig. 8 may be modified by mounting the secondaries S', S<2> on opposite sides of the primary P, and this arrangement may be applied, as shown in Fig. 13, for use with polyphase circuits. Primary coils P<1>, P<2>, P<3> and secondaries S<1>1 S<2>1 ; S<1>2 S<2>2; S<1>3 S<2>3 are mounted on the legs of the core A. The movable members F<1>, F<2> are arranged to moved simultaneously, and each member serves both to shunt -simultaneously the secondary coils of all three phases adjacent to it, and also to vary the reluctance of the magnetic circuits passing the secondary coils at the opposite end of the core.