Abstract: Method and apparatus for reducing harmonic distortion. In one embodiment, the method comprises determining an inverter output current waveform; determining a plurality of harmonic components of the inverter output current waveform; determining, based on the plurality of harmonic components, a plurality of harmonic compensation components; and generating a compensating current comprising the plurality of harmonic compensation components.

Abstract: The system provides for one or more photovoltaic panels (3) or other energy sources, connected to a series of inverters (5) in parallel, the outputs of which are connected to a load (Z) and/or to an electricity distribution grid (7). One of the inverters operates as master unit and generates a power control signal in order to track the maximum power point that can be obtained from the panels (3). The other inverters operate as slave units. The control is performed so that all the inverters absorb a variable quantity of power according to the fluctuations in the power available at the output of the photovoltaic panels (3) or other source subject to fluctuations.

Abstract: When applying a high frequency voltage which alternates on positive and negative sides to a permanent magnet synchronous motor, a driving system of synchronous motor switches the applied voltage phase by 120 degrees successively and applies resultant voltages to three phases. A pulsating current generated by applying a high frequency voltage is detected at timing of elapse of a predetermined time ?t since an output voltage of at least one phase has changed from a state in which all output voltages of the three phases of a power converter are positive or negative. Current detection is conducted by using a DC resistor or a phase current sensor provided on a DC bus. A magnetic pole estimation unit calculates the rotor magnetic pole position of the permanent magnet synchronous motor on the basis of differences between positive side and negative side change quantities in three-phase currents obtained from detected current values.

Abstract: The invention relates to a power supply having two inverters (A, B) in series for powering an electromechanical actuator having an electric motor including a plurality of windings (R1, R2, R3) forming phases, each inverter being connected to its own ground (50; 51) and having a voltage source (U1; U2) having as many arms (A1, A2, A3; B1, B2, B3) as there are windings to be powered, each arm including two controlled switches (5, 6) connected in series, with a point therebetween being provided for connection to one end of one of the windings. According to the invention, each inverter includes an additional arm (A4; B4) having two controlled switches, the two additional arms being interconnected by a bridge (7) that is connected to each of the additional arms at a point that is situated between the switches.

Abstract: The present invention provides a technical solution to reduce electromagnetic interference generated by a high-frequency switching electronic circuit. By adding a disturbance signal whose amplitude varies with time to the input pin of the active power factor correction module of the high frequency switching electronic circuit which is intended to receive an input power control signal, the switching frequency of the active power factor correction module varies with time, so that the electromagnetic interference energy is dispersed in a frequency domain and the electromagnetic interference is reduced. While the effect is even more apparent particularly when the power supply of the high-frequency switching electronic circuit is a DC power source.

Abstract: Exemplary embodiments of the present disclosure provide a method and controller for damping multimode electromagnetic oscillations in electric power systems which interconnect a plurality of generators and consumers. The controller for damping such oscillations includes a phasor measurement unit (PMU) and a power oscillation damper (POD) controller. Each oscillating mode signal is damped and then superposed to derive a control signal. A feedback controller is used to feedback the control signal to a power flow control device in the power system.

Abstract: Embodiments of systems and methods for powering a load are provided. In one embodiment, a method may include providing a power converter comprising electrical circuitry comprising at least a first leg and a second leg, supplying an input power signal to the power converter, supplying at least a first gating control signal to the first leg, supplying at least a second gating control signal to the second leg, and outputting at least one output power signal to the load responsive at least in part to the first and the second gating control signals supplied. According to this example embodiment, the first gating signal and the second gating signal may each comprise a waveform comprising a notch, and the second gating control signal may be phase shifted relative to the first gating control signal.

Abstract: Various embodiments are disclosed relating to wireless transmitters, and also relating to multi-band transformers. According to an example embodiment, an apparatus may include a multi-band transformer configured to receive as an input a signal associated with a first frequency band or a signal associated with a second frequency band. The transformer may include one or more inputs and a first output and a second output. The transformer may also include one or more switches coupled to the transformer and configured to selectively output a received input signal onto the first output and/or the second output of the transformer.

Abstract: A zero-current, synchronous switching waveform is provided for a three-phase, wye-connected H-Bridge to power an electric motor. The switching waveform includes two notches per cycle on the switching waveform provided to each of the semiconductor switches to minimize total harmonic distortion and switching loss. Positioning of the notch with respect to the zero-current crossing is optimized to reduce switching loss and minimize total harmonic distortion.

Abstract: A control system for an AC line voltage distribution system includes a DC energy storage system and an inverter coupled to the DC energy storage system adapted for coupling to the AC line distribution system. A proportional-integral voltage regulator coupled to the DC energy storage system receives a voltage signal for the DC energy storage system and receives a voltage reference. In an exemplary embodiment, the voltage regulator includes a proportional path and an integral path to receive the DC voltage information and the voltage reference signal information, a filter to remove an AC component having a predetermined frequency contained in the DC voltage signal, and an output terminal to output a control signal with the AC component removed.

Abstract: A reverse current detection unit detects the direction of the motor current during the synchronous rectifier period based on the polarity of the on voltage of a switching device contained in the motor current path, and outputs a reverse current detection signal representing the result of this detection to the PWM control unit. Change in the output of the PWM control unit that generates the drive signal for a particular switching device in the drive unit is controlled based on the reverse current detection signal and the energizing pattern of the drive unit is changed when motor current is detected in the synchronous rectifier period to be flowing in the opposite direction as in the urging period. The flow of motor current to the power supply is thus reduced and a rise in the power supply voltage can be prevented.

Abstract: A power supply electromagnetic interference (EMI) filter circuit and technique. In one embodiment, a method of filtering EMI in a power supply includes rectifying an AC signal from an AC source, smoothing the rectified AC signal with a bulk storage capacitor to provide a DC output as an input to a power conversion circuit and filtering the EMI generated by the power conversion circuit from reaching the AC source by using the bulk capacitor and one or more inductors in combination with the AC source capacitance as an EMI filter. In one embodiment the method also includes the use of one or more of the inductors as a fusing element.

Abstract: A zero-current, synchronous switching waveform is provided for a three-phase, wye-connected H-Bridge to power an electric motor. The switching waveform includes two notches per cycle on the switching waveform provided to each of the semiconductor switches to minimize total harmonic distortion and switching loss. Positioning of the notch with respect to the zero-current crossing is optimized to reduce switching loss and minimize total harmonic distortion.

Abstract: The invention recognizes that filter size can be reduced substantially as power factor is permitted to deviate below unity in systematic ways. Preferred methods of the invention provide specific, computable waveforms that permit use of a minimum filter size given a desired target power factor.

Abstract: An apparatus generates sine waves of electromotive force (i.e. alternating current) from a battery. The battery includes a given number of cells connected in series. A stator and commutator is formed by a multiple of segments. Each of the segments is connected in sequence to a respective cell of the battery. The apparatus can be incorporated in a rotary switching device that further includes a rotor having at least one brush contacting the segments of the stator and commutator to carry a step waveform approximating a sine wave. The rotary switch can be included in various setups to provide a backup or alternate generator that provides alternating current.

Abstract: A negative ions generating circuit design with decreasing high frequency noise includes a power indication circuit, an oscillation circuit, an amplifying circuit and a radial frequency filtering circuit. The power indicating circuit, the oscillation circuit and the amplifying circuit are used for generating negative ions. The radial frequency filtering circuit has a capacitance to be utilized for limiting the high frequency in a coil so that the high frequency will not be amplified by through the transistor of the oscillation circuit. The coil creates an inductance to limit the high frequency so as to effectively eliminate the high frequency created by the oscillation circuit.

Abstract: An interrupt signal is generated at each of rising timings of PWM signals which are produced on the basis of phase-shifted triangular wave carrier signals for phases, and voltage command values for the phases. At timings of the interrupt signals, A/D conversion of motor currents of the phases detected by a shunt is started. Interrupt signals are also produced at timings of valleys of the triangular wave carrier signals. Additionally, peak interrupt signals and valley interrupt signals are respectively produced at timings of peaks and valleys of triangular wave carrier signals for phases. Based on each of the peak interrupt signals, normality/abnormality of a switching element of an upper side of the phase corresponding to the interrupt signal is checked, and, based on each of the valley interrupt signals, normality/abnormality of a switching element of a lower side of the phase corresponding to the interrupt signal is checked.

Abstract: An electric machine drive (50) has a plurality of inverters (50a, 50b) for controlling respective electric machines (57, 62), which may include a three-phase main traction machine (57) and two-phase accessory machines (62) in a hybrid or electric vehicle. The drive (50) has a common control section (53, 54) for controlling the plurality of inverters (50a, 50b) with only one microelectronic processor (54) for controlling the plurality of inverters (50a, 50b), only one gate driver circuit (53) for controlling conduction of semiconductor switches (S1–S10) in the plurality of inverters (50a, 50b), and also includes a common dc bus (70), a common dc bus filtering capacitor (C1) and a common dc bus voltage sensor (67). The electric machines (57, 62) may be synchronous machines, induction machines, or PM machines and may be operated in a motoring mode or a generating mode.

Abstract: The present invention allows users to open and join a chat by means of a simple procedure from a video game machine, the present invention includes creating an opening message for opening an electronic conference and creating an opening request signal for setting an area in a database, based on the opening message. Also included is transmitting the opening request signal to the database and creating an invitation message prompting particular users to join the electronic conference, based on the opening message. Finally, the present invention further includes transmitting the invitation signal to the particular users.

Abstract: A dc offset compensator receives a three phase ac current signal as an input and provides a dc offset signal correction voltage as an output. The dc offset compensator comprises a processor configured to sample the ac current signal, generate a rotating vector (r) from the sample, extract a dc offset from the sample and to generate a dc offset signal correction voltage from the dc offset. A method of compensating for dc offset in a three phase ac current signal is also presented.

Abstract: A method for use in a power converter which includes: monitoring a magnitude of an input of a power-flow controller; generating a pulse-width modulated signal wherein at least one pulse has width correlated with a difference between a reference and the monitored magnitude; and varying an output power flow of the power-flow controller in response to the pulse-width modulated signal. In another embodiment of the method, the power converter is characterized by a power converter selected from the group including but not limited to a power supply, a power controller, and a power regulator. In one or more various embodiments, related systems include but are not limited to circuitry and/or programming for effecting the foregoing-referenced method embodiments; the circuitry and/or programming can be virtually any combination of hardware, software, and/or firmware configured to effect the foregoing-referenced method embodiments depending upon the design choices of the system designer.

Abstract: Notching in a switch-mode converter is compensated for to restore a sinusoidal output voltage waveform to the output of the converter, regardless of the load current level, power level, or power factor (both distortion and displacement power factor). Waveform smoothing for a waveform in a switch-mode converter having a DC bus voltage and an output filter inductance comprises determining a ripple current in the converter; determining a time-to-zero; determining a turn-on time; determining the lesser of the time-to-zero and the turn-on time; determining a duty cycle modification based on the lesser of the time-to-zero and the turn-on time; and applying the duty cycle modification to the waveform.

Abstract: The controller for a power converter of the present invention:calculates the range number in which the voltage command vector for a multi-level converter is present;rotates the voltage command vector through a specified angle;performs coordinate transformation of that vector to a vector in an oblique coordinate system which takes the vector in the a axis direction and a vector which has been rotated through a specified angle anti-clockwise from the a axis as two unit vectors;splits the converter output-enabled portion of the vector diagram of the -30 degrees +30 degrees range of the spatial vector diagram in which output vector is positioned, which has undergone oblique coordinate transformation, into square-shape patterns so that the outputs vector is positioned in the upper left/the lower right/both the lower left and upper right of each square-shape pattern;splits any square-shape pattern which holds the output vector in both its lower left and its upper right into two triangular domains by a segment which

Abstract: Described is an active filter (10) for removing harmonic currents from a neutral wire (24) to reduce the current I.sub.n in the neutral wire. The filter (10) typically is located away from the source (26) and near the load (28). The filter (10) comprises generally a multi-phase transformer (12), a neutral current monitoring device (14), and a harmonic current injection device (16). The components of the present invention operate to draw a corrective harmonic current (I.sub.N) from the neutral wire (24) at a tap point (T) near the load (28) and inject the corrective harmonic current (I.sub.N) through the multi-phase transformer (12) into the phase wires (20). The corrective harmonic current (I.sub.N) substantially cancels the harmonic current (I.sub.n) in the line on the source side of the tap point (T) and therefore eliminates over-current conditions in the neutral wire. The device preferably includes a rectifier (36) connected by the secondary windings (34) of the transformer (12) to power a DC bus (38).

Abstract: Apparatus is disclosed for measuring the fundamental voltage, fundamental frequency and the fundamental voltage divided by the fundamental frequency of the output of a device, such as an inverter. Through the use of an isolation amplifier connected across the output of the inverter and proper component selection, the output signal produced by the isolation amplifier is representative of the fundamental voltage of the output of the inverter divided by the frequency of the fundamental voltage. The output signal from the isolation amplifier is converted into a pulse having a fixed width w, fixed height h and period 1/f to produce a signal representative of the fundamental frequency of the output of the inverter. The output signal from the isolation amplifier is also rectified and applied to a multiplier along with a signal having a fixed width w, height E.sub.in /f and period 1/f and then averaged to produce an output signal representative of the fundamental voltage of the output of the inverter.

Abstract: Power transistors used as high-side power switches are typically subjected to a variety of potentially destructive conditions, such as loss of bias current or loss of a ground connection in associated control circuitry. In order to protect the power transistor upon occurrence of such a potentially destructive condition, a control electrode disable circuit is provided to ensure that the power transistor will be turned off upon the occurrence of such a condition, or when the control circuits are deliberately turned off or placed in a standby mode. Turn-off of the power transistor is ensured by shunting a disable transistor across the input of the power transistor, and providing a disable circuit for activating the disable transistor in the event of loss of bias or loss of ground in the control circuitry. Reliable activation of the disable transistor is ensured by a bootstrap capacitor circuit in the disable circuit.

Abstract: A control unit for an inverter determines an objective function based upon harmonic content in a minimum number of the phase-to-phase AC voltages produced by the inverter and controls the switches of the inverter so as to minimize the objective function to thus control the harmonic content in the inverter output voltages.The objective function may be defined according to the following equation: ##EQU1## where W.sub.k are scaler weighting factors, A.sub.kA, A.sub.kB and A.sub.kC are the Fourier cosine coefficients of the kth harmonic of the inverter phase A, B and C outputs, B.sub.kA, B.sub.kB and B.sub.kC are the Fourier sine coefficients of the kth harmonic of the inverter phase A, B and C outputs, k is the number of the controlled odd harmonic (i.e., k=1, 3, 5 . . . ), and NHARM is the number of the highest controlled odd harmonic.

Abstract: Apparatus and method for eliminating or reducing to a filterable minimum the relevant harmonic frequencies which otherwise occur in an AC output voltage from a multi-phase static inverter circuit operating from a symmetrically notched source of DC input voltage. The inverter circuit is electronically switched and controlled to provide notched phase voltages with the notch positioning being optimally variably placed in the periodically occurring waveform and with a controlled interval of the notch for controlling the fundamental component independently of the source voltage, while substantially eliminating the 11th and 13th harmonic components of the fundamental output voltage. A harmonic neutralizing transformer circuit includes paired wye, delta, or wye-delta configurations is connected between the inverter circuit and a composite output transformer circuit which couples or connects paired windings of the harmonic neutralizing circuit.

Abstract: An apparatus and method for reducing certain harmonics in the output of static inverters. Static inverters which employ a switching device arranged in a bridge circuit to convert direct current power to alternating current power produce undesired harmonics in the output of the inverter. Harmonic neutralization techniques are further improved by the invention utilizing selective notching of the inverter pole voltage and a coordinate phase shift between the set of pole voltages produced by the individual inverters. The notch angles in the individual pole voltage outputs are chosen to minimize or eliminate specific undesired harmonics.

Abstract: The present invention relates to a digital servo-control system whose purpose is to control very high precision equipment. The system includes two digital-to-analog converters, one of which is followed by a divider, with the two converters contributing to producing a control signal. A processor responds to a measurement signal and to a reference value to generate the digital values that are delivered to the converters. The system is particularly suitable for application to servo-controlling a voltage-controlled oscillator.

Abstract: A three phase alternator is driven by a variable speed prime mover, and its rectified output is pulse width modulated by a gate controlled H-bridge power switch circuit. Predetermined pairs of power switches are gated on and off according to programmed duration and timing instructions contained in a read only memory. In a first embodiment, a sine wave output is produced by successive pulse trains. The first pulse train has alternating positive and negative constant amplitude pulses, with the widths of positive pulses varying sinusoidally and the widths of negative pulses being constant. The second pulse train has alternating positive and negative pulses of constant amplitude, with the pulse widths of the negative pulse components varying sinusoidally, and the pulse widths of the positive components being constant. The components of the first and second pulse trains have an energy distribution which corresponds to one cycle of a sine wave having a fixed frequency.

Abstract: A method for reducing the signal harmonics of the output fundamental signals of a three-phase inverter systems made up of an N number of inverter bridges achieves harmonic signal reduction by combining the outputs of immediately adjacent bridges separated by 60.degree./N relative to one another and then summing the combined sum signal with the outputs of the next immediately adjacent bridge.

Abstract: At times, it may be necessary to operate switches of a PWM inverter to provide a low output voltage. However, in order to produce such a low voltage, it may be necessary to operate the switches near their minimum on time limit, which can in turn lead to damage or destruction of the switches. In order to overcome this problem, a control for an inverter which produces an output voltage having two levels wherein the inverter includes first and second switches coupled to an inverter output produces first and second switch control signals each having alternating switch on and switch off portions wherein each switch on portion is of a duration in excess of the minimum on time limit of the switches.

Abstract: A field-oriented controller for a 3 phase induction motor is powered by a dc power source through a static inverter. Current reference signals are compared with current feedback to produce error signals. They are amplified by a proportional plus integral amplifier, whose output goes to a threshold comparator having negligible hysteresis. Flip-flops, through which the threshold comparators' gating signal outputs are fed, are clocked at a fixed frequency to introduce pseudo-randomness into the gating times. This reduces apparent acoustic noise of the motor. Asymmetrical anti-overlap delays for the gating signals are made long enough to serve also as the principal means for limiting the maximum frequency of gating. Locking circuitry overrides the proportional integral error signal in one phase at a time, and holds the inverter's gating in one switching state throughout the approximate middle 60.degree. interval of each phase. During each such 60.degree.

Abstract: An induction motor drive including a current source inverter system having controlled turn on and turn off semiconductors in a load side inverter selectively places notches in the waveshape of the current supplied to the parallel combination of the motor and a capacitor bank for the minimization of harmonics.

Abstract: An inverter current controlling method wherein output currents of an inverter having a plurality of switching elements and connected to a three-phase load are detected, and the switching elements are ON/OFF controlled so that the waveforms of the output currents are approximated to set output current wave commands, respectively, comprising: maintaining a specific switching element in a specific state so that a specific output terminal of the inverter is fixed to a specific polarity during a period of time when a specific ideal phase voltage of the three-phase load corresponding to the output current wave command is in a predetermined phase; and ON/OFF controlling the switching elements other than the specific switching element during the period of the predetermined phase so that the output current waveforms are approximated to the output current wave commands, respectively. Also disclosed is an inverter current controlling apparatus suitably employed in the above-mentioned method.

Abstract: In an inverter-drive controlling apparatus in accordance with a simulated sinusoidal wave non-uniform PWM system, data of one carrier period comprises data region of integer number, and at least one HALT region, and the carrier period T.sub.0 and data unit timer T.sub.2 are produced by frequency division from a common reference oscillator, and the frequency divisions to obtain the carrier period T.sub.0 and the data unit timer T.sub.2 are controlled individually from each other, thereby output frequency to the inverter and output voltage thereto can be desirably controlled in digital process; thereby even utilizing limited area for storing sinusoidal wave data, accurately simulated sinusoidal waveform and good characteristic of the voltage-frequency is attainable and completely synchronized switching of plural waveform data regions are obtainable, thereby enabling adjusting of the revolution speed of electric motor in extremely wide range and up to a very high speed, and the waveform becomes very good.

Abstract: A modulating wave signal whose phase abruptly changes is compared with a carrier signal to generate a pulse width modulation pulse. The carrier signal is a sine wave signal having a frequency n times as high as that of the modulating signal and synchronized with the modulating signal. A phase of the carrier abruptly changes by a factor of n as the phase of the modulating signal abruptly changes. Thus, a pulse with modulation pulse which causes an output voltage of a pulse with modulation inverter to be sinusoidal is generated even if the phase of the modulating wave signal abruptly changes.

Abstract: An apparatus for controlling a current type inverter including a bridge circuit of bridge-connected self-extinguish elements triggered by pulse width modulation signals. A current is provided for applying a single or plural triggering pulses having a desired pulse width to those self-extinguish elements connected in series with the other self-extinguish elements forming the pairs in the bridge circuit and which other self-extinguish elements are turned on by the pulse width modulation signals. By the above manner of control, the current type inverter can generate output currents of sinusoidal waveform, and the value of the output currents can be controlled over a very wide range.

Abstract: The invention comprises a photovoltaic panel for converting solar energy into electric energy, a load and a capacitor connected to the photovoltaic panel for receiving current produced by the panel and storing the current to produce an output voltage which increases with the amount of stored current. A relay connects the photovoltaic panel and capacitor to the inductive load when the output voltage of the capacitor has reached a predetermined level which corresponds to an optimum operating voltage range of the photovoltaic panel.

Abstract: A control unit for DC-to-AC inverter having an addressing memory which is loaded with an addressing table by a microprocessor for a respective frequency range of the inverter output voltage. In the addressing table, a predetermined portion of information is provided for each addressing combination of the switches of the DC-to-AC inverter, the portion of information containing the addressing combination itself and the number of clock pulses for which the addressing combination will be present. The portions of information are interrogated at different speeds depending upon the desired inverter output frequency. A frequency divider is addressed by a clock generator, the frequency divider receiving a division factor from the memory, the division factor being inversely proportional to the desired DC-to-AC inverter output frequency. The output signal of the divider decrements a counter which is loaded with a number of clock pulses associated with the respective addressing combination.

Abstract: The d.c. power supplied by a photovoltaic solar panel to a load is controlled by monitoring the slope of the panel voltage vs. current characteristic and adjusting the current supplied by the panel to the load so that the slope is approximately unity. The slope is monitored by incrementally changing the panel load and indicating whether the resulting change in current derived from the panel is above or below a reference value, indicative of the panel voltage. In response to the change in the monitored current being above the reference value, the slope of a voltage vs. current curve is greater than unity and the load is adjusted to decrease the current supplied by the panel to the load. Conversely, in response to the current being less than the reference value, the slope of the voltage vs. current curve is less than unity and the load is adjusted to increase the current supplied by the panel to the load.

Abstract: The switching intervals for the power transistors in a three-phase inverter are generated by a microprocessor. DC content control is provided separately for each phase by modulation of the duration of the switching intervals through adjustment of the length of the sequences of instructions carried out by the microprocessor.

Abstract: A pulse width modulated three-phase inverter has notches in the output waveforms to control the harmonic content thereof.

Abstract: A sinusoidal synthesizer is shown which produces a sinusoidal AC power output from a modulated pulse train. The pulse train is modulated by two independent feedback loops which each use the sinusoidal output as its reference. The first loop controls output voltage by a high gain negative feedback signal to a pulse width modulator, while the second loop shapes the sinusoidal output by a less than unity gain, positive feedback signal to a second pulse width modulator.

Abstract: A voltage source inverter has a main circuit with a switching device to which is connected a DC power source through a load, and a control circuit for controlling the on-off operation of the switching device. The control circuit includes a function generator for outputting a first signal representative of the voltage-time-integration value in correspondence with the phase of the load voltage, a time counter for outputting a second signal representative of total time of the integrated time of the period during which the DC voltage is applied to the load, and a comparator for comparing the first signal with the second signal. The output of the comparator controls the on-off operation of the switching device through a logic circuit and supplies a pulse-width-modulated AC voltage to the load.

Abstract: A method and apparatus for producing control signals for operating an inverter circuit to convert a DC voltage into multitiered steplike notched N phase AC output signals (N=some positive integer number other than zero). A plurality of N reference sine waves are generated 90.degree. out of phase with one another for N=2, and for N greater than 2, successive ones of said N reference sine waves are generated 360.degree./N out of phase with each other. First through third triangular sampling or timing waveforms are generated and concurrently compared with the uppermost, central and lowermost portions, respectively, of each individual one of said N reference sine waves, for producing N sets of first, second and third pulse width modulated pulse trains, respectively. Decoding logic networks are receptive of these N sets of first through third pulse trains, for decoding these pulse trains into the necessary control signals for operating a particular inverter circuit.

Abstract: A particular control waveform actuates the half-bridge switching elements of a three-phase power inverter in such a manner as to balance harmonic cancellation between waveform notching and low impedance filtering in obtaining a substantial sinusoidal output signal. The control waveform allows a small amount of lower order harmonics which inherently decreases the higher order harmonics generated by the notches in the control waveform so that a small filter, e.g., a five percent filter, can be used which eliminates the need for voltage regulation under various current loads and yet both the unregulated voltage fluxations and overall harmonic content of the output signal is well within acceptable tolerances for use by an electrical power utility or the like. At the same time, the control waveform employs a relatively low per cycle switching rate which minimizes the number of off-on transitions of each of the high-current, solid state switches in the inverter thereby retaining high inverter efficiency.

Abstract: An adjustable speed AC electric motor drive has a static inverter energized from a unidirectional power source through a semiconductor series chopper and eliminates a filter between chopper and inverter and controls the fundamental inverter output frequency as a function of an analog speed reference signal and also pulse width modulates the series chopper at a constant frequency as a function of the speed reference signal and synchronizes the series chopper to the fundamental inverter freqency to provide variable voltage and variable frequency power to the motor. The drive has a shunt chopper at the output of the series chopper and switches it to the opposite conductive state from the series chopper so that it coacts with the feedback diodes to form substantially continuous, low impedance, bidirectional free-wheeling paths for motor current and provides constant harmonic content current to the motor with reduced ripple.

Abstract: Pulse width modulation is produced by digital means. Pulse width modulated waves are stored digitally in a memory and retrieved under control of a voltage signal in order to generate a pulse width modulated wave of predetermined pattern for any discrete value of successive desired output voltage levels. Optimal waveforms are selected and stored which extend only for one quadrant but an alteration of the addressing code based on symmetry yields the mirror image of the stored quadrant while sign modification provides symmetry about the abscissa axis. Also, only a single phase is stored and phase shifting by code alteration of the coded information provides the other phases after retrieval.The notches characterizing a particular pattern are stored in the form of a digital representation one level along several possible levels defining subdivisions of a given time interval which is itself a submultiple of the total duration of the stored quandrant.