Improvements in and connected with Electrical Distribution of Power by Alternating Currents.
Year: 1890

page_text: Date of Application, 27th Nov., 1890
Complete Specification Left, 17th Aug., 1891-Accepted, 14th Nov., 1891
PROVISIONAL SPECIFICATION.
Improvements in and connected with Electrical Distribution of Power
by Alternating Currents.
1, JAMES SWINBURNE, of Broom Hall Works, Teddington, Surrey, Electrical
Engineer do hereby declare the nature of this invention to be as follows:-
My invention has reference to distribution of power by alternating currents,
chiefly by means of transformers.
Any arrangement which makes an alternating current lag relatively to the electro-
motive force, such, for instance, as a choking coil may give rise to difficulties in
distribution.
For instance, suppose a station supplies a 100 volt secondary circuit by means of
transformers with 2000 volts primary pressure, & suppose there are 200 arc lamps,
each taking 33 volts & 10 amperes arranged on the 100 volt circuit with a choking
coil in series with each. Suppose, for simplicity, that there are no incandescent
lamps in use. The arc lamps then take 2000 amperes and 100 volts; but this does
not amount to more than 66000 watts, as the current is not cophasedly synchronous
with the electromotive force. The dynamos thus have to supply 2000 volts &
100 amperes, whereas the same power, if the current did not lag, would be supplied
by 2000 volts & 33 amperes. This gives rise to several troubles. Suppose each
machine has an armature wound to give 2000 volts & 33 amperes, or 66000 watts, it
takes three instead of one to work the lamps. In addition to this the lagging of
the current weakens the field of the dynamos, so that they need more excitation to
give 2000 volts than they would need even on full load on a noninductive resistance.
Moreover, running three engines and dynamos at a third load instead of one at full
load is not economical. The same difficulty is apt to occur during the day if a
large number of open-circuit transformers are used, or if synchronising motors are
employed.
To overcome this difficulty I put condensers in shunt to the primary circuit. A
condenser takes a current which leads relatively to the pressure, so that it counter-
acts the effect of the lagging current. For instance, in the case of the arc lamps,
the current of 100 amperes may be regarded as compounded of a current of
33 amperes, in step with the primary pressure, & 95 amperes lagging a quarter of a
period. A condenser of about 85 microfarads will supply the 95 ampere component,
while the dynamos supply the 33 ampere component. One engine and dynamo is
then enabled to supply the arc lamps.
The condenser may be made up of tinfoil & a suitable dielectric. A good dielectric
is difficult to find. Some substances, though good insulators, waste power by
absorption. I use paper soaked at a high temperature in ozokerite & resin, or
desiccated paraffin oil or nitrobenzol or nitrotoluol, or xylonite, or pyroxylin paper
soaked with hydrocarbon. A high temperature is always necessary to desiccate the
paper thoroughly.
Each condenser is subdivided, so that a breakdown does not destroy the whole.
It is sometimes advisable to make the connections to the condenser plates so small
that they act as fuses in case of a local breakdown.
The condensers can be used in conjunction with transformers, motors or choking
coils. For use with arc lamps, I prefer to combine the choking coil & transformer, so
that a transformer has constant pressure on its primary and gives an approximately
constant secondary current. This is secured by winding an open iron circuit trans-
former with the coils side by side, instead of in alternate layers. Such a trans-
former is also useful for working an alternating motor designed for approximately

page_text: constant current.
Whether a constant current motor is used with a constant current
transformer, or with a special choking coil, I prefer to use condensers in conjunction
with the system.
When a station feeds several alternating circuits in parallel, if metallically
connected, it is difficult to find leaks or faults, & such leaks or faults are especially
troublesome. In such cases I use a local circuit or set of mains for each district,
and couple these noumetallically by means of transformers. For example, a town
may require 100,000 lights distributed with more or less irregularity. If the supply
mains are at low pressure, an arrangement I prefer, each district has its own mains,
which have no metallic connection with those of the next district. They are con-
nected however through a transformer so that the advantages of equal pressure are
secured. Each district is then supplied by feeders, but the feeders are not necessarily
low pressure. They may be under high pressure with transformers at the points
where they feed the main circuit. One district may thus have an earth on the positive
main & another on the negative without any disastrous results. The whole town may
thus be fed in parallel from a high pressure station without substations or low
pressure feeders. The whole town may then be thoroughly & easily worked from
one high pressure station.
Dated this 20th 1... C NT
1
1000
JAS. SWINBURNE.
COMPLETE SPECIFICATION.
Improvements in and connected with Electrical Distribution of Power
by Alternating Currents.
I, JAMES SWINBURNE, of Broom Hall Works, Teddington, Middlesex, Electrical
Engineer, do hereby declare the nature of this invention and in what manner the
same is to be performed, to be particularly described and ascertained iu and by the
following statement :-
My invention has reference to distribution of power by alternating currents,
chiefly by means of transformers.
Any arrangement which makes an alternating current lag or follow relatively to
the electromotive force, such, for instance, as a self induction coil may give rise to
difficulties in distribution.
For instance suppose a station supplies a 100 volt secondary circuit by means of
transformers with 2000 volts primary pressure, & suppose there are 200 arc lamps,
each taking 33 volts & 10 amperes arranged on the 100 volts circuit with a choking
coil in series with each. Suppose, for simplicity, that there are no incandescent
lamps in use. The arc lamps then take 2,000 amperes & 100 volts; but this does
not amount to more than 66,000 watts, & may be less as the current
not in step
with the electromotive force.
The dynamos thus have to supply 2,000 volts & 100 amperes, whereas the same
power, if the current did not lag, would be supplied by 2000 volts & 33 amperes.
This gives rise to several troubles. Suppose each machine has an armature wound
to give 2000 volts and 33 amperes, or 66,000 watts, it takes three instead of one to
work the lamps. In addition to this the lagging of the current weakens the field
of the dynamos, so that they need more excitation to give 2,000 volts than they
would need even on full load on a noninductive resistance. Moreover, running
three engines and dynamos at a third load instead of one at full load is not economical.
The same difficulty is apt to occur during the day if a large number of open circuit
transformers are used, or if synchronising motors are employed.
To overcome this difficulty I put condensers in shunt to the primary circuit. A
condenser takes a current which leads relatively to the pressure, so that it counter-
acts the effect of the lagging current. For instance, in the case of the arc lamps,.
the current of 100 amperes may be regarded as compounded of a current of
33 amperes, in step with the primary pressure, & 95 amperes lagging a quarter

page_text: of a period. A condenser of about 85 microfarads will supply the 95 ampere com-
ponent, while the dynamos supply the 33 ampere component. The engine and
dynamo is then enabled to supply the arc lanips.
Some forms of alternate current motors have been designed in which the excita-
tion is produced by the alternate current itself without the aid of a direct current
exciter.
Such a motor acts like an induction coil; that is to say it takes a large current
in proportion to its output.
The current may be regarded as being compounded of two currents differing in
phase by a quarter of a period.
One of these is the active current, which is in step with the pressure, & the other
is an exciting current, which lags a quarter of a period. The exciting current can
be nearly all supplied by a condenser, without burdening the dynamo. The con-
denser does not increase the output of the motor; it merely increases the possible
output of the dynamo. It has also been proposed to employ condensers in connection
with alternate current motors so as to get two currents differing in phase. This is
not my invention, it is entirely different in principle. The condenser is in that
case an adjunct to the motor, not to the dynamo. According to my invention the
condensers may be placed anywhere on the high pressure circuits, it is generally best
to have them at the central station, though this gives rise to some slight extra loss
in the mains.
The condensers used according to my invention may be regarded as a convenient
method of supplying alternate exciting currents for motors, transformers, or choking
coils which would otherwise have to be supplied by the station dynamos.
In making condensers for these purposes the dielectric I employ is thin paper.
I prefer the kind known as butter skin; but many other kinds will do. The con-
denser is built up of layers of paper and tinfoil, and is then compressed and baked
in a suitable oven for several days at a temperature of about 100 C. It is then
immersed in paraffin oil. To make sure that the oil finds its way into all the
interstices I sometimes exhaust the vessel containing the condenser before running
the oil in.
The finished condenser is packed in a cast iron box, the plates being still clamped
together under pressure. The leads are taken out through suitable blocks made of
celluloid, or other insulating material that is not soluble in paraffin oil.
The condensers can be used in conjunction with transformers, motors or choking
coils. For use with arc lamps, I prefer to combine the choking coil and transformer,
so that a transformer has constant pressure on its primary and gives an approximately
constant secondary current. This is secured by winding an open iron circuit trans-
former with one coil at each end, so that the coils are side by side instead of
alternate layers. Such a transformer is also useful for working an alternating motor
designed for approximately constant current. Whether a constant current motor is
used with a constant current transformer, or with a special choking coil, I prefer to
use condensers in conjunction with the system.
When a station feeds several alternating circuits in parallel, if metallically con-
nected, it is difficult to find leaks or faults, & such leaks or faults are especially
troublesome. In such cases I use a local current or set of mains for each district,
and couple these nonmetallically by means of transformers. For example, a town
may require 100,000 lights distributed with more or less irregularity. If the
supply mains are at low pressure, an arrangement I prefer, each district has its own
mains, which have no metallic connection with those of the next district. They are
connected however through a transformer so that the advantages of equal pressure
and parallel running at the station are secured. Each district is then supplied by
feeders, but the feeders are not necessarily low pressure. They may be under high
pressure with transformers at the points where they feed the main circuit.
One district may thus have an earth on the positive main and another on the
negative without any disastrous results.

page_text: The town may thus be fed in parallel from a high pressure station without sub-
stations or low pressure feeders. The whole town may then belthoroughly and easily
worked from one high pressure station.
DESCRIPTION OF DRAWING.
The accompanying drawing is a diagram of electrical distribution carried out
according to my invention.
A B C D E F are districts each being fed by a pair of low pressure mains which
are shown as squares.
The mains are fed by feeder transformers TUSVR W, which are themselves
supplied, by high pressure feeders ghfiej. These feeders are supplied by the
station transformers L M N O P Q whose low pressure primaries are connected to the
low pressure bars J K. The low pressure bars are fed by the dynamos G H I
coupled in parallel. The transformers L M N O P Q have their ratios of trans-
formation adjustable so that the pressures in the feeders can be independently
adjusted without trouble or waste. The low pressure systems of mains are also
coupled together by one to one transformers that is to say transformers with the
same number of turns in the coils. For instance A & B are coupled by trans-
former Z, and A & C by the transformer Y. If an abnormal number of lights
were used in the district A it would be supplied chiefly by the feeder g and trans-
former T, but the transformers Z & Y would transfer power from the mains of the
districts B & C. Should a fault occur on the positive mains in the district B and
on the negative mains of district A there will be no short circuit for there is no
metallic connection between the systems.
The consumers for example in the district E may be using motors which take
large exciting currents, and those in Fare lamps with choking coils. Condensers c
and d are therefore arranged in shunt to the high pressure or feeder circuits for
those districts, so that the exciting currents necessary need not be supplied by the
dynamos.
Having now particularly described and ascertained the nature of my inven-
tion and in what manner the same is to be performed, I declare that what I
claim is
1. The use of condensers to reduce the armature current in dynamos substan-
tially as described.
2. The use of condensers in parallel with circuits containing self induction or its
equivalent, which would otherwise cause a larger armature current in the
generators.
3. The use of condensers at a supply station to counteract the evil effects of self
induction or its equivalent in distant or external translating devices.
4. In electrical distribution neutralising the effects of self induction by means of
condensers.
5. The use of condensers in connection with transformers, motors, or choking coils
which take lagging currents.
6. Coupling various districts of a distribution area in parallel without metallic
connection, substantially as set forth.
Dated this 15th day of August 1891.
JAS. SWINBURNE.