Improvements in and relating to Dynamo-Electric Machines, and in their Combination with Transformers Principally, Applicable for Electric Welding.
Year: 1889

page_text: [Communicated from abroad by HERMANN LEMP, of Lynn, Massachusetts, United
States of America, Electrical Engineer.]
Improvements in and relating to Dynamo-Electric Machines, and in
their Combination with Transformers Principally, Applicable for
Electric Welding.
I, HENRY HARRIS LAKE, of the firm of Haseltine Lake & Co. Patent Agents,
Southampton Buildings, in the County of Middlesex, 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 dynamo electric machines in which field excitation is
produced by current taken from the armature coil which supplies the work, and more
particularly to machines which are arranged to supply alternating currents to the
work while being at the same time self excited by commuted current derived from the
same armature coil which supplies the work.
The invention is especially useful in connection with dynamo machines which
supply alternating current to the primary of a converter the secondary of which being
properly constructed or wound supplies a current of large volume but low electro
motive force to suitable clamps one or both movable and holding pieces of metal to be
welded by the passage of current from one piece to the other while they are subjected
to pressure after the now well known process of electric welding, or supplies a large
volume of current for any other kind of work demanding a variable amount of electric
energy.
The said invention involves the compounding of the electric energy from different
sources in the maintaining of the field of the machine, and the object is to do away
with the disadvantages attending the operation of machines where the action or
behaviour is similar to that of a shunt supplied field as well as those which attend the
operation of a series machine, while at the same time securing the advantages
belonging to each. These disadvantages and advantages are particularly noticable in
the case of dynamo machines supplying current to the primary of an induction coil
for electric welding or other metal working operations.
The invention consists essentially in passing an exciting current through the same
field magnet coil both from the main circuit coil of the machine or that which supplies
current to the work and from a separate exciting source which latter is preferably,
for the sake of simplicity, on the same armature or in the same magnetic field with
the work circuit armature coil although it may be an entirely separate machine.
The said invention consists further in certain preferred arrangements and com-
binations in which the exciter coil and work circuit coil are both on the same machine
and the regulation is effected by changes in the circuit of the exciter coil only, as will
presently appear.
In the accompanying drawings:
:-
Figures 1 and 2, each illustrate diagramatically and in plan view machines and
circuits employed prior to the invention.
Figure 3 shows in plan view a machine and circuits embodying the said invention.
Figure 4, is a diagram of the circuits of Figure 3, removed from the machine.
Figure 5, illustrates an arrangement the equivalent of that shown in Figure 3.
Figure 6, shows in plan a modified arrangement, and
Figure 7, is a diagram of the circuits of Figure 6, removed from the machine.
In order that the principles and advantages of the invention may be better under-
stood I will first describe the peculiar actions of the machines illustrated in
Figure 1, which behaves in a similar manner to a shunt wound machine. This

page_text: machine is a form heretofore used in electric lighting work where it is desired to
obtain an alternating current on the main circuit together with self excitation, and
has likewise been employed for supplying alternating current to the primary of a
welding coil" or transformer the secondary of which connects to the clamps of an
electric welding apparatus.
N, indicates a coil or coils wound on the armature of the machine and forming the
work circuit coil of the machine which coil supplies alternating current to the work
through suitable contact rings a, b, secured to the armature shaft and provided with
stationary contact brushes to which the terminals of the work circuit may be connected.
P, is the primary of the transformer or welding coil in such work circuit, and T, the
secondary connected with the welding clamps. The parts shown are merely typical
of any similar devices for a similar purpose.
M, indicates another armature coil usually of a small number of turns and applied
to the armature in any desired manner either the same or differently from N, and
forming an exciter coil for the machine, for which purpose it is connected with the
field coil F, through a commutator C, constructed to change its connections simul-
taneously with the reversals of current in M. A rheostat R, in circuit with M,
controls the excitation and the output of the machine.
With a machine thus constructed and with a given number of turns in the primary
of the welding coil, if it be undertaken to weld, a piece of iron say one inch in
diameter in the clamps connected to the secondary, the machine will start with a
certain current depending on the amount of resistance in the rheostat usually
employed in the circuit with the exciting coil to govern the output of current from
the machine, and as the work heats the current will gradually increase thus requiring
a shifting back of the rheostat controlling the work in order to prevent burning of
the pieces. This increase in the current passing to the work is due to the fact that
when the iron is cold the current in the welding circuit has a comparatively free path
and the coil N, drains the energy from the coil M, thus subtracting current from the
field coils of the machine, while as the metal heats up and the resistance increases in
the circuit of the coil T, less energy is consumed in such circuit and more energy is
developed in the exciting coil. The behaviour of the machine in this respect is very
similar to that of a simple shunt wound machine. Any bad contact in the clamps or
at the point where the metals to be welded touch does not affect the building up of
the machine, and in fact it will pick up the quicker the worse the contact.
If now a
change be made from work one inch in diameter to work one half inch in diameter
and if the rheostat controlling the work be set in the same position as for one inch
stock, the exciter armature coil will develope more current because of the increased
resistance in the work circuit and the machine will generate too great a current the
result being a danger of burning the metals at the weld. The only remedy for this
is to increase the number of turns in the primary of the welding coil. Though it is
not necessary to keep rheostat at same positions for one half inch work, a certain
minimum resistance is required to have the machine pick up at all and even that may
be too much for small work if operated on a large dynamo.
In the arrangement of machine indicated in Figure 2, the difficulty is of a converse
nature. In this form of machine the coils M N, upon the armature supply energy
which passes through the work circuit coil and also feeds the exciting current to the
field magnet coils F, of the machine. In this case as before the work of circuit is
supplied with current through the two contact rings a, b, upon which bear fixed
brushes as shown connected to the primary P. The circuit after passing through the
work and through the rings and brushes is carried to the commutator C, which in
obvious fashion commutates the alternating currents after they pass the work and
turns them into currents of one direction for exciting the field magnet. The circuit
is as indicated from one terminal of the armature coil to a contact ring and brush
- therefor, thence through the work to the brush for the other contact ring, from the
latter to one side of the commutator and one of the brushes therefor, thence through
the field magnet coil, back to the other brush of the commutator, to the side of the

page_text: commutator upon which said brush for the time being bears, and thence to the
opposite terminal of the armature coil.
The rheostat R, controls the excitation of the machine by shunting the current
around the commutator and field magnet to the determinate or required amount.
The characteristic of this method of excitation when applied to welding work
is that practically the machine cannot build up and generate current unless there is a
very good contact between the pieces to be welded, because the welding coil is
practically in series with the field inagnet and the reaction or counter-electro motive
force in the circuit of the primary is so great when the contact is bad as to prevent a
free flow of current through the armature coil of the machine. In this form if the
contact should be poor it would be necessary to remove the shunt provided by the
rheostat R, almost entirely in order to make the machine build up. When the machine
starts under the conditions supposed the shunt must be brought back quickly to the
proper point in order to prevent injury to the welding.
Moreover the resistance of the pieces to be welded being smallest at the start the
current will, with a given setting of the rheostat, be a maximum at the start-and will
greatly diminish as the work heats up.
If the same winding be used on the welding coil for small work as for large work,
the condition of the shunt being at the same time such as required for normal working,
or even entirely removed, the dynamo will not begin to generate at all the smaller
pieces acting like an imperfect contact for the larger current carrying piece. In order
to make the apparatus work properly the number of turns on the primary P, must be
reduced. This method is in some respects advantageous as the work is not likely to
be burned by an unskilful operator but the action is very fickle. The machine.may
start, or it may not, and it will be often found that much manipulation is required in
order to make it perform its duties properly under adverse circumstances.
In both the arrangement shown in figures 1 and 2, a different number of turns on
the welding coil is required for different sizes of work in order that the machine may
operate to advantage. Both require the setting of the rheostat at a different point at
the start from that proper at the finish which obviously is undesirable in the case
of machinery which may be placed in the hands of inexperienced persons. A preferred
arrangement would be to have the rheostat set in a given position for a given size of
work, and to close the switch in the primary which permits current to be generated
in the secondary and flow to the work and finally open it when the work is done
without any manipulation of rheostat or brushes during the whole operation. This
desirable result may be accomplished by the arrangement to be now .described
involving the employment of two exciting sources for the field magnet coil F, one
source being the work circuit armature coil and the other an independent source as
will be described which supplies current to the field coil in multiple with the work
circuit armature coil.
One arrangement involving this principle is indicated in Figures 3 and 4.
Mindicates the exciter coil wound on a proper armature and having its two terminals
connected to the segments of a commutator C. The brushes of said commutator
connect with the field magnet coil P so that the commuted current passes through
said coil. The coil M, may be termed the short circuit coil. The coil N, revolving in
the same field with M, has one of its terminals connected to the same commutator.
segment with one terminal of coil M, while its other terminal connects in obvious fashion
by means of contact rings a, b, and brushes therefor through the work with the commutator
segment to which the other end of coil M, connects. The direction of winding or the con-
nections are such that the current generated in both coils will flow in the same direction
through the field magnet coil P. The rheostat R, is in the circuit of the current flowing
from both coils. As the coil M is short as compared with coil N, and its electro
motive force small, it is obvious that any change in the resistance R, will produce a
great effect in the delivery of exciting currents from the coil M, and comparatively
little effect on the current flowing from coil N, through the field and to the work...
By the use of the resistance thus arranged the influence of the exciting coil M, may

page_text: be varied to suit the different sizes of stock to be welded, or in other words to the
differences in the work to be performed by the machine. The influence of the main
circuit coil N, will be slightly changed but the design is that it should be as far as
possible, once for all determined in constructing the machine. A little adjustment of
it may be desirable under certain conditions and that is provided in the arrangement
to be presently described in connection with Figure 5.
With the arrangement shown in figures 3 and 4, it does not make any difference
what size stock is welded so far as the winding of the welding coil P, T, is concerned,
and the apparatus will work with advantage for all sizes of stock, as far as the capacity
of dynamo and coils permit, with a constant number of turns in the primary P, of
the welding coil.
Any bad contact does not effect the building up of the machine as it builds up
with the exciting coil M alone.
The rheostat may be set at the start in a certain position and the switch turned
to throw on the current, and when the work is completed the current may be shut
off without any regulation being required during the operation. The current may
be kept constant during the whole action or it may be made to drop or rise as
special work may require, this difference of action being obtained by giving
the preponderance to the exciting influence of either the separate or independent
exciter M, or to the series exitation of the coil N.
Instead of using an exciter M, on the same armature or in the same field with the
work circuit coil N, I may use as indicated in figure 5 a separate exciting machine M²,
which is connected with the field magnet coils through the rheostat R, in obvious
fashion. The work circuit armature coil N, in the field excited by M2, supplies current
to the work through the rings a, b, and its current is also delivered to the field magnet
coil F, as a continuous current and in multiple with the current from exciter M²; by
means of a commutator C which locally commutates the alternating currents after they
pass through the work.
In this arrangement the rheostat is obviously in the circuit only of the exciter and
it may be used to change the action of the machine in obvious manner. The influence
of the work circuit should be once for all determined in constructing the machine. A
capacity, for a little adjustinent is however provided by the shunt S2 around the commu-
tator which may be of any desired variable character. This shunt will obviously only
affect the current in the work circuit. In this arrangement the current generated
in M² may be regulated by means of the rheostat R in circuit with the same which
current traverses the field magnet F and excites the machine to a degree depending
upon the setting of the rheostat. When the rheostat is set the current in such circuit
can never increase but may be diminished if the current flowing through the main or
work circuit to the field coil should become such as to materially increase the difference
in potential at the terminals of the field magnet. In the case of a great increase the
current furnished by the exciter would be greatly diminished. The increase of current
in the field due to the influence of the work circuit coil N will obviously be propor-
tionate to the work performed in that circuit.
The rapidity of field excitation may be hastened or retarded by means of the
rheostat in series with the exciter M just as it would by setting the rheostat in the
arrangement shown in Figures 3 and 4.
A preferred arrangement similar in most respects to that of Figures 3 and 4 is
illustrated diagramatically in Figures 5 and 6. The arrangement of the two latter
Figures permits the employment of a variable resistance in the circuit of the exciter
coil M, only the current developed by the work circuit coil N flowing to the work
independently of such exciter but at the same time flowing through the field coil Fin
multiple with the current of the exciter M. Two of the terminals of the coils M N
are connected to the same segment of the commutator as clearly shown and the
opposite terminal of the coil N connects with the opposite commutator plate through
the work circuit by means of the rings 2, 3 corresponding to rings a, b of Figure 3 as
explained in connection with that Figure. The corresponding terminal of M however

page_text: instead of being connected directly to the same commutator segment passes throughout
through a collector ring I mounted on the shaft of the machine so as to revolve with
coil M and having a fixed brush as shown which connects with a variable resistance L
and thence by means of a fixed brush and revolving contact ring with the commutator C.
For convenience I employ the ring 2 which permits connection of the work with said
revolving commutator.
The variable resistance L is in the present instance made up of a coil having a large
counter-electro motive force when traversed by alternating. currents which effect is
produced by winding said coil upon a mass of iron in a way well understood in the
art. Any other resistance might be used in place of this counter-electro motive force
coil or kicking coil. I prefer a resistance such as indicated because it does not absorb
energy to the same extent as an ordinary resistance and is smooth in its action when
the variation of action is produced by any of the ordinary means known in the art as
for instance by shifting the position of the core with relation to the coil. Any adjust-
ment of this coil will obviously affect only the circuit of the coil M. By the adjust-
ment of this coil the machine may be made to act more or less like a shunt machine in
accordance with the will of the operator.
The particular arrangement shown possesses also the advantage that the number of
leads heretofore necessary between the welding table and the dynamo machine is
lessened. Where a rheostat is employed for controlling the dynamo it is obvious that
there must be two connections from such rheostat to the welding table where the
rheostat is within reach of the operator and that in addition there must be the two
leads from the armature to the primary of the welding coil. By connecting the
variable resistance L, as shown to the brush bearing on the ring 2 and by employing
the auxiliary ring 1 and fixed brush I am enabled to obtain the same regulation by
the use of the additional lead only which connects the variable resistance with the
fixed brush for ring 1.
It is obvious that in conjunction with the kicking coil the effects produced by the
coil S placed similarly to S' of Figure 5 may be employed.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed as communicated to me by
my foreign correspondent I declare that what I claim is :-
First In a dynamo electric machine the combination with the field magnet coil fed
by an armature coil in circuit with the work, of a separate exciting source feeding the
same field magnet coil in multiple with the said armature coil.
Second The combination of a transformer whose primary is in the uncommuted
portion of the circuit for the armature of the dynamo, a field magnet coil in a locally
commuted portion of said circuit and in series with the primary, and an exciter
armature coil operated in a field excited by its own currents and also connected to the
field magnet coil as and for the purpose described.
Third The combination with a transformer for supplying large volume electric
currents of a dynamo machine having a work circuit armature coil in series with
the primary of the transformer and a separate exciter connected in multiple with
the first to the field magnet exciting coil, as and for the purpose described.
Fourth In a dynamo electric machine, the combination with a work circuit
coil, of an exciter coil, a commutator between the same and the field coil, a
collector ring between a terminal of the exciter coil and the commutator and a
variable resistance between the collector brush for said ring and the commutator.
Fifth In a dynamo electric machine the combination with the work circuit
coil connected to the work through a suitable collecting ring, of an exciting
armature coil connected to a separate collecting ring and a variable reactive coil
in the connection from the brush of said ring to the circuit of the first named
coil as and for the purpose described.
Sixth-In, a dynamo electric machine, the combination with two revolving
armature coils, of a field magnet coil and a commutator to which one terminal of

page_text: each coil is connected collector rings to which the opposite terminals of the coils
are connected and a third ring connected to the opposite side of the commutator
as and for the purpose described.
Dated this
£ Tuna 1000
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, Agents for the Applicant.