IEEE Transactions on Industry Applications

While the market for energy management systems (EMS) has been exploding, there are many indications that the pendulum of high expectations may have swung too far. A simple seven-day time clock can usually provide 80-95 percent of the potential savings of many EMS features. For several hundred additional dollars, a small microprocessor based time clock with features such as automatic holiday and daylight savings adjustments, optimal start, and four separate load stop/start schedules (ventilation, heating, and air conditioning, indoor lights, and outdoor lights) can be purchased which can increase the savings an additional 5-20 percent on most buildings. Owners of multiple building systems or large commercial and industrial buildings can often justify a complex EMS with increased load scheduling capability. However, EMS features such as duty-cycling and demand limiting are usually overrated in their energy savings capability, not only because slowing down the fans can save more energy than cycling them, but also because duty cycling can cause personnel discomfort and equipment maintenance problems. Moreover, any temperature control modifications which save energy can usually be installed without an EMS for less initial cost and with an equivalent energy savings. Additional expenses for EMS features such as temperature monitoring and remote set point adjustment are not usually of value if a building's heating, ventilating, and air conditioning (HVAC) system is operating properly. EMS features such as metering and report logs can be useful diagnostic tools in the hands of a qualified individual, but often they provide data diarrhea.

The use of flexible intermediate bulk containers (FIBCs), or “big bags” as they are commonly known, is becoming widespread in a variety of industries, including chemical, pharmaceutical, and foodstuffs. Typically, FIBCs, roughly cubic in shape and constructed from woven polypropylene, are used to store and transport powdered or granular material in loads of between 300-1000 kg. In many cases, FIBCs are used in the vicinity of sensitive flammable atmospheres which may arise from the presence of dispersed combustible dusts or solvent vapors. Over the years, there have been a number of serious fires and explosions (particularly during the discharging of the bag contents) which have been attributed to static electricity. As a result, various “antistatic” FIBC designs have been produced containing intrinsic features aimed at minimizing the risk of electrostatic ignition. This paper presents the results of a rigorous assessment of a variety of FIBC designs with regard to electrostatic ignition hazard in flammable atmospheres of minimum ignition energy 0.12, 0.25, and 1.5 mJ. The study involved setting up a test rig to enable the FIBCs to be filled and emptied under controlled conditions of relative humidity. During these operations, the electrostatic activity in terms of surface potentials, electric field, and electrostatic discharge energy was monitored. Incendiary discharges were quantified by using a calibrated propane/oxygen/nitrogen gas probe. The findings of this paper indicate which of the designs can be safely used in various industrial processes without risk of ignition

Bipolar charging experiments were performed on particles in the 1-13 μm diameter size range, and the data were used to evaluate continuum regime models for predicting charge acquisition. Particles were exposed to countercurrents of positive and negative ions in the presence of an external electric field. Particle charge was determined from observations of particle trajectories in a uniform electric field. Data were obtained for dimensionless charging times from approximately 1 to 40, dimensionless electric fields from 1 to 20, and positive-to-negative ion conductivity ratios of 3, 10 and ∞. The data were compared to predictions of field-diffusion theory, classical field theory, classical diffusion theory, and an empiricism formed by adding the field and diffusion approximations. Comparisons were also performed using data obtained previously for particles in the 0.3-1.1 μm diameter size range. Predictions were found to be in excellent agreement with the data

Placing major pieces of electrical equipment in service is aided by a systematic approach to selection, specification, inspection, shipment, storage, check-out, and run-in. This paper describes the detailed planning that helped assure a successful start-up of a large electrical motor. Although a specific installation is described, it will be found that many of the procedures will be generally applicable.

With today's concerted effort to save energy and operating costs in petroleum and chemical processes, much attention is being paid to the study of the economics of constant-versus adjustable -speed motor drives for pumps, compressors, and blowers. A recently installed 10 000-hp compressor drive application is used as an example of such a study. To obtain the required variable flow from the compressor, a case using a constant-speed drive with throttling of the compressor is compared with cases using adjustable-speed drives utilizing a constant-speed motor and hydraulic coupling, an adjustable- frequency drive, and a steam turbine drive. A format is provided for making such a study, and other considerations of constant-versus adjustable-frequency drives are discussed.

The trend in compressors for fuel cells, heat pumps, aerospace, and automotive heating, ventilation, and air-conditioning systems is toward ultracompact size and high efficiency. This can be achieved by using turbocompressors instead of scroll, lobe, or screw compressors, increasing the rotational speed and employing new electrical drive system technology and materials. This paper presents a miniature electrically driven two-stage turbocompressor system running at a rated speed of 500 000 r/min. The design includes the thermodynamic analysis, the electric motor, the inverter, the control, and the system integration with rotor dynamics and thermal considerations. Experimental measurements such as the compressor map are presented for air under laboratory conditions. The two-stage turbocompressor has been tested up to a speed of 600 000 r/min, where a maximal pressure ratio of 2.3 at a mass flow of 0.5 g/s has been reached. To the authors' knowledge, this is the highest rotational speed achieved with an electrically driven turbocompressor.

A 5 kV, 300 A, variable DC source is described. This source will be used by Hydro-Quebec to determine the short-circuit impedances of HVD (high-voltage direct current) links. The converter is composed of four eight-thyristor bridges connected in series in a 24-pulse arrangement. The triggering pulses are transmitted to the thyristors by fiber-optic cables

This paper presents the implementation of a digitally controlled parallel active filter for a thyristor rectifier with inductive load. Using a state-of-the-art digital signal processor (DSP) platform (ADSP21020 and ADMC200), a fully digital control of the system, based on the dead-beat control of inverter currents and space vector modulation, is implemented. The intrinsic calculation delay of the dead-beat algorithm is shown to represent a serious hurdle for the achievement of a satisfactory compensation quality. In particular, meeting the IEC 1000-3-2 standards for class A equipment appears to be quite difficult, especially in the high-frequency range. This paper investigates the effects of the input passive filters and power converter design on the system's performance and describes the implementation of the digital control by means of the specified hardware. Experimental results are finally given to evaluate the achieved performance

The feasibility of the single-phase, full-bridge rectifier with an LC filter to meet the IEC 1000-3-2, class-D specifications is assessed. It is found that this passive LC-filter approach can meet the required specifications if a proper inductance value of the filter choke is selected. Choke design considerations and performance evaluation results that include the power loss, volume, and weight estimates for applications with power levels between 75 and 600 W are presented. Index Terms- Electromagnetic compatibility, IEC 10003-2 specifications, passive input-current shaping, passive power-factor correction, rectifier with LC filter.

Present Federal regulations which specify maximum instantaneous circuit breaker settings for the short-circuit protection of coal mine trailing cables are discussed. The characteristics of mine power systems that limit short-circuit current in three-phase trailing cables are analyzed and minimum expected short-circuit currents for three-phase 480-, 600-, and 1040-V trailing cables are tabulated. New maximum instantaneous circuit breaker settings, based on minimum expected short-circuit currents and typical breaker tolerances, are proposed with emphasis on safety. Finally, atypical mine power systems are discussed and field tests cited.

A high-performance fully digital controller has been designed for the control of a switched reluctance (SR) motor built for vehicle propulsion. The SR machine is specifically designed and built to have high density and low noise. The controller is designed to maximize the machine efficiency, the peak overload capability, and to minimize torque ripple at low speed. Lookup tables are stored in a digital-signal-processor-based controller to calculate the control parameters online. Three interpolations, between torque command, motor speed, and battery voltage, are performed to obtain the control parameters. Difficulties associated with the interpolation scheme are addressed. A high-bandwidth fully digital proportional plus integral current regulator has been designed for the control of the phase current. Advantages as well as the difficulties with the operation of the SR machine and its control have been addressed. A complete characterization of the controller for the entire torque-speed plane has been made through extensive dyno testing. Simulation and dyno test results have been presented to demonstrate the performance of this controller.

Voltage-source inverter (VSI) technology, suitable for synchronous-motor applications, now exists with high power ratings producing high output voltage (≥ 11 kV) with significant benefits over the widely used load-commutated-inverter drives. This paper covers an existing VSI technology applied for the first time at a higher operating voltage. This 15.5-MW 11-kV VSI adjustable-speed drive (ASD) installation is used to soft start three synchronous motors and speed control one of these for a process gas compressor application. Challenges faced during commissioning are described, and associated solutions are presented. A failure analysis of the ASD during commissioning is presented. An ASD design review was undertaken, which has resulted in an improved alternative to the conventional high-voltage busbar design. A protection-coordination study incorporating incoming switchgear and internal drive protection functions is presented. Improved protection schemes and settings are described to obtain faster coordinated fault clearance and improved ASD availability. This paper provides operating experience since the modified ASD has been placed in service in January 2006. Key recommendations are made to enhance the reliability, availability, and performance of medium-voltage drive systems. Also, suggestions are made for additions to the 2006 IEEE 1566 medium-voltage ASD standard.

The effect of an electric field on boiling refrigerant R-11 was investigated experimentally. The test section consisted of a flat plate and a single tube with several rows of electrode wire. The influence of refrigerant oil, the surface roughness of the test tube, and polarity of an applied voltage on the heat transfer performance were studied. The following results were obtained: as the applied voltage increased, the number of boiling bubbles decreased but the heat transfer coefficient increased; no deterioration of heat by the oil contamination occurred; and the polarity of the applied voltage affected the boiling heat transfer

A review of National Fire Protection Association (NFPA) 110, a standard for emergency and standby power systems, is presented with particular emphasis on transfer switching. NFPA 110 goes beyond the National Electrical Code in stipulating coordinated installation, maintenance and operational and testing requirements. It is shown how this standard is now leading to safer and more reliable emergency and standby power installations

The purpose of this paper is to specify the main components of the stray load loss of induction motors from both results of measurement and analysis. The IEEE standard 112 Method B is applied to the cage induction motor for the measurement of the stray load loss. On the other hand, the losses generated at the stator core, the rotor core, and the rotor cage are calculated directly by the finite-element method considering the magnetic saturation and the harmonic fields, which vary due to the load condition. The measured and the calculated torque, losses, and efficiency agree well. It is clarified that the main parts of the stray load loss in the case of the analyzed motor are the increase of harmonic losses due to load, which are the harmonic Joule losses of the rotor cage and the harmonic core losses of the stator and the rotor. The relationships between the losses separated by the measurement and the losses calculated directly by the finite-element method are also clarified.

Since 1998, 817 motor efficiency test data sets, in the 1-500 hp (0.75-375 kW) range have been collected from several sources in different countries around the world, for 50 and 60 Hz. The test data include the motor efficiency using the IEC 34-2 and IEEE 112-B test standards, and the quantification of the stray load losses (SLLs), using the IEEE 112-B method. In 125 cases, the test data include the efficiency computed with both methods. The aim of this paper was the quantification of the discrepancy between the two mentioned standards, and to establish an approximate method to allow the comparison between motors tested with the two standards. Based on the significant number of collected motor data sets, it was concluded that, when compared to the IEEE 112-B standard, the IEC 34-2 standard is less accurate, and gives typically higher efficiency values, mainly because of the SLLs estimation procedure. The IEEE 112-B SLLs computed values are typically higher than the IEC SLLs predefined values, on average of 1.0 and 0.8 percentage points for 50-Hz and 60-Hz motors, respectively. Also, the average SLLs values vary slightly with the motor power. Using efficiency measurements made with both standards on the same motors, it was possible to confirm that the SLLs are the main reason for the observed discrepancy in the efficiency values. The results of the analysis carried out in this paper offer the possibility of comparing the efficiency of motors tested under the IEC 34-2 standard with motors tested with IEEE 112-B, leading to a choice of the most cost-effective option. This paper also provides a key contribution to the ongoing revision of the IEC 34-2 standard

Plasma chemical decomposition, aerosol generation and product distribution of trichlorotrifluoroethylene (CFC-113 [CCl₂F-CClF₂]) were investigated using a ferroelectric plasma reactor. CFC-113 decomposition was the highest with dry hydrogen, but was not significantly affected by background gases (N ₂ and air) and humidity. Most of the aerosols produced under plasma were of a particle size less than 0.1 μm. The aerosol generation rate increased with applied voltage and concentration, but was not affected by humidity and background gases, indicating that aerosol generation is associated with plasma energy per volume (plasma power density). Aerosolization of 1000-ppm CFC-113 was approximately 10 aerosols/cm³ for air, significantly greater than N₂. The greatest quantity of reaction gas phase byproducts was for dry H₂, followed by dry N₂, wet N₂, wet air and dry air. Reaction gas phase byproducts were minimal with aerated condition. The plasma reaction starts out by breaking the C-C bond to form radicals, which react with background gas radicals. The formation of CHClF-CClF₂ during CFC-113 decomposition indicates that the C-F bond is much stronger than the C-Cl bond and the C-Cl bond with more P atoms is stronger than that with fewer F atoms

The electric performance and the economics of four supply options for a specific 12.5 kV radial distribution feeder were examined. Options included upgrading to 34.5 kV and/or sectionalizing. Feeder losses, voltage regulation, and system voltage dips due to feeder faults were analyzed. It was found that distribution transformer losses were a significant component in the total feeder loss and an important factor in the loss comparison of the two voltage levels. In this case, sectionalizing the existing feeder at 12.5 kV was the preferred option based upon cost, system voltage dip performance, and ease of back feed

The authors compared the economic and electrical performance factors on one specific overhead radial distribution feeder that is in operation at 12.5 kV, but whose present load and growth require that it be upgraded. They examined the economics and electrical performance of several feeder upgrading options for a particular feeder on the Green Mountain Power system (USA) with respect to: feeder losses; feeder voltage regulation; capital costs and cost of losses: and voltage dips on the local 115 kV transmission system caused by feeder faults. The performance of four feeder configuration options is assessed. It is shown that there is no clear economic advantage to 34.5 kV and that there may be a disadvantage with respect to voltage dip performance

A 120 kW coaxial winding transformer has been built and tested to verify previous indications that a high power transformer is feasible with the key attributes of this novel design, namely: low leakage inductance, minimal effect of leakage field on core losses, low copper losses, and a convenient “nesting” structure well suited for separability of the findings. The power transfer capability is more than double that of any previously published result for coaxial winding transformers. The application chosen for the fabricated transformer was an inductive coupler for fast charging of electric vehicles. Presented are the key parametric decisions, their impact on transformer fabrication and characteristics, and the results of these design choices as observed in the experimental data. The final design has active cooling to facilitate high power density and a separable core to allow the primary and secondary windings to be coupled and uncoupled. The experimental data shows performance better than expected, with a magnetizing to leakage inductance ratio of 1000:1, efficiency well over 99% and power density of 25 kW/kg

The most serious accidents with 120/240-V appliances are probably those involving electric shock and fire. To aid in the investigation of such incidents, some fundamental concepts are presented for the accident investigator. For electric shock cases a knowledge of the effects of electricity on the human body and the electrical parameters related to these effects is important. Since most shock cases involve a question as to the path of current to ground or whether the grounding was proper, present day grounding procedures are described for appliances. To aid in investigations of accidents involving older equipment or systems, a history of the National Electrical Code's (NEC) grounding requirements and allowable use of double insulation for cord- and plug-connected equipment is included. In the investigation of fires of possible electrical origin, the investigator is usually confronted with arc damage that either caused the fire or was caused by the fire. A discussion of the fundamentals of electric arcs and of circuit protection is presented to aid in this determination.

Over the years, many fires have been blamed on the failure of electric equipment or wiring in residential or commercial installations. To help resolve the question of whether or not these accusations have substance, many tests have been performed to evaluate various types of wire and insulation in different environments on 120- and 240-V ac circuits. Evidence from a recent fire in a local commercial installation at 208/120 V indicated that paper products lying on the exterior of a conduit were ignited due to an internal arc between a conductor and the metallic conduit wall. The fault current did not trip a standard 100-A plastic case panel breaker. Laboratory tests were performed in an attempt to duplicate the conditions and confirm the conclusions. The results are reported.

This paper presents the enhanced characteristics of a newly developed low-loss and low-noise 1200-V insulated gate bipolar transistor (IGBT) module. In order to realize low-noise emission, it is necessary not only to improve the reverse recovery characteristics of the free wheeling diode (FWD) but also to reduce the low-current turn-on dI_C/dt of the IGBT. The new IGBTs with high turn-on dI_C/dt controllability and low turn-on power dissipation have been successfully developed by the reduction of Miller capacitance resulting from an optimization of the surface. The 1200-V 450-A IGBT module utilizing the new IGBT and optimized FWD chips has been able to realize 30% reduction of the switching power dissipation when compared to the conventional IGBT module under the operating condition to set the same noise emission level

In this paper, static and switching characteristics of a 1200 V 4H-silicon carbide (SiC) bipolar junction transistor (BJT) at a bus voltage of 600 V are reported for the first time. Comparison was made between the SiC BJT and a 1200 V Si insulated gate bipolar transistor (IGBT). The experimental data show that the SiC BJT has much smaller conduction and switching losses than the Si IGBT. The SiC BJT also shows an extremely large reverse bias safe operation area, and no second breakdown was observed. This removes one of the most unattractive aspects of the BJT. The results prove that, unlike Si BJTs, BJTs in 4H-SiC are good competitors for Si IGBTs.

The estimating chapter has been reintroduced to the Red Book in the sixth edition. The purpose of this chapter is to describe estimates for various purposes and to outline a method for developing an engineering-type estimate. Design concepts leading up to the preparation of a cost estimate are reviewed, with attention to obtaining necessary information so the estimate-will be meaningful. The review of Chapter 13 will address the problem of preparing an estimate under conditions of uncertain and rising costs; will touch on the time value of money; and will show how to work through a problem. The sixth edition of the Red Book, IEEE Standard 141, "Recommended Practice for Electric Power Distribution for Industrial plants," is scheduled for publication in late 1983.

The National Electrical Code (NEC) permits the use of lower voltage cables on power-limited circuits as defined in Article 725 of the NEC. Underwriters Laboratories (UL) developed Subject 13 to define the cable constructions and the physical and electrical requirements for cables intended for use on power-limited circuits. Optional protective coverings are also included. A reference is provided to the engineer on the various cable types available, the UL requirements for each, and the NEC requirements for various installations and environments.

Actual ground faults were applied to a high-resistance grounded 13.8-kV electrical distribution system supplying power to a large chemical plant. These tests show that such a system will restrict overvoltage transients and reduce damage to equipment under ground fault conditions. Such a system is inherently safer and more reliable than an ungrounded system and offers some operating features not possible with a low-resistance grounded system. The maximum overvoltage transient recorded during many ground faults, involving several different ground conditions imposed on the system during six hours of testing, was about 2000 V. The effect of these ground faults on the 13.8-kV electrical distribution system supplying an operating plant was negligible. In fact, the operating personnel, anticipating the worst, were not aware that the tests had been performed.

This paper is based on modifications implemented in the protection and grounding systems of a large paper mill and describes selective ground fault protection for a 13.8-kV system with multiple bus-connected generators, synchronous bus ties, and utility interconnections. The ground fault current in the system is reduced from the existing 3400 A to 500 A, and a hybrid grounding system is implemented for each of the generators. As the ground fault currents are reduced to limit the fault damage, the sensitivity and selectivity of the ground fault protection become important. Directional ground fault relays with coordinating pickup settings are applied to achieve this objective. The new platform for directional elements (numerical relays) drives its performance from sequence impedance measurements

Actual ground fault tests were conducted to determine the behavior of low-magnitude arcing ground faults in a closed air-filled 13.8-kV terminal chamber. Ground current magnitudes between 10 and 50 A were allowed to flow under various ground fault conditions. The tests that were performed support the value of high-resistance grounding to promote safety and reduce damage to equipment. At higher ground fault current levels the ionization of the air-filled chamber progresses at a rapid rate, and the arc is sustained or phase-to-phase faulting quickly occurs. The lower the ground fault current can be limited the less damage that occurs and the less possibility there is of creating a phase-to-phase fault. The practical consideration appears to be that if ground fault current can be limited to 10 A or less then initial ground faults will either clear themselves or create solid ground paths. This can allow the system to operate until an orderly shutdown procedure can be initiated.

This paper considers the major design factors which constrain the maximum acceleration capability of surface-mounted neodymium-iron-boron permanent magnet motors as used in servo drives. Expressions are derived for typical achievable values of the air-gap flux density and the linear current density around the stator periphery. For applications with small values of the duty factor, the stator linear current density is limited by the need to avoid demagnetization. For larger values of duty factor, the constraint is the ability of the cooling system to remove the heat losses within the magnet and insulation temperature limits. The paper derives general approximate expressions for maximum torque and acceleration limits, and shows graphs from which the range of acceleration capability of a permanent magnet motor in a given application can be assessed. The constraints involved in matching the motor design to an inverter with given maximum voltage capability are also discussed

This work presents an overview of IEEE 1349-2001, a Guide that assists individuals, organizations, and suppliers with the application of motors in Class I, Division 2 locations, where flammable gases and vapors may occasionally be present. Three-phase and single-phase ac synchronous and induction electric motors in sizes from fractional horsepower through 10 000 hp and beyond are covered in the Guide. Primary emphasis is on the use of general-purpose enclosures and precautions against excessive surface temperatures and sparking of rotor bars and enclosure joints. The Guide also provides guidance for maintaining the life-cycle integrity of motors in Division 2 locations. Existing codes and standards, such as the National Electrical Code, contain cautionary notes for general-purpose motor applications in Division 2 areas. This Guide documents industry experience and established practices for the application of general-purpose motors in Division 2 locations and provides guidance for applying motors in these locations. It is not a specification and is not intended to be used as a specification for purchasing motors installed in Division 2 locations. This paper does not replace the Guide, but should be used to supplement and understand the Guide. Significant motor temperature information is contained in the Guide including maximum recommended Division 2 exposed surface temperatures at full load. Manufacturers, users, and other industry experts worked about eight years to develop this consensus standard. It was approved by the IEEE-SA Standards Board in December 2001 and published in June 2002.

The fine print note (FPN) No. 1 in 2005 National Electrical Code (NEC) Article 501.8 (B) [ANSI/NFPA 70, National Electrical Code, 2005 (NEC)] cautions users to "consider the temperature of internal and external surfaces that may be exposed to the flammable atmosphere" when putting a motor into service in a Class I, Division 2 environment. Thus, it is critical that manufacturers and users of industrial electric motors understand that internal peak temperatures exceed the external peak temperatures. This paper presents three common IEEE 1349 [IEEE 1349-2001, IEEE Guide for the Application of Electric Motors in Class I, Division 2 Hazardous (Classified) Locations] test methods used by manufacturers to determine these internal peak temperatures. Potential test method error and the test results from the three test methods are also presented. IEEE 1349 provides only guidance when performing these test methods so this paper intends to provide additional clarification. The test motors presented in this paper are low voltage, ac induction, severe-duty, energy-efficient, totally enclosed fan-cooled motors commonly used in the "Petrochemical Industry."

The authors discusses the effects of switching low inductive currents with 138 kV SF₆ breakers in a petrochemical plant. Switching transients are believed to have contributed to the failure of a 13.8 kV PT and a 13.8 kV air magnetic circuit breaker. The high-frequency transient surge can transfer across a transformer due to transformer capacitances between the high- and low-voltage windings. The electromagnetic transient program system (ETPS) model and different case studies are discussed with the effect of different transformer winding capacitances. The interruption mechanism of low inductive currents is also described. This analysis demonstrates the need to conduct switching transient studies and the need for surge arresters on transformer secondary terminals under certain system conditions

This paper describes the rewrite of The Chlorine Institute Pamphlet 139, “Electrical Safety in Chlor-Alkali Cell Facilities”. The steps taken by the task group in rewriting the pamphlet are described. The survey of electrical incidents in cell facilities is summarized. The major changes to the pamphlet are discussed from both the technical and safety points of view

In this paper, thermal analysis for a 42-V/14-V bidirectional dc/dc converter with integrated inductors is performed. An interleaved dc/dc converter system with four channels was chosen for the automotive-converter topology with 42-V/14-V dual-output voltages. Coupled inductors were designed and used for the four-channel dc/dc converter. A 3-D thermal model based on finite-element modeling using I-DEAS is presented and the thermal behavior of the dc/dc converter system is simulated and analyzed. The thermal model includes a printed circuit board, integrated inductors, a heat sink, and switching devices (MOSFETs). The analyzed thermal result can help to design a converter system under severe ambient-temperature conditions

Self-excitation of induction motors compensated by permanently connected capacitors is investigated in this paper. Theoretical analyses of self-excitation phenomenon are carried out by using some simplified equivalent circuits, and a hybrid mathematical model in ABC/dq axes, respectively, in steady state and transient state. An unusual operating condition about water pumping stations is reported, in which water within the pipeline may drive the motor in the reverse direction at speeds higher than synchronous, when a supply interruption coincides with a check-valve failure. In order to prevent the motor from dangerous overvoltages due to self-excitation, it is recommended to connect a simple static protection circuit consisting of a resistor in series with a thyristor switch between any two lines of the motor. Critical resistance boundaries, which will lead to loss of excitation, and demagnetization of the rotor core are determined separately as a function of operating speed. A suitable resistance value chosen in the safe design area constitutes a reliable protection mechanism against self-excitation.

This paper describes the design aspects, fabrication, and testing of a 14200-hp two-pole cylindrical-rotor synchronous motor used with a load-commutated inverter (LCI) adjustable-speed drive (ASD) to drive a refrigeration compressor for a refinery alkylation plant. The motor design aspects include extensive finite-difference analysis of the rotor cage assembly and laboratory bench testing of a wedge assembly to verify finite-difference analysis results prior to fabrication. Torsional and harmonic analysis results are also presented. Special considerations are discussed regarding rotor heating due to harmonic currents and mitigation methods for handling the harmonic currents and heating. Mechanical design aspects are presented of the rotor cage, including rotor slot design, wedge, and end ring assembly. Two motors and drives were built, for companion projects, allowing for verification of the rotor-cage assembly by a back-to-back (BTB) test. Test preparation, setup and results are presented, including rotor temperature mapping, vibration data and torsional results. Finally, test results are compared with calculated values

This paper describes the new IEEE Standard 1459, Definitions for the Measurement of Electric Power Quantities Under Sinusoidal, Nonsinusoidal, Balanced or Unbalanced Conditions. The information is presented in the context of historical events that explain the reasons for new definitions. The new definitions originate from S_e, the effective apparent power definition attributed to F. Buchholz and W. Goodhue. The resolution of S_e extends from well-established concepts. The need for the separation of 60/50-Hz powers from the non-60/50 Hz-powers is emphasized. The standard serves users who want to evaluate the performance of modern equipment or to design and build the new generation of instrumentation.

This paper describes the design, construction, and testing of a 150-kVA closed-loop vector-controlled matrix converter induction motor drive. The primary objective of this research effort is to evaluate the utility of the matrix converter in electric vehicle applications, primarily for motor control. A prototype converter has been built using 600-A 1400-V insulated gate bipolar transistors. Closed-loop vector control has been implemented and tested using a 150-hp induction motor load. This paper presents the design of this converter along with practical test results, representing the largest matrix converter built to date.

The application of variable-frequency drives (VFDs) in industrial and commercial facilities has seen a tremendous increase. However, when multiple VFDs are fed from one dedicated power transformer, care should be taken not to drive the transformer into saturation. At one industrial location, nine VFDs rated at 200 HP each, and fed from a single 1500 kVA air-cooled transformer, showed saturation phenomenon, which had the potential of causing serious damage to the transformer. This paper discusses the input AC current waveform asymmetry caused by the interaction of the transformer and the nine 200 HP VFD load fed from it. The term waveform asymmetry is used when the positive half of the input AC current cycle is not equal to the negative half of the input AC current cycle. This results in the existence of DC components along with even harmonics in the input at current waveform. The various tests and the eventual solution to the waveform asymmetry caused by the VFDs is presented. The value of the inductance in the DC smoothing inductor (DC-link choke), which is included as part of the VFD, was found to contribute significantly to the waveform asymmetry. Experimental results showing the performance of a reconfigured DC-link inductor to reduce its interaction with the power transformer are presented

The improved reliability of power electronics and the development of motors capable of operating directly at high speeds have made electric motors a viable alternative to steam turbines in process plants. This paper discusses the application of a large high-speed, adjustable-speed synchronous motor with a load commutated inverter as a recycle compressor driver in a petrochemical facility

A power electronic converter is applied to control the speed of a 5 kV motor. The motor is directly coupled to a 6500 r.p.m. compressor and replaces a steam turbine. Dual converters are used in a twelve-pulse arrangement at both the utility and the motor. The motor is of solid rotor construction, with dual 30° displaced stator windings. Finite-element analysis is used to optimize the motor design for use with a variable-frequency static converter. Full-power tests are completed which confirm theoretical predictions on losses, performance, and operation. The electrical drive takes up considerably less space and is much more efficient than the steam turbine it replaces

The principle of the gearless drive has already been applied to some large mills. A synchronous motor is ``wrapped'' directly around the mill cylinder and supplied by a thyristor frequency converter at approximately 10-percent system frequency. The drive thus operates at the low mill speed and dispenses with interposed gearing.

It is well known that conventional two-level pulsewidth modulated (PWM) inverters generate high-frequency common-mode voltages with high dv/dt. Similarly, commonly used multilevel inverter modulation schemes generate common-mode voltages. Common-mode voltages may cause motor shaft voltages and bearing currents and conducted electromagnetic interference (EMI). Premature motor bearing failures and electronic equipment malfunctions have been reported to be directly related to bearing currents and EMI. In this paper, approaches to eliminating common-mode voltage when using multilevel PWM inverters are presented. It is shown that inverters, which have an odd number of levels, will generate zero common-mode voltage by switching among certain states. Therefore, motor bearing currents will be eliminated and conducted EMI will be reduced. Both sinusoidal PWM and space-vector modulation (SVM) schemes are discussed and detailed comparative simulation results between conventional and novel modulation schemes are provided. The value of the proposed technique is demonstrated experimentally by applying the novel SVM approach to a conventional multilevel inverter.

The direct results on the mining industry of the research program sponsored by the US Bureau of Mines over the last decade and a half include increased safety, increased productivity, a better working environment for miners, and a more secure supply of minerals to the US economy. Some important technical developments in the electrical area that have taken place are: the development of mine monitoring systems; improved hard-wired and wireless communications systems; improved grounding systems including ground check monitors, reliability databases, and models for power system safety; improved power system protection and analysis; and a growing effort to use expert systems to improve the operation of mines. Side benefits of this research program include the availability of technically trained manpower, an improved body of technical knowledge, continuing education opportunities, and improved channels of communication for technical knowledge

The experience gained during the growth of a chemical manufacturing facility from a 65 to 170-MW load in multiple stages is presented. Large filter banks are required to control harmonic current and provide reactive power compensation for the rectifiers that energize the chemical process. As the load grows and the filters become larger and more numerous, utility-generated harmonics are drawn into the filters, resulting in difficulties to comply with IEEE 519. The large size of the filters creates voltage rise issues for local equipment and the transmission system on load upset. Filter stress due to utility capacitor switching and in-plant filter element switching is compared for the initial load stages and the final load stage. Filter stress is reduced as the number and size of the filters are increased.

The recommended practice for electric vehicle battery charging using inductive coupling (SAE J-1773), published in January 1995 by the Society of Automotive Engineers, Inc., outlines values and tolerances for critical vehicle inlet parameters which must be considered when selecting a coupler driving topology. The inductive coupling vehicle inlet contains a significant discrete capacitive component in addition to low magnetizing and high leakage inductances. Driving the vehicle interface with a variable-frequency series-resonant power converter results in a four-element topology with many desirable features: unity transformer turns ratio; buck/boost voltage gain; current-source operation; monotonic power transfer characteristic over a wide load range; throttling capability down to no load; high-frequency operation; narrow modulation frequency range; use of zero-voltage-switched MOSFETs with slow integral diodes; high efficiency; inherent short-circuit protection; soft recovery of output rectifiers; and secondary dν/dt control and current waveshaping for the cable, coupler and vehicle inlet, resulting in enhanced electromagnetic compatibility. In this paper, characteristics of the topology are derived and analyzed using two methods. Firstly, the fundamental mode AC sine-wave approximation is extended to battery loads and provides a simple, yet insightful, analysis of the topology. A second method of analysis is based on the more accurate, but complex, time-based modal approach. Finally, typical experimental results verify the analysis of the topology presented in the paper

Diode rectifiers with large dc-bus capacitors, used in the front ends of variable-frequency drives (VFDs) and other ac-to-dc converters, draw discontinuous current from the power system, resulting in current distortion and, hence, voltage distortion. Typically, the power system can handle current distortion without showing signs of voltage distortion. However, when the majority of the load on a distribution feeder is made up of VFDs, current distortion becomes an important issue since it can cause voltage distortion. Multipulse techniques to reduce input current harmonics are popular because they do not interfere with the existing power system either from higher conducted electromagnetic interference, when active techniques are used, or from possible resonance, when capacitor-based filters are employed. In this paper, a new 18-pulse topology is proposed that has two six-pulse rectifiers powered via a phase-shifting isolation transformer, while the third six-pulse rectifier is fed directly from the ac source via a matching inductor. This idea relies on harmonic current cancellation strategy rather than flux cancellation method and results in lower overall harmonics. It is also seen to be smaller in size and weight and lower in cost compared to an isolation transformer. Experimental results are given to validate the concept.

A study of the reliability, availability, and maintainability (RAM) characteristics of diesel and gas-turbine power systems producing less than 2 MW is discussed. The study included collection and examination of source data for power systems at commercial and military facilities operating in continuous or standby service. A database of system, subsystem, and component RAM data was established. These data will be useful in the design of primary and standby power systems for military or commercial facilities

Not Available