of Electrical Power Chiefly by Alternating Currents.
Year: 1888

page_text: of Electrical Power Chiefly by Alternating Currents.
We ROOKES EVELYN BELL. CROMPTON & JAMES SWINBURNE, of Arc Works
Chelmsford, electrical engineers do hereby declare the nature of this invention to be
as follows:
In distribution of electrical power it is often necessary to couple two or more.
alternating current machines in parallel. When two or more alternating current
machines are coupled in parallel there is often a tendency for them to get out of
step. This causes waste of power in the armatures, & may even destroy them by
undue heating. To avoid such mischances we use what we call an induction coupler.
If two machines, are to be run in parallel on a circuit, one terminal of each is con-
nected directly to one terminal of the circuit, & the other terminals of the dynamos
are connected with the other terminal of the circuit through some turns round a soft
iron core such as used in transformers. The coils are so arranged that when the
machines supply equal power to the external circuit the turns on the core neutralise
each other so that the core is not magnetised but if the machines begin to get out of
step the induction coupler has the effect of inserting self induction in the circuit
Encluding both armatures, so that they tend to come into step again.
When several machines are run together each pair may have its own induction
coupler & may be coupled to another pair by means of another induction coupler so
that four machines need three-couplers and so on.
Another method is to have a number of couplers with one wire in series with the
main circuit, the other wire being in the circuit of one machine only. Thus suppose
the station demands from one to six dynamos.
There would be a coupler with an equal number of turns in each coil for the first
two machines.
The third machine is thrown in by a coupler with two turns on the machine coil
for every one on the main. The fourth has three to one & so on. Of course the main
coil is short circuited when the machine is not coupled else it would give a back
electromotive force in the main circuit.

page_text: There is sometimes considerable danger arising from the high electromotive force
on the mains in systems of distribution. To obviate this we use the following arrange-
ment. Take for simplicity the case of a direct current first. The whole is insulated
from the earth but an intermittent contact worked by the shaft of the engine makes
a connection between one terminal & the earth & then between the other terminal &
the earth say once every half minute. If there is a ground contact due to leakage
anywhere a current passes when the automatic contact is made & this works an
electromagnet which breaks the automatic circuit instantly, & leaves a bell ringing
till the matter is attended to. The result is that the existence of a single leak is found
automatically without using a permanent earth. If a man is making contact with one
end of the circuit & earth he feels nothing till the automatic contact is made. He
then gets an instantaneous shock only, & the bell is left ringing.
In cases where the circuit is earthed half way between the terminals an electro-
magnet is put in the earth circuit. If any one makes an earth contact elsewhere the
earth current breaks the earth circuit instantaneously & by a polarised arrangement,
makes contact between the earth & the terminal to which the main is-connected, so
that he is released.
As an unsuspected dead earth at the middle would interfere with this arrangement
the automatic leak finder should be in use also, so that the middle earth contact is
only occasionally made. The advantage of keeping the installation generally insulated
from the earth is that if anyone accidently touches the conductors he does not get
burnt as there is no complete circuit.
This arrangement is modified for alternating currents, as currents due to the capacity
of the system would give shocks & would work the cutouts. The circuits are therefore
made through a revolving toothed wheel or other such contrivance which is in step
with the dynamos so that contact is only made at one part of the period. The middle
wire arrangement is also applicable.
For reading large alternating currents we prefer to insert a small transformer so
that a small current my be led through the instrument. One instrument can then be
used to measure the current in any one of a number of different circuits.
To save the main switches a short piece of thin lead or other fusible wire is put in
shunt to each. This entirely prevents the formation of an arc at the switch, & thus
prevents the burning of the contacts.
The lead wire lasts till the switch is opened, & then fuses with a flash interrupting
the circuit. When the switch is closed a new wire is inserted.
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page_text: SI and Connected with the Generation and Distribution
of Electrical Power Chiefly by Alternating Currents.
ROOKES EVELYN BELL CROMPTON & JAMES SWINBURNE, of Arc Works Chelmsford,
Electrical Engineers, 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 :-
Our invention relates to central station electric light & power distribution, &
apparatus connected with it.
In distribution of electrical power it is often necessary to couple two or more
alternating current machines in parallel. When two or more alternating current
machines are coupled in parallel there is often a tendency to get out of step. This
causes waste of power in the armatures by undue heating. To avoid such mischances
we use what we call induction couplers. If two machines are to be run in parallel
on a circuit one terminal of each is connected directly to one terminal of the circuit &
the other terminals of the dynamos are connected with the other terminal of the circuit
through some turns round a soft iron core such as used in transformers. The coils
are so arranged that when the, machines supply equal power to the external circuit
the turns on the core neutralize each other so that the core is not magnetised, but if
the machines begin to get out of step the induction coupler has the effect of inserting
self induction in the circuit including both armature so that they tend to come in
step again.
When several machines are run together each pair may have its own induction
coupler & may be coupled to another pair by means of another induction coupler so
that four machines need three couplers and so on.
Another method for several machines is to have a number of couplers, with one
wire in series with the main circuit, the other wire being in the circuit of one
machine only. Thus suppose the station demands from one to six dynamos. There
would be a coupler with an equal number of, turns in each coil for the first two
machines.
The third machine is thrown in by a coupler with two turns on the machine coil for
every one on the main. The fourth has three to one & so on. Of course the main
coil is short circuited when the machine is not: coupled, else it would give a back
electromotive force in the main circuit.
The cores should be only just large enough to prevent the machines going out
of step:
There is sometimes considerable danger arising from the high electromotive force
on the mains in systems of distribution.
To obviate this we use the following arrangement. Take for simplicity the case of
a direct current first. The whole is insulated from the earth, but an intermittent
contact worked by the shaft of the engine makes a connection between one terminal

page_text: & the earth, and then between the other terminal and the earth say every half
minute.
If there is a ground contact due to leakage anywhere a current passes when the
automatic contact is made and this works an electromagnet which breaks the automatic
circuit instantly and leaves a bell ringing till the matter is attended to. The result
is that the existence of a single leak is found automatically without using a permanent
earth. If a man is making contact with one end of the circuit & earth he feels
nothing till the automatic contact is made. He then gets an instantaneous shock only
& the bell is left ringing.
In cases where the circuit is earthed half way between the terminals an electromagnet
is put in the earth circuit.
If anyone makes an carth contact elsewhere the earth current breaks the earth circuit
instantaneously & by a polarized arrangement makes contact between the earth & the
terminal to which the man is connected, so that he is released. As an unsuspected
dead earth at the middle would interfere with this arrangement the automatic leak
finder should be in use also, so that the middle earth contact is only occasionally made.
The advantage of keeping the installation generally insulated from the earth is that
if anyone accidentally touches the conductors he does not get hurt as there is no
complete circuit, so we prefer this arrangement.
This arrangement is modified for alternating currents, as currents due to tho
capacity of the system would give shocks & would work the cutouts.
The circuits are therefore made through a revolving toothed wheel or other such
contrivance which is in step with the dynamo so that a contact is only made at one
phase.
The middle wire arrangement is also applicable.
For reading large alternating currents we prefer to insert a small transformer, so
that a small current may be led through the instrument or voltmeter. One instrument
can then be used to measure the current in any one of a number of different
circuits.
To save the main switches a short piece of thin lead or other fusible wire is put in
shunt to each. This entirely prevents the formation of an are at the switch, & thus
prevents the burning of the contacts. The lead wire lasts till the switch is opened, &
then fuses with a flash interrupting the circuit.
When the switch is closed a new cutout is inserted.
DESCRIPTION OF THE DRAWINGS.
Fig. (1) shows two alternating current dynamos A A coupled together by an
induction coupler B. the windings on the coupler being equal and opposite.
couplers
Fig. (2) shows 4 machine: A 1; A 2. A 3. and A 4. A 1 and A 2. are coupled by
the induction coupler C; and A3; and A4, by D, E then couples the two parts
together. In Fig. 3 an alternative arrangement is shown, 6 machines and
being taken A 1. and A 2 are joined through the coils of F. The turns are equal.
The current from A 1 and A 2 goes through one coil of G. which couples A3 to
the main circuits A 3 has twice as many turns on its circuit on G as the main similarly
H and I and J couple in A 4 A 5 and A 6.
On F a small coil K is shown. This may be used to give warning, or to cut A 2
out if the machine is not doing its proper work.
Such a coil may be used on any of the couplers.
Fig. 4 shows a safety arrangement for a direct current installation. The arm M is
rotated slowly being connected with the engine or shaft. Suppose there were an
earth on the positive lead. When the arm touches N electricity passes from the
positive wire through the leak to the earthplate E thence to the tumbler S to the
armature R through the coils of the electromagnet Q, to M, and when M touches N
it gets back to the dynamo. As soon as R moves the circuit is broken. The weight
of S presses the contact T and leaves the bell U ringing.
Fig. (5) is a similar arrangement for alternating currents. It is nearly the same A

page_text: wheel w rotating rapidly in step with the dynamos is inserted in the alarm circuit
and a condenser X is placed in shunt to the magnet. If there are many circuits
each may have a contact for the arm M to touch. In circuit with P a safety earth
contact is shown. This earths the other lead perfectly so that if a man were holding
it when M touched P he would be released.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed we declare that what
we claim is :--
(1) Induction couplers to make alternators run in parallel.
(2) Induction couplers substantially as and for the purposes set forth.
(3) The automatic leak finder substantially as described.
(4) Reading the main current in a lead by transforming up and using a voltmeter
substantially as described.
(5) Reading one or any of several alternating currents by means of transformers
and a voltmeter as described.
(6) A switch with a fuse in shunt to it substantially as and for the purpose set
forth.