appar for studying dynamoal machines
Year: 1887

page_text: Date of Application, 28th Apr., 1887
Complete Left, 28th Jan., 1888
Complete Accepted, 6th Apr., 1888
1, JAMES SWINBURNE, of Shona, Chelmsford, in the county of Essex, Electrical
Engineer do hereby declare the nature of this invention to be as follows:-
My invention relates to induction apparatus for studying dynamo electrical
machines.
The object of my invention is to lessen the expense at present consequent on
developing a new type of dynamo or motor, and to adinit of the inore easy exainination
of many of the phenomena.
When it is wanted to design a new type of dynamo it is almost impossible to
determine by calculation alone what a machine made according to a given design will
do, and whether the iron and copper, and disposition of the machine are as good as
desired.
According to my invention a sort of model is made to scale. This consists of field
magnets made to scale, wound with a known number of turns of wire; and of a scale
model of the iron of the armature. The armature is also wound with wire but it is
unnecessary to have an ordinary commutator, as two terminals are arranged to lead
the circuit in and out of the armature.
The armature is not necessarily rotated, but is held in position in the field so that it
can be moved round into an angular position representing any desired lead of the
brushes.
The induction through the armature corresponding to any magnetising force due to
any current round the field is measured by means of a suitable induction balance,
such as that described by me to the Physical Society this winter. The induction
through any section of the armature is taken by a pilot wire wound round that part.
Similarly the induction through any part of the magnetic circuit can be measured.
By passing current through the armature the conditions corresponding to the

page_text: dynamo's giving current can be investigated, & the cross magnetisation and lead of
brushes can be determined.
A pilot coil is put round the armature at a point corresponding to the position of
the brushes in the dynámo, and the induction is then found for that, section, and for
one or two neighbouring sections, so that the lead of the brushes can be determined.
By my method and apparatus the whole of the data required, apart from the
question of ventilation, can be determined from a model costing a few shillings; and
the shape and disposition of the iron can, in many cases, bo altered by a few strokes
of the file.

page_text: Use of it in Studying Dynamo Electric Machines.
I, JAMES SWINBURNE, of Shona, Chelmsford, in the county of Essex, 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 induction apparatus for studying dynamo electrical
machines.
The object of my invention is to lessen the expense at present consequent on
developing a new type of dynamo or motor, and to admit of the more easy examination
of many of the phenomena.
When it is wanted to design a new type of dynamo it is almost impossible to
determine by calculation alone what a machine made according to a given design will
do, and whether the iron & copper, and disposition of the machine are as good as
desired.
For instance the waste field in the case of a dynamo whose poles are almost
surrounded by an iron bedplate, can only be very roughly determined by calculation.
Again the determination of the waste field is in many cases so much a matter of guess
work, that it is better to resort to more accurate methods.
According to my invention a sort of model is made to scale. This consists of field
magnets made to scale, wound with a known number of turns of wire; and of a scale
model of the iron of the armature. The armature is also wound with wire, but it is
unnecessary to have an ordinary commutator, two terminals being all that is needed.
They represent the brushes.
The armature is not rotated, so as give an electromotive force, but is held in
position in the field so that it can be moved round into any angular position representing
any desired lead of the brushes.
The induction through any part of the model is then measured by means of a pilot
wire and a suitable ballistic galvanometer or such an induction balance as that
described by me to the Physical Society last winter. The galvanometer or balance is
calibrated by means of a pair of coils whose coefficient of mutual induction is
calculated or otherwise known. A long evenly wound solenoid with a pilot coil
outside it is an easy case to calculate.
To find the no load curve of the machine gradually increasing currents are passed
round the fields & the arinature induction noted by observing the galvanometer on
reversal of the exciting current. To take full load readings the armature wire also
has its current. Both armature and field circuits are reversed. The induction is
then measured by means of a pilot wire, the armature circuit proper being no longer
convenient for the purpose.

page_text: The distribution of the induction in the air space at different loads is measured by
means of a pilot wire circuit.
The change of induction through a section of armature conductor corresponding to
one pair of commutator sections is taken by reversing the current in a model section
without reversing the armature & field currents propor. This will vary with different
positions of the section. From the data so obtained and the air space induction
distribution the non sparking position for any breadth of collector at any load can be
found.
In the case of alternating current machines the no load curve is not obtained
directly from the total induction through the armature circuit; but as the electro-
motive force at any instant depends on the rate of change of the total induction the
curve is readily found. To get full data a pilot wire is used & the induction is
determined at each armature position for a number of armature current values.
It is not generally necessary to make a model of more than two poles of an
alternating machine, with the corresponding part of the armature.
The models are apt to get very hot when made to a small scale, so the currents
& connections are manipulated by a switch, so that the heating lasts a very short
timo.
By my method & apparatus the whole of the data required, apart from the question
of ventilation, can be determined from a model costing a few shillings; and the
shape & disposition of the iron can, in many cases, be altered by a few strokes of
the file.
Having now fully described and ascertained the nature of my said invention and
in what manner the same is to be performed I declare that what I claim is
1. Induction apparatus for studying dynamo machines consisting of a scale model
and apparatus for measuring the induction in parts of it.
2. Dynamo electric machines or motors constructed from data obtained from a scale
model substantially in the manner described.
Dated this 26th day of January 1888.