GB301438A - Improvements in or relating to means for regulating the voltage of electrical transformers - Google Patents

Abstract

301,438. British Electric Transformer Co., Ltd., and Whish, A. C. June 30, 1927. Regulating tr a n sformers.-The voltage of a transformer is regulated by means of a tapping switch having a pair of movable contacts 1, 2 connected through separate o i l switches 5, 6 to opposite ends of an auto-transformer or choke 7 the mid-point of which is connected to the external circuit either directly or through a further portion of the main winding B. In effecting regulation from the tap C to the tap C', current through the contact 2 is first interrupted by opening the oil switch 6 thereby diverting the current through the contact 1, oil switch 5, and the upper half of the auto-transformer winding. The contacts 1, 2 may then be shifted to the dotted position without causing sparking in the main transformer tank. The oil switch 6 is then reclosed placing the winding 7 in parallel with the section C, C<1>, and affording a voltage corresponding to a virtual tapping between the tappings C, C<1>. Further adjustment of voltage is effected by movement of the contacts 1, 2 so that both engage the tapping C<1> after temporarily diverting current through the contact 2, oil switch 6, and the lower half of the winding 7 by temporarily opening the oil switch 5. Drop of voltage during opening of the oil switches 5. 6 due to the inductance of the winding 7 may be minimized by providing the oil switches 5, 6 with back contacts connected to the corresponding halves of the winding 7 so that as each switch is opened, the half winding removed from the circuit is short-circuited. The tapping switches may be either of the sliding or rotary type and may be arranged either inside or outside the main transformer tank which may also house the auto-transformer.