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Volume 48, Issue 485
Displaying 1-9 of 9 articles from this issue
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Problems of Underground StructureT. Hattori1928 Volume 48 Issue 485 Pages 1245-1273
Published: 1928
Released on J-STAGE: May 20, 2013
JOURNAL FREE ACCESSDownload PDF (4171K) -
S. KIMURA, T. AIZAWA, T. TAKEUCHI1928 Volume 48 Issue 485 Pages 1274-1277
Published: 1928
Released on J-STAGE: November 20, 2008
JOURNAL FREE ACCESSH. L. Curtis and his co-workers have published their works on the electrical properties of rubber-sulphur compounds in the scientific paper of the Bureau of Standards No. 560. Their results are insufficient to ca ch the true features of the electrical properties of rubber-sulphur compounds and consequently their interpretation of the results and conclusions have fallen into entire mistake.
They have measured dielectric constant, power factor, resistivity and dielectric strength about some twenty kinds of the rubber-sulphur compounds containing sulphur from 0 to 32 percent. Their measurement has been carried out at only one definite temperature, i. e. 25°C. This is the cause of having lead them into mistake. Their conclusions are as follows:
1) The dielectric constant increases until a maximum value is reached at 10.5 per cent of combined sulphur, decreases to 19 per cent and then increases slightly from this composition to 32 per cent. (see Fig. 1)
2) The power factor behaves similarly, except that the maximum value comes at 13 per cent of combined sulphur. (see Fig. 2)
3) The curves show, therefore, distinct changes in direction at about 10.5, 13, and 19 per cent of combined sulphur.
4) It is no eworthy that all of these changes occur at compositions which may be represented by simple formulas i. e. (C5H8)4S, (C5H8)3S and (C5H8)2S.
Moreover they have assumed another definite compound (C5H8)4S3 corresponding 26 per cent combined sulphur where the resistivity curve has a maximum. But the resistivity as well as the dielectric strength give very scanty contribution to the conclusions.
The authors' investigation on the dielectric constant and tanδ about the vulcanized rubber-sulphur system from 0°C. to 100°C. tells, that
1) tanδ-temperature relaton makes counter-ν curve as usual, (Fig. 4)
2) Dielectric constant has a fairly steeply ascending range corresponding to the counter ν portion of the tanδ-temperature curve. This is the general feature of dielectrics. (Fig. 3)
3) Both the tanδ-temperature and the dielectric constant-temperature curve shift towards the upper temperature side with the increase of combined sulphur.
4) This being the case, if we cut these groups of curves at one definite temperature, we have also counterν-curves for the dielectric constant-combined sulphur and tanδ-combined sulphur relation.
5) These counterν-curves also shift to the side of the greater combined sulphur per centage with the rise of temperature.
6) If, thereforc, the direction change of these curves relate with the definite compounds in the rubber sulphur system as Curtis and his co-workers insist upon, then an infinite number of the definite compounds having indeterminate percentage of combined sulphur must be considered.
7) This result, namely, contradicts to the stepwise formation of the definite poly prene monosulphide in the vulcanized rubber-sulphur system.View full abstractDownload PDF (243K) -
Kazukiyo OGAWA1928 Volume 48 Issue 485 Pages 1278-1298
Published: 1928
Released on J-STAGE: November 20, 2008
JOURNAL FREE ACCESSThe paper describes the principle and the construction of the author's noloss condenser for alternating current bridges, and its some applications. The author's no-loss condenser is an air condenser of such a construction that the insulators which support both pates of the condenser are all covered with metallic cases which are connected to earth. The air condenser of this cous truction has been already published by Giebe and Zickner, by Shackelton and Ferguson, & c; but the author found a remarkable benefit by using that condenser in an alternating current bridge with perfect earthing device. As its some applications, the author gives the method of measuring the loss angle of ordinary condensers, the effective resistance and inductance of inductance coils, & c.
The author's air condenser is also suitable as standard of capacity, since its capacity is constant for any frequency. The author's method of determining the capacity in terms of resistance and frequency is given.View full abstractDownload PDF (1453K) -
S. KATO1928 Volume 48 Issue 485 Pages 1299-1311
Published: 1928
Released on J-STAGE: November 20, 2008
JOURNAL FREE ACCESSThe rotary converter will continue synchronous running when the shunt field circuit is opened, so long as the reluctance of the magnetic circuit is reasonably low. The machine is then called the "reaction converter." As the reaction converter is excited solely by the longitudinal component of the armature reaction, it should be so constructed as the armature air gap may be so small that the mechanical construction may permit, in order to minimize the lagging component of alternating carrent and to improve power factor. It seems at first sight, that with such a small air gap, the machine can not be able to operate as a d.c. machine in view of commutation. In reality, however, such a machine, if properly designed, may operate favourably without commutation difficulties, as later shown.
It is a well known fact that the armature m.m.f. at the commutating zone of a converter is very small compared with that of an ordinary d.c. machine, the former being about 15 per cent. of the latter. put this figure is with machines of 100 per cent. efficiency and p.f., or of very large capacity, and it is still smaller with machines of small and medium siges, whose mechanical friction and iron losses can never be negligible; for example, in the 3K.W converter, quated in the paper, the m.m.f. in the commutating zone amounts to about +27 per cent. of the d.c. m.m.f. for full load and zero lead of d.c. brushes (+ sign of m.m.f shows the commutatating m.m.f.)
The power factor of the reaction converter, as in induction motors, improves with load, and the more rapidiy if proper negative load be given to d.c. brushes; in the latter case the longitudinal component of the d.c. armature reaction acts the magnetizing action and reduce the lagging part of a.c. current
Laggging of d.c. brushes hardly affect commutation, although the commutating field decreases in its positive value or reverses its direction. In such conditions, resistance commutation due to carbon brush contact may prove satisfactory commutation, as is shown in actual cases.
Reaction converters have the following specialities: cheap in cost, good efficiency and Power factor, simplicity in construction and starting, smaller floor space.
Reaction converters of series type present still better characteristics than ordinary ones in many respects, and also be able to be used as series traction motors in battery cars and tractors, which operate as battery chargers with no alternation.
For larber capacities and heavy current types, in which commutation difficulties are expected to occur, reaction converters should be supplied with commutating poles, the ampere-turns of which are very small compared with the cases of ordinary converters.
In the present paper, the actual test results of the following reaction converters are given:
(i) 3K.W., D.C. 60V, 50A, A.C. 45V. 50-, 3phase, 4pole 1500r.p.m.,
(ii) 2.5K.W., D, C. 150V, 167A, A.C. 100V, 50-, 3phase, 4pole, 1500 r.p.m., series type.
(iii) 100watts, D.C. 10V, 10A, A.C. 100V, 50-, single phase. 4pole, 1500 r.p.m., dynamotor type (polarized.)View full abstractDownload PDF (2469K) -
Y. TORIYAMA1928 Volume 48 Issue 485 Pages 1312-1327
Published: 1928
Released on J-STAGE: November 20, 2008
JOURNAL FREE ACCESSThe author describes a method of measurement of impulse ratio of various kinds of spark gaps. He measures the max. value of break down voltage of a spark gap by using surface charge figure on an ebonite plate which was published in his previous paper (studies on discharge). As he uses the equal impulse voltage always, the time lag is the larger the larger the impulse ratio.
The experimental results agree with those of the other authors. The impulse ratio of 1 mm gap length of sphere electropes of 5 cm dia. is about 2.75 in the case of an over voltage being 5 times as large as static break down voltage. If the sphere electrodes are illuminated by a quartz lamp from a distance of 12 cm the impulse ratio reduces to 1.7. The impulse ratio of needle electrodes, needle and sphere electrodes, and surface discharge on ebonite or glass plate is an order of 3.5-5.5.View full abstractDownload PDF (5852K) -
S. MOCHIZUKI1928 Volume 48 Issue 485 Pages 1328-1336
Published: 1928
Released on J-STAGE: November 20, 2008
JOURNAL FREE ACCESSThe dielectric strength of some oiled paper under the various conditions of the humidity have been investigated and the following facts have been observed: -
(1) Under the relatively low humidity, the variation of the humidity of the air has a remarkable effect on the dielectric strength of the oiled paper in the puncture test with the D.C. source, while it has a feeble effect in the case made with the A.C. source.
Under the high humidity, however, the effect of the humidity becomes the same order independent of the source.
(2) Although the dielectric strength ratio between alternating and direct current voltages is greater than the unity at the relatively low humidity, (this case is more common) it is reversed, the higher the humidity is.
(3) The relation between the A.C. and D.C. dielectric strength of the oiled paper and the humidity is similar with the relation between the A.C. and D.C. dielectric strength of glass and the temperature obtained by L. Inge, N. Semenoff and A. Walther.
Although the dielectric strength ratio of A.C. and D.C. voltage in the case of them is always greater than the unity, the ratio in our case is not always greater than the unity. Such a difference in character of the dielectric strength of the solid insulation seems to depend on the different condition of the contact between the solid insulation and the e:ectrodes.
(4) As the history of the test sample exposed under the various condition of the humidity has a remarkable effect on the dielectric strength of the test sample, the D.C. conductivity measured with the Cathode ray oscillograph instead of the A.C. dielectric loss is utilized to express the effect of the humidity.
From such a Braun tube figure, it is ascertained that the direct current through the test sample is pulsating and the degree of the pulsation is very irregular.View full abstractDownload PDF (458K) -
K. KOBAYASHI1928 Volume 48 Issue 485 Pages 1337-1344
Published: 1928
Released on J-STAGE: November 20, 2008
JOURNAL FREE ACCESSThe same author has shown in the paper, presented to the annual convention of this institute this year, that the intensity of a sound field and volume of sound emitted by any surface can be masured directly and easily by using the vibrometer, provided with a rigid piston diaphragm. Using these two functions the image impedances at both ends of and the hyperbolic angle subtended by any acoustic transmittimg system can be determined. In this paper, the theory and arrangement of apparatus of the experimemt are shown in detail together with the experimental results carried out on some simple acoustic transmitting systems being of well known character. These results were surprisingly accurate. The author believes that the method can be used as a valid means for the study of the character of acoustic transmitting systems.View full abstractDownload PDF (423K) -
N. KATO1928 Volume 48 Issue 485 Pages 1345-1368
Published: 1928
Released on J-STAGE: November 20, 2008
JOURNAL FREE ACCESSA calculation of the mean torque acting on the rotating disc of induction type watthour meter is given in this paper under the following assumptions;
1) the disc is extremely thin,
2) the magnetic flux is known and confined under the magnetic pole, elsewhere it is zero
3) the magnetic pole is a circle and the magnetic induction is uniform within it, but the voltage and current flux distributions are overlapping.
The result of this calculation is compared with the result in the previous paPer issued in 1925 under the assumption that the voltage and current distribution are not overlapping.View full abstractDownload PDF (769K) -
1928 Volume 48 Issue 485 Pages 1374
Published: 1928
Released on J-STAGE: November 20, 2008
JOURNAL FREE ACCESSDownload PDF (42K)
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