Improvements relating to Dynamo-electric Generators and Motors.
Year: 1888

page_text: COMPLETE SPECIFICATION.
Improvements relating to Dynamo-electric Generators and Motors.
I, JAMES FEAVERYEAR of No. 20 High Holborn, London W.C. 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 :-
The object of my invention is to arrange the magnetic field of what is generally
known as a continuous current dynamo-electric generator in such a manner as to
allow of a constant electro-motive force being maintained at the terminals, irrespective
of any variation of the resistance of the external circuit; or, if required, the same
generator or electric motor may have its field magnets placed in series with the
external circuit, in which case any variation of the external resistance would cause a
corresponding variation of the electro-motive force at the terminals when the apparatus
is used as a generator; in other words, I am able, according to my invention, to
construct a dynamo-electric generator that may be readily converted into a "series,"
a "shunt" or a combination of both at will, or an electric motor that may be converted
into a "series " or "shunt" at will.
In order that my invention may be the better understood I have appended the
accompanying sheet of drawings in which Figure 1 represents a front elevation of a
dynamo-electric generator or motor showing a pair of vertical field magnet coils
mounted upon a swivel stage; Figure 2 is a plan of the same. Figure 3 shows a
front elevation and Figure 4 a plan, of an alternative arrangement suitable for
generators or motors designed for a larger electrical output or absorption of electrical
power. Figure 5 is a front elevation of a double field, in which the conversion is
effected by means of a horizontal pivot. Figure 6 is a diagram illustrating the
method of altering or converting the field magnets electrically as an alternative
arrangement to the mechanical conversion illustrated in the foregoing Figures.
Figure 7 represents a switch for varying the electrical connections according to the
arrangements above referred to.
Figures 8 and 9 represent elevational views of two compact forms of the apparatus
where the conversion is carried out electrically.
In carrying out my invention I employ two pole pieces A A' of cast iron or other
suitable magnetic material which aro rigidly fixed with respect to the bore of the field
surface B by means of plates a a¹ of brass or other non-magnetic material. Two
extensions CC formed upon, or attached to the pole pieces are arranged to carry a
vertical field magnet, preferably a cylindrical coil or bobbin. Two such coils or
bobbins D D having suitable tubular cores are mounted upon a transverse yoke /

page_text: "
"
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pivoted at c to the extension c¹ of the lower pole piece A¹ which forms the bed of the
machine. A bolt or set screw d passes freely through a hole formed in the extension
of the upper pole piece, and may be screwed into the lower pole piece. The bolt or
set-screw d therefore forms the actual central magnetic core of the particular coil
or bobbin that may be required to generate the magnetic strength of the field while
the dynamo electric generator or motor is in action. I prefer to wind one of the
coils or bobbins with thick wire, so as to be included in the external electrical circuit
when said coil or bobbin is in action, and the other coil or bobbin I prefer to wind with
a smaller wire possessing, say from 250 to 300 times greater electrical resistance than
that of the external circuit; therefore, according to my invention I am enabled to
readily convert the generator or motor into a shunt
ог series" machine according
to the requirements of the work to be done in the external circuit by simply unscrewing
and removing the bolt or set screw d and turning the pivoted yoke bar 6 upon its
pivot c until either of the coils or bobbins are opposite the corresponding holes for
the bolt or set screw d aforesaid, which may then be inserted and screwed up, so that
perfect magnetic contact may be ensured. As an alternative method to the foregoing
may arrange the yoke b carrying the two coils or bobbins D D' upon a suitable
sliding yoke instead of a pivoted yoke as above described in which case the bolt or
set screw d would be used in a similar manner, either of the coils-whether "shunt"
or series" being moved by means of the sliding yoke into the required position of
magnetic contact, which may then be secured by the insertion and tightning of the
bolt or set screw d¹ Figures 1 and 2.
"
A further modification of the foregoing arrangement is shown at Figure 5 in which
the double field magnet is wound on one side S₁ to suit the requirements of a
"shunt" field, and upon the other S a "series" field. Said field magnets are pivoted
* or suspended at a point g coincident with the centre of the axis of the armature, so
that only two limbs of the double field magnet may be used at one time, either
"shunt 66
or series"
as may be required a bolt or set screw d being employed to
ensure perfect magnetic contact as in the arrangement previously described.
I may however dispense with the mechanical conversion exemplified by the two
preceding descriptions, and substitute therefor duplicate and immobile pairs of field
magnets, as shown in elevation and plan respectively in Figures 3 and 4 and also in
Figures 8 and 9 one of which pairs is wound in "shunt" and the other pair in
" series
a switch m in this case being employed to vary the circuit. The switch
above referred to, is represented more particularly at Figure 7, the electrical connec-
tions of which are shown in the diagram Figure 6 in which the movement of the
switch lever h to the slip i brings the "series field magnet D into the electrical
circuit, through the main terminal f', which latter is attached to the arm or lever h of
the switch aforesaid. The corresponding terminal of the "shunt" wound magnet Di
is permanently attached to one of the brushes ; and the other end of the "shunt"
coil D is attached to the small slip k beside the slip i and the "series" and "shunt"
coil may both be in action at the same time by allowing the arm or lever / to cover
and bear upon the slips i, k and putting them both into electrical contact with the
terminal. This arrangement allows of what may be termed a "shunt-series" field
magnet, and, as the intensity of the field is kept constant irrespective of any variation
of the external resistance, it is evident that the electro-motive force at the terminals
will also be constant with a constant speed, and the lighting of lamps, or other work
done that is arranged in "parallel" or
" multiple arc may be cut out or placed in
the circuit one by one without the slightest variation of the potential.
In order to convert the machine into a simple "shunt" I connect the two slips n, n',
which are respectively connected to the brush j¹ and to the opposite terminal of the
shunt coil D. I may perform this connection by means of a peg 4, or a separate and
insulated branch of the switch lever h, or by any other equivalent method. The
switch lever h must also be moved so as to connect the slip o to the brush j¹ and the
terminal f¹.
In order to counteract any diminution of the magnetic intensity of the field due
to the inert or non-magnetic cores of the portion of the field that may be cut out of

page_text: the electrical circuit; since the poles of the field magnet would be (in the case of a
machine arranged upon the lines illustrated at Figures 3, 4, 8 and 9) connected or
magnetically short circuited," I provide a suitable coil O of high resistance between
the slips of the compound switch, so that the limbs of the field magnet that are cut
out, may still be sufficiently polarized as to prevent said inert mass from neutralizing
the magnetic field, the fraction of current utilised for this purpose being negligible
relatively to the output of the dynamo electric generator.
Having now particularly described and ascertained the nature of my said Inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is :-
First: In a dynamo electric generator or motor the arrangement of the field
magnets whereby the functions of the machine may be varied, either by mechanical
means or by the variation of the electrical circuits appertaining to the field magnets
by the employment of a compound switch, so that the dynamo electric generator or
""series
be converted into "shunt,"
"shunt and series " according to
may
the requirements of the external electrical circuit or mechanical power developed
substantially as herein described and shown.
motor
"
ог
Second In a dynamio electric generator or motor, the arrangement of "shunt"
and "series" coils upon a pivoted yoke, to allow of the ready adaptation of either
for producing the requisite intensity of the magnetic field, and the electrical
connections appertaining, and ancillary thereto, substantially as herein described and
shown.
Third In a dynamo electric generator or motor the employment of a double
field magnet moving upon a pivot and coincident with the axial line of the armature,
so as to engage each pair of field magnets with either yoke according to the require-
ments of a
"
"shunt" ог series" magnetic field relatively to the external circuit, or
mechanical power developed, substantially as herein set forth.
Fourth In a dynamo electric generator the method of and means employed for
establishing a constant electro-motive force at the terminals without reference to the
resistance of the external circuit, the variation of the latter having no influence upon
said electromotive force with a constant rate of speed of the armature, and the method
adopted for altering the field magnet circuit electrically, to fulfil the conditions of a
66 shunt,"
""series" or "shunt and series" machine at will substantially as herein set
forth.
66
Fifth In a dynamo electric generator or motor the employment of a compound
switch for varying the field magnets so as to convert the machine into a shunt,"
" series " or combined "shunt and series" machine as and for the purposes herein-
before described, and the high resistance coils interposed between the slips of said
switch for polarizing the limb of the magnet that is cut out of action with the
absorption of a negligible amount of the whole current substantially as herein set
forth and shown.
Sixth In a dynamo electric generator or motor the utilisation of "shunt" wound
and "series" wound limbs of a duplex or quadruplex field magnet, with a common
polar surface, said limbs being arranged to act magnetically upon the polar surface
either singly or together to fulfil the requirements of a "shunt "series" or combined
"shunt and series" machine substantially as and for the purposes herein decribed and
set forth.
00.
JAMES STEVENSON,
Gray's Inn Chambers,
20, High Holborn, London, W.C.,
Agent for Applicant.