other Motive Power Engines.
Year: 1889

page_text: Date of Application, 22nd Jan., 1889
Specification Accepted, 23rd Feb., 1889
other Motive Power Engines.
I, RANKIN KENNEDY of the Electric Lamp Works, 115 Woodside Road,
Glasgow, Lanarkshire, Electrical Engineer, do hereby declare the nature of my said
invention and in what manner the same is to be performed to be particularly described
and ascertained in and by the following statement in writing reference being bad to
the accompanying Sheet of Drawings and to the letters and figures marked thereon
that is to say :-
In driving an ordinary dynamo electric machine by a steam engine governed by a
centrifugal governor acting either on a throttle or expansion valve, the speed of the
engine slightly decreases, as the load on the dynamo increases, and necessary so
because no centrifugal governor can admit more steam to the engine unless the speed
be first actually decreased somewhat, and conversely no centrifugal governor can cut
off steam from the engine when load is thrown off without allowing the engine to
first run slightly quicker.
In a dynamo electric machine driven by the engine governed by a centrifugal
governor, there is a fall in the terminal pressure due to this fall in speed as more
current is taken off by putting on lamps in the circuit of the dynamo; and further if
the machine is simply shunt wound, there is an additional fall in terminal pressuro
due to the internal resistance of the armature of the dynamo becoming apparent as
more and more current is taken from the dynamo, which is here taken as a shunt
wound dynamo to give variable current and constant pressure.
The same thing occurs in constant current and variable pressure dynamos, in this
case the current falls off as lamps are switched on and the centrifugal governor
instead of accelerating the speed of the engine to keep up the constant current when
the lamps are switched on, actually tends to decrease the speed of the engine.
Various cummbrous and expensive electrical appliances have been devised to over-
come these difficulties such as compound winding for constant pressure dynamos, and
shifting the brushes by mechanism operated by the current, in constant current
dynamos.

page_text: My invention consists in a new or improved method of controlling centrifugal
governors by the electric current from the dynamo which is being driven by the
engine running the dynamo, whereby an increase of speed in the engine is obtained
when load or more work is thrown on to it. The amount of the increase is just
sufficient to counteract the fall of terminal pressure in a constant pressure dynamo
due to internal resistance in the armature as more current is turned on to the lamp
circuit. And the increase of speed is just sufficient in a constant current dynamo to
counteract the fall in current strength due to the increase of resistance in the
external circuit by switching on more lamps in series. And vice versa the fall in
speed is made equal to the fall in load or work thrown off the engine. In constant
pressure dynamos shunt wound the rise and fall of terminal with full load and no
load or current in the external circuit is not much perhaps about ten per centum of
the full pressure, that is a dynamo may have 100 volts with no current in external
circuit and be found to fall to 90 volts with its full current in external circuit when
driven by an engine governed by a centrifugal governor.
In constant current dynamos the rise and fall of the current strength is not very
great in itself, but the rise and fall in the speed required for say only one lamp and
twenty lamps is very great apparently, but really it is not if the dynamo is made for
constant current and its field magnets and armature are so proportioned to give a
characteristic curve which drops down when the current exceeds the constant.
According to my invention L employ solenoids of insulated wire to carry the whole
or part of the electric current flowing from the driven dynamo, and this solenoid or
solenoids act upon a core of soft iron, or bundle of soft iron wires, attached to the
governor in such a
manner and at such a point that the solonoids by pushing or
pulling this core oppose the centrifugal force and allow the spring or weight of the
governor to open the steam valve more and more as the work is thrown on the
engine.
And in order that my said invention, and the manner of performing or carrying
the same into effect or practice may be properly understood, I have hereunto
appended an explanatory Sheet of Drawings, in which the same reference letters are
used to indicate corresponding parts in all the figures where shown. Figure 1 is an
elevation of a spring centrifugal governor G, G, as fitted with one arrangemont of
my improvements, in which a single solenoid A and core B, are used for controlling
the action of the governor G, G, as herein described. Figure 2 is an elevation of a
corresponding spring centrifugal governor G, G, as fitted with another arrangement
of my improvements, in which a duplex solenoid of thick and thin wires A, and H,
respectively, and a central core B are used for controlling the action of the governor.
Figure 3 is an elevation of a compound high speed engine Z, as fitted with my new
or improved solenoids for controlling the action of the governor G, which is shown
applied as actuating the inlet regulating-steam valve V indicated in section.
Referring to Figure 1 of these Drawings, this shows a spring governor in which
the springs F, F, F, oppose the centrifugal force of the balls G, G, G, and the balls
fly out and lift the lower head C, of the governor G, when the speed rises, thus
shutting off steam. To the head I screw or attach a core B, of soft iron, herein
shown as a tube, which revolves with, and rises and falls with, the governor head C
and spindle c, within the case or tube A¹, and solenoid of wire A. When the
governor is at rest the core B is nearly entirely inside of the solenoid of insulated
wire A A' in circuit with the driven dynamo and with the valve of the engine closed.
On starting the engine Z, with no lamps on the dynamo, which is here taken as a
shunt wound constant pressure not shown in the Drawings, the governor acts as
an ordinary centrifugal governor and checks the engine at normal speed, that is with
terminal pressure of dynamo equal to the constant pressure desired. In this stato
of affairs the governor balls G will be almost full open and the core B withdrawn
considerably from its solenoid A, A'. On turning on current to the lamps through
the solenoid A, this current will tend to pull in its core B, and this assists the
springs F, F, F, to lift the central spindle c and open ti e steam valve V, to admit steam
to give the increased speed sufficient for constant pressure. Whereas without the

page_text: solenoid the engine would slow down sufficient to allow a fall in the centrifugal force
of the balls G, G, G, enabling the springs F to open the steam valve further, but the
speed could not be equal to the nominal speed. In this solenoid A the wire should be
thick enough to carry the maximum current of the dynamo required to pass through
it without heating the wire, and the number of convolutions of wire in it are just
sufficient for pulling enough to give the increase of speed with increase of current.
The terminals D, E, are connected in the main circuit of the dynamo placing the
solenoid A in series with all the lamps or other load. For an engine driving a
constant current dynamo the governor is fitted with the same arrangement only the
solenoid is wound with fine wire and connected as a shunt across the terminals of the
dynamo.
Referring to Figure 2, this illustrates the arrangement where great delicacy is
required especially for large governors, a second coil H, is added to the solenoid, of
fine wire, when the governor is at rest the core B occupies the lower portion of the
solenoid, when the engine is at normal speed with no external current from the driven
dynamo the core B occupies a position slightly above the middle line between the two
coils. the fine wire coil H, has its terminals I, K., connected as a shunt across the
terminals of the driven dynamo and the thick wire coil A. is in series. For working
with a constant pressure dynamo the thick wire solenoid A, assists the springs F, in
admitting more steam, and the fine wire solenoid H, assists the centrifugal force and
tends to prevent the thick wire solenoid A from overpowering the centrifugal force
when the current rises to high values.
When the core B is lifted into position by the increased speed of the governor it
is pulled into the thick wire coil A by the current from the dynamo passing through
its convolutions, the amount of the pull being equal to the amount of the current
multiplied by the number of convolutions, and thus as the current increases the steami
is admitted more, as the pull more and more opposes the centrifugal force. The pull
of the fine wire solenoid H, is upwards, and with constant pressure does not vary in
value, but if by any disturbance the thick wire A should pull too hard and increase
the speed too much, the pressure at terminals would rise, and the pull of the fine wire
coil would then increase and counteract the disturbance. and conversely if the
speed did not rise sufficient the terminal pressure would fall and the fine wire coil H,
would decrease in pulling power, thus compensating for any small disturbances.
For engines driving constant current dynamos, the solenoids A, H, Figure 2, are
inverted but still connected the same, in this case the pull of the thick wire A is
nearly constant and the pull of the fine wire H varies as lamps are switched on or off.
The pressure rises at terminals as lamps are switched into series, and the current
slightly falls and this allows the fine wire coil H, to assist the governor G in opening
the steam valve as the fine wire H now pulls down, this being the lower coil of the
solenoid.
When these new or improved electric governors are applied to engines driving
alternating current generators, the bobbin A' carrying the solenoids A, H, is either
slit into divisions, or inade of non-conducting material for the purpose of preventing
induced currents therein. And for the same reason the core would be made of
laminated iron, or a bundle of iron wires.
Or when used for alternating current dynamos, the exciter may be driven by a
separate engine governed by this new or improved electric governor, the main
current from the alternator being passed through the solenoid so that the speed of
the exciter may increase as the current increases in the main circuit.
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 claim is :-
:-
First. In steam or other motive power engines, the combination of a centrifugal
governor with a core of soft iron and a solenoid of thick wire in series circuit with
a shunt wound dynamo driven by the engine carrying said governor, substantially as
herein described in reference to and shown in the accompanying Drawings.

page_text: Second. In steam or other motive power engines the combination of a centrifugal
governor with a core of soft iron and a solenoid of fine wire in shunt circuit with a
constant current dynamo or series wound dynamo driven by said engine, substantially
as herein described, in reference to and shown in the accompanying Drawings.
Third. In steam or other motive power engines the combination of a centrifugal
governor with a core of soft iron, and a solenoid having a coil of thick wire in series
circuit with a shunt wound dynamo and another coil of wire in shunt circuit with
same dynamo driven by said engine, substantially as herein described, in reference to
and shown in the accompanying Drawings.
Dated the 16th Tony 18ga