IEEE TRANSACTIONS ON ELECTRON DEVICES J for preparing the manuseript, and the reviewers of these The proposed charge control model of diode assumes TRANSACTIONs for their constructive comments and re- linear relationships between Ir and Q, and between in commendations and Q, given by(2)and(10), respectively. The experi mental results show that Tp and TR are very constant; REFERENCES thus the assumption is justified. Analytical verification [1] R. Beaufoy and J. J. Sparkes, "The junction transistor as a may, however, be carried out by solving the diffusion Autom.Teleph. Elect.J.,vol. 13 quation for P(, () and integrating over the region (2) RE. bye 0≤x≤t, though it is a very complicated task devices, J, Appl. Phys., vol. 28, pp. 878-881; The good agreement of the experimental results with 3A. Ht Kingston, "Switching time on diodes and 834;May,19 reverse switching transient of p-n junction diodes of 4 iade KiRE The revere ancien vol. ED-8, pp any type by measuring Tr, Te, and Ci The proposed model may also be applied to collector- 16)C LeCan, K eart and C DeRuyter, "The Junction Transistor hing device,” Reinho base junction of a transistor to characterize the storage time of the transistor 6 PN n cha 43-53; ACKNOWLEDGMENt The author wishes to acknowledge V. Plage for his [8] E. L. Ste measuring techniues, S. Mitchell and Mrs. M. Lewis 9)iB T0 25, laboratory assistance, W. Meadows for developing many ill ook Co, Inc, New York, N. y f Transistors,"MeGraw- Impedance Characteristics of an AC MHD Generator' L J. KIJEWSKI, J. B. FANUCCI, AND N. NESSt Summary--A study is made of those parameters, associated with power to the load. This method is summarized by Steg the impedance of an ac mhd generator which affect the power and Sutton. DC generators have the disadvantage, for material in the region external to the plasma causes a significant certain applications, of requiring a dc-Ac converter increase in the power factor. An expression for the actual electrical The second approach, which is the one considered ower extracted from the generator, as determined by electrical herein, utilizes a traveling-wave type magnetic field, the impedance methods, is shown to be identical to the expression power being extracted by induction. The phase velocity derived by considering Lorentz forces on elements of the fluid for of the traveling magnetic field may be larger or less than the plasma velocity. In the former case, the plasma is ac- celerated; that is, electrical energy is converted into inter INTRODUCTION nal and kinetic energy. In the latter situation, the process HE INTERNAL and kinetic energy of a flowing is reversed; the behavior of this device is then analogous plasma in the presence of a magnetic field may to an induction generator. The induction generator is, of convert some of ita energy directly into electrical course, ac, and electrodes and converters are not required form. This process of energy conversion has been investi- The purpose of this paper is to investigate the various gated extensively of late and is known as"magnetohydro- parameters which affect the impedance characteristics of namie" power generat the traveling-wave MHD power generator, the primary There are two basic schemes for MHD power extraction. aim being to improve the power factor. In the paper of In the first scheme, electrodes are adjacent to the plasma. Bernstein et al., it was noted that for a generator which These electrodes are connected to a load resistance causing will deliver a sizeable power, the power factor is ex- a de current to fow through the circuit, thereby delivering Reecived June 17, 1963. This work was performed under Contr. ation, astronautics, vol, 5, pP 22 26: Agu et. Mod power gener- MHD generator by the Aeronautical System Divi- of Magnetohydrod ion, Wright-Patterson AFB, Ohi Mather, Eds, Columbia University Press f Defense Electronic Products, RCA, Moorestown, N.J. Authorized licensed use limited to: IEEE Xplore. Downloaded on December 15, 2008 at 03: 47 from IEEE Xplore. Restrictions apply14 IEEE TRANSACTIONS ON ELECTRON DEVICES January DISCUSSION The proposed charge control model of diode assumes linear relationships between IF and Q, and between iR and &, given by (2) and (lo), respectively. The experi￾mental results show that rF and 712 are very constant; thus the assumption is justified. Analytical verification may, however, be carried out by solving the diffusion equation for P(z, t) and integrating over the region 0 5 x 5 w, though it is a very complicated task. The good agreement of the experimental results with the theory indicates that proposed model can characterize reverse switching transient of p-n junction diodes of any type by measuring T~, rR, and Ci. The proposed model may also be applied to collector￾base junction of a transistor to characterize the storage time of the transistor. ACKNOWLEDGMENT The author wishes to acknowledge V. Plage for his laboratory assistance, W. Meadows for developing many measuring techniques, S. Mitchell and Mrs. M. Lewis for preparing the manuscript, and the reviewers of these TRANSACTIONS for their constructive comments and re￾commendations. REFERENCES [l] R. Beaufoy and J. J. Sparkes, “The junction transistor as B charge controlled device,” Autom. Teleph. Elect. J., vol. 13, pp. 310-327; October, 1957. [2] M. Byczkowski and J. R. Madigan, “Minority carrier lifetime in p-n junction devices,” J. Appl. Phys., vol. 28, pp. 878-881; [3] R. H. Kingston,,, “Switching time in junction diodes and junc￾August, 1957. [4] W. H. KO, “The reveme transient behavior of semiconductor tion transistors, PROC. IRE, vol. 42, pp. 829-834; May, 1954. diodes,” IRE TRANS. ON ELECTRON DEVICES, vol. ED-8, pp. 123-131; March, 1961. [SI C. LeCan, K. Hart and C. DeRuyter, “The Junction Transistor as a Switching Device,” Reinhold Publishing Corp., New York, [6] J. L. Moll, S. Krakauer, and R. Shen, “P-N junction charge N. Y.; 1962. [7] S. Y. Muto and. S. Wang, “Switching response of graded-base stored diodes,” PROC. IRE, vol. 50, pp. 43-53; January, 1962. P-N junction diodes,” IRE TRANS. ON ELECTRON DEVICES, vol. ED-9, pp. 183-187; March, 1962. [SI E. L. Steele, “Charge storage in junction diodes,” J. Appl. 191 L. B. Valdes, “The Physical Theory of Transistors,’’ McGraw￾Phy~., VO~. 25, pp. 916-918; July, 1954. Hill Book Co., Inc., New York, N. Y.; 1961. Impedance Characteristics of an AC MHID Generator* L. J. KIJEWSKI, J. B. FANUCCI, AND N. NESS? Summary-A study is made of those parameters, associated with the impedance of an ac MHD generator, which &ect the power factor. It has been found that the addition of a ferromagnetic material in the region external to the plasma causes a signislcant increase in the power factor. An expression for the actual electrical power extracted from the generator, as determined by electrical impedance methods, is shown to be identical to the expression derived by considering Lorentz forces on elements of the fluid for a particular approximation mentioned in the report. INTRODUCTION HE INTERNAL and kinetic energy of a flowing plasma in the presence of a magnetic field may convert some of its energy directly into electrical form. This process of energy conversion has been investi￾gated extensively of late and is known as “magnetohydro￾dynamic” power generation. There are two basic schemes for MHD power extraction. In the first scheme, electrodes are adjacent to the plasma. These electrodes are connected to a load resistance causing a dc current to flow through the circuit, thereby delivering No. AF33(616)-7913, sponsored by the Aeronautical System Divi- * Received June 17, 1963. This work was performed under Contr. sion, WrightrPatterson AFB, Ohio. ’ Defense Electronic Products, RCA, Moorestown, N. J. power to the load. This method is summarized by Steg and Sutton.’ DC generators have the disadvantage, for certain applications, of requiring a DC-AC converter. The second approach, which is the one considered herein, utilizes a traveling-wave type magnetic field, the power being extracted by induction. The phase velocity of the traveling magnetic field may be larger or less than the plasma velocity. In the former case,’the plasma is ac￾celerated; that is, electrical energy is converted into inter￾nal and kinetic energy. In the latter situation, the process is reversed; the behavior of this device is then analogous to an induction generator. The induction generator is, of course, ac, and electrodes and converters are not required. The purpose of this paper is to investigate the various parameters which affect the impedance characteristics of the traveling-wave MHD power generator, the primary aim being to improve the power factor. In the paper of Bernstein et al.,’ it was noted that for a generator which will deliver a sizeable power, the power factor is ex￾ation,” Bstronautics, vol. 5, pp. 22-25; August, 1960. 1 L. Steg, G. W. Sutton, “The prospects of MHD power gener- 2 I. B. Bernskin et al., “An electrodeless MHD generator,” in N. W. Mather, Eds., Columbia University Press, New York, N. Y.; “Engineering Aspects of Magnetohydrodynamics,” C. Manna1 and 1962. Authorized licensed use limited to: IEEE Xplore. Downloaded on December 15, 2008 at 03:47 from IEEE Xplore. Restrictions apply