AUTOMATIC CONTROLLER FOR MAGNETIC JACK TYPE CONTROL ROD DRIVE MECHANISM

Apparatus and method are disclosed for continually generating data values (M) indicative of the time dependent waveform of the current (I.sub.C) in a control rod latch actuation circuit (28), during application of a pulsed drive voltage (30). A data value is selected that represents a value limit (M.sub.min) characteristic of the waveform during the time before the latch (14) has reached a critical position of interest. The most recently generated data value (M.sub.N) is compared to the value limit (M.sub.min), and a control signal (e.g., 74, 52, LH) is generated when the most recently generated data value (M.sub.N) exceeds the value limit (M.sub.min). The data values (M) preferably indicate the time derivative of the waveform (I.sub.C) at a plurality of predetermined times during application of the drive voltage. Latch movement to the critical position is indicated when the algebraic value of the waveform time derivative exceeds, by a predetermined setpoint, the minimum algebraic value computed at regular time intervals during application of the drive voltage.