Improvements in and Connected with Dynamo Electric Machines.
Year: 1887

page_text: Date of Application, 14th Sept., 1887
Complete Specification Left, 14th June, 1888
Complete Specification Accepted, 7th Sept.,
1888
PROVISIONAL SPECIFICATION.
Improvements in and Connected with Dynamo Electric Machines.
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 exciting large dynamos for central station and similar work, irregularities in the
exciting current are reproduced in the main circuit. Moreover any break down in the
exciter, or stoppage of its engine causes extinction of a very large number of lights.
To obviate this we arrange secondary cells in shunt to the exciter, or to the field
magnets of the excited dynamo.
Dated this Thirteenth day of September 1887.

page_text: COMPLETE SPECIFICATION.
Improvements in and Connected with Dynamo Electric Machines.
We 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 :-
In exciting large dynamos for central station & similar work, any irregularities in "
the engines driving the exciters produces irregularities in the main circuit. Moreover
any breakdown in the exciter, or stopping of its engine cause extinction of a very
large number of lights. To obviate these difficulties, we, either arrange cells or
accumulators in shunt to the excitor or we excite the dynamo by their means.
Separately excited machines are generally used where the station electromotive 1
force is very high or where alternating currents are used. In all cases it is desirable
to have as low electromotive force as possible on the field magnets, so that there is less
chance of ground loaks, & it is also better not to have them electrically connected with
the main circuit for the same reason.
When special exciting machines and cells are used, the machines charge the cells & 1
the cells may be used alone or in conjunction with these machines for exciting the main
field magnets.
When the main machines give high pressure direct currents we prefer to insert the
cells in the main circuit to charge them, & to disconnect them completely when they
are used to excite. This demands duplicate batteries, of course, but it is a safer
arrangement. Sometimes, however, we do not disconnect them, so that the whole
corresponds to a series machine with batteries or cells in shunt to its field
magnets.
Having now particularly described and ascertained the nature of our said
invention, and in what manner the same is to be performed, I declare that what we
claim is:
1. Exciting the field magnets of high tension dynamos wholly or partially by means
of accumulators substantially as described.
2. Exciting the field magnets of high tension direct current dynamos wholly or
partially by means of accumulators charged by the said dynamos.
Dated this Eleventh day of June 1888.
2
JAS. SWINBURNE.

page_text: Date of Application, 14th Sept., 1887
Complete Specification Left, 14th June, 1888
Complete Specification Accepted, 14th Sept, 1888
Wo ROOKES EVELYN BELL CROMPTON & JAMES SWINBURNE of Arc Works
Chelmsford, electrical engineers do hereby declare the nature of this invention to be
as follows:-
According to our invention electrical measuring instruments for measuring electro-
motive force or current may be made as follows. A hard steel needle is placed inside
a coil, as in a vertical detector. As the current increases the needle is deflected. To
increase the angle of deflection the needle is balanced so as not to stand at right
angles to the axis of the coil. By balancing the needle so as to make different angles
when there is no current we obtain a scale of any desired character; that is, we can
make an instrument that will read well throughout its whole scale. The needle should
be magnetised so as not to weaken with age. For ship use, and other purposes the
magnet needle may be controlled by a spring instead of by the action of gravity.
Dated this 12th day of September 1887.

page_text: Electrical Measuring Instruments.
We 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 :-
According to our invention electrical measuring instruments for measuring electro-
motive force or current may be made as follows. A hard steel needle is placed inside
a coil as in a vertical detector. As the current increases the needle is deflected. To
increase the angle of deflection the needle is balanced so as not to stand at right
angles to the axis of the coil when no current passes. By balancing the needle so as
to make different angles when there is no current we obtain a scale of any desired
character, that is we can make an instrument that will read well throughout its whole
scale, for instance between ten ampères and a hundred ampères or ten and a hundred
volts, or that will give wide readings through any desired part of its scale; for instance
between 95 volts and 105 volts. The needle should be magnetised so as not to
weaken with age. It may be strongly magnetised to begin with, & then shaken
about roughly and heated in boiling water & cooled. The needle should be made up
of a number of small thin wires, as if made solid the direction of its magnetisation
is apt to alter. For large currents the deflecting coil or coils are replaced by a strip
carrying the main current. The instrument may be detachable from the strip, so
that in a central station each circuit has a strip in it & the instrument can be applied
to any one of them, so that any of the currents may be read without breaking the
circuits. Another method is to make the instrument as a low reading voltmeter & put
it in shunt to a resistance in any circuits wanted, the resistances being arranged so
that the readings are direct in ampères.
Instead of gravity we sometimes use a spring to control the needle. This should
not be of steel.
Two needles may be used to make the instrument astatic, so that it is not affected
by external fields.
Instead of mounting the needle on a steel arbor with pivots it is best to use a hard
brass arbor with jewels in the ends, & to arrange fixed steel pivots, otherwise the arbor
becomes magnetised, & interferes with the action of the instrument.
DESCRIPTION OF THE DRAWINGS.
In the accompanying drawings fig. 1 shews a voltmeter seen from below. Fig. 2
shews a front elevation & fig. 3 a side elevation of the same instrument. a a are
two hard steel magnetised needles attached to the arbor c. bb are two deflecting
coils fixed to the back of the instrument g. d is a counterbalance weight, & e is the
index &f the scale. The index is shewn at zero & the counterbalance holds the
double needle at an angle to the axis of the coils, so that when the coils deflect

page_text: the needles a large reading is obtained. This instrument can be wound as a voltmeter
or ammeter. The support for the outer end of the arbor is not shewn, for the sake
of clearness. The deflecting coils may be circular as shewn, or may be rectangular
so as to give a stronger field, though that form is a little more expensive.
Figs. 4, 5, & 6 shew a spring instrument for large currents. Figs. 5 & 6 are the
front & sido elevations, & Fig. 4 is a view from below. a is the needle, b the
deflecting strip carrying the current ; c the arbor d the spring, made of non-
magnetisable material; e the index, the scale & g the back. The spring holds the
needle & index at the zero position when there is no current. The needle is then
inclined to the strip so that a large deflection can be got.
To make this into a gravity instrument, the spring is replaced by a weight as in
figs. 1, 2, & 3. Similarly the instrument shewn in figs. 1, 2 & 3 may be made to
work as a spring instrument by exchanging the counterbalance for a spring.
Having now particularly described & ascertained the nature of our said inven-
tion & in what manner the same is to be performed we declare that what we
claim is :
1. In an electrical measuring instrument in which a magnetised needle is deflected
by a strip coil or coils & controlled by the action of gravity, balancing the needle
so as to give a large, or a convenient deflection substantially as described.
2. In an electrical measuring instrument in which a magnetised needle is deflected
by a strip coil & coils & controlled by a spring or springs, arranging the needle so
as to give a large or a convenient deflection, substantially as described.
3. An electrical measuring instrument in which a magnetised needle is deflected
by a strip coil or coils & controlled by a spring arranged to read directly in volts
or amperes, substantially as described.