Improvements in Alternate Current Rectifiers, and Apparatus connected therewith.
Year: 1894

page_text: Date of Application, 6th June, 1894
Complete Specification Left, 6th Mar., 1895-Accepted, 11th May, 1895
PROVISIONAL SPECIFICATION.
Improvements in Alternate Current Rectifiers, and Apparatus
connected therewith.
SEBASTIAN ZIANI DE FERRANTI, Charterhouse Square in the County of
London, Electrical Engineer, do hereby declare the nature of this invention to be
as follows:-
:-
This invention has for its object improved means of producing continuous currents
specially applicable to arc lighting. In a Patent granted to me and numbered 17220
of 1891 apparatus for commutating alternating current is described. According to
my present invention where I wish to rectify a high tension current I couple two
or more commutators all on the same shaft and run by the same synchronous motor
in series. In order that this may be beneficially done it is necessary to feed each
commutator from a separate coil on a converter or from independent converters.
The commutator collectors are then coupled in series and a current of any desired
tension may be obtained. The commutators are preferably fed by self-regulating
converters or from circuits in which is a large amount of inductive resistance or
with the current limited in quantity by some other means. According to another
method I obtain the same useful result by using one commutator of special
construction fed from several independent coils or circuits, the resulting commu-
tated current being given off on two collector rings. Where such a commutator is
made for rectifying the current given off by two coils of a constant current trans-
former working for example at 50 cycles per second and the commutator running
at 1500 revolutions per minute, I place a collector ring at one end of the apparatus;
on to this are coupled two segments of the commutator, which extend nearly half
across the face of the commutator, and which occupy each nearly a quarter of the
circle. At the other end of the commutator, I place segments exactly similar in
shape and size and occupying the same relative position, and connected to a
collector at their end. Two quarters of the circle of the whole width of the
commutator are thus occupied, I fill up the remaining two quarters of the circle,
by sections unattached to any collectors and extending across the whole width of
the collectors, a pair of brushes set at an angle of 90 degrees bear upon the left
hand side of the commutator, and a corresponding pair make contact with the
sections on the right hand side. The right hand pair of brushes are connected
with one coil of a transformer and the left hand, pair with another coil or circuit.
Brushes also press on the collector rings at each side and serve to take off the
commutated current. Commutators may thus be constructed for two three or
more circuits, and giving off one continuous current. I sometimes prefer to use a
condenser in series with the current to be commutated to limit the amount flowing
besides neutralising the self induction of the circuit. I prefer to build the commu-
tators according to the method described in the Patent, already granted to me as
cited above, in which air is used as the insulator between the segments, and in
which the brushes are supported whilst passing from one segment to another by
means of insulated metal supports. The commutators I sometimes fix upon the
shafts of the alternators in an electric light station; instead however of feeding
them direct from the machine I prefer to pass the current to be commutated and
which is generated by the machine or others in parallel with it through an inductive
resistance, condenser, self regulating transformer, or a combination of these to limit
the amount flowing, and to prevent accidents by short circuiting at the commutator.

page_text: I also construct a special form of alternator for running arc lamps in series, and
fitted with a commutator as above described. Where an electro motive force of
say not more than 1000 or 1200 volts is required I use a single commutator_and
wind the armature with a single circuit. Where however it is desired to produce
a higher tension I prefer to use two or more commutators, and wind the armature
in two or more circuits, coupling the coils and commutators, as already described,
or I may use several separate circuits in the armature each finding its own pair of
brushes on a commutator; arranged as already described to take several alternating
currents and give off one continuous current on two collector rings, according to
any of the above arrangements. I may make my arc lighter with standing armature
and revolving fields which under certain circumstances is very advantageous.
I prefer to build these machines in such a way that the air clearance is very small,
and the resistance of the magnetic circuit in armature and magnets reduced to a
minimum. In order that they may give only a limited quantity of current I wind
the fields with a number of turns only slightly in excess of the turns in the
armature so that when the current rises in the armature it demagnetises the field
and acts to stop more being generated.
According to one method, I construct self regulating converters by putting a
primary and secondary winding in the form of flat coils, Iving in a horizontal plane
around a vertical core of laminated iron which has its circuit closed on either side
of the coils. The lower coil is fixed and the upper one which is connected to a dash
pot is free to nove upwards.
Where necessary a counterbalance lever with shifting or variable weight is
added to act to reduce the weight of the moving coil.
According to another method I hang the coils in a vertical plane as by so doing
they are more easily held and better ventilation is obtained. They are then
suspended by vertical levers attached to knife edges or to trunnions about their
centres; the top ends of the vertical levers have horizontal levers attached to them
with moveable or variable weights which enable current to be regulated as desired.
In order to compensate for the diminished repulsion between the fixed and moveable
coils as they get further apart, 1 arrange the counterbalance weights on levers at
an angle so that the weight tending to force the coils together diminishes as the
coils become further apart. Better regulation of the current is thus obtained.
In either the horizontal or vertical pattern above described I prefer to wind two
coils for every converter and place them on separate arms of the magnetic circuit,
the coils being rigidly fixed together in pairs and moving in the same direction.
A much less length of wire is thus obtained for the same result and the coils being
of less depth are more easily ventilated.
Dated this 6th day of June 1894.
COMPLETE STEIFICATION.
Improvements in Alternate Current Rectifiers, and Apparatus
connected therewith.
SEBASTIAN ZIANI DE FERRANTI, Charterhouse Square in the County of
London, Electrical Engineer, 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 has for its object improved means of producing currents continuous
in direction, which are specially applicable to arc lighting.
Figure 1 is a diagram showing arrangement of two commutators fixed upon the
same shaft, and driven by a synchronous motor, feeding a circuit of arc lamps from
two coils of a constant current transformer.

page_text: Figure 2 shows the same result accomplished by one commutator, feeding in a
similar manner.
Figure 3 is a diagram showing alternators working in parallel at a central
station supplying a network for incandescent lighting and showing four different
methods of feeding arc lamps through commutators, which may be fixed on one or
several of their shafts.
-
Figure 4 is a self-regulating constant current alternator with standing armature
and several separate circuits, each one of which is commutated for a circuit of
arc lamps.
Figures 5 and 6 are views of a constant current transformer of simplified form.
Figures 7 and 8 are views of a constant current transformer in which the coils
are placed vertically to improve the ventilation and facility of suspension.
Figures 9, 10 and 11 are elevation, plan and end elevation of an improved form
of constant current transformer with coils on both limbs of the magnetic field, with
coils placed vertically for facility in hanging and ventilation.
In a Patent granted to me and numbered 17220 1891 apparatus for commuting
alternating current is described. According to my present invention where I wish
to rectify a high tension current I couple two or more commutators c and c¹
Figure 1 in series, all mounted on the same shaft and run by the same synchronous
motor. In order that this may be beneficially done it is necessary to feed each
commutator c or c¹ from a separate coil a or a¹ of a converter, or from independent
converters in order to limit the maximum electro motive-force dealt with by each
commutator, thus in Fig. 1 the current from a self-regulating transformer b is
supplied by the secondary coils a and a to two commutators c & c¹ to an arc light
circuit, each of the commutators dealing with one half the electro motive force.
The current enters the commutator c by brush i on to segment h. This is in
metallic connection with the continuous ring d, it then leaves by brush k traverses
through the arc lighting circuit to commutator c' which it enters by brush k¹, this
The current then flows to
brush being in connection with the continuous ring d¹.
segmenty leaves the commutator by brush j traverses the secondary coil a¹ back to
commutator c¹ by means of the brush j¹ on to the segment h¹. From here it flows
to continuous ring d leaves the commutator c by brush k², flows back to commu-
tator c, enters at brush k³ on to continuous ring ³, flows to segment g², leaves the
commutator by brush and back to coil a, these commutators being run by a
synchronous motor a reversal takes place of the connections for each reversal of
the alternator-thus the four part commutator as shown, running at 1,500 revolutions
per minute will rectify a current of 50 periods or 6,000 reversals per minute and
maintain a current of continuous direction in the arc lighting circuit.
The commutators are preferably fed by self-regulating converters or from circuits
in which is a large amount of inductive resistance, or with the current limited in
quantity by some other means.
According to another method I obtain the same useful result by using one
commutator, Figure 2, of special construction, fed from several independent coils
or circuits. The resulting commuted current being given off on two collector rings.
Where such a commutator, c, Fig. 2 is made for rectifying current given off by the
two coils a and a¹ of constant current transformer : working for example at
50 cycles per second. The commutator e running at 1,500 revolutions per minute
being driven by a synchronous motor, I place a collector ring & Figure 2, at one
end of the apparatus. On to this are coupled two segments f, of the cominutator
which extend nearly half across the face of the commutator and which occupy
nearly one quarter of the circle. At the other end of the commutator I place
segment g exactly similar in shape and size and keeping the same relative position
and connected to a collector d' at their end. Two quarters of the circle of the
whole width of the commutator are thus occupied. I fill up the remaining two
quarters of the circle by sections h unattached to any collectors and extending
across the whole width of the collectors but separated by an air gap from the
continuous rings. A pair of brushes and Figure 2 set at an angle of 90° bear

page_text: upon the section
and the section h immediately in front of it on one side of the
commutator. The corresponding pair of brushes ; and j' also at 90° make contact
with the sections on the other side of the commutator with the section h and f.
The brushes and are connected to one secondary coil of a constant current
transformer and the brushes ; and j' with a second secondary coil of the same
transformer. Two further brushes k and k¹ press upon the continuous rings on
either side d and d¹, these brushes are connected to the arc light circuit and serve
to take off the commuted current. In this way each pair of brushes upon the
commutator only deals with a limited electro motive force. Commutators may
thus be constructed supplied by two, three or more sources of current but giving
-off one continuous-current.
I prefer to build the commutators as shown in diagrams 1 and 2 according to
the Patent already granted to me as cited above, in which air is used as the
insulator between the segments and in which the brushes are supported whilst
passing from one segment to another by means of insulated metal supports.
At Figure 3 show a diagram of a general arrangement of an alternating
station in which three alternators A', A2 and A³ are feeding on to a high tension
main B and B which is feeding several different circuits. Circuit C is feeding low
tension networks D and D' through transformers T and T' in the ordinary manner.
Circuits E, F, and G, H, are feeding four arc lighting circuits L, L², L³, L^
by means of rectified current from commutators M1, M2, M3, M4, the com-
mutators being fixed direct on the shaft or driven by means of positive
gearing from the alternators, depending upon the periodicity. Instead however
of feeding M1 M2 M3 M' direct from the machine I prefer to pass the current to
be commutated, and which is generated by the machine or machines in parallel or
another machine, as shown in circuit E, through a non-inductive resistance i which
prevents the current through the commutator exceeding a certain value, or as
already shown in circuit F, through a condenser J, which also limits the amount
of current passing. Or through, as in circuit H a self-regulating converter K, or
as in circuit G a condenser J and a transformer K combined so as to limit the
amount of current flowing to the rectifier and thus to the arc lighting circuit and
so prevent accidents by short-circuiting at the commutator.
In
At Figure 4 I show a special form of self-regulating alternator, with standing
armature A and revolving field magnets B, for running arc lamps in series.
order to supply the arc lamps with a current continuous in direction it is fitted
with one or more commutators C as before described. When an electro motive
force of not more than 1,00 to 1,200 volts is required I use a single commutator
and wind the armature A in a single circuit, where however it is desired to
produce a higher tension I prefer to use two or more commutators C¹, C², C³ so as
to limit the pressure to each commutator to about the above mentioned electro
motive force and I wind the armature in two or more circuits L1, L2, L³, shown at
Figure 4, coupling the coils and commutators as already described. Or I may
use several circuits in the armature each with its own pair of brushes on one
commutator arranged as already described in Figure 2, to take several alternating
currents and give off one continuous current on to two collector rings, according to
any of the before mentioned arrangements.
I may prefer to make my arc lighting alternator with standing armature A,
Figure 4 and revolving fields B, which under certain circumstances is very advan-
tageous. I prefer to build these machines in such a way that the air clearance is
very small and the resistance of the magnetic circuit in the armature and magnets
reduced to a minimum. In order that the machine may only give a limited
quantity of current I wind the field magnets with such a number of ampere turns
that they are only slightly in excess of the turns of the armature so that when the
current rises in the armature it may demagnetise the field and thus limit the output
of the machine.
In Figures 5 and 6 I show a simple form of self-regulating converter by using
one primary coil a and a secondary winding in the form of flat coils lying in a

page_text: horizontal plane around a vertical core c of laminated iron which has its circuit
closed by limbs e and d of laminated iron surrounding the coils. The lower coil a
is fixed, and the upper one b suspended and connected to a dashpot through the
guide rods i, is free to move upwards. Where necessary a counter balance lever m
with a shifting or variable weight n is added so that the weight of the moving coil
may be added to or reduced so that adjustment in the output of the trausformer
may be given.
In Figures 7 and 8 I show another form of self-regulating converter in which I
support the coils a a¹ b in a vertical position as by so doing they are more easily
held and better ventilation is obtained. The primary coils a and a' are suspended
by vertical levers and attached to knife edges e and e¹ or to trunnions about
their centres. The top ends of the vertical levers and have horizontal
levers m and m¹ attached to them with movable or variable weights n and n' which
enable current to be regulated as desired. The upright levers and being
carried on knifed edges c and c¹. In order to compensate for the diminished
repulsion between the fixed coil b and the movable coils a and a¹ as they get
further apart I arrange counter balance weights p and pl on levers q & q' at an
angle so that the weight tending to force the coils a and a¹ together diminishes as
these coils become further separated from the coil and better regulation of the
current is obtained. The dashpot f is fitted to prevent sudden fluctuations of
the coil.
In either the horizontal or vertical pattern above described I prefer, as shown
in Figures 9, 10 and 11 to wind two sets of coils for every converter and place
them on separate arms of the magnetic circuit, the coils being rigidly fixed
together in pairs and moving in the same direction. The same result is thus
obtained by using a considerably less length of wire and the coils being less in
depth are more easily ventilated. Figures 9, 10 and 11 show such an arrangement.
a and a² are fastened
a, a', a², a³, are primary coils, 6 & 61, are two secondary coils.
together by means of an insulated band c which is sub-divided at d². Both sets of
coils a and a², a¹ and a³, are carried upon upright arms and the coils being
supported in a similar manner to those as described in Figures 7 and 8, the general
arrangements being otherwise the same.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is-
1. In apparatus for commutating alternating currents of electricity two com-
mutators run from a synchronous motor each fed from a separate coil in a
transformer, the collecting rings being so coupled that the alternating commuted
currents are given off in series for external use.
2. In apparatus for commutating alternating currents, feeding two commutators
run from a synchronous motor, each from a separate coil in a self-regulating
transformer, the collecting rings being so coupled that the alternating commutated
currents are given off in series for running a circuit of series arc lamps.
3. In apparatus for commutating alternating currents the use of a commutator
to which two or more separate currents are supplied, and which gives, off one
direct current being the result of the other two currents commutated in series.
4. In apparatus for commutating alternating currents the use of a commutator
fed from two or more separate coils of a self-regulating transformer and which
gives off one commutated current which is equal in quantity to the quantity
produced by one coil and in tension to the electro motive forces of the two coils
in series.
5. In apparatus for commutating an alternating current the use of a commutator
or commutators fed from two or more independent circuits of limited quantity and
which give off the current equal in quantity to the limited quantity of the source
of supply and in tension. equal to the electro motive force in series of the said
supplies.

page_text: 6. In electric central stations producing alternating current of approximately
constant potential the use of a commutator or commutators run direct or by
gearing from one or more of the alternators which are fed with current limited in
quantity either by a self-regulating transformer, a self-regulating transformer with
a condenser in series; from the main supply with a condenser in series, or from the
main supply with self-induction in series, so as to limit the current and which give
off a commutated current limited in quantity for feeding series circuits.
7. A dynamo electric machine capable of giving alternating currents of limited
quantity and with a standing armature, each circuit of which supplies a commutator
either run direct on its own shaft or by gearing therefrom, which commutators convert
the alternating current into direct current of limited quantity for supplying series
circuits.
8. Dynamo electric machines arranged to give a limited quantity of current
running commutators direct or by gearing which commute the alternating currents
produced and give them off for use on series circuits.
9. In converters which are designed for giving a limited quantity and variable
electro motive force according to the work to be done, the use of a vertical core
of laminated iron and side arms and ends of laminated iron to make up the circuit,
a fixed coil surrounding the core and a movable coil above the fixed coil controlled
by a counter balance weight and dashpot which will be repelled by the fixed coil
on the quantity of current becoming too great, or which will approach it as the
current diminishes.
10. In transformers designed to give an approximately constant quantity of
current from a constant electro motive force circuit, the use of a horizontal
laminated core surrounded by a yoke and arms of the same material and fitted with
a fixed coil and two movable coils hung upon levers and controlled by counter-
balance weights and dashpot and in which the increased current causes a repulsion
in the movable coils and consequent diminution.
11. In transformers designed to give an approximately constant quantity of
current the use of two circular or approximately circular magnetic cores placed
horizontally and with their ends connected by suitable yokes of laminated iron, a
fixed coil being placed upon each of the said cores and two movable coils being
hung round each of the said magnetic cores which coils are controlled by means of
weights and dashpots in such a way that they recede from the said fixed coils upon
an increase of current taking place and so maintaining an approximate regulation
of current given off by the transformer.
12. In alternating current self-regulating transformers with movable coils the
use of tumbler weights or springs arranged in such a manner that as the movable
coils recede from the fixed coils so the mechanical force tending to pull them
together diminishes in amount with the distance from the fixed coils.
13. Apparatus for transforming and commutating alternating current substan-
tially as described and illustrated.
14. Alternating current transformers fed from a constant electro motive force
source and giving an approximately constant quantity with varying electro motive
force substantially as described and illustrated.
15. In an alternating current system of distribution with constant electro motive
force apparatus substantially as described and illustrated, for the purpose of feeding
series circuits with direct current and limited quantity.
Dated this Sixth day of March One thousand eight hundred and ninety-five.