Improvements in Appliances for Distribution of Power by Alternating and Commutated Electric Currents.
Year: 1889

page_text: PROVISIONAL SPECIFICATION.
Improvements in Appliances for Distribution of Power by Alternating
and Commutated Electric Currents.
I, JAMES SWINBURNE, of 49 Queen's Road, Wimbledon in the County of Surrey,
Electrical Engineer do hereby declare the nature of this invention to be as
follows:-
The present invention has reference to the utilisation of transformed electric
currents for distribution of power. Transformers are used to transform alternating
currents, and these alternating currents are, when desired combined to form
direct currents, and may themselves be produced by the commutation of direct
currents.
An ordinary dynamo develops alternating currents which are rectified & com-
bined by the commutator. Suppose it is a low tension dynamo. I lead the inain
current to a commutator which connects the terminals with two transformers of the
kind commonly used with alternating currents. The cominutator makes connection
with these in such a way as to produce two alternating currents differing in phase
by a quarter of a period. Two similar alternating currents are generated in the
secondaries. These are connected up by a cominutator so as to combine to produce
a direct current again. The direct current thus obtained may have any pressure
desired. The two commutators must synchronise, & they are therefore preferably
rigidly connected & driven by the same motor. A similar transforming arrangement
may be used at the distant station. When each transformer is complete, that is to
say, when at each station a direct current is transformed into a direct current, the
commutators at the two stations need not synchronise.
In many cases it is not advisable to convert the current into a direct current at
the dynamo The dynamo may have a commutator for exciting the field only, & two
alternating currents may be led by the three wires to a distant point & may there be
transformed to a low pressure by two transformers.
In this arrange-
A synchronous commutator then converts into a direct current.
ment the high pressure circuit may be entirely insulated, so that there is no source of
danger.
Such an arrangement as this is specially useful for tramway & electrical railway
work. Local transformers reduce the pressure & the currents are commutated in the
motor car, & a direct current motor is used. Cells may also be charged.
Instead of two any number of transformers can be used with a suitable com-
mutator. This arrangement is suited for distribution on a large scale, as it admits
of doing everything with direct currents which can now be done with alternating, &
in addition renders the power specially available for storage, electrometallurgy, &
motor work in cases where the motor is required to exercise considerable torque on
starting.
774
000
COMPLETE SPECIFICATION.
Improvements in Appliances for Distribution of Power by Alternating
and Commutated Electric Currents.
I, JAMES SWINBURNE, of 49 Queen's Road, Wimbledon, in the County of Surrey,
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 in
and by the following statement
--
The present invention has reference to the utilisation of transformed electric
currents for distribution of power for lighting or other purposes.

page_text: Transformers are used to transform alternating currents, and these alternating
currents are, when desired, combined to form direct currents, and may themselves be
produced by the commutation of direct currents.
The
For example, suppose the generator is a low tension direct current dynamo
giving 100 volts and 100 ampères, and it is desired to transmit the power to a
distant station and there to charge accumulators. The 100 ampere arinature circuit
is led to a rotating commutator which is in connection with two ordinary alternating
current transformers with primary circuits wound for an alternating current having
a maximum value of 100 ampères & a maximum pressure of 100 volts.
secondary circuits are wound for, say 2000 volts & 5 amperes, maximum values.
The secondary circuits of the transformers are also connected to the commutator, so
as to deliver a direct current into the mains. The commutator thus cominutates the
currents in the transformers alternately so that the dynamo current has always one
path open to it; otherwise there would be a destructive spark every time the main
circuit was broken Even then there is some spark due to the exciting current in
the transforiner In commutating the currents in one of the transformers both
primary & secondary circuits are for an instant open, whichever is open lust has the
imagnetising current spark. I use closed iron circuit transformers so that the energy
stored up is least, & I open the high tension cirenit just before the low, so that the
spark is on the low tension circuit. The commutator sections are arranged as in many
arc machines so that the spark is not on the peripheral surface of the commutator,
and is thus not destructive. The commutator is, pieferably driven by a small electric
motor. The spark, and its waste of power, can then be avoided as follows. The
armature of the motor has a few special turns of wire which are connected at the
right instants with one of the circuits on each of the transformers When the
special armature circuit is connected to the circuit on the transformer, the electio-
motive forces are equal & opposite, so no current passes. The high tension circuit is
then broken. There is no spark, for the exciting ampère turns then starts in the low
tension circuit. The fewarmature turns then emerge from the field so that their electro-
motive force falls, & the electrokinetic energy of the magnet is discharged into the
motor. As soon as the exciting current is zero, that circuit is broken too.
A transformer with a closed iron magnetic circuit is best for this purpose, as though
it is less efficient than my hedgehog form, the hysteresis lessens the sparking,
especially if the iron is of a suitable quality, and the electrokinetic energy is very
small.
At the distant station there is a similar apparatus to transform down to 100 or 50
volts as may be required.
It is possible to transmit the power without previous commutation back into a
direct current, & to transform down & cominutate into direct current at the distant
station. Three leads are then needed, and the power is transmitted as two alternating
currents differing a quarter of period in phase. The distant commutators must then
be driven synchronously. prefer to distribute by direct currents, as the alternating
cuments are not much use as such, for the circuits cannot be used as a three wire
system unless the two loads are equal, otherwise there is trouble at the commutators.
The generator is preferably an ordinary direct current machine, but a double circuit
alternator might be used. A synchronising commutator is then needed at the distant
stations only.
Instead of two, three or more transformers may be used in connection with each
commutator, but two should be enough.
I am aware that it has frequently been proposed to commutate a direct current
into an alternating, but if the direct current is continuous it seems to be impossible
to avoid serious sparking. It has also been proposed to commutate an ordinary
alternating current into an intermittent direct current, but this also seems to be a
suggestion without practical value. According to my invention a continuous current
is made interchangeable with two or more alternating currents differing in phase so
that the sum of their values from instant to instant is practically constant,

page_text: DESCRIPTION OF THE DRAWINGS.
In fig. 1 M. N. are primary commutators & m, n, secondary cominutators.
A. B, a, b, are rings for leading direct current into or out of the moving system.
A. B. a, b, M. N. m, n, are all mounted on a hub which is rotated by a small motor,
and are merely shown separated for clearness. The direct low tension electricity
enters at A by the brush, & finds its way to the section C, E, thence by the
brushes G. I. to the transformers L. K. The secondaries are connected to a similar
pair of commutators m, n, & the secondary line connections are made to a & b.
In the position shown, the transformers L. K. are fed in parallel, but the
primary of L. bas only been in circuit a short time, & that of K is just going
to be broken, by the brushes coming on the insulated segments. Just before the
primary of K. is broken. the secondary is broken, as the secondary brushes have a
little trail. The whole direct current is then taken by L, K. merely gets the
excitation current. The excitation current of K. is then broken by the brushes J. I.
coming on the insulated sections, & a slight spark only is produced, for the trans-
foriners, leaving closed iron circuits, do not lose their magnetisation when their
exciting current is stopped. When E comes under J, & Fuuder I the currents in K
are reversed, & the commutator m, collects in the same direction as before. The
apparatus shown in Fig. transforms from a direct current to a direct current, but
the secondary part might be placed at the distant station, & the power sent to it by
the two alternating current circuits o p & qr, or by three wires, one being connected
to p & g. In such a case the secondary or high tension circuits have another pair of
transformers at the distant station to transform down again, and the commutators
must be driven synchronously with those at the sending station. I therefore prefer,
in most cases to duplicate the whole apparatus, & use a direct current circuit between
stations.
Fig. 2 shows a case in which special circuits on the armature of the motor are
used to avoid sparking in large machines. The primary or low tension part of the
commutator is alone shown. The brushes I. J. are just about to leave the
sections E F. The corresponding high tension circuit will have been already
broken, there is thus only the exciting current in K. The sections T. U. are con-
nected to a special armature circuit on the motor, which gives the same e.in.f. as
the primary, so that it now supplies the exciting current. The amature circuit then
emerges from the field, & the exciting current dies down. The brushes then come
on the insulating segments, & then pass on to E. & F. & so on.
With this arrange-
ment it is possible to use open iron circuit transformers & to take advantage of their
higher efficiency.
Having now particularly described and ascertained the nature of my said Inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is:
1. The improved appliances for distributing electrical power substantially as
described.
2. Distributing power by the apparatus described or its equivalent.
3. A direct current transformer which commutates a direct current into two or
more alternating currents differing in phase, transforms these, & commutates the
transformed alternating currents into a direct current.
4. A conversion apparatus which commutates a direct current into two or more
alternating currents differing in phase, substantially as & for the purposes set forth.
5. A conversion apparatus which commutates two alternating currents differing in
nhase into a direct current. substantially as & for the pornoses set forth
JAS. SWINBURNE.