Patent GB-1250292-A (GB)
IPC: G05F1/455
Filed: 1970-03-31
Abstract: 1,250,292. Control systems for consuming apparatus. BROWN BOVERI & CO. Ltd. 31 March, 1970 [2 April, 1969], No. 15267/70. Heading H2H. [Also in Division G3] Apparatus for continuously varying the A.C. voltage supplied to a load by way of a quadripole network has one terminal of an A.C. source connected to one of the quadripole input terminals by means of a pair of anti-parallel controlled rectifiers, the same A.C. source terminal also being connected by a further pair of antiparallel controlled rectifiers, to a tapping on a voltage divider connected across the input terminals of the quadripole network. An oscillatory load LC, such as a betatron, is supplied from an A.C. source U by way of a quadripole network in the form of a transformer Tr, the primary winding of which constitutes a voltage divider connected across the quadripole input terminals. One of the terminals of the source U is connected to one of the terminals of the primary winding by anti-parallel thyristors T 1 , T 3 , and by anti-parallel thyristors T 2 , T 4  to a tapping on the primary winding of the transformer Tr. In operation the betatron is energized in three phases, in the first two of which the voltage applied thereto is gradually increased and in the third phase the applied voltage is maintained constant'at a desired value. The first operational phase is initiated application of a signal E in  which enables registers S 1 , S 6 , starts a timing clock pulse generator TG and a function generator FG which latter generator produces a rising voltage signal U ST . The signal U ST  is fed to pulse generators W 5  (the cross hatched element being duplicated) to develop output pulses A, B which are in antiphase to one another. These pulses are supplied to a register S 5 , at this time inhibited, and to an AND gate 14 thereby to control thyristors T 1 , T 3  by way of OR gates 15, AND gates 1, amplifiers 2, transformers 3 and rectifiers 4 so as to conduct for increasing periods. When a certain current value is sensed by a current transformer W 1  a Schmidt trigger G 1  is operated which stops the operation of the function generator FG, full conduction of the thyristors T 1 , T 3  being maintained however by a monostable delay circuit t 1  for a predetermined time, say 50 m. sees. At the end of this time t 1  resets and the function generator FG restarts to begin the second operational stage of the betatron. The function generator again develops a rising voltage signal U ST  which produces antiphase signals AB as before. During this phase the register S 5  is enabled so that the signals A, B control both pairs of thyristors T 2 , T 4  and T 1 , T 3  in a firing order T 1 -T 2 -T 3 -T 4  under control of a voltage limiter P responsive to signals generated by a current transformer W 2 . When the load current of the betatron reaches, say 95% of its full value, the signal from a current transformer W 3  triggers a Schmidt circuit C 2  which by way of a register S 6  stops the function generator FG, and by way of an AND circuit 13 enables the W 3  signal to be compared with a set value signal SW in an amplifier device R, the error signal from which is fed to the pulse generator W 5  thus to control the thyristors T 1 -T 4  to produce a constant voltage at the betatron terminals.