Improved Means and Apparatus for Commutating Electric Currents.
Year: 1891

page_text: Date of Application, 9th Oct., 1891
Complete Specification Left, 9th Aug., 1892-Accepted, 8th Oct., 1892
PROVISIONAL SPECIFICATION.
Improved Means and Apparatus for Commutating Electric Currents.
I, SEBASTIAN ZIANI DE FERRANTI, of 120 Fellows Road, Hampstead, in the
County of Middlesex, Electrician, do hereby declare the nature of this invention to
be as follows:-
This invention has for its object improved means and apparatus for commutating
electric currents.
The general arrangement is as follows: Upon the circuit of an alternating current
dynamo, at any station where I may require a commutated current, I arrange a
transformer by which I reduce to a conveniently low pressure, a portion of the main
high pressure current sufficient to drive a synchronising motor of small power.
This motor gives motion to the barrel of a commutator.
Another transformer on the main circuit, suitable to supply the current required
to be commutated, is connected with the strips of the commutator barrel.
The commutated current is led away by brushes in contact with the commutator
barrel. The whole is arranged so that each strip of the commutator when positive
is in contact with one brush and when negative is in contact with the other brush.
Means are provided for bringing the motor in the first instance to the syn-
chronising speed and then it continues to run at this speed for an indefinite time
by power derived from the current from the transformer by which it is supplied.
The rectified or commutated current is most useful as applied to feeding arc
lamps in series from a transformer (preferably of constant current or as much self
regulating as possible) which in its turn receives its current from the omnibus bar
in an alternate current parallel generating station.
The current from the commutator is ordinarily of an intermittent but direct
nature much like that obtained from a Brush or Thomson Houston arc dynamo.
The apparatus may be arranged to feed tram cars or railways and may be placed
on the motors, by the side of the road or in the generating station.
It may be arranged to charge batteries but it is not so suitable for this purpose
as for the running of motors or are lighting as explained above.
Nevertheless a near approach to continuity may be obtained by the supply of a
circuit from several commutators supplied by suitably adjusted converters all on
the same main circuit.
The apparatus may be arranged to commutate a quantity current; in which case
it is modified so as to provide ample conductivity when the current wave is strong
and a sharp make and break at the beginning and end of the wave when the current
is weak.
In some cases the magnets of the synchronous motor may be steel permanent
magnets. In others they may be electro magnets. In the latter case the magnets
may be excited from the exciting current in the station if the commutator is placed
there. If it is at a sub-station they may be fed from an accumulator or battery
This may be in duplicate and can be placed in the commutated current circuit for
charging. Or the magnets may have a double winding one being fed from a battery
during synchronising and the other being fed by the commutated current during
work.
Or a small dynamo may be fixed on the shaft to excite the motor magnets when
once the apparatus is brought up to speed.
The armature is more preferably without iron and of strip copper similar to that
in my ordinary alternating dynamos either of a zigzag form of winding or of

page_text: separate bobbins
; or the armature may be of any suitable ordinary pattern with an
iron core, plain circular or with projecting poles.
The motor may be so arranged that it forms a non-synchronous motor for starting
by means of a variable phase and two windings until it is up to speed and then
becomes or is made synchronous. Either the moving or standing coils may be
short circuited and have current induced in them instead of being separately
excited. Or the motor may have a commutator which enables the motor to start
from rest and then gives a direct current to excite the magnets, or can be cut out of
circuit when up to speed. In some of the above cases the motor magnets may be
made of laminated iron.
The apparatus may be run up to speed by means of a non-synchronous motor of
any of the well known forms, fed from the alternating current. Or by the con-
tinuous current obtained from a battery or from the exciting circuit if in the
station. It may also be satisfactorily started by means of a small turbine or
water motor.
If at the station this water may be obtained from the feed pumps or from a steam
injector, or from a vessel containing water with steam pressure on top.
It may also be got up to speed by a steam turbine but in this case it is desirable
to gear down the speed to the commutator shaft, or the speed may be got up by
a steam, gas, water or hot air engine, or any similar apparatus.
Hand or foot multiplying gear may in some cases be advantageously used, or the
motors may be run by any of the well known methods from any moving body.
It is desirable to have a special transformer supplying low pressure current to
run the motor portion; but the current fed out from the apparatus may be first
used for this purpose, but special precautions have then to be taken to insulate the
apparatus.
The commutator itself is made in two parts one of which takes the current by
means of a brush or collector from one pole of the current source and the other
receives current from the other pole the segments come in between each other and
collecting brushes press upon these. The number of segments of the commutator
and also its speed must be arranged to suit the periodicity of the current to be
worked with.
The commutator is preferably a hollow one with air insulation, it may form its
own air blast by running it at a high surface speed or it may have an internal fan
or may be encased and have an exhausting fan to make a draft between the segments
for the purpose of blowing out an arc. The whole or a portion of the commutator
may run in oil or other suitable insulating medium.
One or more separately insulated filling pieces may be placed between each of the
segments to hold up the brushes in the break and assist the draft between the
segments.
An auxiliary commutator may be placed on the same shaft where the current to be
collected is a heavy one. This second commutator may be made a solid one with
wire or gauze brushes of large conductivity it is however desirable to have the
commutator so arranged that there is ample clearance to prevent the brushes over-
lapping opposite pole segments. It is convenient to form this commutator like an
ordinary continuous current dynamo commutator, using some of the segments as
dummies or spacing and others as current carriers, for example four of the segments
may be dummies, then four connected to one pole, four dummies, then four to other
pole and so on round the commutator.
Heavy brushes may then be used and the surface of the commutator is uniform
even and solid all round, which will give an even mechanical wear which would not
be obtained if the segments or spaces varied in width.
As applied to tram cars and railways the motors on the cars may by the ineans
described be supplied with approximately a continuous current whilst the electric
mains along the line supply an alternating current.
Or commutating apparatus may be arranged at sub-stations along the line.
Where heavy currents are to be dealt with it is advisable to employ two com-

page_text: mutators, the barrel of one revolving at a comparatively slow surface speed and
the other at a much higher surface speed. The slow moving commutator takes by
far the greater part of the current, whilst the high speeded commutator commutates
somewhat more closely and prevents sparking..
An automatic regulating gear may be provided to fix the position of the brushes
(which may be done through the medium of a relay working an electro-magnet, or
solenoid) according to the amount of load and the consequent retardation of the
phase of the current. This is for use where the load varies on the commutator.
The sparking at the commutator may be prevented by means of a jet of oil
driven on to the edge of the brushes where the sparking takes place, and so drowning
the spark. This jet may be applied from the inside of a hollow commutator, and
will squirt through the segments as the openings come opposite the jet. This jet
may be supplied by a small pump, preferably on the same side of the shaft as the
commutator. In this case the commutator must be closed in.
In case neither of the above plans are adopted I may use a running roller under-
neath the commutator and pressed against it by a spring, which roller will dip into
the oil, rotate, and lubricate the surface of the commutator.
When it is desired to get a specially even continuous current, I use two or more
commutators or sets of segments on the same shaft fed with currents whose phases
are at an angle to each other, and which may be obtained from an ordinary
alternating current by means of condensers, or progressive winding upon trans-
formers. The currents from the commutators are collected in parallel and so form
an even current.
Dated this 9th day of October 1891.
CARPMAEL & Co.,
Agents for the Applicant.
COMPLETE SPECIFICATION.
Improved Means and Apparatus for Commutating Electric Currents.
I, SEBASTIAN ZIANI DE FERRANTI, of 120 Fellows Road, Hampstead, in the
County of Middlesex, 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 has for its object improved means and apparatus for commutating
electric currents.
The general arrangement is as follows. Upon the circuit of an alternating
current dynamo, at any station where I may require a commutated current,
arrange a transformer by which I reduce to a conveniently low pressure, a portion
of the main high pressure current sufficient to drive a synchronising motor of small
power. This motor gives motion to the barrel of a commutator.
Another transformer on the main circuit suitable to supply the current required
to be commutated, is connected with the strips of the commutator barrel.
The commutated current is led away by brushes in contact with the commutator
barrel. The whole is arranged so that each strip of the commutator when positive
is in contact with one brush and when negative is in contact with the other brush.
Means are provided for bringing the motor in the first instance to the
synchronising speed and then it continues to run at this speed for an indefinite
time by power derived from the current from the transformer by which it is
supplied.
Figure 1 of the drawings annexed is an end elevation of the motor commutator.
Figure 2 an opposite end view showing the starting motor and Figure 3 a side
elevation.
Figure 4 shows another form of starting motor to replace that shown in
Figura 9

page_text: a are circular magnet poles of the synchronous motor. the armature which
may be of the same construction as in my Patent of 1882. c the commutator on the
axis 61 of the armature b. dd' are rings on the axis upon which bear brushes e e
to supply the commutator with alternating current. are brushes bearing upon
the segments of the commutator and conveying away the commutated current-
alternate segments being in connection with d and d-9 is the starting motor which
may be a small ordinary continuous current motor-which may be fed with current
from a secondary battery.
The coils of the magnet a of the synchronous motor may also be fed with current
from a secondary battery.
The armature may be supplied with alternating current from a transformer fed
from the source of alternating current through brushes in the ordinary way.
The starting motor shown in Figure 4 is worked by jets of water issuing from
nozzles acting upon buckets upon the motor axis.
The rectified or commutated current obtained is most useful as applied to feeding
arc lamps in series from a transformer (preferably of constant current or as much
self regulating as possible) which in its turn receives its current from the omnibus
bar across the mains in an alternate.current parallel generating station the con-
struction of transformers to act in this manner is well understood.
An inductive resistance in series with the current to be commutated will effect
the same object as making the transformer in such a manner as to give constant
current.
The current from the commutator is ordinarily of an intermittent but direct
nature much like that obtained from a Brush or Thomson Houston arc dynamo.
The apparatus may be arranged to feed tramcars or railways and may be placed
on the motors, by the side of the road or in the generating station.
It may be arranged to charge batteries but it is not so suitable for this purpose
as for the running of motors or are lighting as explained above.
Nevertheless a near approach to continuity may be obtained by obtaining the
circuit from several commutators supplied by suitably adjusted converters all on
the same main circuit.
The apparatus may be arranged to commutate a quantity current; in which case
it is modified so as to provide ample conductivity when the current wave is strong
and a sharp make and break at the beginning and end of the wave when the current
is weak-one commutator with light brushes to make an accurate contact and break
and the other with heavy brushes make contact during a shorter period coinciding
with the strongest period of the pulsation of current.
In some cases the magnets of the synchronous motor may be steel permanent
magnets. In others they may be electro magnets as before described. In the
latter case the magnets may be excited from a continuous source of exciting current
in the station if the commutator is placed there. If it is at a sub-station they may
be fed from an accumulator or battery. This may be in duplicate and can be
placed in the commutated current circuit for charging. Or the magnets may have
a double winding one being fed from a battery during synchronising and the other
being fed by the commutated current during work.
Or a small dynamo may be fixed on the shaft to excite the motor magnets when
once the apparatus is brought up to speed as shown in the drawings annexed.
The armature is more preferably without iron and of strip copper similar to that
in my ordinary alternating dynamos either of a zigzag form of winding or of
separate bobbins or the armature may be of any suitable ordinary pattern with an
iron core, plain circular or with projecting poles.
The motor may be so arranged that it forms a non-synchronous motor for starting
by means of a variable phase and two windings until it is up to speed and then
becomes or is made synchronous. Either the moving or standing coils may be
short circuited and have current induced in them instead of being separately
excited. Or the motor may have a commutator which enables the motor to start
from rest and then gives a direct current to excite the magnets, or can be.cut out of

page_text: circuit when up to speed. In some of the above cases the motor magnets may be
made of laminated iron.
The apparatus may be run up to speed by means of a non-synchronous motor of
any of the well known forms, fed from the alternating current. Or by the
continuous current obtained from a battery or from the exciting circuit if in the
station. It may also be satisfactorily started by means of a small turbine or water
motor as for example in the way shewn at Figure 4.
If at the station this water may be obtained from the feed pumps or from a steam
injector, or from a vessel containing water with steam pressure on top.
It may also be got up to speed by a steam turbine but in this case it is desirable
to gear down the speed to the commutator shaft, or the speed may be got up by a
steam, gas, water or hot air engine, or any similar apparatus.
Hand or foot multiplying gear may in some cases be advantageously used, or the
motors may be run by any of the well known methods from any moving body.
It is desirable to have a special transformer supplying low pressure current to
run the motor portion; but the current fed out from the apparatus may be first
used for this purpose, but special precautions have then to be taken to insulate the
apparatus.
The commutator itself is made as hereinbefore described in two parts one of
which takes the current by means of a brush or collector from one pole of the
current source and the other receives current from the other pole the segments
come in between each other and collecting brushes press upon these. The number
of segments of the commutator and also its speed must be arranged to suit the
periodicity of the current to be worked with.
The commutator is preferably a hollow one with air insulation as shewn, it may
form its own air blast by running it at a high surface speed or it may have an
internal fan or may be encased and have an exhausting fan to make a draft between.
the segments for the purpose of blowing out an arc. The whole or a portion of the
commutator may run in oil or other suitable insulating medium.
One or more separately insulated filling pieces may be placed as shewn between
each of the segments to hold up the brushes in the break and assist the draft
between the segments by acting as fans..
An auxiliary commutator may be placed on the same shaft where the current to
be collected is a heavy one. This second commutator may be made a solid one
with wire or gauze brushes of large conductivity it is however desirable to have the
commutator so arranged that there is ample clearance to prevent the brushes over-
lapping opposite pole segments. It is convenient to form this commutator like an
ordinary continuous current dynamo commutator, using some of the segments as
dummies or spacing and others as current carriers, for example four of the segments
may be dummies, then four connected to one pole, four dunimies, then four to other
pole and so on round the commutator.
Heavy brushes may then be used and the surface of the commutator is uniform
even and solid all round, which will give an even mechanical wear which would not
be obtained if the segments or spaces varied in width.
As applied to tram cars and railways the motors on the cars may by the means
described be supplied with approximately a continuous current whilst the electric
mains along the line supply an alternating current.
Or commutating apparatus may be arranged at substations along the line.
Where heavy currents are to be dealt with it is advisable to employ two com-
mutators, the barrel of one revolving at a comparatively slow surface speed and
the other at a much higher surface speed. The slow moving commutator takes by
far the greater part of the current, whilst the high speeded commutator commutates
somewhat more closely and prevents sparking.
An automatic regulating gear may be provided to fix the position of the brushes
(which may be done through the medium of a relay working an electro-magnet, or
solenoid) according to the amount of load and the consequent retardation of the
phase of the current. This is for use where the load varies on the commutator.

page_text: The sparking at the commutator may be prevented by means of a jet of oil driven
on to the edge of the brushes where the sparking takes place, and so drowning the
spark. This jet may be applied from the inside of a hollow commutator, and will
squirt through the segments as the openings come opposite the jet. This jet may
be supplied by a small pump, preferably on the same side of the shaft as the
commutator. In this case the commutator must be closed in.
In case neither of the above plans are adopted I may use a running roller
underneath the commutator and pressed against it by a spring, which roller will
dip into the oil, rotate, and lubricate the surface of the commutator.
When it is desired to get a specially even continuous current I use two or more
commutators or sets of segments on the same shaft fed with currents whose phases
are at an angle to each other, and which may be obtained from an ordinary
alternating current by means of condensers, or progressive winding upon trans-
formers. The currents from the commutators are collected in parallel and so form
an even current.
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. The combination of a commutator fed with alternating current a synchronous
motor driving the commutator and itself driven by a portion of the alternating
current the balance being given off as direct current.
2. The combination with a high pressure alternating system of a synchronous
motor supplied with current through a transformer a commutator carried or driven
by the synchronous motor and a separate transformer or separate transformer
winding for supplying current to the commutator.
3. The combination with a high pressure alternating system of approximately
constant potential, of a regulating transformer (such as herein described) a
synchronous motor a commutator carried or driven by the synchronous motor
which commutates the current from the regulating transformer and a circuit of
series arc lamps.
4. The use of an inductive resistance in series with the current to be commutated
when this is obtained from a parallel or constant E.M.F. circuit.
5. Where heavy currents have to be collected the combination of 2 commutators
in parallel upon an axis driven by a synchronous motor one made to ensure a rapid
and certain break and the other with large conducting surface making contact
during a lesser portion of each phase for conveying the heavy current flowing
during that time.
6. In an electro locomotive engine the combination of a continuous current
driving motor, fed with a commutated current obtained from an alternating one by
means of a synchronous motor commutator upon the car or along the roadway.
7. For obtaining a current as nearly continuous as possible the use of several
commutators all driven by the same synchronous motor (arranged upon the same
shaft) and fed with alternating currents varying slightly in phase the one from the
other. These currents being commutated and collected in parallel for any useful
purpose.
8. The means and apparatus substantially as hereinbefore described for com-
mutating alternate electric currents.
Dated this 9th day of Avonst 1809
CARPMAEL & Co.,
Agents.