GB1149709A - Line voltage regulator apparatus in x-ray systems - Google Patents

Abstract

1,149,709. Automatic voltage control. WESTINGHOUSE ELECTRIC CORP. Jan.22, 1968 [Feb.16, 1967], No.3190/68. Heading G3R. [Also in Divisions H1 and H2] In an automatic A. C. voltage regulator of the type including a transformer with a tap selector switch having a pair of jointly movable contacts which normally engage a single stationary tapping- contact on a winding of the transformer and which momentarily bridge adjacent contacts when jointly moved from one contact to another, there is provided an interlock arrangement which ensures that the movable contacts do not stop in the bridging position when a tap change is effected. As shown, a load such as an X-ray tube X is supplied from an A. C. source by way of an auto-transformer T1, a transformer T4 and a rectifier R; the primary winding of the auto-transformer T1 has tappings connected to stationary contacts 32, 33, 34 co-operable with a pair of jointly movable contacts 30 which are inter-connected by a choke coil Xl and which are driven by a reversible motor MD1. A regulating circuit RM, including a voltage divider R1-R11, a reference tube V3, thyratrons V1, V2 and relays Kl, K2, controls the motor MD1 in dependence upon fluctuations in the secondary voltage of the auto-transformer so that the contacts 30 are moved in one direction or the other in a sense to restore the secondary voltage to a predetermined value. The choke coil Xl has a centre tap connected to one side of the A. C. supply source so that the ampere-turns of the two winding halves will cancel each other when the contacts 30 are on the same stationary contact; when a tap-changing movement is effected by the motor MD1 under control of the regulator RM, however, the contacts 30 will momentarily bridge adjacent stationary contacts. In this position, the winding halves of the choke coil Xl carry unequal currents and a signal is produced in a detector winding DW electromagnetically coupled to the coil Xl ; this signal is applied to modify the action of the regulator RM to ensure that the motor MD1 will not stop while the movable contacts are in the bridging position, thus providing protection from burn-outs of the auto-transformer winding during operation of the tap selector switch. When the load is an X-ray tube as shown, it is desirable to prevent operation of the tap selector switch while an X-ray exposure is being taken, and to prevent the taking of an X-ray exposure while the tap selector switch is being operated; the relays K3 and Kt are inter-connected, as shown, with the relays K1 K2 for this interlocking function.