Showing papers on "Inverter published in 1977"

Self-excitation in inverter driven induction machines

Abstract: If the dc supply to a voltage source inverter driving an induction machine is removed, self-excitation as a result of circulating currents in the inverter can occur whenever the inverter switching frequency is below the machine speed. In this mode the inverter-machine system functions as a stable self-excited induction generator capable of supplying dc or ac power to a load. The electrical output of the system is readily governed by slip control; thus the inverter makes practical the development of efficient induction generators capable of operating over wide speed ranges. A theoretical treatment based on a first harmonic approximation of inverter performance is presented. The results indicate that the magnetization characteristic and the stator and rotor resistances of the machine are the important parameters controlling system performance. Experimental results which confirm the validity of the analysis and illustrate the behavior of the self-excited systems are also presented.

High power factor conversion circuitry

Abstract: A high power factor conversion circuit suitable as a ballast circuit for lamps includes a full-wave rectifier coupled to an AC potential source and providing a pulsating DC potential. A high frequency inverter is coupled to a load circuit and to a feedback rectifier circuit supplying a rectified high frequency potential to an energy storage feedback circuit which provides energy in a manner to inhibit a decline in the pulsating DC potential thereby providing a substantially uniform DC potential to the high frequency inverter.

Inverter oscillator with current feedback

Abstract: A power source for operating gas discharge lamps and other loads at high frequency, typically utilizing a 120 volt ac source rectified to provide a 150 volt dc input and providing a 20,000 hertz output. An inverter with current feedback in place of the conventional voltage feedback providing voltage turn off and voltage turn on in less time and providing increased base current during the conduction time for reducing the voltage-current product and heat generated in the inverter. Voltage limiting and current limiting features are provided for the basic circuit. Inverter circuits with two transistors for increased loads are also provided.

Inverters and logic gates employing inverters

Abstract: A so-called "programmable inverter" provides either a direct or an inverse signal path between its input and its output depending on a previously applied programming signal which is arranged to cause selective fusing of a fusible link. Such a circuit element may be incorporated in an input or an output of a logic gate so that a single type of gate may be programmed to perform a selected function from a number of functions.

Inverter-Induction Motor Drive for Transit Cars

Abstract: The advent of large power semiconductors has made it possible to apply inverters and ac motors to traction applications. Either synchronous or induction motors and several types of power converters can be considered. The induction motor and the pulsewidth modulated (PWM) inverter are selected as favorable for application to a transit car drive. A general method of sizing the PWM inverter and induction motor in terms of the car performance requirements is out-lined. This method results in a minimum size inverter and allows optimization of system weight and cost. A discussion of wheel size effects and the optimization of regenerated energy is included.

Protective circuit for an inverter

Abstract: The invention relates to a protective circuit for an inverter having semiconductor control elements. The protective circuit includes a series regulator in its inlet branch and an intermediate filter circuit with the capacitor thereof extending between the inlet and outlet branches. First and second signal generators control the series regulator and the inverter. A control unit controls the first signal generator for normal operation. Parallel comparator units have monitoring inputs connected to different parts of the protective circuit for detecting abnormal conditions and outputs connected to both of the signal generators to effect the immediate turning off of the series regulator and the inverter when abnormal conditions are sensed. The inverter is off concurrently with the comparator output signal but a multivibrator switch having a predetermined period causes the series regulator to be off during that whole period independently of the comparator output signal. With the series regulator off and the inverter turned on, the filter capacitor is allowed to discharge through the inverter. If the abnormal condition does not disappear during this operational sequence, the sequence is repeated.

Single secondary dimming inverter/ballast for gas discharge lamps

Abstract: A highly efficient, energy saving ballasting and transfer circuit, utilizing a single high frequency inverter ballast unit, capable of powering multiple lamp loads from any direct or alternating electric power source, comprises a current feedback inverter in combination with a leakage transformer, which operates to permit coupling of the single inverter unit to any number of lamps, particularly the gas discharge type. The leakage transformer can power any number of lamps from a single source which, because of its linear transfer function, achieves controlled light output of the lamps proportional to the power input. Thus, an excellent dimming capability is achieved. It is important to note that this leakage transformer is a special case of a certain type of multi-path leakage transformer, where only one secondary coil is used to achieve the same dimming capabilities of multiple secondary embodiments.

Static controlled AC motor drive having plug reversal capability

Abstract: Plug reversal of an induction motor supplied by an N-stage inverter system operating under harmonic neutralization technique is provided by reversing the polarity of the square-shaped voltages combined at π/N from each other and by reversing at the same time the sequence of the stages as well as the logic of dissection of the reference time wave. A mirror image of the time scale is effected at the instant of reversal. Digital means are used. Reversible ramp forming generators of the UP-DOWN type are associated in each stage with a phase shifter in order to create the mirror image of the logic controlling the inverter system. A reversible ring counter is used to reverse the sequence of the stages. A reversible pulse generator is used to accommodate an integer number of elementary time intervals in each ramp and between each ramp for the given number of stages.

Circuit for increasing the output current in MOS transistors

Abstract: In order to increase the output current of an MOS transistor, its gate is provided with a switched capacitor drive. A tri-state inverter is used to drive the output transistor gate from an input source. A pair of delay elements are cascaded to drive one input of a NOR gate, the other input of which is fed an undelayed signal. The NOR gate is used to switch a capacitor that is also coupled to the output transistor gate. The juncture between the delays is coupled to the control electrode of the tri-state inverter. During the first delay interval, the capacitor and the output transistor gate electrode are charged. Then after the second delay interval, which is shorter than the first, the capacitor is discharged into the output transistor gate electrode which is thereby driven substantially in excess of the conventional drive level.

Fault protection circuit

Abstract: An a-c supply system includes an input bridge circuit, connected to receive a-c input voltage and produce an output d-c voltage which is passed through a filter to an inverter having a plurality of thyristor switches, which switches are regulated to produce an a-c output voltage for supplying a load. If two of the switches are inadvertently triggered on to produce a fault across the bus, the rapid discharge of the filter capacitor into this fault is sensed, and the protection circuit provides both simultaneous turn-on of all of the inverter power switches, and turn-off of the input bridge. The input bridge turn-off is achieved by simultaneous removal of the gate drive from all the power switches in the input bridge and commutation of all the power switches in the input bridge circuit, or by interrupting power transfer from the input bridge toward the inverter. In addition to sensing the filter capacitor current, the level of current supplied to the input bridge is monitored so that a sudden rise is detected and utilized to initiate the same protective functions.

Drive for a yarn feeder for a textile machine

Abstract: The drive motor for the yarn storage device is controlled by a circuit arrangement which converts a direct current into a variable-frequency three-phase alternating current. The circuit arrangement includes an integrator to produce a trapezoidal control voltage as well as an oscillator, digital counting circuit, three inverter stages and three amplifiers which emit sinusoidal phase currents to the windings of the drive motor. An electromagnetic brake is also used to brake the drive motor.

Sense circuit employing complementary field effect transistors

Abstract: A sense circuit suitable for use with semiconductor memory arrays which, in contrast to sense circuits of similar type, exhibits no voltage offset in the latched condition between the input-output (I/O) nodes and the supply lines. The sense circuit includes first and second complementary inverters with inputs connected to first and second I/O nodes, respectively, and with outputs capable of being clamped to one or the other of the two supply lines powering the inverters. Selectively and sequentially enabled cross-coupling transmission gates are connected between the output of each inverter and the input to the other inverter, and selectively enabled biasing transmission gates are connected between the input and output of each inverter. In the operation of the circuit, the two input nodes are first precharged to a predetermined value by enabling the biasing gates. A signal is then applied to one I/O node causing its potential to vary from its quiescent value. Then, the cross-coupling gate connected to the output of the inverter whose input is connected to the one I/O node is first enabled and, subsequently, the other cross-coupling gate is enabled. When the two cross-coupling gates are enabled, the inverters are latched and form a flip flop with the first I/O node clamped to the supply line having the same binary signal and the second I/O node clamped to the other power supply line.

Control systems for pulse width control type inverter

Abstract: A control system for controlling the conduction period of the switching elements of a pulse width control type inverter is provided having a reference pulse generator that determines the output frequency of the inverter output voltage, a constant voltage control circuit for generating an analogue output voltage, an A-D converter for converting the analogue output voltage into a digital output signal and a up-counter which counts clock pulses. The outputs of the up-counter and the A-D converter are compared with each other by a digital comparator. The up-counter is cleared by the reference pulse when another up counter counts a predetermined number of output pulses from the comparator. The up-counter repeats a predetermined number of counting up and clearing operations until it produces a carry signal, and the conduction period of the switching element is determined by an interval between the generation of the reference signal and the generation of the carry signal. In a modified embodiment the up-counter is substituted by a down counter.

Semiconductor integrated flip-flop circuit device including merged bipolar and field effect transistors

Abstract: A semiconductor integrated circuit comprises a pair of load transistors and a pair of inverter transistors to constitute a flip-flop circuit. The load transistors are formed of p-channel field effect transistors serving as carrier injectors for the inverters formed of npn bipolar transistors. The p-type drain region of each load transistor is merged into the p-type base region of each inverter transistor. The absence of carrier storage effect in the field effect transistors improves the operation speed of the flip-flop remarkably and the high impedance gate electrode can be utilized as the clocking electrode to achieve clocking with voltage pulses without substantial power consumption. A plurality of such flip-flops are connected in cascode one after another to constitute a shift register.

Offset compensation for harmonic neutralized static AC generator

Abstract: In an inverter system using parallel transformers to generate a reconstructed sinewave by harmonic neutralization method direct current offset in any of the transformers is eliminated by shifting one edge of one of the square pulses logically determining the conduction angle of the inverter A hall device mounted in an auxiliary reactor connected with the primary of the transformer is used to sense flux conditions during sampling periods which are in time relation with the logic period in the control of the inverter system and the detected flux asymmetry is used to control the ON-OFF ratio of such logic period thereby to compensate for the offset

Constant voltage circuit comprising an IGFET and a transistorized inverter circuit

Abstract: A constant voltage circuit comprises an IGFET for deriving an output voltage for a load from a power supply and an inverter circuit responsive to the output voltage for controlling the IGFET in a negative feedback manner to stabilize the output voltage against fluctuations in the supply voltage and the load. The IGFET may be a depletion or an enhancement MOSFET. The inverter circuit preferably comprises an enhancement and a depletion or an enhancement MOSFET. Either a resistor or another IGFET may be connected between the inverter circuit and ground. The constant voltage circuit is readily manufactured as an IC together with an IGFET circuit used as the load.

Protective circuit for transistorized inverter-rectifier apparatus

Abstract: Inverter-rectifier combinations of the type which include at least a pair of transistors for alternately applying DC current to a transformer to generate alternating voltage from a DC source, and a digital semiconductor type driving means for alternately providing voltage pulses of given duration and at a periodic repetition rate at each of two outputs for controlling such alternating operation of the transistors is improved in a combination containing a protective circuit located in between the driving circuit and the inputs to the inverter transistors. The protective circuit contains first and second inputs and corresponding first and second outputs with the inputs being connected to an associated one of the two driving means outputs, and the outputs being connected to an associated one of the two inverter transistors; cross-gating means, including linear semiconductor switch means, for producing a driving output pulse on a one of the outputs responsive to the presence of a voltage pulse at an associated one of said inputs and only during the absence of a voltage pulse at the other one of said inputs; and delay means for inhibiting the application of said driving output pulse at a one of said circuit outputs until the lapse of a predetermined interval of time subsequent to the termination of application of a driving output pulse to the other one of said circuit outputs, the predetermined time interval being at least as great as the defined charge storage time of the inverter transistors and less than half the duration preferably of the pulses supplied by the digital control circuit; whereby the inverter transistors are not driven into overlapping operation.

Emergency standby system for automatic transfer from utility power to a battery powered system

Abstract: An emergency standby power system for automatic transfer from utility power to a battery powered inverter when a normal source of utility power is interrupted to a given load, and for automatic re-transfer to utility power when it is restored. The inverter includes SCR circuitry whereby commutation failure during start-up and shut-down is prevented by applying power to the inverter prior to the application of the gate drive during start-up, and removing power from the inverter prior to the removal of the gate drive during shut-down. Further, the control circuitry ensures that the first SCR gated on will operate for a complete one-half cycle, thereby fully charging the commutating capacitor for reliable commutation off of the first SCR before turning on the second SCR. The control circuitry also permits the inverter to start up even if it is presented with a short circuit and operate without damage.

Inverter with improved load line characteristic

Abstract: An insulated gate field effect transistor (IGFET) static inverter having an improved load line characteristic is disclosed. The inverter comprises an enhancement mode IGFET active device in a first portion of a semiconductor substrate, having its drain connected to an output node, its source connected to a source potential and its gate connected to an input signal source. The first portion of the substrate is connected to a first substrate potential. A depletion mode IGFET load device is located in a second portion of the semiconductor substrate which is electrically isolated from the first portion. The depletion mode load device has its drain connected to a drain potential and its source, gate and the second portion of the semiconductor substrate all connected to the output node. In this manner, the rise in the source-to-substrate voltage bias during the turn-off transition is eliminated in the depletion mode load device, providing an improved load current characteristic for the inverter. Alternate embodiments are disclosed directed to an all N-channel inverter, an all P-channel inverter, and a complementary inverter consisting of a P-channel load device and an N-channel active device.

Voltage controlled oscillator

Abstract: A voltage controlled oscillator whose frequency is a function of an input voltage having a first and a second pair of switching devices coupled respectively to first and second terminals of a capacitor. The oscillator has a first leg coupled from the first capacitor terminal through first inverter means, a first NOR device and third inverter means back to the first pair of switching devices and the first capacitor terminal. The second leg is coupled from the second capacitor terminal through second inverter means, a second NOR device, fourth inverter means back to the second pair of switching devices and the second capacitor terminal. The first and second NOR devices are directly cross-connected. The first and second legs each have the same number of propagation delays and during state transition, both terminals of the capacitor are coupled to the reference potential for a brief instant of time.

Measurement of pulsating torque in a current source inverter motor drive

Abstract: A method and circuit for calculating the instantaneous pulsating component of torque for use as a cogging feedback signal to stabilize ac motors at low frequencies. An air gap flux signal is generated by integrating the instantaneous voltage across a stator phase winding during the interval the current in that winding is zero. Pulsating torque is the product of the high pass filtered flux signal and the inverter input or dc link current.

Voltage boosting circuits

Abstract: Voltage boosting circuits of a type using a plurality of inverters with parallelled inputs, each inverter arranged to pump charge into a respective pair of booster capacitors--rather than one respective booster capacitor--to develop an output voltage in each stage which is doubled in amplitude over the voltage used to power the inverter in that stage. To this end, the inverter in each successive stage of the voltage boosting circuit is powered by the output voltage of the preceding stage.

MOS-bipolar printer driver circuit

Abstract: In a thermal printer, a print element drive circuit has connected in series a CMOS (Complementary Metal Oxide Semiconductor) inverter gate driving a MOS (Metal Oxide Semiconductor) transistor which in turn drives a bipolar power transistor. The bipolar power transistor provides current pulses to a resistive element which is thermally activated in response to the pulses to cause the printing of characters upon thermal sensitive paper. Character decoding circuitry provides high impedence logic level inputs to the CMOS inverter and these inputs are converted by the printer driver circuitry into corresponding high current drive pulses.

Electronic monitoring system with selective signal inverter

Abstract: A contactless motion detector is energized from a source of direct current via a pair of supply leads and delivers an output signal by way of a further conductor to a control electrode of a binary electronic switch, such as a thyristor, in series with the source and a load to modify the flow of load current upon the approach of a metallic element, for example. An Exclusive-OR gate is inserted in the further conductor to act as a selective signal inverter, one input of this gate being permanently connected to one supply lead while being also selectively connectable to the other supply lead whereby the load current can be either increased or reduced upon the occurrence of the event to be detected.

Voltage supply circuit responsive to plural possible DC input levels

Abstract: A voltage supply circuit comprises an input for receiving a DC input voltage having one of plural possible levels; a DC-AC inverter for inverting the DC input voltage and which includes a boosting transformer having a winding with end terminals and an intermediate terminal and an inverter drive circuit for providing an AC current to the transformer; a connection between the input and the intermediate terminal of the boosting transformer for applying the DC input voltage to the latter; and a control circuit for controlling the inverter drive circuit, and which selects between a first condition, in which the inverter drive circuit is made operative so that a boosted voltage is provided at one end terminal of the boosting transformer, and a second condition, in which the inverter drive circuit is made inoperative, so that the DC input voltage introduced at the intermediate terminal is provided as a DC output voltage at the end terminal of the booster transformer. The control circuit can include a zener diode as a level detector to control a switching transistor so that the first and second conditions are selected on the basis of the level of the DC input voltage.

Design, analysis and test results for a superconducting linear synchronous motor

Abstract: A linear synchronous motor has been designed to propel a 480 km/h magnetically levitated passenger vehicle. The paper describes the motor and presents results of tests which have been performed on essentially full-scale components of the motor using a 7.6 m-diameter test-wheel facility. Controlled starting, acceleration, cruising, deceleration and transient operation have been demonstrated. A 6-component force balance has been used to measure the three forces and three moments acting on a single stationary superconducting magnet due to its interaction with the split 3-phase windings mounted on the rim of the test wheel and energized by a variable-frequency current-controlled inverter power supply. Measured forces and terminal characteristics over complete cycles of force angle are claimed to be in agreement with analysis based on a coupled circuit model of the machine and mutual inductance computations. Moments were measured to be small under all operating conditions. Two modes of control have been demonstrated. The alpha -scheme, proposed for a full-scale system, maintains the angle between induced voltage and phase current at a value which optimizes the motor characteristics, i.e. inverter Mva rating, etc. beta- control, which may be required for starting, uses vehicle position detectors to fire the inverter thyristors at appropriate times.

Phase difference detector

Abstract: There is provided a pair of flip-flops, each of which is set before appearance of every one of two input signals to be compared. One of the input signals is applied to a reset terminal of the first flip-flop through an inverter, and the other input signal to that of the second flip-flop through another inverter. There is further provided a pair of AND gates. A set output of the first flip-flop is led to one of two input terminals of the first AND gate through a delay element, and a reset output of the second flip-flop is connected to the other input terminal of the first AND gate directly. The set output of the output of the second flip-flop is coupled to one of two input terminals of the second AND gate through another delay element and the reset output of the first flip-flop is connected to the other input terminal second AND gate directly.

Inverter oscillation regulating device

Abstract: PURPOSE:An oscillation stopping device which prevents generation of transient voltage on stoppage of an inverter and stops oscillation safely.

Time division switching regulator

Abstract: A time division switching regulator wherein a single power source is connected to a plurality of inverters the outputs from which are rectified and smoothed and appear at respective output terminals, and the output voltages at said terminals are sequentially monitored and are compared with a reference voltage to generate an error signal in response to which the output from the corresponding inverter may be controlled or regulated.