Improvements in or relating to Dynamo-electric Generators or Transformers.
Year: 1899

page_text: Date of Application, 10th Oct., 1899-Accepted, 10th Mar.,
1900
COMPLETE SPECIFICATION.
Improvements in or relating to Dynamo-electric Generators or
Transformers.
I, JOHN KEELER ROBISON, residing at 1216 18th Street, North West, in the
City of Washington, County of Washington, District of Columbia, United States
of America, a Lieutenant in the United States Navy, 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 primary object of my invention is to supply a unidirectional current of
electricity to a working circuit, from a generating machine or transformer devoid
of commutators (and consequently without sparking,) and, wherein, although a
low voltage may exist in the field coils, the voltage of the current induced in the
armature, may, if desired, be extremely high, without the necessity of extra-
ordinary insulation; or wherein the voltage in the field coils may be extremely
high and the voltage of the current induced in the armature may be low; so
that an alternating current of either low or high voltage may be transformed into
a unidirectional current of practically constant value, but or any desired voltage,
without the use of static convertors. A further feature of the invention is that,
in one of its forms, the same generator may be employed to produce, at will, either
an alternating current or a unidirectional current. Furthermore, by the practice
of my invention, I may organize the generator or transformer as a phase-splitter,
for the purpose of affecting the character of the unidirectional current produced,
so as to make its resultant more closely approximate a constant value.
latter organization may also be employed for the purpose of converting a unidirec-
tional current into multiphase currents adapted to supply the windings of a
multiphase motor or to supply any other appropriate translating devices suitably
connected up to the multiphase leads.
This
My invention, moreover, secures for the generator or transformer, all of the
advantages of compound winding, although in reality retaining for it the simplicity
of single winding.
In the accompanying drawings,
Figure 1 represents, diagrammatically, one embodiment of my invention.
Figure 2 represents a diagram of the circuits shown in Figure 1.
Figure 3 represents a diagram of an organization embodying the employment
of the three-phase transformer herein before referred to.
Figures 4 and 5 represent graphically the relative positions of the coils of a
stationary field and rotary armature, at the beginning of the generation of succes-
sive current undulations.
Figures and 7 represent like views of a generator wherein the field rotates
and the armature is stationary.
i
Similar letters of reference indicate similar parts throughout the several views.
The underlying principle upon which my invention is based will be understood
upon reference to what is shown in Figs. 4 to 7, wherein it is assumed that the
field poles are magnetized alternately plus and minus, by reversing the direction
of winding of the field coils, so that, with each alternation of the current, the sense

page_text: of magnetization of each field pole of the generator changes, as indicated in
Figs. 4 and 5, and in Figs. 6 and 7, respectively, wherein the alternating polarities
of the polar extensions of the field are indicated by the letters N S. It will be
noted that the coils of the armatures are each of a width substantially equal to
the width of the pole pieces and to the width of the air gaps between successive
pole pieces. If now we give to the rotary element of the generator, a speed such
that the number of its field poles multiplied by the number of revolutions per
minute is the same as the number of alternations of the alternating current
exciting its field, it will be found that a given armature conductor is always cutting
lines of force in the same direction and is consequently always generating a uni-
directional electro-motive force. The unidirectional current from the armature
can be collected (without the use of commutators) by ordinary collector rings and
brushes.
That the apparatus may be used successfully two things are essential: (1) that
the number of alternations of the alternating current exciting the field be exactly
the same as the product of the number of poles of the generator by the number
of revolutions per minute; (2) that the several parts of the apparatus be adjustable
to take into account the irregularities in the magnetization curve of the field due
to the distortion of the wave form of the energizing current and to magnetic
hysteresis, so that, for the best efficiency, each armature coil shall occupy the
midway position between adjacent field poles just as the magnetization of the
latter is changing sign, i.e., just as it is passing through its zero value.
For simplicity of illustration, I have shown in Figs. 1 and 2, the embodiment
of my invention in an organization wherein the generator A is a two pole dynamo
baving its field coils a excited by au alternating current derived from the two
pole alternating current dynamo B having an armature c, collector rings d, and
brushes e. The fields of the exciter B are preferably provided both with a series
winding and a shunt winding f, the latter having a regulable resistance C.
The current generated in the armature g is collected by the collector rings h
and brushes one of which is connected to the series winding 6 of the exciter B
and to the working conductor or out-going lead n, while the other brush is con-
nected to the second working conductor or out going lead n¹. A regulable resist-
ance D is interposed in the circuit supplying the field of the generator A, and a
branch circuit contains a secondary battery E which may be employed for starting
and which is essential to the continuous operation of the invention only in the
simplest form already described. The several circuits are provided with circuit
making and breaking switches m, r, s, as indicated.
In order that the number of alternations of the alternating current exciting the
field a shall be exactly the same as the product of the number of poles of the
generator A by the number of revolutions, the armatures of the generator A and
exciter B should either be mounted directly upon the same shaft, in which case
the exciter should have the same number of poles as the generator, or, indirectly,
by gearing the shaft of the exciter to the shaft of the generator. In Fig. 3, I
have illustrated a construction wherein the armature of the exciter B is carried
by a sleeve F mounted upon the shaft G of the generator adapted to be set in
any desired position of radial adjustment thereon by means of a set screw t or
the like. It will be apparent without further illustration that this expedient
may be employed for suitably mounting the armatures of the generator and
exciter of Fig. 1, upon the same shaft, and with a like capacity for relative
radial adjustment. This capacity for adjustment, obtained by setting the arma-
ture of the exciter in such relative position to the armature of the generator
that each armature coil of the latter shall occupy the midway position between
adjacent field poles just as the magnetization of the field poles is changing sign,
affords a convenient means for obtaining high efficiency in the apparatus.
The operation of the invention typically illustrated in Figs. 1 and 2 will be
readily understood. If it is desired to operate the generator A for the production
of an alternating current, the alternating current circuit leading from the exciter

page_text: may be broken at m and the secondary battery circuit may be established at r,
thereby energizing the field coils of the generator A with direct current and pro-
ducing in its armature an alternating current taken off as such by the collector
rings and brushes. For the production of a unidirectional current, it will. be
necessary to break the secondary battery circuit at r and complete the exciter circuit
at m, whereupon in accordance with the explanation hereinbefore given, a uni-
directional current i.e. a rectified alternating current, will be received in the out-
going leads n, n'. Another way of employing the apparatus for the production of
an alternating current in the out-going leads would be to so adjust the stationary
elements of the two machines radially with respect to each other (e.g. through
half the angle between the poles) that the point of maximum excitation of the
field poles shall occur just at the moment when the field poles and armature poles
pass each other during the rotation, thereby producing a single phase alternating
current. The secondary battery (which need not be of large dimensions) may
be charged from a shunt taken from the working circuit, and it will be understood
that the field of the exciter is to be energized by any suitable source of direct
current, preferably a secondary battery or accumulator.
It is evident that by means of my invention, it is possible to mount upon the
same engine shaft two generators of the same type, one of them generating an
alternating current and the other generating a unidirectional current, the field of
each being fed by current from the other and the two generators thus supplying
It is also
respectively alternating and unidirectional current for separate use.
evident that in view of the low voltage possible in the field of the generator, the
required insulation is proportionately moderate. This fact, together with the
high voltage possible in the armature of the generator, the absence of sparking,
the elimination of commutators, and the capacity of the apparatus to serve as a
generator of either alternating or unidirectional current give to the organization
advantages in cheapness of construction, durability, and general utility for various
emergencies, that are fully apparent.
Instead of mechanically connecting the armature shaft of the generator and
exciter, it will be understood that I may, in some instances, actuate the armature
shaft of the generator from a synchronous motor supplied from the exciter.
In the organization shown in Fig. 3, the generator plays the part of a phase.
splitter or rotary transformer, and consists of three dynamo machines A', A2, A3,
all of whose armatures are mounted upon the same shaft G, carrying the pairs of
collector rings h¹, h2, h3, and brushes, 2, 3, connected in series with the external
working conductors n, n', and with the series field, winding. 6 of the exciter B:
The armatures of the several machines A1, A2, A3, are set at angles equal to the
In this
angle between the phases of the fields of the machines respectively.
connection it is advisable, in order to allow for differencd in the windings and
in their magnetizing effects, to give to the armatures a capacity for relative radial
adjustment, in order to secure the maximum effect, and to balance the system.
To this end, the armatures may conveniently be mounted upon sleeves F, adapted
to be rotated to the desired positions of adjustment and to be fixed in such adjust-
ment by set screws t, or the like. The exciter, as before, is preferably provided
with a shunt winding f', and its armature is also mounted upon an adjustment
sleeve F. The fields a¹, a, a, are interconnected to three-phase leads r, supplied
from collector rings 2, 3, and brushes e¹, e², e³.
The effect of this arrangement is to cause an overlapping of the undulations
of the current supplied from each of the armatures of the dynamos A1, A2, A³,
to the external circuit, with the effect of causing the resultant current to very
closely approximate a constant value. The system shown in Fig. 3 is reversible
in the sense that upon supplying a unidirectional current to the dynamos, from
the line wires n, n, three-phase currents will be produced in the leads which
may be used for operating three-phase motors, or other translating devices, as
will be understood. The organization therefore, constitutes a generator or trans-
v,

page_text: former for converting multiphase currents into unidirectional currents, and vice
versa, without the employment of commutators. It is evident, moreover, that, in
this instance the windings of the armatures, of the dynamo machines A1, A2, A3,
may be connected up directly in series, in which event it would be necessary to
employ but one set of collector rings and brushes to take off the rectified current.
Having now particularly 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. A source of unidirectional currents, comprising a dynamo electric generator,
having its field coils wound to produce alternating polarities in successive field
poles, in combination with a source of alternate current supply for said field coils,
and collector rings and brushes for taking off the unidirectional current produced;
substantially as described.
2. A source of unidirectional currents, comprising a dynamo electric generator
having its field coils wound to produce alternating polarities in successive field
poles, in combination with a source of alternating current supply for said field coils,
consisting of an exciting machine, and means for establishing synchronism
between the generator and exciter; substantially as described.
3. A source of unidirectional currents, comprising a dynamo electric generator,
having its field coils wound to produce alternating polarities in successive field
poles, in combination with an exciting machine supplying alternate current to
said field coils, the ratio of the revolutions of the two machines being the same
as the ratio of the number of their poles; substantially as described.
4. A source of unidirectional currents, comprising a dynamo electric generator,
having its field coils wound to produce alternating polarities in successive field
poles, in combination with a source of alternate current supply for said field coils,
the width of the armature coils of the generator being substantially equal to the
width of the pole pieces and also to the width of the intervening air gaps; sub-
stantially as described.
...
5. A source of unidirectional currents, comprising a dynamo electric generator,
having its field coils wound to produce alternating polarities in successive field
poles, in combination with an exciting machine whose rotor is adapted to revolve
in unison with the rotor of the generator, and means for adjusting the two radially
relatively to each other; substantially as described.
6. A dynamo electric generator, having its field coils wound to produce alter-
nating polarities in successive field poles, in combination with a source of
alternate current supply, for said field coils, and a source of direct current
supply for said field coils, collector rings and brushes, and switches for
throwing in or cutting out either the source of alternate current supply or the
source of direct current supply; substantially as described.
7. A generator made up of a plurality of dynamo electric machines, having
their fields interconnected by multiphase leads, an exciter for said fields, and
working conductors in series with the field of the exciter and with the armatures
of the generator; substantially as described.
S. A rotary transformer for converting alternating currents into unidirectional
currents or vice versa, comprising stator and rotor coils, in inductive relationship
to each other, one set of said coils being in series with altérnate current leads
and the other set being in series with unidirectional current leads; substantially
as described.
9. A rotary transformer for converting multiphase alternating currents into
unidirectional currents or vice versa provided with sets of stator and rotor coils,
one set being interconnected by multiphase current leads, and the other set being
in inductive relationship to the first set and in series with each other and with
unidirectional current leads; substantially as described.
10. A rotary transformer for converting three phase alternating currents into
unidirectional currents or vice versa provided with sets of stator and rotor coils,

page_text: one set being interconnected by three phase current leads, and the other set being
in inductive relationship to the first set and in series with each other and with
unidirectional current leads; substantially as described.
Dated this 10th day of October 1899.
HASELTINE. LAKE & Co.,
45, Southampton Buildings, London, W.C.,
Agents for the Applicant,