Showing papers in "IEEE Transactions on Industry Applications in 1995"

Space vector modulated three-phase to three-phase matrix converter with input power factor correction

Abstract: Analysis, design, and implementation of the space vector modulated three-phase to three-phase matrix converter with input power factor correction are presented. The majority of published research results on the matrix converter control are given an overview, and the one which employs simultaneous output-voltage and input-current space vector modulation, is systematically reviewed. The modulation algorithm is theoretically derived from the desired average transfer functions, using the indirect transfer function approach. The algorithm is verified through implementation of a 2 kVA experimental matrix converter driving a standard induction motor as a load. The switching frequency is 20 kHz. The modulator is implemented with a digital signal processor. The resultant output voltages and input currents are sinusoidal, practically without low-frequency harmonics. The input power factor is above 0.99 in the whole operating range.

A discussion on IGBT short-circuit behavior and fault protection schemes

Abstract: IGBTs are available with short-circuit withstand times approaching those of bipolar transistors. These IGBTs can therefore be protected by the same relatively slow-acting circuitry. The more efficient IGBTs, however, have lower short-circuit withstand times. While protection of these types of IGBTs is not difficult, it does require a reassessment of the traditional protection methods used for bipolar transistors. An in-depth discussion on the behavior of IGBTs under different short-circuit conditions is carried out and the effects of various parameters on permissible short-circuit time are analyzed. The paper also rethinks the problem of providing short-circuit protection in relation to the special characteristics of the most efficient IGBTs. The pros and cons of some of the existing protection circuits are discussed and, based on the recommendations, a protection scheme is implemented to demonstrate that reliable short-circuit protection of these types of IGBTs can be achieved without difficulty in a PWM power convertor motor drive application. >

Improvements in EMC performance of inverter-fed motor drives

Abstract: An experimental investigation of conducted radio-noise emission from a conventional pulse width modulated (PWM) inverter of medium power feeding an induction motor is described. It is determined that the inverter system generates considerable impulse currents through the power leads feeding the system resulting in serious conducted electromagnetic interference (EMI) problems and significant voltage waveform distortion in the power system. The dominant emission sources in the system are identified. A proposed model of the drive system for the purpose of evaluation of EMI are developed. Several low-cost strategies for improvement in EMC performance of the PWM inverter are then proposed. Experimental results demonstrate that disturbance from the modified system can be dramatically reduced, and that the EMC performance of the system has come very close to meeting the IEC CISPR and FCC limits on conducted emissions for digital devices.

Monitoring of defects in induction motors through air-gap torque observation

Abstract: This paper suggests a method to monitor defects such as cracked rotor bars and the shorted stator coils in induction motors. Air-gap torque can be calculated while the motor is running. No special down time for measurement is required. Data of the air-gap torque for a motor should be periodically kept for comparison purposes. Since more data than just a line current are taken, this method offers other potential possibilities that cannot be handled by examining only a line current. The theoretical foundation for this proposed method is presented. Experiments conducted on a 5-hp motor show the validity and potential of this approach. Further studies are planned to extend the proposed method in detail and to monitor defects developed in other types of rotating machines. >

A new compensation strategy reducing voltage/current distortion in PWM VSI systems operating with low output voltages

Abstract: In a voltage-fed PWM inverter, the relation between the reference voltage and the output voltage is nonlinear due to the dead time effect and the voltage drop of the switching devices. The nonlinear voltage distortion invokes serious problems such as current waveform distortion and deterioration of the performance. Especially, the clamping of current around the zero crossing point is the most serious problem in the low-frequency region. In this paper, the analysis of the zero current clamping phenomenon is discussed. From this analysis, a novel distorted voltage compensation method which eliminates zero current clamping is presented. Experimental results are also presented to demonstrate the validity of the proposed method. >

AC/DC/AC PWM converter with reduced energy storage in the DC link

Abstract: The paper introduces the family of quasi-direct converters, i.e., forced-commutated AC/DC/AC power converters including small energy storage devices in the DC link. In particular, the case of the three-phase to three-phase quasi-direct power converter is considered. Since energy storage minimization calls for instantaneous input/output power balance, a proper control strategy is needed. The paper describes a simple and effective control technique which also provides high-power factor and small distortion of the supply currents. After a discussion of the general properties of quasi-direct power converters, design criteria of both power and control sections are given, and experimental results of a 2-kVA prototype are reported. >

An integral battery charger for four-wheel drive electric vehicle

Abstract: In this study, an integral battery charger is proposed, which fully uses the hardware of the four-wheel drive electric vehicle. It has no extra component except a mechanical transfer switch. The inverters and the traction motors for the propulsion of the vehicle are transformed to a battery charger. It is verified by a prototype experiment that the charger can be operated at unity power factor and can match any kind of charging mode, such as constant voltage or constant current. >

A new design concept of permanent magnet machine for flux weakening operation

Abstract: In this paper, a new design concept of a PM machine for flux weakening operation is proposed. The feasibility of strong flux weakening capability without permanently demagnetizing the permanent magnet is investigated. Results from the finite element analysis on the proposed PM machine structure are presented to verify the new design concept. >

Analysis and comparison of PM synchronous motor and induction motor type magnetic bearings

Abstract: In this paper, a general solution of radial position control applicable to PM synchronous type and induction type rotating motors is presented. The rotor of the permanent magnet motor is assumed to have sinusoidally distributed magnetic poles along the axial surface, while the rotor of the induction type motor is assumed to have uniform magnetic property. The inner wall of the stator is also assumed to have a current sheet, which can produce an arbitrary current distribution. The same number of magnetic poles gives the rotating torque to the rotor, while plus/minus two poles of the motoring control produces a pure radial force to the rotor. By controlling the magnitude and phase of the plus/minus two-pole current distribution relative to the motoring magnetic pole, the radial force can be controlled in the radial coordinate. This general solution is experimentally confirmed by using a simple experimental setup. >

A new energy optimizing control strategy for switched reluctance motors

Abstract: This paper describes a new and machine-independent method to minimize the energy consumption of a speed controlled switched reluctance motor (SRM). The control strategy is to vary the duty cycle of the applied DC voltage in order to obtain the desired speed quickly and when operating in steady-state vary the turn-on angle (a/sub on/) of the phase voltage to minimize the energy consumption. The power flow is measured in the DC-link and used to control the turn-on angle. Simulations carried out on a three-phase 6/4 pole SRM justify the algorithm and the physical implementation in a Siemens SAB 80C517A microcontroller is described. Measurements on two different load systems show it is possible to minimize the energy consumption on-line in a speed controlled switched reluctance motor without losing the dynamic performance. A comparison with an ordinary mode-shift controlled SRM shows more than an 8% increase in overall efficiency for some operation points. The algorithm is fully applicable to other switched reluctance motors at other power levels or with other pole configurations. >

Control method for a combined active filter system employing a current source converter and a high pass filter

Abstract: This paper describes a control method with a combined filter system which senses load current, source current, and line voltage to create reference signals for an active filter. The transfer function of the active filter is identified and is used for the control system design. It is shown that the source current feedback is most effective in suppressing the harmonic-enlarging effects due to parallel resonance and the harmonic current generated by source harmonic voltages. A small setup controlled by a DSP was built, and the validity of the proposed method was demonstrated by experimental results. >

Interpretation and analysis of power quality measurements

Abstract: This paper describes advances in power quality monitoring equipment and software tools for analyzing power quality measurement results. Power quality monitoring has advanced from strictly problem solving to ongoing monitoring of power system performance. The increased amount of data being collected requires more advanced analysis tools. Types of power quality variations are described and the methods of characterizing each type with measurements are presented. Finally, methods for summarizing the information and presenting it in useful report formats are described.

Adjustable speed drive for residential applications

Abstract: This paper describes a demonstration of an adjustable speed drive suitable for use in residential applications such as compressors and fans in heat pumps, air conditioners, and refrigerators. The adjustable speed drive uses only a four-diode rectifier and a six-transistor six-diode inverter and does not require a source-frequency filter inductor or capacitor. Motor speed is adjusted with source-frequency phase control eliminating the switching loss and electromagnetic interference caused by the more commonly used high-frequency pulse-width modulation. Low source-current distortion and high power factor are obtained at a full-load operating point which is found using a parametric analysis.

Reactive absorption of NOx using wet discharge plasma reactor

Abstract: In this paper, the authors report the results of laboratory experiments on NO/sub x/ removal (DeNOx) using a nonthermal plasma process. Studies were conducted on a dry-type plasma reactor and several wet-type reactors to evaluate DeNOx efficiency. The reactor geometry was coaxial with an inner discharge electrode and an outer ground electrode wrapped on an insulating glass tube. Simulated flue gas was used in the experiment. The dry-type reactor performed better with the addition of ammonia and water vapor to the simulated gas. In the wet-type reactors, water and NaOH solution were used as absorbents and DeNOx performance was found to be the same in each case. Also, with water as the absorbent and with its pH value dropping below 3, the performance of the wet-type reactors remained constant. Studies on wet-type reactors, further, suggested that about half of NO removed by the plasma was dissociated into N/sub 2/ and O/sub 2/ and the rest was absorbed by water. The studies indicate that wet-type reactors performed better than the dry-type reactor in the removal of NO/sub x/.

A finite-element analysis of bipolar ionized field

Abstract: This paper describes a new iterative method for the analysis of the bipolar ionized field in HVDC transmission lines without resorting to Deutsch's assumption. The finite-element technique (FET) is used to solve Poisson's equation where the constancy of the conductors' surface field at the corona inception value is directly implemented in the finite-element formulation. The proposed method has been tested on laboratory and full-scale models. The calculated V-I characteristics agreed well with those calculated and measured previously. The dependence of the corona current as well as its monopolar and bipolar components on the conductor height is discussed. The simplicity in computer programming in addition to the low number of iterations required to achieve convergence characterize the proposed method of analysis. >

Application, design, and specification of harmonic filters for variable frequency drives

Abstract: The proliferation of variable frequency drives in industry has led to serious concerns about power quality in electrical distribution systems. This paper presents tables and charts to help the system design engineers address some basic concerns such as the need for harmonic filters, their effect on displacement power factor, etc., without going into a full-scale harmonic analysis of the distribution system. Relative harmonic performance of the different types of drives such as the load commutated inverter (LCI), the current source inverter (CSI), and PWM drives is discussed. A factor called the harmonic factor is defined which can characterize the performance of a drive by a single number. The relation between harmonic factor and the total harmonic voltage distortion is derived. Attenuation of the harmonic voltages by the filters is calculated and presented in the form of generalized curves. >

Improved cage rotor models for vector controlled induction motors

Abstract: Variations in motor model parameters lead to the detuning of vector controllers which, in turn, cause a deterioration in performance, particularly during transient and field weakening operation. Parameter adaptation schemes seek to change the model parameters based on observed performance, but are still based around a simple model for the machine which is not adequately representative. Improved motor models, based on deeper phenomenological understanding of the machine offer a viable alternative. In this paper, the authors present a model which enables rotor leakage and main flux path saturation and deep-bar effects to be taken into account. The model is verified experimentally using a 7.5-kW 4-pole motor, mounted on a piezoelectric force table which enables transient torques to be measured. >

Design of the clamped-current high-power-factor boost rectifier

Abstract: This paper examines a high-power-factor boost rectifier where the peak switch current is clamped at a constant value during the input voltage line cycle. Optimum parameter values are derived to minimize the harmonic distortion in the input current. Advantages of the clamped-current control include overall simplicity, relatively low inductive energy storage and component stresses, and a fixed operating frequency. Results are experimentally verified on a 1.3 kW prototype featuring high efficiency and high power factor over a wide load range. >

High-efficiency, high-density MHz magnetic components for low profile converters

Abstract: A highly efficient (99.5%) transformer and resonant inductor with very high power density (1500 W/in/sup 3/) and low profile (height 40) of small gaps to reduce the effect of fringing fields. The high-frequency loss measurements for such highly efficient inductors requires a special ring down measurement set-up which is also described. >

Determination of mechanical resonances in induction motors by random modulation and acoustic measurement

Abstract: Acoustic noise emission from PWM-VSI inverter driven induction motors is a well-known problem. The generated noise depends mainly on two factors: the harmonic content of the supply voltage waveform; and the mechanical resonance frequencies of the induction motor. It is necessary to know the mechanical resonances to optimize the switching scheme of the inverter to reduce the noise emission. Measuring the resonance frequencies is normally a laborious process. This paper introduces a new method for estimating the mechanical resonances from acoustic noise measurements. Employing random modulation of the output voltage of the inverter, the voltage spectrum can be spread over a wide frequency range. Using the spectrum analysis of the measured acoustic noise, the resonances can easily be estimated as the dominant frequencies of the acoustic noise spectrum. The method was tested on a 2.2 kW induction motor at no load and full load. Some of the mechanical resonances of the motor at no load were calculated by the Holzer method. The calculations showed good agreement with the sound measurements. The influence of the fan cowl was investigated and it is concluded that this is an important factor in the acoustic noise emission. Finally, it was observed that new mechanical resonances appeared when the induction motor was loaded by a pump drive system, and they were estimated by the measurement technique. >

Electrification of single polymer particles by successive impacts with metal targets

Abstract: Electrification of single polymer particles by successive impacts with separated metal targets was measured separately for each impact. From these experiments, the process of the electrification of the polymer particle due to successive impacts was traced. At the second impact, the initial charge of the particle becomes nonuniform because of the presence of the impact charge generated by the first impact. In order to account for the contribution of this nonuniform initial charge on the impact charging, a new model was proposed in which the electrostatic field around the particle was considered. Our experimental results were discussed based on the new model.

Dynamics and linear stability of charged jets in dielectric liquids

Abstract: The physical system to be considered is a blade-plane configuration in a dielectric liquid. For high electric fields, injection from the blade takes place with ions of the same polarity. The Coulomb force acting upon the injected charges originates an electrohydrodynamic (EHD) flow, referred in what follows as the charged jet. A laminar solution of this EHD jet is obtained using similarity analysis. If transport of charge is dominated by convection, i.e., neglecting molecular diffusion and ion drift, and the electric field is assumed constant, the problem is mathematically equivalent to the bidimensional thermal plume in the limit of large Prandtl numbers. The authors examine the stability of this EHD jet using linear theory and parallel-flow approximations. Neutral stability curves are computed numerically in terms of a nondimensional parameter which is the electrical analogous to the Grashof number. Finally, some experimental observations are presented, followed by a short discussion. The role played by the viscosity correlates reasonable well with the theoretical analysis. >

The Zero Voltage Switching Partial Series Resonant Converter

Abstract: A new high-frequency dc to dc converter, suitable for application in the kilowatt range, is presented. The topology is based on a half bridge series resonant converter, i.e., having only two switches. Resonance occurs only for a part of each switching cycle, and a discrete energy pulse is transferred to the load every half cycle, rendering a variable frequency controller for controlling the output power. The converter features zero-voltage turn-on, and snubbed turn-off at reduced current for the switching devices, and zero current commutation of the rectifier diodes, making it suitable for IGBT switches operating at a switching frequency higher than 20 kHz. The efficiency of the converter is very high under full load and low load conditions, while the dynamic output voltage range is two times larger than that of the conventional half bridge Series Resonant Converter.

Modification of surface energy, dry etching, and organic film removal using atmospheric-pressure pulsed-corona plasma

Abstract: A laboratory-scale atmospheric-pressure plasma reactor, using a nanosecond pulsed corona, was constructed to demonstrate potential applications ranging from modification of surface energy to removal of surface organic films. For surface modification studies, three different substrates were selected to evaluate the surface energies: bare aluminum, polyurethane, and silicon coated with photoresist. The critical surface energy for all materials studied significantly increased after the plasma treatment. The effects of gas composition and plasma treatment time were also investigated. Photoresist, ethylene glycol, and Micro surfactant were used as test organic films. The etching rate of a photoresist coating on silicon was 9 nm/min. Organic film removal using atmospheric pressure plasma technology was shown to be feasible. >

Multiturn High-Frequency Coaxial Winding Power Transformers

Abstract: Previous papers on coaxial winding transformers have focused on designs that use a copper tube to form a single- turn outer winding, and litz wire for a multiple-turn inner winding. In high-power applications, the increased resistance of a solid outer winding due to skin effects can be a limiting factor in achieving good performance, especially at frequencies above several hundred kilohertz. A single-turn outer winding leads to large core cross section areas at lower frequencies and the turns ratio is limited to a ratio of 𝓃: 1, where 𝓃 is an integer. This paper demonstrates several methods for achieving multiturn outer windings to improve design flexibility for the coaxial winding transformer. Experimental measurements on transformers that have multiturn outer windings are included to confirm analytical results and demonstrate the modified designs.

Transient recovery voltage considerations in the application of medium voltage circuit breakers

Abstract: Medium-voltage circuit breakers can fail to interrupt three-phase fault currents when power systems have transient recovery voltage (TRV) characteristics which exceed the rating of the circuit breaker. This paper examines the application of 13.8-kV generation and load switchgear for an oil refinery in which circuit parameters as originally designed would have exceeded the 13.8-kV circuit breakers' TRV ratings had corrective measures not been taken. This paper illustrates this case and discusses the basis of TRV, how TRV is assessed, and alternative actions taken to bring circuits to within the 13.8-kV circuit breaker ratings.

Development of an 11,000 r/min, 3500 hp induction motor and adjustable speed drive for refinery service

Abstract: Faced with the need to revise the refining process to produce reformulated gasoline in compliance with state and federal clean air requirements, the Chevron El Segundo Refinery found justification to purchase special high-speed electric motors with adjustable-speed drives to replace existing steam turbine recycle compressor drivers. This paper explains the decision-making process and rationale that led to this purchase. Further, it describes the design/development process and testing/approval procedures to demonstrate the necessary reliability levels for critical refinery service in this first-of-its-kind application.

Lightning, Grounding and Protection for Control Systems

Abstract: Protection for installations that have been modernized or retrofitted presents a unique mix of problems that require a different perspective from a new installation. The paper addresses lightning, transients, and radiation that cause problems on programmable logic controllers, distributed control systems, and remote electronic transducers. While complex grounding grids and networks were not required for analog systems, newer digital equipment requires a very effective means of maintaining equal potential throughout the facility. Methods of protecting circuits include a variety of sophisticated and not-so-elegant techniques. Special consideration must be given to the impact that towers have on a protection system. The investigation ranges from no air terminals to lightning arrays. The protection problem is compounded when different soils such as clay and rock are encountered. Methods of calculating the grounding circuit resis- tance are identified. Although the paper is based on a retrofit, the techniques are appropriate for any industrial installation using distributed control.

Analysis of No-Load Characteristics of a Bearingless Induction Motor

Abstract: This paper presents the design and analysis of a bearingless squirrel-cage induction motor. There are two sets of stator windings. The main winding is a four-pole arrangement, while the control winding is a two-pole type. The latter is utilized to produce radial forces on the rotor shaft. The two-pole winding currents are regulated by radial position sensors and control strategies in order to maintain the rotor shaft position near the air gap center. The voltage and current relationships of the two-pole windings were derived from the machine inductance model and equivalent circuits. The influences of the secondary rotor circuits were also taken into account. The theoretical values of current, voltage, and radial force were compared with the experimental results. It was found that the two-pole windings need only about 2 percent of the voltampere (VA) requirements of the main motor windings.

Arc and flash burn hazards at various levels of an electrical system

Abstract: This paper discusses the effect on humans of arcing and flashing from high energy electrical equipment It reviews the results of a survey of several large petrochemical facilities in the US about personal protective equipment (PPE) and other equipment used for protection from arcing and flashing This paper also presents the results of calculations done for typical industrial and large commercial electrical distribution systems and supports the use of personal and other protective equipment for work performed on or near high energy electrical equipment