Abstract: A control system, for a motor which may be subjected to stalling loads, provides a non-linear increase in motor current during stalling conditions to maintain rated horsepower. When the maximum transient overload current is reached, this current is maintained to keep the motor torque at a maximum until the motor is stalled. This provides maximum motor torque down to a stalled condition and resists stalling. A limit controller determines the maximum time a particular overload motor current can be maintained and when this time has passed the motor current is reduced to rated current. If the motor should stall completely a further reduction in motor current is made automatically.

Abstract: A modular arrangement of DC to DC Power conversion units which permits variation of power handling capability without changing the power control system. The conversion units of the stagger-mode type including two pulse width modulated converter sub-units are separated into two individually powered and controlled units. First units of all converters are connected in one series string across a power source and similarly the second units of all converters are connected in a second series string across the power source. Each unit has a capacitor connected across its power input terminals so that the source voltage is evenly divided between converters. With this configuration only one converter need have its current monitored in order to balance the current between the two strings of converter units. The system includes current and voltage protection features appropriate to a high current and high voltage environment.

Abstract: A plurality of stationary markers (A, B, C, and D) are symmetrically placed at predetermined locations in the right of way of an electrically propelled traction vehicle on opposite sides of a transition point coinciding with a gap (14) between adjacent sections (13a, 13b) of a wayside conductor. Proximity sensing means (PSR, PSL) on the vehicle provide discrete output signals on a first line (43) upon passing the first and third markers (A and C) and on a second line (44) upon passing the second and fourth markers (B and D). Receiver logic means (42) includes means (108, 111-115, and 118-127), responsive to the output signals on the first and second lines, respectively, for producing a first control signal (on line 51) during the first-to-third marker interval and a second control signal (on line 50) during the second-to-third marker interval.

Abstract: An improved automatic control system for a train of transit vehicles which regulates the velocity of the train and its braking rate in accordance with a predetermined velocity/distance profile. The system includes apparatus for compensating for variations in wheel diameter and train length in such a manner as to assure that the center of the train regularly stops at a predetermined point with respect to a desired station stopping point. On board receivers are responsive to wayside signal devices for establishing the operating velocity of the vehicle and for initiating entry into the predetermined braking profile. Since vehicle control is effected by wayside signal devices, the distance between stopping points may be indefinite. The system includes apparatus which permits passing selected stopping points when desired.

Abstract: A self-propelled traction vehicle equipped with an a-c traction motor energized by the a-c output of a controlled current inverter is propelled by a process comprising the steps of providing a traction alternator on-board the vehicle, rotating the rotor of the alternator, exciting the field winding of the alternator, converting the output current of the armature windings of the alternator to a unidirectional current, and feeding the unidirectional current to d-c terminals of the controlled current inverter without appreciably smoothing the unidirectional current. A system for carrying out this process is also disclosed.

Abstract: A propulsion system for an electrically driven traction vehicle includes a chopper, a d-c traction motor, and means effective when the system is operating in a motoring mode for connecting the chopper in series with the armature and the field windings of the motor to a d-c electric power source that includes a filter capacitor. Cyclically operative means provides periodic gating signals for alternately turning on and turning off the chopper, and it can be smoothly changed from a constant frequency, variable pulse width mode to a variable frequency, constant (minimum) off time mode so as to vary the "duty factor" of the chopper over a wide range extending up to 100 percent on time. Brake set up means is operative in response to a motoring-to-braking command for reconnecting the chopper in parallel with the motor and the filter capacitor and for reversing the polarity of the connection of the series field winding relative to the armature.

Abstract: Apparatus for controlling the voltage on a commutating capacitor in a thyristor time ratio control power circuit whereby the energy stored in the capacitor may be continuously adjusted to a magnitude required for commutation so that the size of the commutating circuit can be significantly reduced. An inductive circuit is provided in a charging current path for the capacitor so that the capacitor can be charged above available source voltage by capacitive/inductive action. A controllable switch connected in parallel with the inductive circuit provides a short-circuit path for terminating charging of the capacitor. A logic circuit monitors capacitor voltage, source voltage and load current and closes the controllable switch when the capacitor voltage reaches a magnitude established by the logic circuit as sufficient to commutate the measured magnitude of load current.

Abstract: A combination of integrating and logic means in an electrical circuit responds to inputs from a variable analog control signal and from a constant frequency train of digital pulses. The magnitude of the control signal is variable between predetermined low and high extremes. The logic means periodically generates discrete output signals in synchronism with the digital pulses. When the control signal is lower than a predetermined intermediate magnitude, the integrating means is saturated and the logic means is able to produce the output signals at a constant frequency. When the control signal is between its intermediate and high extreme magnitude, the integrator is active and governs the operation of the logic means in such a manner that the average frequency of the output signals varies between its constant magnitude and zero as an inverse linear function of the control signal magnitude.

Abstract: A pulse shaping and amplifying circuit is formed by connecting a capacitor in series with the primary winding of a pulse transformer, connecting normally open switching means in parallel with the capacitor and primary winding, and connecting this parallel combination through a series inductor to a source of d-c control power, whereby the capacitor accumulates a charge from the control power source and then, during periods when the switching means is closed, discharges through the switching means and the primary winding. During its closed periods the switching means also conducts current from the control power source through the inductor, but when the switching means is opened the current in the inductor is transferred to the capacitor and the primary winding and thereby assists recharging of the capacitor.

Abstract: An a-c induction motor powered from an adjustable frequency and adjustable magnitude power source is provided with a feedback control system whose gain is varied as a function of the magnitude of flux developed in the motor in order to normalize system response throughout the motor operating range. The control system is a two-loop system in which one loop adjusts excitation frequency and the other loop adjusts excitation magnitude with the excitation frequency loop being responsive to a torque command signal and a torque feedback signal to generate an error signal which is utilized to adjust the excitation frequency of the power source. System gain is varied by modifying the error signal as a function of the magnitude of flux developed in the motor. Preferably this modification is performed by dividing the error signal by a signal representative of the magnitude of motor flux.

Abstract: For detecting electrical overloads in a traction vehicle propulsion system wherein the output of a prime mover-driven electric generator is controlled by varying the on-off duty cycle of an intermittently conductive switch connected in series with a field winding of the generator excitation means, monitoring means is connected across the field switch to produce an output signal in response to the field switch being continuously conductive for an abnormally long period of time which is indicative of an over-excited condition.

Abstract: The axial gap between the rotatable hub of a locomotive wheel and the relatively stationary thrust flange of an adjacent axle bearing is covered by a dust guard comprising an annular band of elastomeric material firmly secured to the circumference of the thrust flange and having a portion that overlaps the wheel hub. On the inside circumference of the overlapping portion of the annular band there is attached a narrow felt tape that slidingly engages the perimeter of the rotatable wheel hub to form a seal therewith, and the overlapping portion is encircled by a large-diameter hose clamp that enables a desired amount of radial pressure to be applied substantially uniformly around the felt tape.

Abstract: A locomotive is provided with an enlarged cab having "split level" sections for accommodating the engineer and other members of the train crew. A first upper section includes seating space for the engineer adjacent to the console with good visibility to the front and back, the engineer's line of sight being above the crew members in a lower section of the cab, and on the opposite side of the cab there is an additional upper section that provides an operating station for the engineer's assistant. In the lower section of the cab seating space is provided for at least one crew member. A writing surface (for performing clerical work) adjacent to seating space for the train conductor, with external visibility along a line of sight parallel to the sides of the railroad cars being propelled by the locomotive, is provided either in the lower section or in the additional upper section of the cab.

Abstract: To detect a d-c component of alternating current in the primary winding of an electric power transformer, a pair of current transducers are provided. Each current transducer has a saturable core adapted to be magnetized by the same current as flows in the transformer primary winding, and bias means associated with both transducers presaturate their respective cores in opposite directions by equal predetermined amounts of magnetomotive force. Secondary windings on the cores of the respective current transducers are connected to means for deriving an output signal in response to voltage induced in one but not both of the secondary windings as a result of alternating current containing a d-c component in the power transformer if such current has sufficient magnitude to unsaturate the core of one of the current transducers, a condition typifying the surge of inrush magnetizing current that flows in the transformer primary when initially energized.

Abstract: A shorted diode in an array of parallel diodes is detected by connecting between normally equipotential points in each pair of adjacent branch circuits of the array an inexpensive indicating device comprising signaling means for visually indicating that a malfunction has occurred if appreciable current flows in an associated resistor. The signaling means comprises heat sensitive material that changes appearance when its temperature is raised to a predetermined high degree by the heat generated in the resistor when current flows between the aforesaid connection points due to the potential difference that develops therebetween as a result of a diode failing shorted.

Abstract: A brushholder is adapted to be secured to the frame of a dynamoelectric machine by means of either insulated steel studs or resin-bonded fiber glass studs. The frame of the brushholder contains at least two holes which are spaced apart and in parallel. Each hole is adapted to receive one end of the steel stud as an interference fit or one end of the fiber glass stud as a clearance fit. An adhesive is used to bond the fiber glass stud in the hole. The wall surface defining the hole contains groove means which helps key the adhesive to the surface but does not detract significantly from the interference fit of the steel stud.

Abstract: For use with an adjustable speed a-c electric motor comprising a stator having effective direct and quadrature axes and a rotor spaced from the stator by a gap, said stator including windings adapted to be connected to a source of excitation of variable frequency and amplitude, a scheme is provided that comprises means for deriving a "torque angle" feedback signal representative of the phase angle between current and flux that interact in the motor to develop electromagnetic torque tending to move the rotor relative to the stator, in combination with means responsive to the torque angle feedback signal for controlling the source of excitation so as to control the frequency of stator excitation as a function of the torque angle feedback signal. In one aspect of the invention, means is provided for controlling the source of excitation so as to control the amplitude of stator excitation as a function of a variable command signal that is prevented from deviating below a predetermined limit.

Abstract: For use with an adjustable speed a-c electric motor having a stator adapted to be coupled to a source of variable frequency excitation and a rotor in which torque is developed when the motor is excited, the strength of said torque being dependent on interacting current and flux in the motor, a scheme is provided that comprises means for deriving an angle feedback signal representative of the actual phase angle between the aforesaid current and flux and means responsive to said angle feedback signal for controlling the source of variable frequency excitation so as to control the frequency of stator excitation as a function of the angle feedback signal.

Abstract: A reactor winding in the form of a high current, multi-turn, multi-layer insulated coil stack embracing an inner member of a magnetizable core assembly of a reactor is resiliently supported by the outer member of the core assembly by inserting a plurality of ripple spring sheets of non-magnetic material between the outer member and selected adjacent surfaces of the outer periphery of the windings. The inner core member is resiliently supported within the coil stack by an additional plurality of ripple spring sheets disposed between adjacent surfaces of the coil stack and inner core member. Ripple spring sheets are also positioned between adjacent surfaces of the inner and outer core members. The ripple spring sheets are preferably disposed between flat side sheets to provide uniform distribution of the spring forces.

Abstract: Alternating voltage for energizing an adjustable speed a-c motor is derived from unipolarity input voltage by means of electric power inverting apparatus comprising at least one pair of alternately conducting controllable electric valves. The conducting states of these valves are periodically switched by control means responsive to frequency and amplitude command signals, whereby the frequency and the amplitude of the fundamental component of the alternating voltage are varied as functions of the respective command signals. The control means includes means for implementing a triangle interception mode of pulse width modulation (PWM) of the alternating voltage so long as the amplitude command signal does not exceed a predetermined reference value (which is less than 1.