Circuits where Alternating Currents are Used.
Year: 1886

page_text: Circuits where Alternating Currents are Used.
We JULIAN MONEY VERNON KENT of Connaught Mansions, Westminster in
the county of Middlesex, and WILLIAM HENRY SNELL of "Lamorna," Oxford
Road Putney in the county of Surrey, 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:-
This invention relates to improved means and apparatus for controlling the
potential on circuits where alternating currents are used. The object of the
invention is to control or regulate the difference of potential on the working
circuit so that if one lamp or group of lamps or other resistance be switched out
or in the potential at the terminals of the other lamps or resistances remaining
in circuit is unaffected.
This object may be effected in two ways the principle involved being the same
viz: the insertion into or withdrawal from the circuit of a virtual resistance to
balance any change in the actual resistance of the other part of the circuit.
Figure 1 shows one method of carrying our invention into practise in a case
where the alternating current is supplied through a transformer the external
circuit being a lamp circuit. a is the main lead, 6 the transformer, c the external
circuit. A single two way switch S of any suitable type is provided for each lamp
or group of lamps and arranged in such a way that when the lamp or group of
lamps is thrown out of circuit an equivalent virtual resistance is simultaneously
thrown in.
The virtual resistance in this case consists of a coil R having a suitable
actual resistance wound upon a core or cores of iron in the usual well known
manner.
Figure 2 illustrates a modification of this arrangement, in this case the switch S
of the virtual resistance R is not connected with the lamp switch as described in
reference to figure 1, but is moved independently thereof as and when required,
and the virtual resistance R is inserted in series with the lamps or resistances.
This arrangement is shown in figure 3 and consists of a number of coils r of copper
wire wound in series on the same iron bar or ring T. Each of these coils r is
connected to a separate block 8 upon the switch S in such a way that by turning
the handle of the switch the resistance inserted can be varied according to require-
ments from zero when all the lamps or resistances are in circuit to that of the

page_text: total number of coils r upon the ring forming the virtual resistance. It will be
seen that by this arrangement we are also enabled to economically vary the
intensity in the light of the lamps. Although in the above examples lamp circuits
are more particularly described it is obvious that by slight modification the inven-
tion is applicable to circuits containing any kind of resistance such as motors or the
like without departing from the main features of the invention.
Having now particularly described and ascertained the nature of our invention
and in what manner the same is to be performed we declare that what we
claim is :-
1. The hereinbefore described method of controlling the potential in circuits
where alternating currents are used whereby the insertion or withdrawal from the
circuit of any actual resistance simultaneously withdraws from or inserts into the
circuit an equivalent virtual resistance.
2. For controlling the potential in circuits where alternating currents are used
the use of a switch both connected with each actual resistance and with an
equivalent virtual resistance and arranged in such a manner as to simultaneously
with inserting or withdrawing the one to withdraw or insert the other respectively,
in the manner herein before set forth.
3. For controlling and regulating the potential in circuits where alternating
currents are used the use of a combined switch and virtual resistance such as is
specified placed in the circuit in series with the resistances which it controls
adapted to operate as and for the purposes set forth.