GB961926A - Improvements in and relating to control means for electric motors - Google Patents

Abstract

961, 926. Electric selective signalling systems; controlling reactors. SPERRY GYROSCOPE CO. Ltd. July 15, 1960 [July 25, 1959], No. 25594/59. Headings G4H and G6C. A step-by-step motor driving the control rod of a nuclear reactor has stator windings W1, W2, W3, each controlled by a transistor T1, T2, or T3 having its base connected to the emitter of an auxiliary transistor T1A, T2A, or T3A. The auxiliary transistors are controlled from a ring circuit 3 comprising transistors T4, T5, T6, which are interconnected so that a control pulse from diode D1 causes a control potential to be applied to one of the auxiliary transistors, a succeeding control pulse causing the potential to be transferred to another auxiliary transistor. The opening of switch SW1 enables the windings W1, W2, to be energized with a steady current for retaining the motor in a stable position. The ring circuit is formed by coupling the collector of each transistor to the bases of the other transistors. Thus, the coupling between transistors T4, T5, is made through pulse-shaping network R16, C1, whilst the coupling to transistor T6 is through resistor R17. The pulses from diode D1 are derived from A.C. source 4, 5 through squaring device 6 and frequency divider 7. The control rod is support by a tape wound on a drum which is driven by the motor through gearing and a flexible coupling. An additional motor is adapted to over-ride the stepby-step motor for rapid movement of the rod, Fig. 2 (not shown). A nuclear reactor has three control rods, each provided with a step-by-step motor associated with transistors controlled from two ring circuits selectively. The two ring circuits each provide control potentials in a different sequence for raising or lowering the rods, the operation of each ring circuit being controlled by an oscillator, Fig. 3 (not shown). Alternatively, one ring circuit only may be used, with a switch to provide the control potentials in the desired sequence. The oscillators may have variable frequency for variable speed control of the motors.