Improvements in Switches for Controlling Electric Current Circuits in Parallel Supply Systems.
Year: 1893

page_text: Date of Application, 18th Nov., 1893-Accepted, 20th Jan., 1894
COMPLETE SIECIFICATION.
Improvements in Switches for Controlling Electric Current Circuits
in Parallel Supply Systems.
I, WILLIAM LOWRIE, of 117 Bishopsgate Street Within, in the City of
London, 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 ascer-
tained in and by the following statement :-
My invention relates to improvements in switches for controlling electric current
circuits, whereby when certain conditions are produced either automatically or by
hand-electrical contacts are made or broken automatically.
In the case of two dynamos,-working in parallel, and generating current for one
supply system-it is known that the failure of one of the generators to maintain its
supply would cause the safety fuses of the active dynamo to be cut out, leaving
those of the failing dynamo intact. This is due to the active machine discharging
both through the failing machine and through the supply system, thus causing a
total stoppage of the supply in the distributing system.
The same difficulty might occur with motor or other transformers, accumulators,
or primary batteries when arranged in parallel and feeding a supply system; the
safety fuses being useless to prevent this. The failure might be of short duration,
but it is desirable that the feeding apparatus-when regaining its power to supply―
should be automatically connected to the distributing system.
Furthermore, in any distributing system, it is very desirable that the system
should be supplied by means of two or more feeder mains, attached either directly
to the distributing mains, or through stationary or motor transformers, or accumu-
lators; and if some automatic means can be used to make or break the connection
with, and close to, the distributing mains, by simply making or breaking the
primary circuit at the distant supply station end of the feeder mains, then many
advantages would accrue. For example, such automatic means would enable us to
control distant converters or transformers, and at the time of low load one or
more converters of those employed could be cut out of action, and the magnetizing
current thereof saved until the load increased; when additional converters could
be switched in, to maintain the supply required.
It has been proposed to accomplish the objects indicated above by hand worked
switches at the connecting point of the feeder mains with the distributing system.
This is not safe in dealing with powerful high tension currents, nor is it practicable
where immediate control is required to meet the exigency of a variable demand, as
indicated by the indicating instruments at the station. It has also been proposed
to accomplish the said objects by separate control wires, run from the generating
station (or other operative point of control) to each point of connection between
the feeder mains and the distributing mains; but the expense, complications, and
difficulties in practice have prevented this method from being adopted.
By my invention I remove difficulties hitherto met with and obtain both safety,
and easy control of electric current circuits, where two or more units of supply
apparatus are worked in parallel, as in the examples following.
(a.) Two or more primary generators, working in parallel, directly supplying a
distributing system of mains.
(b.) Two or more primary generators, working in parallel, supplying a trans-
former or group thereof.
(c.) Two or more primary generators, working in parallel, supplying two or more

page_text: transformers whose secondary windings are connected in parallel to a distributing
system of mains.
(d.) Two or more feeder mains, each supplied from a separate source, feeding in
parallel a distributing system of mains.
(e.) Two or more feeder mains, supplied from a common source, feeding in
parallel a distributing system of mains.
(f.) Two or more feeder mains, supplied from a common source, feeding the
primary circuits of transformers.
(g.) Two or more feeder mains, each supplied from a separate source, feeding
transformers which are arranged in parallel to supply a distributing system of
mains.
(h.) Two or more transformers arranged in parallel to supply a distributing system
of mains.
In the accompanying drawings
Figs. 1 and 2 are diagrams of one form of automatic switch with electric con-
nections thereto; in which the arrangement shown in Fig. 1 is adapted for use with
alternating or interrupted currents, and
Fig. 2 for continuous or other currents; the difference between them consisting
mainly of an extra shunt winding in Fig. 2.
Figs. 3 and 4 are also diagrams indicating the relative positions of the said
switches in a system of mains for the distribution of electrical energy; Fig. 3
being adapted for alternating currents, and Fig. 4 for continuous currents.
In these diagrams (except as hereinafter stated) A, A', indicate the omnibus or
feed bars (or their equivalents) in a central or other station, fed by two or more
generators a, a¹. Two or more separate mains B, B, and 132, B³, are connected
directly to the bars A, A', at the station, and thence are connected alternately to
the primary windings b, b, and 62, 63, of two or more tranformers or converters C,
and C. The secondary windings c, cl, and c, c³ of the said transformers are con-
nected to the distributing system of mains D, D', which connect together the
secondary terminals d d of the transformers; and all the supply or lamp wires (not
shown) are joined to the distributing mains D, D'.
When the primary circuit B (for example) is put in action at the station, by
hand at F, or otherwise, the automatic switch E operates to put the secondary
terminals d, d, of the transformer C, in connection with the distributing mains D, D',
and consequently with all the supply wires joined thereto. If the load increases
the second converter shown (C) is similarly put into action at the station by
joining up the primary circuit B2, B3 with the bars A, A'; and the same method
is employed with any other converters, similarly arranged, that may be on the
circuit D, D. Each converter C, shown on the drawings, is intended to represent
either a single converter or a group of converters fed by a separate primary main
or conductor, whatever may be the number of converters in the group; but these
primary feed mains B, B', may be laid close to, though insulated from, each other;
so that the primary current may be operating in one pair of conductors, and not in
another pair adjoining thereto.
In the diagram Fig. 1 of the automatic switch E an electro magnet is shown
having two limbs pivoted together at e, one limb e¹ being rigidly fixed, the other
limb e being pivotally moveable on the joint e. Polar projections are formed in
any convenient manner, and the core is laminated. The moveable limb e carries
four contact pieces (suitably connected to the secondary circuit c, c¹ of the con-
verter E, as in Figs. 3 and 4, for example) operating simultaneously in one
direction, and two contacts operating simultaneously in the opposite direction.
These are so arranged that when the contact pieces are in circuit, the contact
pieces are out of circuit; and conversely when the latter are in circuit, the
connection is broken at all four of the contacts. The several h contacts each
form a two pole switch on the mains, and all the parts are suitably insulated, as
well understood by electricians. The other two contact pieces j, when in circuit,
form a short circuit for a series coil S through the circuit n, n, in Figs. 1 and 2.

page_text: In these switch diagrams, (Figs. 1 and 2), the mains A, A', are to be taken as
feeder mains to the switch, whether supplied from a primary or secondary source,
and D, D' the distributing mains, fed by two or more sources (primary or secondary)
of electrical energy. The series coil S is connected by the circuit L, L to work in
Beries with the main circuit A, A'; while the shunt coil S₁ is placed across the
circuit by the conductors M, M. The action of the switch, as shown in Fig. 1 is
as follows. The circuit is closed on the right hand side at all the contacts, the
feeder mains A, A' being in action on the distributing mains D, D¹. The current
in the feeder mains A, A', is designedly a little lower in electro motive force than
that in the circuit D, D', but the voltage is increased to that in the circuit D, D',
(after passing the switch) by the action of the shunt coil S₁ upon the series coil S,
which is in series with the feeder mains A, A'; from which it will be seen that
the electro magnet E acts as an auxiliary transformer. The series and shunt
coils S, and S are adapted to produce poles of the like name, and when this occurs
the moveable limb eis repelled, the contacts h are made, and the short circuit
contacts are broken, as shown in the drawings, Figs. 1 and 2. When the current
potential falls in the feeder mains A, A' (from any cause) and so fails to maintain
its power to feed the distributing mains D, D', then the direction of the current
through the series coil S will be reversed, (through the higher back electro motive
force from the mains D, D', fed by other sources in parallel), while the direction
of current in the shunt coil S¹ would remain the same, thus bringing about unlike
poles of the limbs e, e², with mutual attraction, which-breaking all the contacts h
in one direction, would make the j contacts in the opposite direction-and, short
circuiting the series coil S through the circuit n, n, the feeder mains A, A¹, and
both series and shunt coils S and S', are rendered dormant.
When the current is again switched on-or, the necessary potential maintained-
in the feeder mains A, A¹, the shunt coil S¹ is at once put in action through the
circuit M, M', but it could not act on the series coil S if it were not for the short
circuit contact j, as the said coil would be on open circuit. The short circuit,
therefore, will admit of a strong current being induced in the coil S, which,
producing like polarity in the limb e¹ to that of e³, repels the latter or moveable
limb, thus making good all the contacts, and breaking that of the short circuit j,
makes all the circuits good for feeding the distributing mains D, D'.
Fig. 2 is a diagram of an automatic switch and its connections adapted for
working with either alternating or continuous currents. The arrangement is
similar to that of Fig. 1, and the description of the latter will apply likewise
to Fig. 2, with the exception that the short circuit upon the series coil S by
the line n, n, is omitted and replaced by the shunt coils, wound on the same
limb e as the series coil S; while its circuit (the circuit of s) is made or broken
at j. The connections are so made when using continuous currents that when
the mains A, A' are put into action, the two shunt coils S¹ and s, by producing
like poles, repel each other, and so make good the circuit through the contacts,
and series coil S, while at the same time the second shunt coil circuit s is broken.
On the other hand, on the cessation or reduction (to any required degree) of
potential energy in the feed mains A, A' a reversal of current takes place in the
shunt coils thus bringing about unlike poles of the limbs e¹, e, with mutual
attraction, consequently breaking the h contacts and making the j contacts, as
before.
It is to be noted that solenoids only may be employed instead of the electro
magnet described; and that the limbs or coils referred to may be reversely
arranged, or even both limbs moveable, without departing from the nature of this
invention. Moreover, I may use the aforesaid automatic control switch in carrying
out my invention as described in the Specification of my application for Letters
Patent No. 3666, dated 18th day of February 1893, and as some parts of this and
the drawings are also given in the aforesaid Specifications, I desire it to be
understood that I do not claim hereby anything claimed in the said Specification
No. 3666 of 1893.

page_text: Having now particularly described and ascertained the nature of the said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is ;-
1. An automatic control switch, adapted to be operated by back electro motive
force on the cessation or predetermined reduction of potential energy in the primary
of a parallel supply system to break the secondary circuit of the said parallel
supply, and to make the said secondary circuit on the restoration of the required
degree of potential in the primary circuit, substantially as and for the purpose
herein described.
2. An automatic control switch wound and acting as a transformer adapted and
operating by the production of like poles and unlike poles. to alternately and
reversely make and break the electrical contacts in one of the secondary circuits
of a parallel supply system, substantially as and for the purpose herein described.
3. In an automatic control switch the combination of an electro magnet having
shunt wound and series wound limbs relatively moveable one to the other, contact
devices operated by a moveable limb whereby contacts are made and broken
simultaneously in one direction when the current in the said shunt and series coils
produces poles of like name, and the said contacts are broken and made simul-
taneously in a reverse direction when the current produces poles of unlike name,
and a short circuit device or second shunt coil, substantially as and for the purpose
herein described.
4. The herein described improvements in switches for controlling secondary
circuits in parallel systems, substantially as shown in the drawings, Figs. 1 and 2.
Dated this 18th day of November 1893.
FAIRFAX & WETTER,
433, Strand, London, Agents for the Applicant.