Abstract: A subsynchronous resonance mitigation system, including a method and apparatus, for damping undesirable subsynchronous resonance oscillations in a generator, which, if left unchecked, may damage the shafts of a turbine-generator set. A remote coupling apparatus, such as a thyristor controlled series capacitor (TCSC) system, a sourced inverter device, or a static phase shifter, is coupled to the generator by a transmission line. In response to a firing command, the coupling apparatus introduces subsynchronous resonance mitigating currents into the transmission line. Sensors monitor power line parameters and/or the generator speed, and in response thereto, a higher-level controller generates a voltage command. A vernier controller responds to the monitored power line parameters and the voltage command to provide the firing command to the coupling apparatus.

Abstract: Current converters of a high-voltage d.c. transmission system or other current-converter installations often require control loops for several controlled variables. Only one control loop thereby determines the delay angle, while the other control loops must be held ready to override this control loop in case of rapid changes in the operating state. According to the invention, the system deviations of all controlled variables are in fact acquired, and the controller parameters of a pre-programmed, general controlling structure are made available for each controlled variable. However, only one controller is available that has the preprogrammed, general controlling structure. This controller is always operative; however, it only interferes in the minimum value or the maximum value of the system deviations and, in each case, uses the controller parameters, which belong to the control loop activated at any one time.

Abstract: A voltage-to-current converter in MOS technology includes a signal resistor formed by a channel of a MOS signal transistor (11, 12, 13, 14) with a source electrode and a drain electrode which form terminals of the channel. A gate electrode is provided for connecting a gate voltage (V.sub.g) for adjusting the resistance of the channel and a bulk electrode is provided for connecting a bulk voltage (V.sub.b), and a supply is provided for supplying source, drain, gate and bulk voltages to the electrodes, for non-saturated operation of the signal transistor. The supply includes control circuitry (30) for controlling the bulk voltage in response to the gate voltage. Consequently, the third-order distortion of the voltage-to-current converter is reduced.

Abstract: A dynamic braking system resistor for stabilizing a power system during power system disturbances includes a braking resistor for coupling with a power system bus. A controller monitors a power system parameter, such as the speed of a generator coupled with the power system bus, and determine therefrom a thyristor control signal. The controller uses the power system parameter to establish a desired modulation and then provides a bias to the desired modulation. The controller conditions the biased desired modulation signal to provide the thyristor control signal. A thyristor valve responsive to the thyristor control signal couples the braking resistor with a ground potential. A method is also provided of damping subsequent oscillations on a power system following a power system disturbance using the dynamic braking resistor.

Abstract: A power converter apparatus for an electric train, including at least a first modular power converter unit having a main circuit formed of switch for interrupting power from a D.C. power source, a first D.C.-A.C. power converter connected to the switch, an isolation transformer connected between the D.C.-A.C. power converter and a rectifier and a second D.C.-A.C. power converter connected to the rectifier. The switch and the first D.C.-A.C. power converter are controlled by a control signal derived from the difference between the output voltage of the first D.C.-A.C. power converter and the sum of a delayed soft starting control signal and a settable reference signal. The second D.C.-A.C. power converter is pulse width modulated. Preferably a second modular power converter unit having the same construction as the first unit is provided and has inputs connected in series or in parallel with inputs of the first unit.

Abstract: When dimensioning electrical plants for high voltages for regions exposed to earthquakes, it is necessary to design the current paths between the different apparatuses in such a way that the apparatuses in case of great oscillations are not subjected to abnormally great forces at the points of connection. The problem arises particularly in connection with convertor plants for high-voltage direct current designed with suspended valves, since the oscillating amplitudes there may become considerable. The invention relates to a current path intended for such plants, which is flexible its longitudinal direction and comprises at least two parallel, non-insulated straight conductors which are each connected to a respective end of the current path and electrically interconnectd via roller contact elements, the contact force of which is individually resilient.

Abstract: A high dynamic performance, DC-DC converter system with time sharing cont is described, comprising at least one main control circuit loop for a direct output voltage and at least one further circuit loop for a direct output average current which is internal to the main control loop, the voltage and current loops acting onto two autonomous circuit loops having first order transfer functions.

Abstract: A circuit structure is described for a switched-mode DC-DC converter to eliminate the degrading effect of magnetization current on sensed load current, by forming the power transformer with an additional winding, other than its usual primary and secondary windings. The additional winding is coupled magnetically with the power transformer to obtain a voltage proportional to the voltage on the primary of the power transformer, but the additional winding is connected electrically in series with the secondary winding of a current-sensing transformer. A current-sensing circuit is described that includes the additional winding and the current-sensing transformer in order to effectively eliminate the effects of the magnetization current from the sensed load current.

Abstract: A method for controlling a power converter and an associated auxiliary commutation circuit ensures soft-switching of all switching devices employed therein. Such a power converter includes an inverter with at least two main switching devices per phase. Across each main switching device are connected an antiparallel diode and a relatively large snubber capacitor. The auxiliary resonant commutation circuit comprises two antiparallel-coupled auxiliary switching devices coupled in series with a resonant circuit including an inductor and the snubber capacitors. The gating and conduction times of the main and auxiliary switching devices are controlled so as to add boosting energy to the resonant operation, thus ensuring that the inverter output voltage at least reaches the positive and negative inverter rail voltages during each resonant commutation cycle. As a result, the control achieves commutation of the converter pole with substantially no switching losses.

Abstract: A process for supplying a current consumer with current from an accumulator for electrical energy, in which electrical energy pulses of very short duration each are supplied to the current consumer from a superconducting accumulator (2) made with superconductors (8) of very small diameter or very small layer thickness. The superconductors (8) are preferably high-temperature superconductors.

Abstract: In an inverter-type power supply, a self-oscillating full-bridge inverter is powered by unfiltered full-wave-rectified 120 Volt/60 Hz power line voltage and controllably triggered into oscillation each half-cycle of the power line voltage by way of triggering two of the bridge's four transistors into conduction simultaneously. This is accomplished by way of discharging a charged-up capacitor by way of a Diac through a special trigger winding on each of two saturable current feedback transformers; each of which controls a pair of the bridge transistors.

Abstract: A circuit (20, 40, 50, 60) for generating an optimal compensating ramp voltage signal V.sub.cramp, with the minimum necessary slope, m.sub.c for a current mode DC/DC converter is shown. The adaptive compensating ramp generating circuit (20) is comprised of two voltage dividers (22, 24), the first voltage divider 22 divides an input voltage V.sub.IN and the second voltage divider 24 divides an output voltage V.sub.OUT. The first voltage divider (22) has two resistors (26, 28) in series: the first resistor (26) has a resistance of (1/B-1) * R ohms and the second resistor (28) has a resistance of R ohms. V.sub.OUT is divided by the second voltage divider (24) having two resistors (29, 30) in series: the first resistor (29) has a resistance of (1/A-1) * R ohms and the second resistor (30) has a resistance of R ohms. The constants A, B, and C are selected for the particular type of DC/DC converter employed. The divided voltages A * V.sub.OUT and B * V.sub.IN are input into a voltage controlled current source (32).

Abstract: A synchronous rectifier circuit employs therein a pair of synchronously-operated switches, each switch being coupled between a separate respective input terminal and an output terminal of the circuit. One of the synchronously-operated switches is gated ON when a voltage applied across the synchronous rectifier circuit input terminals is of one polarity, and is gated OFF when current therein becomes substantially zero. The second switch is gated ON when a voltage applied across the input terminals is of the opposite polarity, and is gated OFF when current therein becomes substantially zero.

Abstract: The invention is to provide a more economical and practical multi-channel inverter with reference particularly to a modulation process of the time width, wherein a DC output is fed to each of a multiplicity of output channel circuits through time division to a multi-channeling, each of the time widths is modulated pertinently according to each output, thereby obtaining DC and AC multi-channel outputs independently of each other between said channels.

Abstract: A resonant power converter has a plurality of transformers, each having a primary winding and a secondary winding coupled thereto; the primary windings of all of the plurality of transformers are connected in series. The plurality of transformer secondary circuits are effectively connected in parallel, for current addition. a relatively small portion of the resonance capacitor is placed across each primary winding to insure a low impedance which causes the secondary-winding-connected rectifiers to commutatively switch substantially independently and share the entire output current substantially equally. A plurality of lower power transformers are thus utilized to replace a single high power transformer, so that leakage inductance is reduced and a higher operating frequency can be maintained.

Abstract: A microfilm reader-printer including an image formation device having an image baring roll, a charger, an exposure apparatus, an apparatus which carries out the normal development of the image bearing roll, an apparatus which carries out the inverted development of the image bearing roll, and an apparatus which transfers the toner image which is formed on the image bearer. The reader-printer further includes a switch which specifies the size of the recording paper, an exposure shutter device, and a microcomputer. The microcomputer directs forming a toner image only in a region on the image bearer that can be transferred to the recording paper, in accordance with the size of the recording paper that is detected by a detector, in such a way as to control, in the case of the inverted development, the opening and closing of the exposure shutter device, and to control, in the case of the normal development, the charger.

Abstract: An apparatus for controlling power conversion from alternating current (A.C.) to direct current (D.C.) by a converter has a D.C. voltage detector connected to receive a D.C. output of the converter for detecting the D.C. side voltage of the converter, a phase detector connected to an A.C. power source for detecting the phase of the A.C. power source, and calculating means for making a first calculation of a first current command value based on the output of the D.C. voltage detector, a second calculation of a phase angle of the A.C. power source voltage based on the first current command value, and a third calculation of second current command values based on the phase angle of the A.C. power source voltage and the output of the phase detector.

Abstract: A high efficiency current limit circuit comprises a current sensor, a control unit responsive to the current sensor for providing a control signal to a solid-state series pass element which limits load current. A thermal safety circuit provides overtemperature circuit protection. Together, the current limit circuit and thermal safety circuit provide continuous short circuit protection (of indefinite time duration) with automatic recovery upon removal of the short.

Abstract: A parameter setting system for an electronic musical instrument has a predetermined number of panel switches to which desired parameters can be selectively assigned by the player. The system comprises a RAM having a parameter area in which a group of parameters determining characteristics of a tone are stored, the number of parameters being greater than the number of the panel switches. The RAM also has an identification-number area for storing identification numbers of those parameters which are assigned respectively to the panel switches. When a reassignment switch is depressed with an entry switch, the system is brought into a reassignment mode. In this condition, the player selects a desired one of the parameters using up and down switches for changing the identification number and a display unit for displaying the identification number.

Abstract: The present invention provides a precision current source wherein a reference current level is established by the inter-dependent operation of three current stages. The first stage provides first and second current paths and functions to mirror the current level through the first and second current paths. A second stage, coupled to the first and second current paths, defines a first current/voltage relationship at respective points in the first and second current paths. A third stage, also coupled to the first and second current paths, defines a second current/voltage relationship again at the respective points in the first and second current paths. In accordance with the present invention, the first and second current/voltage relationships are chosen to be mutually solvable for a discrete, non-zero pairing of voltage and current levels, thereby establishing a reference current level at the defined current set point.