Showing papers in "IEEE Transactions on Industry Applications in 1984"
TL;DR: In this paper, a new instantaneous reactive power compensator comprising switching devices is proposed, which requires practically no energy storage components, and is based on the instantaneous value concept for arbitrary voltage and current waveforms.
Abstract: The conventional reactive power in single-phase or three- phase circuits has been defined on the basis of the average value concept for sinusoidal voltage and current waveforms in steady states. The instantaneous reactive power in three-phase circuits is defined on the basis of the instantaneous value concept for arbitrary voltage and current waveforms, including transient states. A new instantaneous reactive power compensator comprising switching devices is proposed which requires practically no energy storage components.
3,331 citations
TL;DR: In this article, a measure of third harmonic to the output of each phase of a three-phase inverter was proposed to obtain a line-to-line output voltage that is 15 percent greater than that obtainable when pure sinusoidal modulation is employed.
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.
383 citations
TL;DR: In this paper, a phase asymmetric PWM (PAPWM) control of a three-phase squirrel-cage machine with a simplified bridge inverter with only four switches was investigated.
Abstract: Possibilities for minimizing component cost in variable- speed drives with frequency control by solid-state converter are investigated. It is shown that in a three-phase system voltage and frequency control of a three-phase squirrel-cage machine may be attained by PWM of the output of a simplified bridge inverter with only four switches. As the phase voltages are in principle asymmetrical, this technique is called phase asymmetric PWM (PAPWM). The operational region of PAPWM control is investigated theoretically in the frequency plane, compared to PWM control of a six-element bridge, and shown to have application possibilities. The system was experimentally tested on a 1O-kVA four-transistor inverter and experimentally compared to the operation of a six-transistor inverter of the same rating. The entire signal electronics subsystem was also minimized regarding components by using a specially dedicated IC circuit developed for PWM applications in three-phase systems. These results prove that a PAPWM system with a B4 bridge can be operated to give the same operational drive characteristics as a B6 bridge with PWM. The price to be paid for using a bridge with only four switches lies in the higher pulse frequencies required to give the PAPWM the same characteristics as a conventional system. Since transistor switches may be operated at high switching frequencies with low switching losses, the system is well suited to transistor inverter control of induction machine drives.
303 citations
TL;DR: In this paper, a six-phase six-step voltage-fed induction motor is presented, where the stator is rewound with two three-phase winding sets displaced from each other by 30 electrical degrees.
Abstract: A six-phase six-step voltage-fed induction motor is presented. The inverter is a transistorized six-step voltage source inverter, while the motor is a modified standard three-phase squirrel-cage motor. The stator is rewound with two three-phase winding sets displaced from each other by 30 electrical degrees. A model for the system is developed to simulate the drive and predict its performance. The simulation results for steady-state conditions and experimental measurements show very good correlation. It is shown that this winding configuration results in the elimination of all air-gap flux time harmonics of the order (6v ±1, v = 1,3,5,...). Consequently, all rotor copper losses produced by these harmonics as well as all torque harmonics of the order (6v, v = 1,3,5,...) are eliminated. A comparison between-the measured instantaneous torque of both three-phase and six-phase six-step voltage-fed induction machines shows the advantage of the six-phase system over the three-phase system in eliminating the sixth harmonic dominant torque ripple.
234 citations
TL;DR: In this article, a typical control actuator system consisting of a brushless synchronous motor and a transistor chopper inverter is described, and several types of construction are described.
Abstract: High-quality electrical servo drives can only be designed and manufactured by using especially compatible and sophisticated components. A typical control actuator system is described consisting of a brushless synchronous motor and a transistor chopper inverter. Important aspects of the design and rating of a three-phase motor with rare-earth permanent magnets are pointed out. Several types of construction are described. The machine control system used is the familiar method of cascade control. By application of "space vectors" two special methods for fast response current control are developed. In the first case, inverter control signals are derived only from measured quantities. In the second case, the optimum controller output can be calculated if additional information about the controlled system exists. Finally, experimental results prove the excellent performance of this drive system.
229 citations
TL;DR: In this article, a self-controlled permanent-magnet (PM) synchronous motor drive with rectangular current excitation has been investigated and it was shown that the pulsating torque can be minimized by a combination of steps including proper adjustment of the rotor magnet pole atc and effective use of rotor speed feedback compensation.
Abstract: Special features of torque production in self-controlled permanent-magnet (PM) synchronous motor drives with rectangular current excitation have been investigated. Addressed issues include the generation of undesired torque pulsations at low speeds and system operating locus limits imposed at high speeds by saturation of the current regulator. Attention is limited to motors in which sources of reluctance torque are suppressed by surface-mounting of the rotor magnets and skewing of the stator slots. Results from the low-speed investigation indicate that the pulsating torque can be minimized by a combination of steps including proper adjustment of the rotor magnet pole atc and effective use of rotor speed feedback compensation. High-speed saturated-regulator performance is significantly influenced by the 120 electrical degree inverter switch conduction intervals inherent with rectangular current excitation. The system torque-speed operating envelope can be expanded by several means, including on-line adjustment of the converter excitation phase angle a, but resulting performance trade-offs require careful scrutiny. A 15-kW prototype PM synchronous motor drive system has been used to confirm key analytical results.
206 citations
TL;DR: In this paper, a new control strategy for a PWM inverter controlled through adaptive hysteresis in an instantaneous feedback loop is theoretically analyzed and verified through simulations and a low-power experimental circuit.
Abstract: A new control strategy for a PWM inverter controlled through adaptive hysteresis in an instantaneous feedback loop is theoretically analyzed and verified through simulations and a low-power experimental circuit. This control gives excellent performance under various load conditions, and it is especially effective in reducing load injected harmonics.
171 citations
TL;DR: In this paper, a new method for the transient analysis of induction machines with saturating leakage reactances is presented, where the equations which define operation under this condition are arranged so that the saturation of stator and rotor leakage as well as magnetizing reactance can be readily modeled with three function generators.
Abstract: A new method for the transient analysis of induction machines with saturating leakage reactances is presented. The equations which define operation under this condition are arranged so that the saturation of stator and rotor leakage as well as magnetizing reactance can be readily modeled with three function generators. The method is equally applicable to the analysis of synchronous machines.
168 citations
TL;DR: In this article, it is shown that substantial power savings can be achieved compared to conventional programmed volt/hertz control and that main flux saturation has a dominant role in determining the optimal operating condition.
Abstract: For a given induction motor under a specified load condition, a combination of stator voltage and frequency exists which results in minimum power losses. This optimal operating point is calculated over the complete speed and torque range using a model of the induction machine including saturation, stray losses, and skin effect. It is shown that substantial power savings can be achieved compared to conventional programmed volts/hertz control and that main flux saturation has a dominant role in determining the optimal operating condition. A detailed analysis of the mechanisms yielding power savings is presented as well as an experimental confirmation of the theoretical results. These results are utilized to study thetinfluence of machine size, rated slip, and other factors on the optimal performance.
158 citations
TL;DR: A theoretical evaluation for Peek's law which yields the corona onset gradient is made in air for positive wire/cylinder and positive point/plane geometries as discussed by the authors, where the physical and geometrical parameters used in Meek's criterion take into account the variation of apparent ionization coefficient?1 of air with humidity, pressure, and temperature and the curvature radius R of the rod tip (or the wire diameter D) A single analytic integrable expression for?1/P which may be used for any value of the reduced field E/p.
Abstract: A theoretical evaluation for Peek's law which yields the corona onset gradient is made in air for positive wire/cylinder and positive point/plane geometries The physical and geometrical parameters used in Meek's criterion take into account the variation of apparent ionization coefficient ?1 of air with humidity, pressure, and temperature and the curvature radius R of the rod tip (or the wire diameter D) A single analytic integrable expression is introduced for ?1/P which may be used for any value of the reduced field E/p The results covering a wide range of parameters 10-7 m < R or D < 107 m (up to a plane/plane geometry) are compared with a variety of experimental results
146 citations
TL;DR: In this article, a two-dimensional field analysis is presented which takes the magnet leakage, the distribution of magnet MMF along its height, and the changing magnet width into consideration, and a comparison of machine performance predicted using this method with test results is also given.
Abstract: The design of the magnetic circuit of permanent magnet machines differs from that of conventional wound field machines mainly due to the low magnetic permeability of the magnets. A two-dimensional field analysis is presented which takes the magnet leakage, the distribution of magnet MMF along its height, and the changing magnet width into consideration. The fundamental component of flux calculated by the model is compared with results obtained by finite element analysis for different magnet configurations covering a practical range of magnet dimensions. A comparison of machine performance predicted using this method with test results is also given.
TL;DR: In this article, it was shown that the chopping frequency of a dc chopper converter depends on the square of the counter EMF of the load, which is a consequence of the fact that three phase currents must sum to zero, rendering one of the three current controllers redundant.
Abstract: In a dc chopper converter having its load current regulated by a feedback controller of the fixed hysteresis type, the chopping frequency is shown to depend on the square of the counter EMF of the load. In a pulsewidth modulated (PWM) inverter, the counter EMF is modulated at the output frequency, so the chopping frequency is modulated at twice the output frequency. For a three-phase PWM inverter feeding a three-wire load, the chopping frequency modulation is not smooth. This is explained to be a consequence of the fact that the three phase currents must sum to zero, rendering one of the three current controllers redundant.
TL;DR: The spontaneous rotation of small spherical and cylindrical objects immersed in liquid dielectrics and subjected to strong electrostatic fields was first recorded by Quincke in 1896.
Abstract: The spontaneous rotation of small spherical and cylindrical objects immersed in liquid dielectrics and subjected to strong electrostatic fields was first recorded by Quincke in 1896. The rotation was found to be threshold-dependent; and certain conditions on the relative conductivities of the liquid and solid particles were discovered necessary for the effect to be observed at all. A review of the literature shows that Quincke rotation has been rediscovered, renamed, and reexplained several times since the original work. Not all published analyses are correct. A very simple solution of the problem is described which nses the effective dipole concept. The relevance of Quincke rotation to various problems in dielectrophoresis (DEP), conduction in liquid dielectrics, etc., is discussed, and a few practical implications are considered.
TL;DR: In this paper, a method to detect slip frequency from rotor slot harmonics of a three-phase squirrel-cage induction motor is proposed, which is obtained by summing the three phase voltages, and after being sampled with a multiple of the stator frequency, it is changed into slip frequency waves, from which a voltage proportional to the slip frequency is obtained.
Abstract: A method to detect slip frequency from rotor slot harmonics of a three-phase squirrel-cage induction motor is proposed. The rotor slot harmonic voltage Is obtained by summing the three phase voltages, and after being sampled with a multiple of the stator frequency, it is changed into slip frequency waves, from which a voltage proportional to the slip frequency is obtained. Sophisticated sampling techniques allow elimination of the third harmonic voltage induced in the sum of the three-phase voltages and also allow reduction of time constant of the slip frequency detector. Expenmental results show that the slip frequency detector has a good linearity in the range of slip frequency of about -50 to +30 percent of the stator frequency.
TL;DR: In this article, the relationship between the stator current and the slip frequency for an optimal efficiency control is derived, and the control loop is suggested, and a small signal analysis is used in order to estimate the transient characteristics.
Abstract: When an induction motor is driven under light loads, the efficiency can be substantially improved by reducing the air-gap flux of the motor. The air-gap flux can be indirectly controlled by adjusting the stator current and slip frequency in the case of a current source inverter induction motor drive system. The relationship between the stator current and the slip frequency for an optimal efficiency control is derived, and the control loop is suggested. By this method, ten percent or more improvement in the efficiency is obtained at a quarter of the full load. Generally, the reduced air-gap flux may result in undesirable dynamic responses. The small signal analysis is used in order to estimate the transient characteristics. The experimental results indicate a stable operation and a good dynamic response.
TL;DR: In this article, a charge simulation technique incorporating discretized equipotential charge shells in the volume is used to approximate the electric field and space charge around a single conductor in corona and to compute the voltage-current relationship for the discharge.
Abstract: A charge simulation technique incorporating discretized equipotential charge shells in the volume is used to approximate the electric field and space charge around a single conductor in corona and to compute the voltage-current relationship for the discharge. No iteration is required in the solution method. Results are compared to corona in coaxial geometry, for which analytical treatment is also possible, and to experimental V-I measurements in line-to- plane geometry.
TL;DR: In this paper, the harmonic performance of the networks of several types of electric vehicle (EV) battery chargers is documented and the cumulative effects at the substation level for random distributions of each of five different charger types are reported.
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.
TL;DR: In this paper, a cycloconverter-fed synchronous machine was used for variable-speed drive system with high dynamic performance and excellent static characteristics over a wide range from zero to top speed, accurate field orientation and high response current control are solved.
Abstract: A high-performance variable-speed drive system using a cycloconverter-fed synchronous machine is described. The principle of the drive control is based on the field-oriented control method. For operating the synchronous machine drive system with high dynamic performance and excellent static characteristics over a wide range from zero to top speed, accurate field orientation and high response current control are particularly important problems to be solved. New methods of solving these problems are presented. This systems was manufactured for a 2500-kW reversible rolling mill drive system, using a six-pulse three- phase cycloconverter and an ordinary rotating field type synchronous machine without any special requirements. The expected performance was successfully obtained.
TL;DR: The most commonly used methods of reduced-voltage starting of three-phase ac squirrel-cage motors are reviewed in this paper, including primary reactor, primary resistors, autotransformer, part winding, wye-delta, and solid state.
Abstract: The most commonly used methods of reduced-voltage starting of three-phase ac squirrel-cage motors are reviewed. They include primary reactor, primary resistors, autotransformer, part winding, wye-delta, and solid state. Other methods are used but less often.
TL;DR: In this article, a semi-empirical induction motor loss model is developed as a function of motor power rating, where losses in rotor, stator and iron (including most important stray losses) are separately estimated and suitably combined.
Abstract: A semiempirical induction motor loss model is developed as a function of motor power rating. The aim is the estimation of losses caused by harmonic-distorted (e.g., PWM) current and voltage supplies. The model may consider harmonics between about 100 and 20 000 Hz and is constructed for power ratings between 1 and 1000 kW. Losses in rotor, stator, and iron (including most important stray losses) are separately estimated and suitably combined. This leads to a simple penalization factor for the time-harmonic currents, which is a function of motor size and which is quasi-linearly depending on harmonic frequency. Total losses are then calculated by the superposition of separate harmonic current or voltage effects. The penalization factor is experimentally verified. The importance of iron (plus stray) losses has been clearly shown. The model predictions are in close agreement with loss measurements on inverter-fed induction motors.
TL;DR: In this article, the authors investigated the energy-saving benefits of two lighting control strategies -scheduling and daylighting-were investigated at demonstration sites in two large commercial buildings, and the influence of switching the zone size on energy savings was examined.
Abstract: The energy-saving benefits of two lighting control strategies -scheduling and daylighting-were investigated at demonstration sites in two large commercial buildings. A continuously dimmable lighting control system was installed at the Pacific Gas and Electric Company Building in San Francisco, and an on/off switching system was installed at the World Trade Center in New York City. By automatically scheduling the operation of the lighting systems to conform with occupancy patterns, lighting energy consumption was reduced 10-40 percent. Several scheduling techniques were investigated, and the influence of switching the zone size on energy savings was examined. Using photoelectrically controlled lighting systems, which switch or dim lighting in accordance with available daylight, the energy consumed for lighting in daylit areas was reduced to 25-35 percent. The influence of clear and overcast conditions on the energy savings associated with daylight-linked controls is discussed.
TL;DR: In this paper, a scalar control method for an induction motor is described in which the dynamic response is enhanced by a feedforward decoupling network, which is inherently simple and does not require intricate signal processing as in vector control methods.
Abstract: A scalar control method for an induction motor is described in which the dynamic response is enhanced by a feedforward decoupling network. The scalar control method is inherently simple and does not require intricate signal processing as in vector control methods. The parameters of the adaptive decoupler are solved by off-line computation and can be implemented by using a microcomputer. A preliminary control schemp using a voltage-fed PWM inverter bas been tested in the laboratory, but more investigation is needed to explore fully the potential of the method. The proposed control scheme is expected to give comparable or better performance than the conventional vector control methods.
TL;DR: In this paper, the authors present a set of criteria with which to judge the suitability of a given motor drive algorithm for a given pump application, such as startup behavior, response to pump overload, and loss of priming fluid as a control system element.
Abstract: Efficient variable-frequency control of the centrifugal pump drive motor is preferable to fluid control by a throttling valve or a bypass valve in many applications. The properties of the centrifugal pump as a motor load are discussed and the implications for the drive design. Also discussed are other properties of the motor drive in a pumping system such as startup behavior, response to pump overload, and loss of priming fluid as well as its characteristics as a control system element. Since fans and centrifugal blowers are similar in operation to centrifugal pumps, much of this discussion is also applicable to them. The aim is to give the specifier of pumping system components a set of criteria with which to judge the suitability of a given motor drive algorithm for his pumping application.
TL;DR: In this paper, a procedure for analyzing train voltages for new railroad electrification systems which utilize single-phase current at 60 Hz and at higher voltages of 25 and 50 kV with and without auxiHary transformers is presented.
Abstract: A procedure is presented for analyzing train voltages for new railroad electrification systems which utilize single-phase current at 60 Hz and at higher voltages of 25 and 50 kV with and without auxiHary transformers. Modern catenary configurations are presented. A computer program is described which calculates the impedances of multiple track configurations and includes the effects of magnetic conductors (rails), of auxiliary transformers and of earth return. References to test results on rail impedances are also presented. A method is described to calculate train voltages for radial feed, centerfeed, and double-end feed systems and for multiple catenaries. Equivalent circuits are derived and specific examples of modern catenary systems are given.
TL;DR: In this paper, an effective braking system suitable for three-phase induction motor drives is discussed, where a single capacitor is connected across two of the motor terminals allowing single-phase self-excitation.
Abstract: An effective braking system suitable for three-phase induction motor drives is discussed. Braking is achieved in four stages using an electronic switching circuit. Initially, a single capacitor is connected across two of the motor terminals allowing single-phase self-excitation. Following a certain speed drop, a second capacitor is added across the same terminals to sustain self-excitation and reduce the speed further. In the third stage magnetic braking is achieved by short circuiting the third terminal. Finally, the motor is brought to a standstill by dc injection. A method of determining minimum capacitor requirements is presented for both single-phase and symmetrical application. Experimental results are included, demonstrating the validity of theoretical results regarding capacitor requirements, and indicating the effectiveness of the proposed braking scheme.
TL;DR: In this paper, three commonly used techniques at drive techniques are reviewed and test data are provided for 100-hp standard and energy-efficient designs operated on each of the three types of drives.
Abstract: Considerations in applying ac motors with solid-state adjustable -frequency controllers are discussed, and guidelines. are offered where possible. As a background, three commonly used at drive techniques are reviewed. Test data are provided for 100-hp standard and energy-efficient designs operated on each of the three types of drives.
TL;DR: A high-performance speed control system for cage induction motors is described which utilizes a PWM inverter and new control methods have been devised; one varies the gain of the current controller in proportion to the primary frequency, and another compensates for the slip frequency by using the deviation between the flux reference value and the actual value.
Abstract: A high-performance speed control system for cage induction motors is described which utilizes a PWM inverter. The effects of primary current coincidence and machine constant variation on system characteristics such as response time, torque precision, and operating noise were investigated. Based on the results obtained, new control methods have been devised; one varies the gain of the current controller in proportion to the primary frequency, and a second compensates for the slip frequency by using the deviation between the flux reference value and the actual value. Effectiveness of the compensation methods was confirmed in tests.
TL;DR: A brief review of the basic theory of induction generators with a discussion of the major differences between induction and synchronous generators can be found in this paper, where the authors compare the performance of a 3000-kW induction generator compared to that of a comparably sized synchronous machine in a typical cogeneration scheme.
Abstract: An induction generator an induction motor which is driven above its synchronous speed byasuitable prime mover and is provided with source sufficient reactive power for excitation. The simplicity, reliability, and low cost of the induction generator makeit well suited for many Industrial cogeneration applications. A brief review is presented of the basic theory ofinduction generators with a discussion of the major differences between induction and synchronous generators. The application of a 3000-kW induction generatoris compared to that of a comparably sized synchronous machine in a typical cogeneration scheme. The comparison focuses on relative costs, equipment, protective relaying, utility tie-in and synchronizing, maintenance, and operating procedures.
TL;DR: In this paper, the design and performance of a unique concentrated winding machine specifically designed for operation with a static power converter is described, and the potential of such a machine operating as a motor is also described.
Abstract: The design and performance of a unique concentrated winding machine specifically designed for operation with a static power converter is described. When operating in tonjunction with a converter supply, the machine is theoretically capable of 15 percent more power output for the same active copper and iron than a conventionally designed synchronous machine of the same rating. The performance of the machine operating as a generator feeding a rectifier load is described, the theoretical predictions are compared with test. The potential of such a machine operating as a motor is also described.
TL;DR: In this article, the duality of the electrostatic and the centrifugal dispersion processes is discussed in the presence of dominant electrostatic forces, dominant centrifugal forces, and a combination of both forces.
Abstract: A 5-cm diameter aluminum disk which may be spun at speeds of up to 10 000 r/min is used to disperse hydrocarbon oils. An electrostatic field may be set up at the edge of the disk by ralsing the potential of a concentric ring elctrode to several kilovolts. The liquid dispersion process from the edge of the disk is studied in the presence of dominant electrostatic forces, dominant centrifugal forces, and a combination of both forces. The duality of the electrostatic and the centrifugal dispersion processes is discussed.