High Response Control of Stator Watts and Vars for Large Wound Rotor Induction Motor Adjustable Speed Drives

Extremely rapid control response (0.01 s) of stator watts and vars has been obtained on a 15 000-hp wound rotor induction machine with a cycloconverter controlled secondary by means of an orthogonal control scheme which linearizes the machine equations and combines both feedforward and feedback error signals. Leading and lagging power factor and positive or negative stator power flow can be smoothly and rapidly controlled over a speed range in excess of ±35 percent of the induction motor synchronous speed. This doubly fed drive may be termed a "Scherbiustat drive" because the wound rotor induction motor secondary power conversion equipment is the static equivalent of the Scherbius machine. This type of a drive does not employ a dc link in the motor secondary power conversion equipment. It should not be confused with a static Kraemer drive which employs a dc link in the frequency conversion process and was so named because of its similarity to the original Kraemer drive which uses a synchronous converter and a dc motor in the secondary power conversion process. Recently obtained field results have verified the original study results discussed herein.     

Evaluating performability: Most probable states and bounds

The number of states examined by most probable state algorithms for performability computations can be reduced dramatically by incorporating simple connectivity-based bounds, even when the performability measure is much more complex than connectivity. Modifications to Yang and Kubat's most probable state method are presented that permit the use of simple auxiliary bounds with only a small effect on the time per iteration. Computational results for a variety of performability measures are given.     

Biasing a differential pair in low-voltage analog circuits: a systematic approach

This paper deals with a systematic approach to the common mode and the differential mode biasing of a differential transistor pair. Four different variants will be shown, two of these variants show practical importance; a practical circuit of one of these variants turns out to be the traditional long-tailed pair. This variant is mainly suited, if the input signal operates at voltage level, whereas another variant has great advantages if operation at current level occurs. Besides, the latter variant turns out to be very favorable in circuits operating with a single low supply voltage. Two practical circuits based on this variant are given.     

Partial scan flip-flop selection by use of empirical testability

Partial serial scan as a design for testability technique permits automatic generation of high fault coverage tests for sequential circuits with less hardware overhead and less performance degradation than full serial scan. The objective of the partial scan flip-flop selection method proposed here is to obtain maximum fault coverage for the number of scan flip-flops selected. Empirical Testability Difference (ETD), a measure of potential improvement in the testability of the circuit, is used to successively select one or more flip-flops for addition or deletion of scan logic. ETD is calculated by using testability measures based on empirical evaluation of the circuit with the acutal automatic test pattern generation (ATPG) system. In addition, once such faults are known, ETD focuses on the hard-to-detect faults rather than all faults and uses heuristics to permit effective selection of multiple flip-flops without global optimization. Two ETD algorithms have been extensively tested by using FASTEST ATPG [1, 2] on fourteen of the ISCAS89 [3] sequential circuits. The results of these tests indicate that ETD yields, on average, 35% fewer uncovered detectable faults for the same number of scanned flip-flops or 27% fewer scanned flip-flops for comparable fault coverage relative to cycle-breaking methods.This work was performed while the author was with the University of Wisconsin-Madison.     

剥离型聚丙烯-蒙脱土纳米复合材料Ⅰ.Ziegler-Natta/有机改性蒙脱土复合催化剂催化丙烯聚合

采用化学反应法制备了Z ieg ler-Natta/有机咪唑盐改性蒙脱土复合催化剂(简称复合催化剂),并通过丙烯单体原位插层聚合制备了聚丙烯-蒙脱土纳米复合材料。考察了n(A l)∶n(T i)、聚合温度、聚合时间及溶剂种类对复合催化剂的活性及定向催化能力的影响。研究结果表明,与商品化CS-2型Zieg ler-Natta催化剂相比,复合催化剂的活性明显降低,在n(A l)∶n(T i)=100、聚合温度60℃、聚合时间1h、正庚烷为溶剂时,复合催化剂的活性较高,可达78.4kg/(m ol.h)。合成聚丙烯的等规度在85%~97%之间,熔融温度在160℃左右,重均相对分子质量达到(3.6~4.6)×105,相对分子质量分布在6.1~6.6之间。溶剂种类对合成聚丙烯的等规度影响较大。     

Multi-heterojunction large area HgCdTe long wavelength infrared photovoltaic detector for operation at near room temperatures

This paper describes a new multi-heterojunction n ⁺pp photovoltaic infrared photodetector. The device has been developed specifically for operation at temperatures of 200–300K in the long wavelength (8–14 μm) range of the infrared spectrum. The new structure solves the perennial problems of poor quantum efficiency and low dynamic resistance found in conventional long wavelength infrared photovoltaic detectors when operated near room temperature. Computer simulations show that devices with properly optimized multiple heterojunctions are capable of achieving the performance limits imposed by the statistical nature of thermal generation-recombination processes. In order to demonstrate the technology, multiple heterojunction devices have been fabricated on epilayers grown by isothermal vapor phase epitaxy of HgCdTe and in situ As p-type doping. The detector structures were formed using a combination of conventional dry etching, angled ion milling, and angled thermal evaporation for contact metal deposition. These multi-junction n ⁺pp HgCdTe heterostructure devices exhibit performances which make them useful for many applications. D* of optically immersed multiple heterostructure photovoltaic detectors exceeding 10⁸cmHz^1/2/W were measured at λ=10.6 μm and T=300K.     

Design rules for an integratable low-power amplifier/filter combination

In this paper design rules for a circuit topology in which there is an inseparable combination of an amplifier and a filter characteristic, are presented. By intentionally using the capacitance of an already present input sensor for the filtering, the total required integrated capacitance is much less than that in circuits, which have a separately designed amplifier and filter function. Consequently, it is possible to have the advantage of a better integratability. Moreover, less complexity in the design is achieved. The presented circuit shows a current-to-voltage conversion and an inherently controllable second-order low-pass filter characteristic. A discrete realization has been designed to test the circuit. This circuit operates down to a 1 V supply voltage and the transfer shows a 1.8 M currentto-voltage conversion with a bandwidth of 6 kHz. Measurement results of this circuit show that a 63 dB dynamic range can be achieved with a total required integrated capacitance of only 31 pF.     

Permeability and alteration within the Soultz granite inferred from geophysical and flow log analysis

The 1993 stimulation tests carried out in well GPK1 at Soultz, Alsace, France, showed that out of the thousands of fractures cross-cutting the granite, only a limited number of natural fractures contributed to fluid flow. A comparison between the petrophysical properties of the rock and the interpretation of the hydraulic test results is proposed as a means of determining the distribution of the natural permeable fractures. Gamma-ray spectral logs and other geophysical logs (caliper, bulk density, P-wave slowness, and photoelectric factor) revealed some petrographical variations within the Soultz massive granite, as well as altered/fractured zones that act as preferential pathways for fluid flow as indicated by flow logs. Fluid losses during circulation tests have been estimated on the basis of statistical analysis of gamma-ray readings, and of potassium and thorium contents.