Abstract: A method and apparatus for generating gating signals for each of a plurality of electric switching devices in electric power conversion circuit includes a microcomputer for computing timing data representative of a relative time for application of gating signals to each of the switching devices for generating a desired electric power output from the conversion circuit. The timing data is provided to a volatile memory which has a plurality of addressable memory locations in which each memory location address corresponds to a selected time increment. Timing signals are generated in an address format for the memory such that each of the timing signals addresses a unique memory location in the memory. The gating signals for the switching devices are stored in memory locations in the memory corresponding to the time with respect to a starting point at which it is desired to have the gating signals generated.

Abstract: A device in which a processor controls a desired frequency and a desired instantaneous angle of a pattern generation circuit. The processor also controls a desired amplitude of the system. The pattern generation circuit includes a ROM having firing data for only a portion of the angles for which the circuit produces output. Output for the angles stored in the PROM and for the remaining angles is generated using the partial data from the PROM. The processor selects the desired voltage levels of the motor output, and can instantaneously set an angle of the output.

Abstract: Apparatus and method for auto-self testing of a power converter and motor system wherein the power converter has three parallel legs, each including two series connected gate-turn-off thyristors (GTO) connected between a pair of DC power source buses. A microprocessor controls the test sequence in which each GTO is individually turned on in a predetermined order so as to create a transient snubber current through the motor and through each GTO when it is turned on. The snubber current and a voltage in each leg is measured and compared to a respective reference to detect wiring errors, and defects in the motor, the GTOs, and other system components. Error messages are generated in response to detection of abnormalities or defects.

Abstract: An electric propulsion system for a traction vehicle includes a controllable power converter operable in either a propulsion or an electric braking mode in which power is withdrawn from a wayside source or returned to the source, respectively. The wayside source utilizes certain preselected frequencies for power generation and for signaling. It is desirable to detect these frequencies quickly and to be able to disconnect the vehicle from the source if some frequencies are being generated by the vehicle and others are not present on the system. Bandpass filters are coupled to the power converter to detect the preselected frequencies. Wayside transients sometimes encroach on these frequencies with large power spikes causing ringing of the filter circuits and delay in detecting the preselected frequencies. The system includes an active power limiter for limiting the peak amplitude of the signals coupled to the filters without interfering with the signal frequency content or affecting filter operation.

Abstract: Apparatus and method for auto-self testing of a power converter and motor system wherein the power converter has three parallel legs, each including two series connected gate-turn-off thyristors (GTO) connected between a pair of DC power source buses. A microprocessor controls the test sequence in which each GTO is individually turned on in a predetermined order so as to create a transient snubber current through the motor and through each GTO when it is turned on. The snubber current and a voltage in each leg is measured and compared to a respective reference to detect wiring errors, and defects in the motor, the GTOs, and other system components. Error messages are generated in response to detection of abnormalities or defects.

Abstract: A method and system for calibration of a primary signal processing path without interruption of signal processing utilizes a calibration signal processing path which is periodically used to process a signal concurrently with processing in the primary path. Any difference is compensated by gain adjustment in the primary path. In one form, a plurality of primary paths are sequentially compared with a calibrated path. The calibrated path is periodically checked using a precision reference and any error is corrected before comparison of the primary paths.

Abstract: A method and apparatus for controlling an inverter circuit to convert dc voltage to variable amplitude and frequency ac voltage use firing pattern tables which are stored and selected in accordance with a required voltage level for the ac voltage. The firing pattern tables are accessed by writable timers which both address the firing pattern tables and define the times between readout of consecutive entires of the firing pattern tables. If requirements of the ac voltage being produced are changed, a new firing pattern table is selected at the end of the currently selected pattern table. Further, as the required frequency of the ac voltage being produced changes during the readout of a selected firing pattern table, the times written into the writable timers are changed accordingly to vary the frequency of the ac signal on the fly. Angle tables corresponding to the pattern tables are stored and accessed by a control processor to determine the times written into the timers.

Abstract: In an electric power converter comprising at least one pair of serially-connected, alternately conducting controllable electric valves spanning a pair of d-c conductors, the conducting state of each valve is detected by comparing the actual magnitude of valve current with a predetermined low threshold level and by comparing the difference between the juncture potential of the two valves and a reference potential of one of the d-c conductors with the potential diffence between both d-c conductors. If both comparisons indicate the valve is in a conducting state and if this state is indicted concurrently for both valves, logic means is operative to indicate that a "shoot through" fault has occurred. In this abnormal event, whatever turn on and turn off signals for the two valves were extant at the time such operation of the logic means commenced will be prevented from changing while both valves are conducting.

Abstract: A variable speed 3-phase a-c motor is connected to a 3-phase source of alternating voltage via a plurality of controllable solid state electric valves which are so arranged and controlled that motor speed can be reduced by skipping selected cycles of the source voltage. For half speed operation 12 valves are arranged to interconnect the source and motor phases, and over two consecutive periods of the source voltage six separate, uniformly spaced "firing windows" are selected during which the conducting states of different pairs of these valves are initiated in a predetermined pattern that results, in each phase of the motor, in a double-pulse current waveform having one-half the fundamental frequency of the source voltage.

Abstract: For starting a rotatable 3-phase a-c electrical machine of the synchronous type, the stator windings of the machine are connected to an electric storage battery via a controllable electric power converter, and the d-c field winding is connected in series with the stator windings by inserting it in the load current path between the converter and battery. Field weakening resistance is connected in parallel with the field winding. The converter includes a plurality of electric valves (thyristors) that are cyclically turned on in a predetermined sequence in synchronism with alternating voltages developed at the line terminals of the stator windings.

Abstract: In a 3-phase third harmonic auxiliary impulse commutated electric power inverter the d-c terminals of which are connected, via a circuit having appreciable electrical inductance, to a voltage source comprising a battery, the commutation capacitor is precharged by cyclically manipulting the conducting periods of selected main and auxiliary valves of the inverter so that a series of discrete pulses of capacitor charging current flow from the battery through a path comprising the aforesaid circuit, part of the inverter load circuit, and the capacitor, with alternate pulses of current traversing the capacitor in one direction and intermediate pulses traversing it in the opposite direction. Such action continues for a sufficient number of cycles to "ring up" the capacitor to a voltage magnitude more than five times higher than the battery voltage.

Abstract: In a 3-phase third harmonic auxiliary impulse commutated electric power inverter, during a commutation interval the firing signal for the oncoming main valve of the inverter is delayed for a programmed interval of fixed duration after the commutation capacitor voltage changes polarity, whereby the peak voltage on the capacitor can automatically vary with the magnitude of load current.

Abstract: A variable speed 3-phase a-c motor is connected via a plurality of controllable bidirectional switches to a 3-phase source of alternating voltage having a variable fundamental frequency (f) and an rms magnitude (v) that varies with f, and the switches are suitably arranged and controlled so that motor speed can be reduced by skipping selected cycles of the source voltage. When operating at a fraction of full speed, the magnitude-to-frequency ratio of motor voltage is maintained substantially the same as at full speed by varying the "firing angle" at which the switches start conducting current so as to minimize any deviation of the rms magnitude of the motor voltage from the product of v times said fraction.

Abstract: A variable speed 3-phase a-c motor is connected to a 3-phase source of alternating voltage via five controllable bidirectional solid state switches which are so arranged and controlled that motor speed can be reduced by skipping selected cycles of the source voltage. For example, for half speed operation three of the switches are arranged respectively to connect phases A, B and C of the source to phases A, C and B of the motor, and over two consecutive periods of the source voltage three separate, uniformly spaced "firing windows" are selected during which the conducting states of these switches are initiated in a predetermined pattern that results in the phase A-to-phase B source voltage being applied to the motor during the first window, the phase C-to-phase A source voltage being applied during the next window, and the phase B-to-phase C source voltage being applied during the last window.

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: 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: Apparatus for providing firing signals to a phase controlled rectifier circuit at a time at which valves in the rectifier circuit are forward biased without the need for providing continuous firing signals. The apparatus monitors the voltage applied across the rectifier valves and provides a signal when a valve is forward biased. This signal is applid to a gating circuit which determines whether a normal phase control firing command was initiated prior to the time the valve became forward biased. If such a command was initiated, the gating circuit passes the signal to a valve firing circuit which provides firing signals to the rectifier circuit. If the firing command was not previously initiated, the signal is inhibited and firing signals are subsequently applied to the rectifier circuit upon receipt of a firing command.