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International Engineering Congress (1901 : Glasgow.

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forms of such a meter have been suggested from time to time



3-4 ELECTRICITY SUPPLY METERS OF ELECTROLYTIC TYPE.

e.g., those of M'Kenna in 1892, Munsberg in 1894, and Gordwitsch
in 1898. In all of these forms the electrolyte is mercurous nitrate,
and the anode is mercury, and the cathode either platinum, or
carbon, or mercury. Advantage was taken of the fluidity of
mercury to measure the volume of deposited metal instead of
weighing it, as was necessary in the meters where copper or zinc
was deposited.

There was one great difficulty, however, and that was to secure
constancy in the resistance of the solution, and to prevent the
formation of crystals on the anode. In all the forms mentioned
above, the anode was placed below the cathode, and consequently
the denser solution remained in contact with the anode, and finally,
when it got too rich in the dissolved salt, it deposited crystals.
There was no means of automatically mixing the solution so as to
secure a uniformity of density. There was also the difficulty of
resetting the instrument after the graduated receptacle became full
of mercury. These defects have all been removed in the
electrolytic meter, to which particular notice is directed in this
paper. Here the anode is placed above the cathode, and is so
arranged that its active surface is concentric with the latter. The
mercury of the anode rises to such a height in its trough that the
dense solution falls off the convex surface of the mercury by
gravity, and the lighter solution rises from the cathode, and
replaces the dense solution. This interchange of solution goes
on continuously, and there is no need for agitation or stirring.
The mercury anode surface is kept above the level of the cathode
on the well-known " bird-fountain " principle. The design is such
that the level and area of the surface always remain constant, and
therefore the internal resistance of the electrolytic cell is also
constant. The mercury deposited is first of all collected in a
graduated tube forming one of the legs of the siphons. As soon
as 100 units have been deposited and the tube is filled, the whole
quantity shifts over into a larger tube. The volume of the siphon
tube is equal to one division on the larger scale. The meter will
thus register up to 1200 units without resetting.

The ratio between the main current and the shunt current
passing through the electrolytic cell is 200 to i. A high resistance
in circuit with the electrolytic cell prevents errors due to change
of temperature, and consequent diminution in the resistance of the
latter. Copper wire is employed, the increased resistance of which
acts as a correction to any change of the resistance of the cell
itself with temperature.

The resetting of the meter to zero is accomplished by tilting
the whole tube in a vertical plane, so that all the mercury which
was deposited in the receptacle flows back into the anode chamber.
The electrolytic cell is connected in the circuit across a shunting



ELECTRICITY SUPPLY METERS OF ELECTROLYTIC TYPE. 325

resistance of platinoid or other similar material, which has a drop
in pressure not exceeding one volt at full load. There is no
danger of a defect in the meter causing an interruption to the
supply, as the main circuit is not completed through mercury.
The electrolyte and the two electrodes are contained in a hermetic-
ally sealed glass tube. This is possible, as no gas is given off from
the chemical action. There is, therefore, no necessity for renewing
any of the parts of which the meter is composed. The mercury
which is deposited from the cathode, on tilting the meter, is trans-
ferred to its original position in the anode chamber, and the whole
cycle of operations can be repeated ad infinitum. There is no
evaporation, there is no deterioration in the quality of the
materials, no efflorescence due to atmospheric conditions, and the
meter is entirely unaffected by changes in the barometic pressure;
and, as the tests show, only to a very small extent by temperature.
There is practically no limit to its starting current, and the
accuracy of its registration can be attained at all loads. Of four
meters tested with a current of .05 of an ampere, two registered
100 per cent., one 95 per cent, of the whole quantity of electricity
passed through them. The advantages of such a meter are
obvious, and the simplicity and convenience of its design ought
to remove the lingering objections which have hitherto applied to
the general body of electrolytic meters. A conspicuous advantage
is that there is no need to renew any of the parts, as, when once
a meter is filled, it contains everything that is essential for its
operation for an indefinite period as long as the glass tube remains
intact. The ease of reading is a point not to be despised, as most
people are familiar with the readings of a thermometer and
barometer, and this is entirely similar. The cost of the meter, as
in the case of most electrolytic meters, is comparatively small.

The author then gives the results of many tests which he has
taken, showing the behaviour of the meter at light loads and at
ordinary loads. Various results are given, showing how extremely
minute is the value of e in the equation

E = Bt + 1 +

i

Tests of records at different temperatures are also given, and
the paper concludes with some observations on the behaviour of
the meter in practice.



On the motion of the Chairman a vote of thanks was accorded
to the author.



" KELVIN'S ELECTRIC MEASURING INSTRUMENTS."
Paper by Professor MAGNUS MACLEAN.

Abstract.

LORD KELVIN has altogether 38 patents on electric instruments,
and particulars of these are given in two appendices.
The instruments were classified under four heads :

I. Electrometers.
II. Electromagnetic Instruments.
III. Electrodynamic Instruments.
IV. Recording Instruments.

I. Electrometers were divided into : -

(a) Symmetrical.

(b) Attracted Disc.

The Symmetrical include :

(1) Quadrant Electrometers.

(2) Multicellular Electrometers.

(3) Vertical Electrostatic Voltmeters.

The Attracted Disc include :

(1) Absolute Electrometers.

(2) Long Range Electrometers.

(3) Portable Electrometers.

(4) Electrostatic Balances.

No description of these well-known instruments was given, but
a standard air Leyden condenser was fully described, as, in con-
junction with a suitable electrometer, it affords a convenient means
of quickly measuring small electrostatic capacities, such as those
<of short lengths of cables.

II. Electromagnetic Instruments include :

(1) Reflecting, differential, and ballistic Galvanometers.

(2) Graded Galvanometers.

(3) Suspended-coil Amperemeters and Voltmeters in six
different types : (a) Edgewise pattern, (b) Round
pattern, (c) Thistle pattern, with or without illuminated
dial, (d) Portable pattern in aluminium case, (e) Port-
able paralleling pattern, and (f) Reflecting mirror
pattern.

(4) Ampere Gauges.




KELVIN'S ELECTRIC MEASURING INSTRUMENTS. 327



The ampere gauges have had two very important improvements
introduced of late years. The first improvement relates to the
coil, and the object is to obtain a coil which will give a more
uniform field than is attained by ordinary methods. The second
improvement relates to the method of suspending the soft iron
plunger which is now suspended from a sector. These two im-
provements were described.

III. The Electrodynamic Instruments include:

(1) Ampere balances.

(2) Watt balances.

(3) Engineroom Wattmeters.

(4) Three-phase Wattmeters.

Particulars and diagrams of the coils of the engine-room and
three-phase Wattmeters were given.

IV. The Recording Instruments include :

(1) Amperemeters of the ampere gauge sector pattern.

(2) Voltmeters of the ampere gauge sector pattern.

(3) A combination of IV., i and 2, called a Feeder Log.

(4) Astatic Voltmeters on the principle of Wattmeter III., 3.

(5) Astatic Wattmeters like IV., 4, except that the fixed

coils are of copper ribbon, and carry the main current,
while the movable coils with electric lamps in series
with them take the shunt current.

The instruments were also classified as follows :

I. Standard Instruments :

(1) Ampere Balances.

(2) Watt Balances.

(3) Multicellular Electrostatic Voltmeters.

(4) Vertical Electrostatic Voltmeters.

(5) Quadrant Electrometers.

(6) Absolute Electrometers.

II. Portable Instruments :

(1) Horizontal Multicellular Voltmeters.

(2) Portable Suspended Coil Amperemeters and Voltmeters.

(3) Testing Set for measuring insulation resistance.

(4) Cell Tester.

(5) Rail Tester.

(6) Paralleling Voltmeters.

(7) Graded Galvanometers for currents and potentials.

(8) Portable Electrometers.

III. Central Station Instruments :

(i) All the Electrostatic Voltmeters.



328 KELVIN'S ELECTRIC MEASURING INSTRUMENTS.

(2) The Suspended Coil Voltmeters and Amperemeters.

(3) The Ampere Gauge Recording Voltmeters and Ampere-

meters, including the Feeder Log.

(4) Earth Current Recorder.

(5) Astatic Recording Voltmeters for alternating currents.

(6) Recording Wattmeters.

(7) All the types of Ampere Gauges.

(8) Engine-room Wattmeters.

(9) Three-phase Wattmeters.
(10) Rail Tester.

The paper was illustrated by twenty-five figures.



Mr. W. A. Chamen took part in the Discussion, and on the
motion of the Chairman a vote of thanks was accorded to Professor
Maclean.

(Appendices, see pp. 329-330.)



KELVIN'S ELECTRIC MEASURING INSTRUMENTS.



329



PATENTS RELATING TO IMPROVEMENTS IN APPARATUS

FOR GENERATING, REGULATING, MEASURING, RECORDING,

AND INTEGRATING ELECTRIC CURRENTS.



Number of
Patent.


Date of
Provisional
Specification and
of Complete
Specification.


TITLE OF PATENT.


Number of
Pages.


V

loo
fc


No. of Figs,
or Diagrams.


3032


July 9, 1 88 1


Improvements in regulating electric










Jan. 9, 1882


currents, and in the apparatus or












means employed therein, -


II


3


9


5668


Dec. 26, 1 88 1


Improvements in dynamo-electric










June 28, 1882


machinery, and apparatus con-












nected therewith,


18


J 3


70


2028


April 21, 1883


Improvements in apparatus and






lapse '




Oct. 20, 1883


processes for generating, regulat-












ing and measuring electric currents


28


25


48


4617


Sept. 28, 1883


Apparatus for generating, regulat-










Mar. 27, 1884


ing, measuring, recording, and






;






integrating electric currents,


41


18


36


4655


Mar. 10, 1884


New or improved suspensions for










Oct. 8, 1884


electrical incandescent lamps, -


4


i


2


5355


Mar. 22, 1884


Improvements in dynamo-electric






j




Nov. 10, 1884 machinery, ....


3


i


5


6410


Mar. 10, 1884


Improvements in breaking electric










Oct. 28, 1884


contact to prevent over-heating












by imperfect contact,


3


2


6


10530


July 24, 1884


Safety fuses for electric circuits, -


7


I


13




April 25, 1885










11106


Aug. 9, 1884


Improvements in apparatus for










May 7, 1885


measuring electric currents,


10


6


7


9016


July 10, 1886
April 9, 1887


Improved apparatus for measuring
the efficiency of an electric circuit












(Amended Oct. 4, 1897), -


13


28


40


18035


Dec. u, 1888


Electrostatic apparatus for measur-










Sept. 7, 1889


ing potentials, -


4


3


7


i8o 35 a


Dec. n, 1888


An improved ampere gauge and










Sept. 7, 1889


connections, ......


3


3


6


i8o 3 5b


Dec. n, 1888


Improved apparatus for continu-










Sept. 7, 1889


ously measuring potentials or












currents, -


3


2


3


^769


Oct. 8, 1889


Apparatus for measuring and re-










July 7, 1890


cording electric currents (allowed












to lapse), -


4


3


4


1004


Jan. 20, 1891


An improved indicator for electric










Oct. 20, 1891


potentials, -


2


i


3


18436


Oct. 27, 1891 1 Improved apparatus for measuring










July 22, 1892 and recording electric currents, - 5


3


6


10230


May 30, 1892


An improved electric condenser, - 2


2


2




July 2, 1892










2198


Feb. i, 1893


Improvements in balances, -


2


I


5




Nov. i, 1893











330



KELVIN'S ELECTRIC MEASURING INSTRUMENTS.



Number of
Patent.


Date of
. Provisional
Specification and
of Complete
Specification.


TITLE OF PATENT.


Number of
Pages.


Number of
Sheets.


II

g


2199


Feb. I, 1893


An instrument for measuring elec-










Feb. i, 1893


tric currents,


3


I


4


5733


Mar. 17, 1893


Improved arrangement for reading










Dec. 1 6, 1893


the deflections of electric instru-












ments,


2


I


2


24471


Dec. 20, 1893


Improvements in electric supply










Oct. 20, 1894


meters,


3


I


2


24979


Dec. 29, 1893


Improvements in instruments for










Dec. 29, 1894


measuring and recording electric












pressures and currents,


i


3


5


15034


Aug. 7, 1894


Improvements in instruments for












measuring electric currents,











226l


Nov. 27, 1895
Sept. 28, 1896


Improvements in apparatus for in-
dicating and recording electric












supply,


5


i


2


18438


Aug. 9, 1897


Improved coil for electric instru-










May 9, 1898




5


i


J


21716


Oct. 15, 1898


Improvementsin electric measuring


O








July 14, 1899


instruments, ....


2


i


I


3937


Mar. i, 1900


Apparatus for indicatingand record-










Dec. I, 1900


ing electric pressure and current,


3


i


4



PATENTS RELATING TO IMPROVEMENTS IN TELEGRAPHIC

APPARATUS.



329


Feb. 20, 1858


Improvements in testing and work-










Aug. 19, 1858


ing electric telegraphs,


36


i


9


329


May 19, 1871


Disclaimer,


19







2047


Aug. 25, 1860


Improvements in the means of










Feb. 25, 1861


telegraphic communication,


37


4


27


1784


July 6, 1865


Improvements in electric tele-










Jan. 6, 1866


graphs,


14


i


9


2147


Tuly 23, 1867


Improvements in receiving or re-










Jan. 23, 1868


cording instruments for electric












telegraphs, ....


10


i


7


3069


Nov. 23, 1870


Improvements in electric telegraph










Not allowed.


transmitting, receiving, and re-












cording instruments, and in












clocks,


33








252


Jan. 31, 1871


Improvements in transmitting,










July 31, 1871


receiving, and recording instru-












ments for electric telegraphs,


24


7


37


810


Mar. 25, 1871


Improvements in clocks and ap-










Void.


paratus for giving uniform motion


4








2086


June 12, 1873


Improvements in telegraphic ap-










Dec. 12, 1873


paratus,


T 4


4


ii


1095


Mar. 13, 1876


Improvements in telegraphic ap-










Sept. 13, 1876


paratus,


16


4


21


24868


Dec. 28, 1895


Improvements in recording instru-










Sept. 28, 1896


ments for telegraphic and other












purposes, ....


4


2


6



THURSDAY, 5th SEPTEMBER, 19O1.

W. LANGDON, Chairman, in the Chair.



The Chairman gave the substance of a communication he had
received from Dr. Glazebrook regarding the National Physical
Laboratory and the Avork which was to be done there.



" THE RELATIVE ADVANTAGES OF THREE, TWO, AND
SINGLE PHASE SYSTEMS FOR FEEDING LOW-
TENSION NETWORKS."

Paper by M. B. FIELD.



Abslract.

A TRACTION system is first considered where the distribution of
power is effected by means of continuous current at 500 volts, from
various sub-stations, these being fed from a single distant generat-
ing station with high tension alternating currents. It is assumed
that the choice of frequency is open.

The choice of converter lies between :

(1) Rotary converters with transformers.

(2) Synchronous motor generators without transformers.

(3) Non-synchronous motor generators without transformers.

Tables are given showing that (i) of rotary converters, the
six-phase rotary used on a three-phase system is the best, owing to
the greater load per unit weight it will carry; (2) the rotary con-
verter is lighter, more efficient, cheaper, and equally as simple and
practicable a converter as a motor generator, provided the fre-
quency be kept low ; (3) the multi-phase converter of whatever type
is preferable to the single-phase converter. The single-phase
rotary is not a practicable converter, and is not considered.

CABLES. It is pointed out that the three-phase system should
theoretically give the minimum weight of copper in the transmission
line per kw. transmitted, with given percentage loss and strain upon
the insulation of generators, cables, etc. A specific case is con-
sidered, a three-phase transmission one mile long at 6500 volts
per phase, transmitting 1000 kw. through three-core cables, being
taken as a working basis of comparison.



332 SYSTEMS FOR FEEDING LOW-TENSION NETWORKS.

The alternatives are for single-phase

(1) One concentric cable.

(2) Two independent single-core cables.

(3) One two-core cable.

For two-phase

(1) Two concentric cables.

(2) Four single-core cables.

(3) Two two-core cables.

(4) One four-core cable.

In comparing the various systems, either the strain on the
insulation of the generators, transformers, etc., may be kept the
same in each case, or the strain in the insulation of the cables may
be kept the same. These are two entirely different conditions,
which do not necessarily hold simultaneously. Conditions are
also varied when the neutral point of the generating system is
earthed, and when it is not earthed. Various cases are considered
and discussed, the result arrived at being in favour of three-core
cables and a three-phase supply.

Board of Trade regulations may have an important bearing on
the choice of the system. For example, if an earthed shield be
required, and for this reason two concentric cables be used for a
two-phase system, the outers forming a common main may have
each a smaller cross section than the corresponding inner con-
ductor. This will mean less copper for the two-phase system than
for the corresponding single-phase system. If no earth shield be
provided, and concentric cables be avoided, and in their place two-
core cables be adopted, the weight of copper is the same for the
two systems. If, on the other hand, three-core cables be used for
a three-wire two-phase system, all cores being insulated from earth,
a greater weight of copper is required for the two-phase than for
the single-phase system, if they are both placed on the same basis
as regards strain on insulation.

GENERATORS. Three-phase generators are cheaper and lighter
than single-phase generators, and the synchronising effects are
greater.

When it is a question of mixed lighting and power, and a higher
frequency is adopted, the advantages of the three-phase system
are not so predominating. Single-phase motors, though not so
efficient, and having a lower power factor than three-phase motors,
are nevertheless very serviceable motors. Frankfort is instanced
as a case where a large amount of motor power is distributed from
lighting circuits successfully. In well laid out three-phase schemes
lights may be connected to motor circuits, and a mixed system may
thus be adopted with very good results.

If the transmission from the generating station to the transform-



SYSTEMS FOR FEEDING LOW-TENSION NETWORKS. 333

ing centres be a long one, economy is obtained by adopting a three-
phase transmission. There is, however, no economy in a three-
phase distribution where lamps are connected between each pole
and the neutral point of the system, as against a single-phase
distribution laid out on the three-wire system.

Hence the adoption of two-phase systems in cases where the
transmission losses are not great, and where both motors and lamps
are connected. The advantage will be emphasised if the system
be hampered by Board of Trade regulations, as stated above.

A three-phase combined system adopted in America has met
with a certain amount of favour where the voltage of one phase
alone is kept constant, all incandescent lamps being connected
across this phase. In such a case the other phases are loaded in
any way in which it is not essential to keep the voltage absolutely
constant. In this case no attempt is made to keep the phases
balanced. Three-phase motors and transformers are connected
across all three phases. The effect of this is to tend to equilibrate
the load on the three phases, since a motor takes most power from
the phase of which the voltage is highest. A good three-phase
generator may be used as a single-phase generator up to about
75 per cent, of its rated output. It is pointed out that an un-
balanced load of this nature goes far to counteract the special
economy of the three-phase system, in which case a two-phase
system would probably be equally advantageous.



The following members took part in the Discussion : the Chair-
man, Herr E. Kolben, Professor H. S. Carhart, Mr. W. B. Esson,
Professor Silvanus Thompson, Mr. W. G. Rhodes, Herr O. T.
Blathy, Mr. Gerald Stoney, Mr. W. Geipel, Mr. F. Broadbent.

The author replied, and a vote of thanks was accorded to Him.



MODERN COMMUTATING DYNAMO MACHINERY,
WITH SPECIAL REFERENCE TO THE
COMMUTATING LIMITS/'

Paper by H. M. HOBART.



Abstract.

IN the design of the continuous current dynamo, in spite of the
lapse of many years since the introduction of such machinery,
there is not that progress observable which has characterised
electrical engineering in general. There is certainly still very
great opportunity for improvement, and much may be done without
any radical innovations, merely by making more general use of the
technical knowledge of the subject at present at our disposal.
One persistent error has been the perhaps natural assumption that
the kilowatts output should be given predominating consideration
in laying down the lines of the design, and that the required volt-
and amperage are of altogether minor importance. This has led
to the frequent use of very inappropriate designs, particularly with
relation to the commutator, the armature winding, and the number
of poles and general construction of the magnetic circuit. Machines
of different voltages, but for the same kilwatts output, have, how-
ever, one set of features in common namely, all those features
relating to the amount of mechanical power to be transformed into
electrical, or vice versa; in other words, the mechanical design in
general. The paper goes on to describe a group of machines
designed with due regard not only to these features of mechanical
similarity, but also to the points where the designs should diverge
in order to suitably comply with the requirements of the different
voltage and current ratings. In these machines, which are
described in considerable detail, the base, stands, bearings, and
shaft are the same for all voltages, but while in the low voltage
design the electro-magnetic part of the machine is extremely
narrow and the commutator wide, the high voltage machine has
precisely the opposite characteristics. Since, however, the
diameter of commutator, armature, field bore, and magnetic yoke
are the same for all voltages, it is quite practicable to use to a
great extent the same drawings and patterns for all voltages, the
patterns being extended or not according as castings for machines
of the one or the other voltage are required. It is shown how
naturally all this works out, and the opinion is put forth that by



MODERN COMMUTAT1NG DYNAMO MACHINERY. 335

the use of these principles the best results for a given outlay may.
be obtained. For the group of machines described, which range
from 80 kilowatts at 580 r.p.m. to 150 kilowatts at 425 r.p.m., the
cost for " net effective material " was quite uniformly 16.3 shillings
per kilowatt for all voltages. The guarantee to which they were
designed is given as follows : 25 per cent, overload for one half
hour without harmful sparking or heating. Thermometrically
measured temperature increase of warmest part not to exceed 50
deg. Cent, above surrounding atmosphere during continuous
operation at rated load. No harmful sparking or heating with
momentary overloads of 50 per cent. Fixed brush position- for
all these conditions. Insulation of entire machine, from copper



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