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Volume 43, Issue 416
Displaying 1-6 of 6 articles from this issue
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E. AOYAGT1923 Volume 43 Issue 416 Pages 173-176
Published: 1923
Released on J-STAGE: November 20, 2008
JOURNAL FREE ACCESSDownload PDF (313K) -
T. KOMARU1923 Volume 43 Issue 416 Pages 195-226
Published: 1923
Released on J-STAGE: November 20, 2008
JOURNAL FREE ACCESSOn Ljungstrom Turbo-generator system, each rotor is directly coupled with each turbine rotor, oppositely rotating. Each rotor is symmetrical electrically and mechanically, and runs in the opposite directions inside of each stator of equal construction, electrically and mechanically. The stator windings are connected electrically in parallel, while rotor windings are in series, and excited by one exciter, which in connected to one of rotors. Exciting ampere is controlled by one field regulator, in series with two rotor windings.
At no load starting, with high resistance of field regulator, or weak excitation of generater fields, both rotors attain to different final speed, in ordinary case, the exciter side get smaller final speed. With 2-pole 1000-3000 KW machines, the write has observed 600-800r.p.m. differe- nee between two final r.p.m.'s. In ordiua.ry constructed turbo generators, synchronism is impossible at so large slip as600-800/3600×2=8-12%.
Energy communication between two synchronous machines of different cycles, has not fixed direction, and is generally periodical. During one half-period, when energy is flowing from high cycle side, to low cycle side, the cycle or speed difference decreases, while during the next one halfperiod when energy is flowing from low cycle side to high cycle side, the cycle or speed difference increases, at the same amount of increment. But in Ljungstrom turbo generator system, by the aid of electrical circuit-, completed by rotor wedge, both rotors large-slipped, come into synchronism, with moderate exciting ampere. These phenomena can be observed directly, during no load saturation test. The writer has experienced that both rotors were out of step, at lower pact of no load situation test, and i both rotors could not come into step, lin the. test to determine synchronous impedance, at weak excitation. With high rotor exciting ampere, the action of wedge circuit becomes effective i. e. lower cycle rotor acts as an induction motor to the higher cycle, and higher cycle rotor acts as an induction generator to the lower cycle, and the cycle difference decreases. so long as cycle difference exists.
If the final slip both sides is within the slip, corresponding to the critical slip as synchronous machines, both rotors suddenly come into synchronism, and phase difference answeres the small unbalance of torque between both sides. The writer has studied the relation between the critcal slip as synchronous machine, and final speed as synchronous induction machines, with examples of actual machines of this type, manufactured by Mitsubishis Elec. Engineering Co., where the writer is cencerned with their manufac- ture, according to the following items.
1. Preface
2. Power Oscillation between synchronous machines of different Frequency, specially referenced to Ljungstrom Turbo-generntor set.
3. Power Communication bctweeu Induction Synchronous machines, under different Frequency, specially referenced to Ljungstrom Turbogenerator set.
4. Ljungstrom Turbo-generator Characteristics, based on no of revolution
a. Exciter Characteristic.
b. Generator Characteristic.
5. Exciting Characteristics of Ljungstrom Turbo-generator set.
6. Semmary of Numerical Calculation and List of SymbolsView full abstractDownload PDF (1334K) -
TOSHIO HASEGAWA1923 Volume 43 Issue 416 Pages 227-230
Published: 1923
Released on J-STAGE: November 20, 2008
JOURNAL FREE ACCESSIn the three phase induction motor with squirrel cage rotor, the problem to increase the starting torque, or to suppress the heavy starting current, have been considered and intended to solve from years in many different ways. Here, the classifications and the tabulations of these different intensions are given with brief discussions of each of them, and also with the explanations of their specialities for the commercial uses. Especially, on the double cage rotor, a sort of theoretical treatments, test results, and the analysis of its characteristics are geven, calling attensions upon its utirizations on some of the ranges of induction motor drives. Finally, the future developments of these types of motors are suggested with also a discussion of character influenced by the material of end ring.View full abstractDownload PDF (805K) -
SHIN-ICHI OGAWA1923 Volume 43 Issue 416 Pages 240-253
Published: 1923
Released on J-STAGE: November 20, 2008
JOURNAL FREE ACCESSOn the design of motor starter, some formulas and graphical methods. to determine the suitable resistance value and its proper divisions, have. been widely recognized and applied. But, on the problems concerning to. the proper time elements, few papers and discussions we.e published. This paper describes one simple graphical method for these purposes, on the design of D.C. shunt and series motor starter and starting compensator.View full abstractDownload PDF (586K) -
S. BEKKU, O. TANNO1923 Volume 43 Issue 416 Pages 254-261
Published: 1923
Released on J-STAGE: November 20, 2008
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YASUJIRO NIWA1923 Volume 43 Issue 416 Pages 262-265
Published: 1923
Released on J-STAGE: November 20, 2008
JOURNAL FREE ACCESSIn the paper "Some Researches on Impulse Voltage" (this Journal, April, 1922) Bekku and Tanno have shown that the sphere gap sometimes discharges and sometimes fails to discharge even with the same condition of impulse circuits. The authors called phis phenomena "the ambiguity of the spark discharge." These experiments were conducted with the sphere gaps of diameters 1.0cm., 3.8cm and 6.25cm. and also with the needle gap. The gap length was 1 to 3mm. The conclusions arrived at were that the ambiguity is most remarkable for 3.8cm. sphere gaps and less for those with 1.0cm, nor 6.25cm, diameters. Also the ambiguity can't be recognized for needle gaps. The creaning of the surface of the sphere electrodes decreases the ambiguity.
The present author suggests that the phenomena may be explained by the casual ions in the air. Assuming the number of the casual ions to be 1500 per cubic cm the mean distance between ions is 0.8mm which is in the same order of the gap length used in the experiments and the intensity of the field at which the casual ion exists varies in considerable degree owing to its position and it is more so if the surface of electrodes is not clean. Thus one cause of the ambiguity is the position of the casual ions.
Another cause is the sweeping effect of the casual ions by the electrode potential. If the casual ion is attracted to the electrode before it has obtained the kinetic energy enough to ionize the neutral molecules, there will not occur any discharge. This sweeping effect is much dependent on the position and the polarity of the casual ion relative to the electrodes.
The non-existence of the ambiguity in the needle gap may be explained by fore-running corona formation in that type.
It is also suggested that the ambiguity will be less and finally vanish as the gap legnth or the density of the casual ions increase.View full abstractDownload PDF (269K)
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