Improvements in and connected with Electric Transformers.
Year: 1890

page_text: Date of Application, 28th Feb. 1890
Complete Specification Left, 25th Nov., 1890-Accepted, 28th Feb., 1891
PROVISIONAL SPECIFICATION.
Improvements in and connected with Electric Transformers.
I, JAMES SWINBURNE, of 49 Queen's Road, Wimbledon, Surrey, Electrical
Engineer, do hereby declare the nature of this invention to be as follows:--
My invention refers to alternating current transformers and to safety apparatus
to be used with them.
To render an installation supplied by a transformer safe from all risks either of
fire or danger, I earth the middle of the secondary circuit through a fine fuse or
cut-out. If a current passes through this fuse or cut-out the primary circuit is
automatically disconnected from the whole system. The fuse may be a fine wire
which holds the catch which locks a double pole switch in the primary circuit. A
small electro-magnet will also do. If the primary makes contact with the secondary
anywhere in the transformer there is at once a current through the fuse which
disconnects the primary completely. It is thus impossible to get high pressure
into the house. Again if a leak developes anywhere in the secondary there is a
current through the fuse which cuts the house off the supply circuit. It is also
impossible for any customer to get a dangerous shock from any fitting as if the
secondary is a 100 volt circuit, the E.M.F. of the fitting only varies 50 effective
volts, as the middle of the circuit is earthed. It is difficult to make a fuse go off
with the current through a man; but a sensitive electro-magnet can be arranged
to cut all the supply off if any one is getting even a 50 volt shock..
:
Transformers of the open circuit or hedgehog type are difficult to construct
substantially. To get over this I arrange a metal frame of cross shaped section
which forms the backbone of the transformer. In the four divisions iron wire is
placed which forms the core. The flanges which form the ends of the coils
are fixed solidly to the metal backbone; and feet, & lifting eyes are also attached
to it. As open circuit transformers cannot be enclosed in thick metal cases I use.
jars of earthenware or stoneware. Where convenient these can be sunk in the
ground and filled with heavy insulating oil, so that the insulation is always
perfect.
1
1000
Datcu
JAS. SWINBURNE.
COMPLETE
SPECIFICATION.
Improvements in and connected with Electric Transformers.
I, JAMES SWINBURNE, of Broom Hall Works, Teddington, 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 :—
My invention relates to alternating current. transformers & to safety apparatus'
to be used with them.
To render an installation supplied by a transformer safe from all risks either of
fire or danger, I earth the middle of the secondary circuit through a fine fuse or
cut-out. If a current passes through this fuse or cut-out the primary circuit is'
automatically disconnected from the whole system. The fuse may be a fine wire
which holds a catch which locks a double pole switch in the primary circuit. A
small electro magnet will also do. If the primary makes contact with the secondary
anywhere in the transformer there is at once a current through the fuse which dis-
connects the primary completely. It is thus impossible to get high pressure into

page_text: the house. Again if a leak developes anywhere in the secondary there is a current
through the fuse which cuts the house off the supply circuit. It is also impossible
for any customer to get a dangerous shock from any fitting; for if the secondary
is a 100 volt circuit the E.M.F. of the fitting only varies 50 effective volts, as the
middle of the circuit is earthed. It is difficult to make a fuse go off with the
current through a man; but a sensitive electro magnet can be arranged to cut all
the supply off if anyone is getting even a 50 volt shock.
This arrangement shown diagrammatically in Fig. 1 on Sheet 1 of the accom-
panying drawings. A is a central station dynamo. B & C the high pressure
mains. J is a house transformer; & D is a double pole switch in the primary
circuit. M M are lamps on the secondary circuit. K K are two resistance or
choking coils; between which an earth connection L is arranged communicating
with the earth plate I. A current along L actuates the electromagnet H, thus
attracting the armature G and releasing the catch F; the weighted lever E then
drops, catches on the pin band opens the switch, thus disconnecting the transformer
altogether. If the leak is on one of the secondary leads nothing further happens ;
but if between primary and secondary there is a current at the station through the
earth plate K to the armature of a sort of one turn motor, or galvanometer. The
field magnet of Q & P are laminated and magnetised by an alternating current.
D is a laminated iron core with a coil on it. The current moves V making contact
with U & T. The electricity passes through an alarm bell R to the middle of the
primary S S being two choking coils or resistances. The contact U or V thus
directly connects the leaky primary wire to earth avoiding danger to life, or of fire.
The apparatus thus protects both high and low pressure circuits from danger, and
gives notice of any fault.
Fig. 2 shows a modification of the switch. W is a very fine fuse, put in the
circuit L of Fig. 1. A. current fuses it. The switch is urged in the direction of the
arrow by a strong spring; but is held by the lever ✗ pressing the pin Y.
The lever being pivoted at Z. When the fuse W goes, the switch is thus opened.
Instead of contacts, metal connections are used at the ends of the switch arms.
A rectangular slip of very thin metal, a, is slit most of its length & then bent up
and down. Very little force will then tear it. The circuit is broken in four places
by tearing the slips d e f g.
Transformers of open circuit or hedgehog type are difficult to construct sub-
stantially. To get over this I arrange a metal frame of cross shaped section which
forms the backbone of the transformer. In the four divisions iron wire is placed
which forms the core. The flanges which form the ends of the coils are fixed solidly
to the metal backbone, and feet and lifting eyes are also attached to it. This con-
struction is shown in Figs. 3 & 4 of Sheet 2. A gun metal casting of cross
shaped cross section carries the flanges ii which form the cheeks of the wire coils.
The terminal board is mounted on the end with the eyebolt k passing through a
central hole. The iron wire core in four parts, is put in the corners, as shown in
section in Fig. 3. The core is not in place in Fig. 2. When the copper wire is
wound into the space the ends of the iron wire are spread out into hedgehogs.
j
As open circuit transformers cannot be enclosed in thick metal cases, I use jars
of earthenware or stoneware. Where convenient, these can be sunk in the ground
and filled with heavy insulating oil or solid or viscous insulator, such as pitch or
bitumen or ozokerite or a mixture of these with vaseline or rosin oil. In fact any
suitable insulating compound that is inexpensive and a good insulator may be
employed. For outside or underground work the material should if possible be
heavier than water.
Having now particularly described and ascertained the nature of my said inven-
tion, & in what manner the same is to be performed, I declare that what I
claim is :-
1. The use in connection with a transformer system of the automatic leak finder
substantially os dosomibod

page_text: 2. The use in connection with a transformer system of an automatic leak finder
which cuts off the primary circuit of a transformer substantially in the manner
described.
3. In an open iron circuit transformer a cross shaped or equivalent backbone
substantially as described.
4. Insulating a transformer by placing it in a vessel of insulating material of the
nature described, or its equivalent.
•
Dated this 28th day of November 1890.
JAS. SWINBURNE.