Abstract: An instrument for measuring cathodic protection voltage levels receives a signal representative of an externally applied, full-wave rectified power line frequency cathodic protection potential, which is subject to electrical interference. The fundamental power line frequency component and odd harmonics of that fundamental component are removed to produce a filtered signal. Selected parameters of the filtered signal are measured to provide an indication of the adequacy of the cathodic protection potential.

Abstract: An ac drive in which the three phase ac current produced by a current controlled inverter is applied to the stator winding of a synchronous or induction motor through an autotransformer equipped with a neutral shorting switch. For starting from zero speed and operation at very low speeds below the speed at which the autotransformer could provide adequate volt-seconds for operation of the motor, the neutral shorting switch is opened so that the current is applied essentially directly to the stator. At normal and high speeds, the neutral shorting switch is closed so that the voltage to the motor stator is increased by the turns ratio of the autotransformer thereby increasing the speed range of the motor. By providing a number of sets of taps on the autotransformer each with a neutral shorting switch, the ac drive mimics the characteristics of a drive with a multi-ratio gear box.

Abstract: A switching system for switching large electric currents such as those utilized in the electromagnetic launching of projectiles, includes a plurality of controllable switching elements such as solid state switching devices which are electrically connected in parallel with each other and are also electrically connected in parallel with a pair of mechanical switch contacts. Current flow through the solid state switching devices also flows through a series connected structure which utilizes electromagnetic forces generated by this current to close the mechanical contacts, thereby shorting across the solid state switching device circuit branches. This switching system can be utilized in an electromagnetic projectile launching system to conduct current between a pulse current source and a pair of projectile launching rails. Launch current flow is initiated by the switching system and the mechanical switch contacts remain closed until current is interrupted at a current zero following a projectile launch.

Abstract: A generator voltage regulator circuit is provided with a switching circuit for alternatively connecting or disconnecting a generator exciter field winding to a DC power source. A discharge circuit is provided for conducting current, produced by a collapsing magnetic field in the exciter winding following disconnection of the winding by the switching circuit, in a revese direction through the DC power source. A driving circuit controls the switching circuit with a series of turn-on pulses. Each of the turn-on pulses is initiated in response to a transition in a clock signal and is terminated alternatively when the current in the exciter field winding reaches a predetermined magnitude or when a second transition occurs in the clock signal. This invention also encompasses a method of regulating exciter field current performed by this circuit.

Abstract: An electric generating system having a discharge circuit for a DC filter capacitor includes an electric power source for producing a DC voltage on a pair of conductors and a DC filter capacitor electrically connected between the conductors. A voltage indicating signal, representative of the actual output voltage of the generator, is combined with a reference signal to obtain a control signal which varies in proportion to the difference between the desired output voltage of the power source and the actual output voltage. Power source output voltage is controlled in response to the control signal. A branch circuit with a solid state switching device is connected across the DC filter capacitor. The solid state switching device is turned on for a limited time in response to a change in the magnitude of the control signal resulting from an increase in the actual output voltage of the power source, thereby discharging the DC filter capacitor.

Abstract: A single phase rectifier circuit produces a full wave rectified voltage by rectifying an AC input voltage, couples the rectified voltage to a filter capacitor through an inductor, and repeatedly switches the sum of the rectified voltage and the voltage on the capacitor across the inductor, thereby reducing input current distortion and improving the power factor of the circuit. When the rectified voltage is of a sufficient magnitude to drive current through the inductor, switching of the capacitor voltage across the inductor can be eliminated. The switching function is performed by a half bridge boost converter.

Abstract: Remote power controllers for controlling power between an external power supply and a load include output stages including MOSFETs and a drive circuit connected to supply gate voltage of a preselected magnitude to each of the MOSFETs in response to a control signal. The magnitude of the gate voltage corresponds to a predetermined maximum drain current for each of the MOSFETs, with the maximum drain current being substantially constant over the expected operating temperature range of the power controller. An overload signal representative of excessive power dissipation in the MOSFETs is sensed and a trip signal is produced when that overload signal exceeds a threshold limit. The drive circuit responds to the trip signal to remove the gate voltage signal from the MOSFETs.

Abstract: A method of selectively isolating faulty channels in a parallel electric power system having at least two controllable AC power sources includes the steps of producing a DC content signal representative of the magnitude of DC voltage in an AC output of one of the power sources and producing a differential current signal representative of differential DC current flowing in connected phases of the power sources. The DC content and differential current signals are combined to produce an error signal which is used to control the operation of the first power source, thereby reducing the magnitude of DC voltage in its output. When the error signal exceeds a predetermined threshold level, a trip signal can be produced and used to selectively isolate a failed channel in the power system. Following isolation of the channels, the differential current signal is disabled such that the error signal is only representative of the DC content signal for split channel operation.

Abstract: An electromagnetic launcher system for small diameter high velocity penetrator projectiles and larger diameter, slower projectiles is provided with a single high current pulse power supply. At least two bores of substantially different cross section are connected to the power supply. Augmentation conductors are utilized adjacent the larger diameter bore to achieve the desired acceleration of the large diameter projectile with a smaller root mean square current than used for the acceleration of the small diameter projectile to a desired high velocity.

Abstract: An inductor assembly is provided with turns of a coil conductor that encircle a leg of a magnetic core and are insulated from the core. Each of the turns includes a portion which extends through an aperture in the core and a second portion positioned outside the aperture. The surface area per unit length of the second portions of selected turns is greater than the surface area of the portions of the turns which extend through the aperture. These portions of increased surface area are spaced apart to permit the flow of cooling medium between the turns.

Abstract: A position detector is provided with an encoded element having indicia representative of a bit pattern of a pair of bits of a Gray code and a pair of sensors responsive to this indicia. The encoded element is capable of being mechanically coupled to a movable member and the sensors are spaced apart by a distance corresponding to a shift in the bit pattern between two bits of the Gray code such that movement of the encoded element past the sensors is used to produce two bits of the Gray code. Additional encoded elements and sensors are used to produce additional bits of the Gray code.

Abstract: A rectifier assembly for use in the rotor of an electrical generator is provided with a plurality of generally disc-shaped diode packages arranged in a stack along a common axis. Radial bus bars are positioned between the diode packages and extend radially beyond the diode stack. Electrically and thermally conductive through bolts extend between a pair of end members on opposite ends of the diode stack and are electrically connected to the radial bus bars. Each of the through bolts includes a longitudinal opening for receiving cooling fluid. Selected ones of the through bolts are held in tension between the end members, thereby axially compressing the diode and radial bus bar stack. Spring terminals are provided for electrically connecting the through bolts to an external circuit and the entire assembly is conveniently packaged as a plug in module.

Abstract: A solid state power controller is provided with an output circuit having a transistor which is connected between a pair of output terminals. Base current to the transistor is provided by a drive circuit which includes a pair of series connected diodes that provide biasing to offset the drive circuit and output transistor base voltage drops. Load current is sensed and a DC bias current is supplied to the diode pair, with the DC bias current being proportional to the load current. For bi-directional operation, a second output transistor is connected in series with the first output transistor and a pair of reverse series connected diode are connected in a circuit branch which parallels the two output transistors. Junction points between the output transistors and the reverse series connected diode circuit branch are connected together to provide for bidirectional load current flow.

Abstract: An electromagnetic projectile launcher is provided with muzzle circuitry which increases the rate of dissipation of inductively stored rail energy following the launch of a projectile and can be used to recover a portion of that stored energy for use in successive launches. The muzzle circuitry includes a pair of conductors which lie adjacent to the projectile launching rails and conduct current in a direction which is opposite to the current flow in the projectile rails. These conductors may be connected to a pulse transformer to increase the post-launch current of an inductive energy storage device. In an alternative embodiment, a capacitive muzzle circuit is used to store the inductive rail energy and inject current into the projectile launching rails during the launch of a successive projectile.

Abstract: A coolant pump system for a variable speed generator includes a variable displacement pump mounted within the generator and coupled to the generator rotor such that the pump is driven at a speed proportional to the rotational speed of the generator rotor. The displacement of the pump is controlled by moving a pump stator with respect to the pump rotor. A spring positioned between the generator housing and the pump stator provides a biasing force which tends to move the pump stator in a direction that increase displacement of the pump. Back pressure in the coolant system is used to provide a force which tends to move the pump stator in a direction that decreases the pump displacement as the back pressure increases. An additional force on the pump stator which tends to further reduce pump displacement is electromagnetically controlled in response to the electrical load placed on the generator and/or the speed of the generator rotor.

Abstract: A method of compactly storing digital data includes the steps of sequentially entering a plurality of digital data entries into a shift register having a plurality of stages and summing successive groups of data entries as they are outputted from the shift register to produce singly compressed data entries that are subsequently entered into a second shift register. Sets of singly compressed data entries which are outputted from the second shift register are again added to obtain doubly compressed data entries which are entered into a third shift register. This process continues until a sufficient number of shift registers have been employed to accommodate all of the expected data entries.

Abstract: An electromagnetic projectile launcher is provided with a firing switch which alternately opens and closes to repeatedly commutate current from a high current supply to a pair of projectile launching rails. A rotor having a transverse conducting element is rotated within and moved axially along a cylindrical stator. Brush members which have widths which decrease in an axial direction along the stator are shorted by the conducting element between shots for varying lengths of time as the rotor travels axially along the stator.

Abstract: A method of determining the rate of change of frequency of a plurality of randomly occurring events begins by counting the number of random events which occur within a plurality of predetermined sampling intervals to obtain a plurality of count values, each corresponding to one of the sampling intervals. These count values are stored in a memory table and the count values which correspond to the most recent set of N of the sampling intervals is summed to obtain a first accumulated count. A second accumulated count is obtained by summing the count values which correspond to a second set of N of the sampling intervals, preceding the most recent set. The rate of change of event frequency is then calculated by dividing the logarithm of (S.sub.1 /S.sub.2) by the number N. The value of the number N is dynamically adjusted for subsequent calculations based on the incoming frequency of random events.

Abstract: An alternator for repetitive pulsing of an electromagnetic projectile launcher is provided with a stator structure having at least one pair of single layer concentric coil portions which are electrically connected in parallel. A rotating magnetic field induces a voltage in these coil portions without producing circulating currents. The alternator is connected through a switch to a pair of genrally parallel conductive projectile launching rails and a sliding conductive armature between the rails. By causing the switch to conduct at a predetermined phase angle, the voltage across the launching rails can be reduced to zero as the projectile leaves the rails. Where a succession of projectiles is to be fired, the phase angle at which the switch begins to conduct is controlled in order to achieve a substantially constant muzzle velocity for each projectile while minimizing the rail voltage as each projectile exits the rails.

Abstract: A bi-directional DC power controller is provided with a bi-directional DC switch connected between a pair of terminals for connection to a pair of line power conductors. A first difference amplifier is connected to receive voltages at these terminals and to produce an output voltage signal which is proportional to the difference in voltages between these terminals when the voltage at one of the terminals is greater than the voltage at the other terminal, and is constant when the voltage at the second terminal is greater than the voltage at the first terminal. A second differential amplifier also receives voltage signals from these terminals and produces an output voltage signal which is proportional to the difference in voltages between the terminals when the voltage at the second terminal is greater than the voltage at the first terminal, and which is constant when the voltage at the first terminal is greater than the voltage at the second terminal.