Improvements in and relating to Electric Motors.
Year: 1891

page_text: Date of Application, 31st Jan., 1891
Complete Specification Left, 31st Aug., 1891-Accepted, 16th Jan., 1892
PROVISIONAL SPECIFICATION.
Improvements in and relating to Electric Motors.
I, GEORGE FREDERICK REDFERN, of the firm of G. F. Redfern & Co., The
General Patent Office, No. 4, South Street, Finsbury, in the County of Middlesex,
Patent Agents, do hereby declare the nature of this invention (a communication
from abroad by Messieurs Wirth & Co., of Frankfort-on-the-Main, in the Empire
of Germany, Patent Agents acting as Agents for Messieurs W. Lahmeyer & Co.,
of Frankfort-on-the-Main, aforesaid, Stock Brokers,) to be as follows
This invention relates to an improved arrangement of shunt for electric motors.
In an electric motor, as in every other motor, not only has the condition to be
fulfilled, that the speed of revolution shall remain the same with all loads, but
also that any such machine shall work properly, that is to say, shall be able to set
increased masses in motion without suffering injury thereby.
This invention fulfils the latter requirement by means of the following arrange-
ment:-
The armature is provided with two coils, one of which is in the circuit of the
supply-current and from its far greater number of turns, serves only for the reception
of current, and operates only as a driving coil. The second coil of the armature,
which is the current producing coil, has a smaller number of turns, is in the same
circuit as the coils of the field-magnets and is connected with a special conductor.
This coil serves as a special dynamo machine. Inasmuch as it moves with the
armature in the magnetic field of the latter, current is generated in it, and this
current is led by the special conductor through the coils of the field-magnets of the
electro-motor.
In the accompanying drawing-
Figure 1 is a diagram illustrating the governing of such an electro-motor.
The conductor A shews the primary coil of the armature, a the secondary
coil, d, d the coils of the field-magnets fed by the latter, R a regulating resistance
interposed in the circuit of the field-magnets. The bridge 1-2 is common to both
circuits. In order to start the electric motor the connection 1-2 is opened, the
primary current then takes the direction I, 1, d, R, d, a, 2, A, II, that is to say,
passes successively through the coils of the field-magnets and both armatures.
In this case the machine works as a main-circuit electro-motor, inasmuch as the
small amount of opposing action of the secondary coil of the armature is withdrawn
from the driving power of the primary coil. The great advantage for the purpose
of starting is by this means gained, that as the strength of the current increases it
gives rise to stronger magnetism, and thereby, as is necessary, greater driving power.
The resistance to conduction offered by the coils of the field-magnets prevents the
current from being too great at first, and by reason of the auto-induction of the
coils of these magnets, the current does not reach its full strength immediately, but
only by degrees.
Figure 2 illustrates the provision which is employed for the regulation of electric
motors.
The important peculiarity of the arrangement consists in the fact that the coils
of the field-magnets are brought in single divisions from the circuit of the primary
current into that of the exciting current. While the machine is running the arm K
stands on the circuit closing surface marked 7, and the primary current then takes
the direction I, A, 11, cut off with lead safety connection S III, coil of the relay E,
armature m of the same, binding screw a, n into p, arm K and IV.
The second circuit is composed of the following a, d, d, 6, R, 7, K, p, a.
If the supply of current fails by reason of its being cut off, or from any other cause,

page_text: the armature m of the relay E falls, the connection at a is interrupted, and in
consequence of the circuit being broken at a no fresh current can find its way to
the electro-motor. This is necessary, in order to prevent the current from passing
through the armature when at rest, or when the current is not required.
To permit
the electro-motor to go on, the arm K has imparted to it a circular motion in the
direction indicated by the arrow. The arm K then lifts the armature m by
pressing on the spring and thus completes the circuit at .c.
The current now takes
the following course :-I, A, II, S, III, E, m, &, n, p, a, d, d, R, IV.
The com-
mencing current is thus compelled to flow through the coils of the armature and of
the field-magnets, one after the other.
The lever K being now moved to the circuit-completing surface indicated by 1,
the division of the coils of the field-magnets which is placed uppermost in the
drawing is shunted into the special circuit a, d, 1, K, p, a. The rest of the divisions
of coils of the field-magnets, together with the resistance R, remain at the same
time in the primary circuit: The further movement of the lever K to the circuit
closing surface 6 causes the whole of the coils of the field-magnets to be shunted by
degrees into the circuit of the exciting current. Thereupon the governor R is short
circuited by turning the lever H, that is to say, the resistance R is shunted out of
the primary conductor. Finally the lever is shifted from the circuit closing
surface 6, to the driving current surface 7, where it can be screwed tight. In this
position the electro-motor has its slowest speed of revolution, since the regulator R
is short-circuited. The lever H of this regulator is now available for the exact
arrangement of the speed of revolution, and during the action of the electro-motor,
the regulator R serves this purpose alone. The twofold employment of the
regulator R as a check-resistance at starting and as an ordinary governing resistance
in working is rendered possible by the fact that the secondary circuit furnishes
a strong current with low tension.
The regulator of a closed secondary circuit machine would naturally not be able
to shunt out the primary current within a short time. In the meantime the
regulator R when shunted in without employment can remain short circuited, if
the number of divisions in the coils of the field-magnets is sufficiently large. The
lever is then by a slow movement made to pass to the surface 7 which completes
the circuit of the driving current. Beyond this an alteration is possible, of such a
kind that the lever, in the position in which it raises the armature m, also touches
the circuit completing surface 1, or that the point 1 is in permanent electrical
connection with p. The primary current is then from the outset excluded from the
path through a and the first division of d, which of themselves form a circuit. The
wire of the armature does not then need to be arranged for the temporary require-
ments of the primary current.
Dated the 31st day of January 1801
G. F. REDFERN & Co.,
4, South Street, Finsbury, Loudon, Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvements in and relating to Electric Motors.
I, GEORGE FREDERICK REDFERN, of the firm of G. F. Redfern & Co., The
General Patent Office, No. 4, South Street, Finsbury, in the County of Middlesex,
Patent Agents, do hereby declare the nature of this invention (a communication
from abroad by Messieurs Wirth & Co., of Frankfort-on-the-Main, in the Empire
of Germany, Patent Agents, acting as Agents for Messieurs W. Lahmeyer & Co.,
of Frankfort-on-the-Main, aforesaid, Stock Brokers) 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 an improved arrangement of shunt for electric motors.
In an electric motor, as in every other motor, not only has the condition to be

page_text: fulfilled, that the speed of revolution shall remain the same with all loads, but also
that any such machine shall work properly, that is to say, shall be able to set
increased masses in motion without suffering injury thereby.
This invention fulfills the latter requirement by means of the following arrange-
ment:-
The armature is provided with two coils, one of which is in the circuit of the
supply-current and from its far greater number of turns, serves only for the reception
of current, and operates only as a driving coil. The second coil of the armature
which is the current producing coil has a smaller number of turns, is in the same
circuit as the coils of the field magnets and is connected with a special conductor.
This coil serves as a special dynamo machine. Inasmuch as it moves with the
armature in the magnetic field of the latter, current is generated in it, and this
current is led by the special conductor through the coils of the field magnets of the
electro-motor.
In the accompanying drawing-
Figure 1 is a diagram illustrating the governing of such an electro-motor.
The conductor A. shews the primary coil of the armature; a is the secondary
coil; d, d, are the coils of the field-magnets fed by the latter; R is a regulating
resistance interposed in the circuit of the field-magnets. The bridge 1-2 is common
to both circuits. In order to start the electric motor the connection 1-2 is opened,
the primary current then takes the direction I, 1, d, R, d, a, 2, A, II, that is to say,
passes successively through the coils of the field-magnets and both armatures.
In this case the machine works as a main-circuit electro-motor, inasmuch as the
small amount of opposing action of the secondary coil of the armature is withdrawn
from the driving power of the primary coil. The great advantage for the purpose
of starting is by this means gained, that as the strength of the current increases it
gives rise to stronger magnetism, and thereby, as is necessary, greater driving power.
The resistance to conduction offered by the coils of the field-magnets prevents the
current from being too great at first, and by reason of the auto-induction of the coils of
these magnets, the current does not reach its full strength immediately, but only
by degrees.
Figure 2 illustrates the provision which is employed for the regulation of electric
motors.
The important peculiarity of the arrangement consists in the fact that the coils
of the field-magnets are brought in single divisions from the circuit of the
primary current into that of the exciting current. While the machine is running
the arm K stands on the circuit closing surface marked 7, and the primary
current then takes the direction I, A, II, cut off with lead safety connection S III,
coil of the relay E, armature m of the same, binding screw c, n, into p, arm K,
and IV.
The second circuit is composed of the following a, d, d, 6, R, 7, k, p a.
If the supply of current fails by reason of its being cut off, or from any other
cause, the armature m of the relay E falls, the connection at is interrupted, and
in consequence of the circuit being broken at x no fresh current can find its way to
the electro-motor. This is necessary, in order to prevent the current from passing
through the armature when at rest, or when the current is not required. To permit
the electro-motor to go on, the arm K has imparted to it a circular motion in the
direction indicated by the arrow. The arm K then lifts the armature m by pressing
on the spring f, and thus completes the circuit at x. The current now takes the
following course-I, A, II, S, III, E, m, a, n, p, a, d, d, R, IV. The commencing
current is thus compelled to flow through the coils of the armature and of the field-
magnets, one after the other.
The lever K being now moved to the circuit-completing surface indicated by 1,
the division of the coils of the field-magnets which is placed uppermost in the.
drawing is shunted into the special circuit a, d, 1, K, p, a. The rest of the divisions
of coils of the field-magnets, together with the resistance R remain at the same
time in the primary circuit. The further movement of the lever K to the circuit

page_text: closing surface 6 causes the whole of the coils of the field-magnets to be shunted
by degrees into the circuit of the exciting current. Thereupon the governor R is
short circuited by turning the lever H, that is to say, the resistance R is shunted
out of the primary conductor. Finally the lever I is shifted from the circuit
closing surface 6, to the driving current surface 7, where it can be screwed tight.
In this position the electro-motor has its slowest speed of revolution, since the
regulator R is short-circuited. The lever H of this regulator is now available for the
exact arrangement of the speed of revolution, and during the action of the electro-
motor, the regulator R serves this purpose alone. The twofold employment of
the regulator R as a check-resistance at starting and as an ordinary governing
resistance in working is rendered possible by the fact that the secondary circuit
furnishes a strong current with low tension.
The regulator of a closed secondary circuit machine would naturally not be able
to shunt out the primary current within a short time. In the meantime the
regulator R when shunted in without employment can remain short circuited, if the
number of divisions in the coils of the field-magnets is sufficiently large. The lever
is then by a slow movement made to pass to the surface 7 which completes the
circuit of the driving current. Beyond this an alteration is possible, of such a kind
that the lever, in the position in which it raises the armature m, also touches the
circuit completing surface 1, or that the point 1 is in permanent electrical con-
nection with p. The primary current is then from the outset excluded from the
path through a and the first division of d, which of themselves form a circuit. The
wire of the armature does not then need to be arranged for the temporary require-
ments of the primary current.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
1. In an electro-motor with two coils on the armature, one of which coils during
working is in the circuit of the supply current, and the other as current producing
coil is in the same circuit as the coils of the field-magnets, a shunting arrangement
by means of which, on starting the electro-motor, both coils of the armature and
the coils of the field magnets, or only the driving coil of the armature, with the
coil of the field magnet or a part of the latter, are shunted one after another first
into the circuit of the supply current, and then into single divisions of the coils of
the field-magnets which lie in the circuit of the supply-current, and also a resistance
is shunted into a special circuit together with the current-producing coil of the
armature, substantially as hereinbefore described with reference to the accom-
panying drawing.
2. In the arrangement described in Claim 1, the employment of a relay the coil
of which is in the primary circuit, and whose armature when in contact, constitutes
a contact which also lies in the primary circuit, and is so arranged that the contact
is made by the turning of a lever which effects the shunt.
Dated the 31st day of August 1801
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicant.