Improvements in Electric-generating Machinery for use in connection with the Electric Lighting of Railway Trains.
Year: 1889

page_text: Date of Application, 17th Dec.. 1889
Complete Specification Left, 10th Sept., 1890-Accepted, 13th Dec., 1890
PROVISIONAL SPECIFICATION.
Improvements in Electric-generating Machinery for use in connection
with the Electric Lighting of Railway Trains.
I, JOHN HENRY HOLMES of Portland Road, Newcastle-on-Tyne in the County of
Northumberland, Electrical Engineer, do hereby declare the nature of this invention
to be as follows:-
This invention relates to improvements in electric generating machinery for use
in connection with the electric lighting of railway trains, and has for its object to
construct an apparatus which will maintain a constant difference of potential at the
terminals of the dynamo electric generator under a considerable variation in speed,
and when driven in either direction.
Practically speaking, the E. M. F. of an ordinary separately excited dynamo varies
directly as the speed at which the armature revolves, so therefore if the speed be
increased say from 500 revolutions per minute to 1000 revolutions per minute
the E. M. F. will be doubled.
The E. M. F. however also varies directly as the strength of the inagnetic field, so
that if the strength of field of the separately excited dynamo be reduced in the same
proportion as the speed at which its armature revolves be increased then the E. M. F.
of the armature will remain practically constant.
To this end according to my invention I construct a dynamo electric machine with
two armatures arranged to revolve together but in separate magnetic fields. The one
is the main generating armature, the other being for regulating the strength of the
magnetic field of the generating armature.
I separately excite the magnets of the machine from some external source such as a
set of accumulators and provide the magnets of the generating armature with two
distinct exciting circuits.
One circuit is a high resistance shunt circuit, and the other is of less resistance and
is coupled up to the source of current so as to have the small regulating arinature in
series with it. The regulating armature is so coupled up that its own E. M. F.
the E. M. F. of the source of supply.
opposes
The high resistance shunt circuit is preferably so proportioned that, at the highest
speed at which the generating armature is intended to be run, it, without the aid of
the second exciting circuit, will give a magnetic field of an intensity proper for the
required E. M. F. in the generating armature.
When thus arranged the second exciting circuit ought to have no current passing
through it a result which is brought about by the E. M. F. of the regulating armature
being at the highest speed equal and opposite to the external source of E. M. F. by
means of which the exciting of the magnets is accomplished.
If however the speed falls the E. M. F. of the regulating armature is lessened in
the same proportion,and being no longer equal to the external E. M. F. a current will
be permitted to flow through the second exciting circuit of the magnets of the
generating armature thus increasing the intensity of the magnetic field to make up
for reduction of speed with the result of maintaining a practically uniform E. M. F.
in the generating armature.
When the speed falls to the lowest limit which I will assume to be half the highest
rate of speed, then the E. M. F. of the regulating armature in the case I am
considering, will be half the E. M. F. of the external source of supply so that it will
be seen that it is necessary to calculate the proportions of the second exciting circuit
of the generating armature magnets upon the basis of only half the electric pressure
of the external source of E. M. F. being available, and the resistance of the regulating
armature forming part of the circuit resistance. At the lowest speed, therefore half

page_text: the exciting power upon the generating armatare magnets will be produced by one
coil having the full difference of potential of the external source of E. M. F. at its
terminals and by a second coil having half the difference of potential of the
external source of E. M. F. at its terminals less of course by the drop of potential
due to the resistance of the regulating armature which forms a portion of this
circuit.
In speaking of the proportioning of the parts I assume that the magnets of the
generating arinature are used with a low magnetic density well below the saturation
point for the iron of which they are composed.
I prefer to use them thus but by careful allowances a sufficiently near result might
be obtained with the iron in a condition more nearly saturated when the full exciting
When I use an electric machine of the nature described for
power is on.
generating electric currents for the lighting of railway trains in conjunction with the
storage batteries I use the latter for the external source of E. M. F. by which I
excite the magnets and drive the armature by means of gearing which tfansmits the
power from the axle of the van or vehicle in which the machinery is placed..
I also arrange a centrifugal governor driven from the same source which is made to
switch on the current from the storage batteries to the magnet coils as soon as the
speed rizes to about the minimum-speed at which the electric generating apparatus is
intended to come into action and which also switches off the current when the speed
falls below the minimum speed.
For switching the armature of the generating machine on to the lamp or charging
an automatic switch of a kind which is well known and
circuit, I prefer to use
frequently used in conjunction with a dynamo and accumulators, and which couples
up the circuit as soon as the E. M. F. rises to the proper amount, and which breaks
the circuit again when the E. M. F. falls below the proper amount. It is however
evident that a centrifugal governor could be inade to do this duty.
As it is desirable that when the railway train ruos backward way the dynaino would
still be able to do its work properly 1 prefer to make the brushes which collect current
from the two armatures of copper wire gauze, and placed in positions radial to the
commutators, being held in brush holders attached to flat springs lying parallel
to a tangent drawn to the surface of the commutator at the points at which the
brushes bear.
I also reverse the "lead" of the brushes of the generating armature when the
direction of rotation changes by means of inechanism of the following description.
The brush holders are carried by arms which in the usual manner can be rotated.
together around the axis of the armature, the motion in either direction being limited
by stops.
The motion is transmitted from the axle of the machine through gearing coupled to
the axle, and by means of a friction clutch which slips round as soon as the brush
carrying arms are hard up against their stops.
To prevent any wear of the friction clutch faces excepting when the speed of the
axle is very slow, I arrange on the axle centrifugal governor, the balls of which at a
slow rate of revolution fly out and separate the faces of the friction clutch, so
that they do not touch, excepting at speeds below this slow rate of revolution.
When the direction of rotation of the armatures is changed, the polarity of the
brushes is also changed. I therefore utilise the notion which reverses the "lead" to
work reversing switches of a kind well understood so as to alter the connections and
keep the polarity at the terminals of the machines the same.
I do not find it necessary to make provision for reversing the "lead" of the brushes
of the regulating armature, because the current running through this armature is
usually small and at maximum speed is in fact wil. I therefore place these brushes in
fixed positions at the "neutral" points.
TAJALI. Nicinanth day of December 1889.

page_text: GUALE LE SPECIFICATION.
Improvements in Electric-generating Machinery for use in connection
with the Electric Lighting of Railway Trains.
I, JOHN HENRY HOLMES, of Portland Road, Newcastle on Tyne, in the, County of
Northumberland, Electrical Engineer, do hereby declare the nature of this invention
and in what manner the same is to be perforined to be particularly described and
ascertained in and by the following statement :-
This invention relates to improvements in electric generating machinery for use in
connection with the electric lighting of railway trains, and has for its object to
construct an apparatus which will maintain a constant difference of potential at the
terminals of the dynamo electric generator under a considerable variation in speed
and when driven in either direction.
Practically speaking, the E. M. F. of an ordinary separately excited dynamo varies
directly as the speed at which the armature revolves, so therefore if the speed be
increased say from 500 revolutions per minute to 1000 revolutions per minute the
electro motive force will be doubled.
The electro motive force however varies, also, directly as the strength of the
magnetic field, so that if the strength of field of the separately excited dynamo be
reduced in the same proportion as the speed at which its armature revolves is
increased then the electro motive force of the armature will remain practically
constant.
To this end, according to my invention, I construct a dynamo electric machine with
two armatures arranged to revolve together but in separate magnetic fields. The one
is the main generating armature, the other being for regulating the strength of the
nagnetic field of the generating armature.
I separately excite the magnets of the machine from some external source such as a
set of accumulators, and provide the magnets of the generating armature with two
distinct exciting circuits.
One circuit is a high-resistance shunt circuit, and the other is of less resistance, and
is coupled up to the source of current, so as to have the small regulating arinature in
series with it.
The regulating armature is so coupled up that its own electro motive force opposes
the E. M. F. of the source of supply.
The high resistance shunt circuit is preferably so proportioned that, at the highest
speed at which the generating armature is intended to be run, it, without the aid of
the second exciting circuit, will give a magnetic field of an intensity proper for the
required E. M. F. in the generating armature.
When thus arranged the second exciting circuit ought to have no current passing
through it, a result which is brought about by the E. M. F. of the regulating armature
being at the highest speed equal and opposite to the external source of E. M. F. by
means of which the exciting of the inaguets is accomplished.
If however the speed falls, the E. M. F. of the regulating armature is lessened in
the samne proportion, and being no longer equal to the external E. M. F., a current
will be permitted to flow through the second exciting circuit of the magnets of the
generating armature, thus increasing the intensity of the magnetic field to make up
for reduction of speed, with the result of maintaining a practically uniform E. M. F.
in the generating armature.
When the speed falls to the lowest limit, which I will assume to be half the highest
rate of speed, then the E. M. F. of the regulating armature in the case I am
considering, will be half the E. M. F. of the external source of supply so that it will
be seen that it is necessary to calculate the proportions of the second exciting circuit
of the generating armature magnets upon the basis of only half the electric pressure
of the external source of E. M. F. being available, and the resistance of the regulating
armature formning part of the circuit resistance. At the lowest speed therefore half
the exciting power upon the generating armature magnets will be produced by one

page_text: coil having the full difference of potential of the external source of E. M. F. at its
terminals and the other half by a second coil having half the difference of potential of
the external source of E. M. F. at its terminals less of course by the drop of potential
due to the resistance of the regulating armature which forms a portion of this
circuit.
In speaking of the proportioning of the parts I assume that the magnets of the
generating armature are used with a low magnetic density, well below the saturation
point for the iron of which they are composed. I prefer to use them thus, but by
careful allowances a sufficiently near result might be obtained with the iron in a
condition more nearly saturated when the full exciting power is on.
When I use an electric machine of the nature described for generating electric
currents for the lighting of railway trains in conjunction with the storage batteries,
use the latter for the external source of E M. F. by which I excite the magnets and
drive the armature by means of gearing which transmits the power from the axle of
the van or vehicle in which the machinery is placed.
I also arrange a centrifugal governor driven from the van axle which is made to
switch on the circuit from the storage batteries to the magnet coils as soon as the
speed rises to about the minimum speed at which the electric generating apparatus is
intended to come into action and which also switches off the current when the speed
falls below the minimum speed.
For switching the armature of the generating machine on to the lamp or charging
circuit I prefer to use an automatic switch of a kind which is well known and
frequently used in conjunction with a dynamo and accumulators and which couples
up the circuit as soon as the E. M. F. rises to the proper amount and which breaks
It is however
the circuit again when the E. M. F. falls below the proper amount
evident that a centrifugal governor could be made to do this duty.
As it is desirable that when the railway train runs backward way, the dynamo
would still be able to do its work properly. I prefer to make the brushes which
collect current from the two armatures of copper wire gauze and placed in positions
radial to the commutators being held in brush holders attached to flat springs lying
parallel to a tangent drawn to the surface of the commutator at the points at which the
brushes nake contact with it.
I also reverse the lead of the brushes of the generating armature when the
direction of rotation changes by means of mechanism of the following description.
The brush holders are carried by arins which in the usual manner can be rotated
together around the axis of the armature, the motion in either direction being limited
by stops.
The motion is transmitted from the axle of the machine through gearing coupled
to the axle, and by means of a friction clutch, which slips round as soon as the brush
carrying arms are hard up against their stops.
To prevent any wear of the friction clutch faces occurring except when the speed
of the axle is very low, I arrange on the axle a centrifugal governor the bolts of
which at a slow rate of revolution, fly out and separate the faces of the friction
clutch so that they do not touch excepting at speeds below this slow rate of
revolution.
When the direction of rotation of the armatures is changed, the polarity of the
brushes is also changed. I therefore utilise the motion which reverses the "lead" to
work reversing switches of a kind well understood so as to alter the connections and
keep the polarity at the terminals of the machine the same.
I do not find it necessary to make provision for reversing the lead of the brushe
of the regulating armature because the current running through this armature i
usually small, and at maximum speed is in fact nil. I therefore place these brushe
in fixed positions at the neutral points.
In order that my invention may be thoroughly understood I will now proceed t
describe an apparatus constructed in accordance therewith, for which purpose I wil
refer to te accompanying drawings, in which Fig. 1 shews a side elevation of the
çɔ n'ined generating and regulating dynaino machines, l'ig. 2 a'cross section o
5

page_text: line T P, Kig. 3 a plan, Fig. 4 a view of the brush reversing gear to an enlarged
scale, and Fig. 5 a diagram plan of the circuits and connections.
...
The generating dynamo. Q has its field magnets L excited firstly by an ordinary
high resistance shunt circuit a and secondly by a circuit 6 of less resistance, coupled,
up to the accumulator C which is charged by the dynamo and having the armature
of the regulating dynamo R in series. with it, the regulating dynamo being so coupled
up that its own electro motive. force opposes the E. M. F. of the accumulator. The
armature of the generating dynamo, and that of the regulating dynamo are both
fixed on the same shaft c driven by pullies d from an axle of the vehicle. This shaft
carries the commutator A of the generating dynamo, and the commutator B of the
regulating dynamo. The brushes. D.of the cominutator A are mounted in spring
holders D¹ carried by bars F¹ projecting from shiftable arms FF.mounted loose.on.
the armature shaft c, so that according as these arms are brought from one inclined
position, such as that shewn at Fig. 4 to an opposite one, the brushes which are held
in a radial position on the com'nutator have the requisite lead imparted to them on the
one or the other side of the vertical centre line, according as the armature shaft is
rotating in the one direction or the other.
-1
The arms FF are connected together by pins F and these pins are made to enter
between the one or other pair of contact jaws S S or S' S¹ connected respectively to
the screw terminals T T for the circuit wires, so that as the polarity of the brushes
are reversed on the reversal of the motion of the armature shaft, their connection
with the circuit is at the same time reversed by the movement of the arms F. The
jaws S S¹ on the right hand side are coupled respectively with the jaws S S¹ on the
left hand side by means of copper bars S² S².
The reversal of the position of the armsand brushes on the reversal of the motion of the
shaft is effected as follows: Loose upon the shaft is a friction disc N to which is fixed a
pinion N gearing with a toothed sector F3 fixed on a spindle passing through the
standard, carrying the. rocking arms; F, which spindle has fixed on its other end
pinion gearing. with a toothed sector F5 on the boss of the arms F.
a
A second friction disc N³ is carried round by the shaft but can slide longitudinally
upon it: this disc has a neck into which take the ends of the arms of the governor M
fixed on the shaft the weights of which are drawn together by springs 0, so as, when
at rest/or moving very slowly, to cause the arms to press the disc N against the
disc N with a certain amount of frictional contact.
From this arrangement it will be seen that if, after having revolved in one direction
the armature shaft is made to revolve in the contrary direction by the reversal of the
notion of the carriage, the disc N³ will carry. round with it the disc N and in thus
turning the pinion N¹, sector. F's and pinion F, will cause the arms F to be brought
into. the opposite inclined position thereby reversing the position of the brushes and
contacts as above described.
As soon as the arms F have passed as far as they can into the jaws S or S¹ so as to
be arrested in that position, the disc N³ will slip upon the disc Nuntil the speed of
the shaft c has increased sufficiently to cause the governor M to draw the disc N
backward out of contact with the disc N, in which position it will continue as long as
the machine is running.
The disc N³ has a groove which is embraced by the fork of an arm N', which when
the disc is slid backwards, to a certain extent by the governor, will act upon the
pivotted arms H of two contacts that couple up the exciting circuits of both dynainos
with the accumulators, the resistance of the governor springs .0 being so arranged
that these contacts are not inade until the armature shaft has attained a certain
speed slightly under the minimum speed at which the dynamo is intended to generate
current.
=
The spindle carrying the sector Fs and pinion F also carries loose upon it an arm G.
which acts upon a switch G so as to reverse the connection of the armature B with
the coils b'of the field magnets 1. at the same time that the polarity of the brushes D
is reversed on the reversal of the motion of the train, the motion of the arm G being
effected by pins G* on the pinion F..

page_text: As before stated, the brushes E of the regulating dynamo are held stationary on
the commutator B.
"
As before explained I prefer to arrange the shunt circuit a of the field.magnets I.
so that when the generating arinature is running at its highest speed the circuit will
unaided, give a magnetic field of the intensity proper for the required E. M. F. in the
generating armature so that at such speed the E. M. F. of the accumulators may be.
entirely balanced by the opposing E. M. F. of the regulating armature, when running
at the same maximum speed. On a reduction of the speed, the resulting reduction
of E: M. F. in the armature A will be entirely compensated for by an increase of
magnetic intensity produced by the circuit b, as the opposing E. M. F. of the
regulating armature will now be decreased to such an extent as to allow a sufficient
current from the accumulators to pass through the circuit to effect such increase of
intensity. The switch K for coupling up the generating armature to the accumulator,
or lamp circuit when a sufficiently high E. M. F. is obtained may be of any known
construction and need not be further described, as it forms no part of this invention..
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, 1 declare that what I
claim is :-
1. In electric generating machinery for use in railway trains and subject to variation
of speed the method of practically maintaining constant the E. M. F. of the generating
dynamo by providing its field magnets with two distinct exciting circuits, one of which
is an ordinary shunt circuit, while the other is connected to an independent source of
current and has also in series with it the armature circuit of a regulating dynamo
driven at the same speed or subject to the same degree of speed variation as the
generating dynamo, such armature being so coupled with the said second exciting
circuit of the generating dynamo that its E. M. F. acts in opposition to that of the
independent source of current, so that the greater the speed of the generating and
regulating armatures is, the greater will be the opposition of the E. M. F. of the
regulating armature to the E. M. F. of the external source of current, whereby a
corresponding decrease in the action of the second circuit will be produced substantially
as herein described.
2. In electric generating machinery for use in railway trains subject to variation of
speed the method of maintaining constant the E. M. F. of the generating dynamos by
providing the field magnets of the generating dynamo with a supplemental exciting
circuit which is subject to two opposing E. M. F.'s, the one proceeding from a constant
independent source of current and the other from the armature of a regulating
dynamo, whose armature revolves at the same speed or is subject to the same speed
variation as that of the generating dynamo, so that as the E. M. F. of the last named
circuit increases with an increase of speed of the generating dynamo, it will tend to
neutralize the E. M. F. of the constant source of current and thereby effect a
corresponding decrease in the current and in the intensity of the magnetic field,
subtantially as described.
3. In electric generating machinery for use in railway trains, the combination of a
generating dynamo L having a shunt exciting circuit a and a supplemental exciting
circuit b connected to an external source of current C, and in series with the armature
of a regulating dynamo R driven at the same speed or subject to the same speed
variation as the generating dynamo, the last named armature being so connected to
the exciting circuit b that its E. M. F. acts in opposition to the E. M. F. of the
independent source of current, substantially as and for the purposes described.
4. In dynamo electric generating machinery wherein the armature is required to
operate when revolving in either direction, the use for effecting the reversal of the
lead of the commutator brushes when the direction of rotation is reversed of a friction
clutch part of which revolves with the armature shaft while the other part is attached
to the brush gear, such clutch being kept in gear when the shaft is stationary or
revolving at a very slow speed, but is moved out of contact by means of a governor
as soon as a certain slow speed is exceeded, substantially as herein described,

page_text: 5. In combination with the friction clutch and governor for actuating the com-
mutator brushes referred to in the preceding claim, the arrangement whereby the said
governor is made to couple up the exciting circuits when the speed requisite for
producing a certain electro motive force bas been attained and to disconnect these
circuits again when the speed falls substantially as herein described.
6. In combination with the arrangement of generating dynamo, and regulating
dynamo, and the mechanism for reversing the position of the commutator brushes
referred to in the preceding claims the use of a switch connected to the brush gear
and so arranged as to reverse the connections of the regulating armature with the
supplemental field magnet circuit of the generating dynamo on the reversal of the
position of the brushes, substantially as described.
Dated this 10th day of September 1890
ABEL & IMRAY
Agents for the Applicant,