Year: 1885

page_text: ز
We, WILLIAM MORRIS MORDEY, of 144 Disraeli Road, Putney, in the County
of Surrey, Electrician, and CHARLES WATSON of 20 Upper Parkfields, Putney,
Electrician, do hereby declare the nature of this invention to be as follows:-
This invention relates to electric motors designed to run at a constant speed or
speeds, to improvements in the design, construction, and operation of such machines,
and to arrangements and devices for starting, stopping, reversing, or inaintaining
at a constant or approximately constant speed the motion of such machines when
connected to a suitable system of mains for supplying electric currents under
standard conditions. And the invention has for its object the attainment of these
ends by simpler and more efficient means than have been hitherto in use.
Many means have heretofore been suggested for governing electric motors, and
in particular various devices for winding field magnets and armatures with a
compound winding of series and shunt coils have been proposed.
Devices have also been proposed for causing the motor automatically to adjust
either the resistance or the connexions of its circuits by mechanical governors,
centrifugal, dynamometric, and the like.
But in our invention we do not employ either compound windings or mechanical
governors to govern the speed of the inotor during its running.
The motors constructed according to our invention are designed to be worked
by connecting them to mains supplying electric energy under the well-known
condition that between the electric mains there shall be maintained a constant
difference of potential between the two points of the mains where the motor is
attached.
The motor must be so constructed that the field magnets are very powerful
relatively to the armature; there being plenty of iron and that iron well magnetised
by a sufficient supply of electric energy in the exciting coils of the magnets.
Hitherto it has been generally declared and supposed that the field-magnets of a
motor should be weak relatively to the armature. But in our invention the
reverse is the case. It is fundamental to carrying out our invention that the
field-magnets should be so much more powerful than the armature as to overpower
the reactions which the armature would otherwise bring about in the magnetic
field.
The matam am ahrent insund

page_text: In the case where, in consequence of the demands on the system, the mains
cannot be maintained at an absolutely constant difference of potentials, we fix to
the motor a centrifugal device whereby under these conditions we are still able
to drive the motors at a constant speed, the said centrifugal device being a governor
which whenever the speed falls below a certain limit shall insert in the shunt
circuit a certain suitable resistance, or shall reverse the connexions of some of its
coils; thus we get a quicker speed by weakening the amount of excitation of
the field magnets. Or the said centrifugal governor may operate upon a carbon
contact resistance introduced into the said shunt circuit; and the varying forces
exerted by the said governor will, at higher or lower potentials than the normal
number of volts, come into operation to aid or check the speed as may be required.
Or as an alternative to the centrifugal governor we may employ a shunt solenoid
with a core, to operate the said arrangement of resistances, or of circuit changers,
or of carbon contacts, the attraction exercised by the solenoid upon its core
varying when the number of volts of potential exceeds or falls short of the
normal value.
In consequence of the high self-induction of shunt magnets it is desirable that
in starting the motor the field magnet circuit should be switched on before the
armature is thrown into circuit. The switch may be arranged to make contact
for the field magnet circuit first and for the armature circuit afterwards; or a
solenoid or an electromagnet is arranged in the circuit and an electric resistance
is also introduced into the circuit and is so arranged that it is gradually short-
circuited by a movement of the core or armature of the said solenoid or electro-
magnet, thereby preventing the rush of an excessive current at starting. An
antagonistic spring or counterpoise weight can be used in .connexion with--the
latter device for the purpose of placing the said resistance again in the circuit of
the motor when the current is switched off the motor. A dashpot and plunger,
or equivalent device is used, the plunger being preferably fitted with a valve for
the purpose of obtaining a slow and gradual motion when short-circuiting the
resistance, and a quick motion when the spring or weight is engaged in removing
the short-circuiting switch or its equivalent.
The resistance may be of any suitable form; for instance, it may consist of wire
connected in the ordinary way to a series of contact pieces, or it may be formed
of carbon in any suitable form preferably capable of compression, or it may be a
-liquid resistance. This resistance is placed in the armature circuit, the field circuit
being connected to the mains and not simply to the brush terminals. Or the
shunt magnet circuit may be wound in two or more sections which at the moment
of turning on the current are grouped in parallel with each other but in series with
the armature, the connections being altered by a suitable switch after starting so
that the shunt magnet coils or sections are then placed in series with one another,
but in parallel with the armature.
Or for the purpose of starting the motor we use in combination with the shunt
winding a comparatively weak series winding which is short-circuited or reversed
either by hand, or automatically by a centrifugal device, after the machine has
started. The series winding enables the motor to start promptly and when thus
cut out after starting is not a cause of interference with the self-governing power
of the motor. Or instead of short-circuiting this series winding we may allow it
to remain in circuit, preventing it from interfering with the speed-regulation. by
saturating the magnetic system.
When it is desired that a motor should be run at several different speeds we
vary the strength of the magnetic field in any suitable known way, as by the
insertion of a resistance in the shunt, or by forming the field winding in several
Bections, the number of which in operation can be varied at will by turning a
suitable switch.
Hitherto it has been customary, when reversing the direction of rotation of
electric motors, to reverse the direction of the current in the armature or in the
field circuit, and at the same time to move the brushes on the commutator through

page_text: a considerable angle, usually employing a separate set of brushes for each direction-
But we obtain the reversal of rotation simply by reversing the direction of the
current through the armature or through the field-magnet circuit. With motors
constructed according to our invention the position of the brushes is practically the
same for either direction of rotation, and therefore no movement of them is
necessary, and one set of brushes only is required. We prefer to make the brushes
of a number of plates placed side by side making contact with the commutator
by the edges which are preferably placed at right angles to the axis of the
commutator.
Any suitable form of armature, ring, drum et cetera may be employed, and any
field-magnet may be used that complies with the above conditions and is adapted
for use with the armature.

page_text: Improvements in Constant-speed Electric Motors.
We, WILLIAM MORRIS MORDEY, of 144 Disraeli Road, Putney, in the County
of Surrey, Electrician and CHARLES WATSON, of 20 Upper Parkfields, Putney,
Electrician, 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 :-
This invention relates to electric motors designed to run at a constant speed or
speeds, to improvements in the design, construction, and operation of such
machines, and to arrangements and devices for starting, stopping, reversing, or
maintaining at a constant or approximately constant speed the motion of such
machines when connected to a suitable system of mains for supplying electric
currents under standard conditions.
And the invention has for its object the attainment of these ends by simpler and
more efficient means than have been hitherto in use.
Many means have heretofore been' suggested for governing electric motors,
and in particular various devices for winding field magnets with a compound
winding of series and shunt coils and for winding armatures with two windings
have been proposed.
Devices have also been proposed for causing the motor automatically to adjust
either the resistance or the connections of its circuits by mechanical governors,
centrifugal, dynamometric and the like.
The motors constructed according to our invention are designed to be worked by
connecting them to mains supplying electric energy under the well known condition
that between the electric mains there shall be maintained a constant difference of
potential between the two points of the mains where the motor is attached.
The motor must be so constructed that the field magnets are very powerful
relatively to the armature; there being plenty of iron and that iron well magnetised
by a sufficient supply of electric energy in the exciting coils of the magnets.
Hitherto it has been generally declared and supposed that the field-magnets of a
motor should be weak relatively to the armature. But in our invention the
reverse is the case. It is fundamental to carrying out our invention that the
field-magnets should be so much more powerful than the armature as to overpower
the reactions which the armature would otherwise bring about in the magnetic
field. The motors are shunt wound.
In our invention we do not require to employ either compound winding or
mechanical governors to govern the speed of the motor during its running when
the standard condition of constant difference of potential is maintained.
In the case where, in consequence of the demands on the system, the mains
cannot be maintained at an absolutely constant difference of potential, we fix to
the motor a centrifugal device whereby under these conditions we are still able to
drive the motors at a constant speed, the said centrifugal device being a governor
which whenever the speed falls below a certain limit shall insert in the shunt
circuit a certain suitable resistance, or shall reverse the connections of some of the
coils, thus we get a quicker speed by weakening the amount of excitation of the

page_text: field magnets. Fig. 1 shews this device arranged to decrease the resistance in the
shunt circuit, when a rise of speed takes place and to increase the resistance on a
fall of speed. A represents the armature with the brushes on the commutator.
F the shunt fields. R the resistance, the amount of which in the circuit F depends
on the centrifugal device G. Or the said centrifugal governor may be arranged,
as in Fig. 2, to operate upon a carbon contact resistance R introduced into the said
shunt circuit F, and the varying forces exerted by the said governor G, will, at
higher or lower potentials than the normal number of volts, come into operation
to aid or check the speed as may be required. The carbon resistance R is
preferably constructed of a number of thin plates the resistance of which is varied
by pressure as required.
The lever L pivotted at L¹ rests on the lower contact piece C¹ when the motor
is at rest, but is lifted from that position by the governor G the carbons being
thus thrown into the shunt circuit. The pressure is gradually increased as the
speed rises and when the full compression is reached the lever L short circuits the
resistance R by making contact with the upper contact piece C. The contact
pieces CC are preferably borne on springs and are adjustable.
In practice the adjustment is such that the lever L maintains a position about
midway between C and C¹ at the normal speed, thus either a rise or fall of speed
is checked and reduced. But where the difference of potential varies for more
than short periods we prefer to employ the device shewn in Fig. III. by which a
given variation of the difference of potential produces a definite effect on the fields
which effect is constant until the variation ceases or alters. This device consists
of a solenoid and core V or other suitable potential controlled arrangement, con-
nected to the motor terminals, and employed to vary the field strength by altering
the resistance R according to the variations of the potential difference from the
standard conditions. Fig. III shews a simple arrangement of resistance but it
should be understood that the device may be used in connection with a carbon-
compression resistance or a resistance in any other suitable form. We do not
however confine ourselves to the method of controlling the field strength by
altering the resistance inserted in the shunt circuit. The devices shown in
Figs. 1, 2 and 3, may be arranged to operate switches for varying the number of
coils of the shunt traversed by the current, or for changing the direction of the
current in some of those coils.
•
In consequence of the comparatively high self induction of shunt magnets it is
desirable that in starting the motor the field magnet circuit should be switched on
before the armature is thrown into circuit. The switch may be arranged as shewn
in Fig. 4 to make contact for the field magnet circuit first and for the armature
circuit afterwards.
Or a solenoid or an electro magnet is arranged in the circuit, and an electric
resistance is also introduced into the circuit and is so arranged that it is gradually
short-circuited by a movement of the core or armature of the said solenoid or
electro-magnet; thereby enabling the motor to start gradually and preventing the
rush of an excessive current at starting. This device is shown by Fig. 5.
A solenoid or electro-magnet C is placed in the motor armature circuit. An iron
core is drawn into the solenoid when the current is flowing and held in, even by
the smallest working current, the entrance of the core into the solenoid being
opposed by a spring or other suitable means. Actuated by the motion of the core
a lever L operating a short circuiting switch is made to short circuit the resistance
coils successively, or in any other way to reduce the resistance gradually, as the
core is drawn into the solenoid. In order to make the action a gradual one we
employ a dashi-pot, D, the plunger of which is preferably furnished with a valve
which closes when a downward movement of the core takes place, allowing only a
slow motion. When the current is interrupted the valve opens and the return
movement takes place freely, and the resistance is quickly reinserted. The
resistance may be of any suitable form, for instance, it may consist of wire
connected in the ordinary way to a series of contact pieces, or it may be formed

page_text: of carbon in any suitable form, preferably capable of compression, or it may be
a liquid resistance. This resistance is placed in the armature circuit, the field
circuit being connected to the mains and not simply to the brush terminals.
When this device is used in connection with a series-wound electric motor, it is
placed in series with the armature and fields. Or the shunt magnet circuit may
be wound in two or more sections which at the moment of turning on the current
are grouped in parallel, or in multiple series with each other but in series with.
the armature, the connections being altered by a suitable switch after starting so
that the shunt magnet coils or sections are then placed in series with one another,
but in parallel with the armature,
Or, for the purpose of starting the motor we use in combination with the shunt
winding a comparatively weak series winding which is short circuited or reversed
either by hand or automatically by a centrifugal device, after the machine has
started. The series winding enables the motor to start promptly and when thus
cut out after starting is not a cause of interference with the self governing power
of the shunt motor constructed according to our invention. Fig. 6, shews the
connections for a simple hand switch for short circuiting the series winding and
Fig. 7 an automatic centrifugal device for performing this operation.
Figs. 8 and 9, shew respectively a hand switch, and an automatic centrifugally
controlled switch, for either short circuiting or reversing the series winding.
In the Figs. 6 to 9, F is the shunt winding, S the series winding. The figures
are self-explanatory. Or instead of short circuiting this series winding we may
allow it to remain in circuit, preventing it from interfering with the speed
regulation by saturating the magnetic system in which case a switch is unnecessary.
When it is desired that a motor should run at one or other of two or more different
speeds (each speed being constant or nearly so under variations of load) we vary
the strength of the magnetic field in any suitable known way, but only to a limited
extent; as by the insertion of a resistance in the shunt (Fig. 11) or by forming
the field winding in several sections, the number of which in operation can be
varied at will by turning a suitable switch (Fig. 10) or by reversing the direction
of the current in a portion of the shunt winding.
Hitherto it has been customary when reversing the direction of rotation of
electric motors, to reverse the direction of the current in the armature or in the
field circuit, and at the same time to move the brushes on the commutator through
a considerable angle, usually employing a separate set of brushes for each direction.
But we obtain the reversal of rotation by simply reversing the direction of the
current through the armature or through the field magnet circuit. With motors
constructed according to our invention the position of the brushes is practically
the same for either direction of rotation, and therefore no movement of them is
necessary, and one set of brushes only is required.
We prefer to make the brushes of a number of plates or ribbons placed side by
side making contact with the commutator at the edges which are preferably placed
at right angles to the axis of the commutator, as shewn in Fig. 12. Each brush is
placed in a radial position with regard to the commutator and is held in contact
therewith by a spring S which presses on the end of it and forces it forward as it
is worn away.
The holders which are supported in any suitable way are carried
down close to the commutator to enable short brushes to be used and to hold them
securely. We make one side or end of the brush holder movable on a hinge or in
other suitable way to allow of the convenient insertion or withdrawal of the brush.
This arrangement of brushes may be used also in motors which are not constructed
according to this invention and in which it is therefore necessary to give the
brushes a considerable "lead," as well as in generators. As the brushes may be
used equally well for either direction of rotation the employment of double sets is
thereby dispensed with.
Any suitable form of armature, ring, drum, etcetera, may be employed, and any
field-magnet (or field-inagnets) may be used that complies with the above conditions
and is adapted for use with the armature,

page_text: Having now particularly described and ascertained the nature of our inven-
tion and in what manner the same is to be performed, we declare that what
we claim is:-
1. The combination of a system of mains supplying electric energy from an
external source at a constant potential, with an electric motor having the fields
wound simply as a shunt to the armature, and having the field magnets of such
dimensions, and wound with wire of such a gauge and length that they are very
powerful relatively to the armature, the said combination being for the purpose of
obtaining a uniform or approximately uniform speed, irrespective of load.
2. In the system of a shunt wound motor arranged substantially as set forth in
Claim 1 the use of a centrifugal device substantially as described for the purpose
of inserting a resistance in the field circuit or otherwise weakening the field
strength if the potential falls below the normal or standard conditions or for
reducing the amount of such resistance or otherwise increasing the field strength if
the potential rises above the normal or standard conditions for the purpose of
maintaining the speed constant or nearly so irrespective of load.
3. In the system of a shunt wound motor arranged substantially as set forth in
claim 1 the use of a shunt solenoid or electro magnet substantially as described
connected to the mains or to the motor terminals and arranged to insert a resistance
in the field circuit or to otherwise weaken the field strength if the potential falls
below the normal or standard conditions or to reduce the amount of such resistance
or otherwise increase the field strength if the potential rises above the normal or
standard conditions for the purpose of maintaining the speed constant or nearly so
irrespective of load.
4. The combination with an electric motor of a switch so arranged as to connect
the shunt field magnet circuit to the mains before so connecting the armature
circuit substantially as described.
5. The combination with an electric motor of an automatic device comprising an
electro magnet or a solenoid and an electric resistance both introduced into the
circuit of the motor, an automatic spring or counterpoise weight and a dash pot,
substantially as and for the purpose described with reference to Fig. 5.
6. The use in electric motors of field magnets wound with two or more wires or
sections of winding with means for connecting the said wires or sections in parallel
or in multiple series with one another the arrangement being such that the said
wire or sections of winding are in series with the armature at starting the electric
motor, and after the motor is started are connected in series with one. another but
in parallel with the armature substantially as described.
7. In a shunt motor substantially as set forth in Claim 1 the use for the purpose
of facilitating starting of a field-winding in series with the armature in combination
with short circuiting or reversing devices substantially as described with reference
to Figs. 6, 7, 8 and 9.
8. Causing a shunt wound motor arranged substantially as described in Claim 1
to run at one or other of two or more constant speeds irrespective of load by
varying the strength of the field substantially as described.
9. The construction and arrangement of brushes and brush holders substantially
as and for the purposes herein before described.