Abstract: SCR devices replace the usual diodes of the rectifier bridge section of a wound-rotor slip-recovery system motor drive, and by selection of the retardation angle of the SCR's between either zero or close to 180.degree., two-quadrant operation is made possible, which includes reverse torque and reverse rotation, while controlling the retardation angle of the power line bridge of SCR's.

Abstract: SCR devices replace the usual diodes of the rectifier bridge section of a wound-rotor slip-recovery system motor drive. By controlling the retardation angle of the SCR devices while controlling the line bridge for acceleration from zero speed to normal speed, the rating of the overall system is reduced. By removing the gating signal of the SCR's while operating at a retardation angle in the range between zero and 90.degree., operation is immediately brought to a stop in case of an emergency.

Abstract: Two inverters in series in the DC line of a slip-recovery motor drive of the SCR controlled type are asymmetrically controlled to allow reduced current reflected back in the transformer. Two secondaries in the transformer are associated with the respective inverters. Reduced rating of the transformer, reduced saturable reactor in the DC link and improved power factor are direct advantages of such arrangement.

Abstract: A slip-recovery AC motor drive includes two inverters connected in series between the DC link terminals derived from the rectifier coupled with the rotor, and the thyristors are controlled asymmetrically between pairs of half-bridges pertaining to different inverters, thereby to by-pass the output of one inverter alternately during successive equal time intervals of conduction. The recovery transformer has two secondaries each connected to a corresponding inverter output.

Abstract: An analog automatic slowdown control system is described for determining the optimum instant of time to initiate slowdown, for a process line in which a coil of material is being unwound from a mandrel at a linear speed. Using the intelligence derived from the linear speed and the speed of the unwind reel, signals are derived for: the instantaneous diameter, the desired remaining portion of the diameter after stopping, and the change in diameter during deceleration. These three signals are algebraically summed with a signal which is a function of the mandrel diameter, and when the summation is zero, slowdown is initiated.

Abstract: A speed control system is disclosed for driving a motor at .omega. radians per second for the purpose of rolling material in a hollow cylindrical form with preselected outside and inside diameter OD and ID respectively. The material to be rolled is fed to the coiler at a linear speed s. An integrator having dual polarity inputs delivers an output .omega./s. A detector has inputs connected to receive a signal which is a function of the preselected diameters OD and ID respectively and the integrated output .omega./s, and an output connected to the dual polarity integrator inputs for selectively and successively activating one of the dual inputs for determining the direction of integration. A multiplier receives the integrated output and delivers multiplied products .omega..sup.2 /s .sup.2 .omega..sup.3 /s.sup.2, .omega..sup.4 /s.sup.2. A signal shaper receives these multiplied products and delivers new products a.omega..sup.2 /s.sup.2, b.omega..sup.3 /s.sup.2, and c.omega..sup.4 /s.sup.