Showing papers on "Total harmonic distortion published in 1984"

The Use of Harmonic Distortion to Increase the Output Voltage of a Three-Phase PWM Inverter

Abstract: By adding a measure of third harmonic to the output of each phase of a three-phase inverter, it is possible to obtain a line-to-line output voltage that is 15 percent greater than that obtainable when pure sinusoidal modulation is employed. The line-to-line voltage is undistorted. The method permits the inverter to deliver an output voltage approximately equal to the voltage of the ac supply to the inverter. Thus an induction motor of standard rating with respect to the ac supply to the inverter can deliver very nearly full power at rated speed when supplied from the inverter. This is achieved without pulse dropping or any other form of mode-changing.

Chromatic dispersion induced distortion of modulated monochromatic light employing direct detection

Abstract: The spectrum of an intensity modulated (IM) and a combined intensity-frequency modulated (IM-FM) monochromatic light source has been generated. The amplitudes of the modulated carrier and the first three pairs of sidebands are plotted showing the influence of IM on an FM signal. The effects of first order chromatic dispersion on the baseband amplitude response and harmonic distortion are determined. The manner in which modulation type and depth, modulating frequency, wavelength, and fiber length alter harmonic distortion is presented. Numerical examples giving the amplitude response of a single-mode fiber system as well as the magnitude of the second- and third-harmonic distortion caused by chromatic dispersion are presented. Based on this material, the limits placed on analog transmission due to chromatic dispersion may be assessed.

Current Harmonics, Voltage Distortion, and Powers Associated with Electric Vehicle Battery Chargers Distributed on the Residential Power System

Abstract: The harmonic performance of the networks of several types of electric vehicle (EV) battery chargers is documented. Cumulative effects at the substation level for random distributions of each of five different charger types are reported. Chargers with and without current- smoothing inductors and with and without controlled rectifiers for maintenance of constant current are included. Results are reported as magnitudes of expected harmonic current; active power; apparent, reactive, and distortive volt amperes; and power factor hour by hour over typical daily recharge cycles for the network of chargers. Results regarding comparisons among chargers demonstrate the desirability of including a current-smoothing inductor in the charging circuit and indicate that constant-current type chargers using controlled rectifiers generate significantly more harmonic current than the simple noncontrolled taper-current chargers. Typical third harmonic current values of 15 A per charger on the 120-V side and 20 A per phase on the 12.8-kV side for a network of chargers (at ten percent penetration of chargers into the residential distribution network) indicate the possibility for harmful effects to customer and utility equipment and for interference into communications circuits. The results reported here should be useful in both predicting harmful effects at various densities of EV chargers on the residential network and in designing chargers to minimize those effects. supported in part by the New England Electric System.

Unity Power Factor off Line Switching Power Supplies

Abstract: A simple circuit is presented that performs the unity power factor function with low harmonic distortion of the input line current. The circuit is of the resistor emulation type. A description of circuit operation and design parameters are included as well as measured performance. An in depth description of the large signal computer model that was used to verify harmonic current content and control loop performance is presented.

Digitally Programmable Gain Amplifiers

Abstract: Following a review of the state of the art, some new circuits are presented for designing a set of digitally programmable gain amplifiers. Design features of these circuits are presented, and critical assessments are made of their relative merits and limitations.

Interlaced pulse-width modulated unrestricted frequency changer system

Abstract: In a static frequency changer controlled by adjusting the time of conduction of the bilateral switching units forming static converters, the time of conduction is split into n time intervals of respective subdurations adding up to be equivalent to the effective time of conduction of the controlled switching unit, and such subdurations are spread and distributed throughout the time period of control of the switching unit both within the original switching pattern of each converter and between the effective times of conduction of the respective converters, thereby to minimize harmonic distortion of the input supply current of the frequency changer.

An Improved Three-Phase Multistepped-Voltage Inverter Combined with a Single-Phase Inverter Through Switching Devices

Abstract: A new multistepped-voltage waveform inverter with a total harmonic distortion (THD) of 6.25 percent is described. The proposed system consists of a three-phase inverter whose conduction intervgl is smaller than 180 °, a triple-frequency single-phase inverter, and power semiconductor switches that link the two inverters. The advantages of the proposed system over conventional stepped-voltage inverters are that it requires only a small number of switching devices, no three-phase output transformers, and an output filter of reduced size. The relation between THD and the number of steps of an output voltage waveform is discussed. Comparison with other stepped voltage inverters and experimental results using power transistors are also presented.

Single-Chip Adaptive Transversal Filter IC Employing Switched Capacitor Technology

Abstract: Development of compact, high-speed, and low power adaptive transversal filters (ATF's) has been of great interest Such ATF's have already been successfully fabricated in monolithic form employing a short channel MOSFET process and switched capacitor technique, using only complete analog circuit technology while eliminating inherent analog problems This IC with five taps works with both ±5 V and 10 V supplies at a clock rate of more than 250 kHz It has been designed for multipurpose applications such as a decision feedback equalizer (DFE), echo canceller (EC), and linear equalizer (LE), the last of which has already been reported [5] The architecture to realize these applications will be described first Much discussion is presented on the investigation of the operation, characteristics, and performance limitations of this IC in the DFE mode, from which those in the EC mode for two-wire full-duplex data transmission can be understood For a single echo with magnitude of one half that of the original signal and delay time of one clock period from the original signal, and convergence factor of 02 for weight adaptation, the DFE operating at the clock rate of 100 kHz completes equalization within about 12 ms resulting in a residual rms distortion of -454 dB The dominant performance limitation factors are found to be both the correlator harmonic distortion and transversal filter noise, but not the convolver harmonic distortion which is the dominant factor for the LE

Sound quality measurements of audio systems based on models of auditory perception

Abstract: Traditional methods of analyzing the sound quality of audo equipment are based on simple test signals as well as on simple measurement procedures. Sine wave or sweep is applied when measuring nonlinear (harmonic) distortion or frequency response. Combinations of sine waves and/or some kind of noise signals are the most complex test signals used in practice. Analysis methods as well are based on oversimplified models of auditory perception. It is easy to demonstrate how measures like harmonic distortion may be misleading when used to describe the perceived quality of sound, A new methodology is introduced here, which is based on a computational model of auditory perception as the analyzer of sound quality. The model makes it possible to use any real signal as a test signal. Some measurements carried out in practice are described.

Low even-order harmonic distortion amplifier and method

Abstract: An amplifying system and method produces a substantial reduction in the D.C. and even-order harmonics in an output signal by employing a first inverting amplifying stage cascaded with an attenuating stage which is cascaded with a second inverting amplifying stage. The electrical characteristics of each of the two inverting amplifying stages are substantially the same. The gain, in dB, exhibited by each of the amplifying stages is substantially equal to the attenuation loss, in dB, produced by the attenuator stage. Conventional components and fabrication techniques allow substantial attenuation of the D.C. and even-order harmonic components produced by the nonlinearities in the active devices of the amplifiers as compared to a single amplifier case producing the same gain A.

FM Demodulator PLL with compensation for nonlinear varactor characteristics

Abstract: There is provided an improvement of an FM demodulator of the PLL system including a VCO, a phase comparator and a low-pass filter, whereby the distortion components of the FM demodulated signal to be caused due to nonlinearity of the frequency vs. control voltage characteristic of the VCO are eliminated. This improved FM demodulator of the PLL system includes a circuit for making the harmonic distortion components from the output signal of the low-pass filter and synthesizing them with the output signal of the low-pass filter so as to obtain the non-distorted FM demodulated signal.

Thin film magnetoresistive vector sensors with submicron gap width

Abstract: The size of gap between adjacent conducting strips In the folded resistor track of a thin film magnetoresistive sensor element has an important effect on its performance. Pattern fabrication methods using electron-beam lithography enable conductor spacings in the submicron range to be used. Sensors with smaller conductor spacing have an enhanced sensitivity and require a much smaller orthogonal bias field than devices made using conventional photolithography. The parameters for optimum linearity of the signal are considered in terms of the amount of harmonic distortion introduced by the sensor when its working range of ±1 oersted is swept by an input field of sinusoidal form. The distortion values are extremely low and the orthogonal field for best linearity is established to be close to that for peak sensitivity. immunity to fields at right angles to the measurement vector is also a function of the bias field: the optimum value in this case is about 75% of that for peak sensitivity. Noise measurements indicate that levels are sufficiently low to permit magnetic signals of less than one gamma to be detected.

Stereo MPX circuit

Abstract: A stereo multiplex circuit which can reduce a distortion of an FM demodulated signal to be generated due to nonlinearity of the frequency vs. amplitude/phase characteristics of a band-pass filter at an intermediate frequency amplifier stage of an FM receiver. This circuit includes a circuit for multiplying signals consisting of right-channel and left-channel signals and for adjusting the level of this multiplication signal into a suitable magnitude and thereafter inserting into the right and left channels, thereby causing a harmonic distortion to disappear.

Harmonic distortion due to laser modulation in multimode fibre optic analogue transmission

Abstract: The effect of laser-diode frequency chirping on harmonic distortions in multimode fibre analogue transmission with direct intensity modulation was clarified experimentally with results in good agreement with the theory. The results show that the harmonic distortion can be greatly reduced by the reduction of the frequency chirping which accompanies diode-laser intensity modulation.

Distortion cancel circuit in FM stereo

Abstract: There is disclosed a distortion cancel circuit in FM stereo receiver, which circuit synthesizes a canceling signal mainly including the distortion component by performing the arithmetic operation for an FM demodulation signal and adjusts the level of this synthesized canceling signal and thereafter subtractively combining it with the FM demodulation signal. This circuit enables the elimination of harmonic distortion which appears in the stereo MPX signal output due to the band characteristic of an intermediate frequency amplifier.

A synchronous phase-lock loop detector for integrated AM radio

Abstract: A synchronous phase-lock loop AM detector has been realized on a single chip in a bipolar process with an f/SUB T/ of 400 MHz. The circuit accepts input signals at an IF frequency of 450-500 kHz with effective values between 20 and 100 mV. The phase-lock loop capture range is about 150 kHz. AM signals with over 80% modulation depth can be demodulated with less than 1% harmonic distortion in the audio output signal. The power dissipation of the chip is 120 mW at 8 V. The total chip size is 1900/spl times/1300 /spl mu/m/SUP 2/. Since the VCO and the 90/spl deg/ phase shift are completely realized on-chip, large signals at the IF frequency do not occur at the pins of the IC, and parasitic feedback of such signals to the IF amplifier input is minimized.

Power quality and protection of electric distribution systems with small, dispersed generation devices

Abstract: There are several operational problems associated with the connection of small power sources, such as wind turbines and photovoltaic (PV) arrays, to an electric distribution system. In one study the harmonic distortion produced by a subdivision of PV arrays connected through line-commutated inverters was simulated. A second simulation study evaluated protection problems associated with the operation of dispersed ac generators. The purpose of these studies was to examine the adequacy of the electric utility industry's traditional practices and hardware for the operation of dispersed power sources. This paper discusses the results of these simulation studies and gives recommendations for hardware and system operation needed for accommodating this new technology.

Optical analog baseband transmission using opto-electronic negative feedback and rf superposition

Abstract: The radio frequency superposition technique (REST) is the most effective means to suppress the modal noise inherent in the analog baseband transmission using a laser diode and multimode Optical fiber.1 However, because REST degrades relative intensity noise and linearity of laser diodes the maximum obtainable SNR and harmonic distortion degrade.

Harmonic and intermodulation performance of double-heterostructure LED's

Abstract: Using the relationship between the power output of a surface-emitting double-heterostructure LED and the total injection current density, closed-form expressions are obtained for the harmonics, intermodulation products, and differential gain, resulting from injecting the LED by a multisinusoidal signal, without recourse to curve-fitting techniques. Predicted values are compared with previously published experimental and calculated results.

An analysis of quasi-synchronous AM mobile radio operation and recommended design parameter values

Abstract: Quasi-synchronous operation of a number of base transmitters is often used to provide extensive area coverage in land mobile radio systems. An analysis is made of the responses of an AM receiver operating in such a system. The effects of automatic level control and the muting action are shown to nullify any predictions made of system performance based on harmonic distortion of sinusoidal modulating tones. A limited analysis of the types of distortion likely to arise from the mismatch of modulation between transmitters is made in order to give a guide to the parameters to be explored in subjective trials. The results of, first laboratory-based and subsequently field-based, trials are presented and from them recommendations are made for the allowable limits which should be used for the design and maintenance of a quasi-synchronous AM system.

Wave form selecting device

Abstract: PURPOSE:To eliminate the occurrence of an arificial miss, by adding a detector for higher harmonic components to an automatic distortion rate measuring device and providing a pass/fail discriminating function wherer ternary values of a total distortion rate, second higher harmonic, and a third higher harmonic are handled as input signals. CONSTITUTION:A detector 6 which detects only second higher harmonic (2f0) components and a detector 7 which detects only third higher harmonic (3f0) components are connected to the output side of a power IC3 to be measured in parallel with a total distortion (THD) meter 5, and respective output signals (THD, 2f0, and 3f0) of the distortion meter 5 and detectors 6 and 7 are inputted to a display device 8 provided with a good or bad (pass/fail) discriminating function. Meanwhile, a control part 9 provided with a function to control a variable resistor 2' is provided with a function to set the output signal of the IC3 in accordance with a reference from the external.

Simple steady-state solution method for networks with harmonic distortion

Abstract: Due to saturation effects in transformers and shunt reactors, the voltages in electric power systems are sometimes distorted by harmonics. To obtain an accurate steady-state solution for such cases, an electromagnetic transients program can be used which starts from an approximate linear ac steady-state solution at fundamental frequency and then goes into the transient simulation with nonlinear effects included. Such a solution technique is not always efficient, especially in lightly damped systems, where it may take a long time before the final steady state is reached. This paper describes an improved solution method for finding the steady state with harmonic distortion directly. It consists of two iterative loops; the first loop deals with the solution at fundamental frequency, and the second loop takes the harmonics into account. The complete steady-state solution is then obtained by superimposing the voltages and currents from the solutions at fundamental frequency and at the dominant harmonics. The method has been developed primarily for obtaining better initial conditions for transient simulations which start from an ac steady state with harmonic distortion, but it can also be used for steady-state solutions alone.

Analysis and design of a high efficiency sinusoidal inverter

Abstract: This paper applies the sinusoidal pulse‐width‐modulation technique to design single‐phase, fixed‐frequency sinusoidal inverters with ratings less than 3 KVA. It investigates the design methods for various circuits comprising the inverter under the considerations of total harmonic distortion, overall efficiency, and volume. Experiments based on an implemented inverter show that the requirements of low harmonic distortion (less than 3%) and high efficiency (approximately 80%) can be achieved.