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Патент USA US2055304

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SePt- 22, 1936-
G. M. PESTARINI
2,055,304
CONTROL OF DIRECT CURRENT ELECTRIC MOTORS
Filed June 24, 1955,
§ Sheets-Sheet 1
INVENPOR
Giuseppe M.Pestarini
By W M
ATTORNEY
Sept. 22, 1936-
G. M. PESTARINI
2,055,304
CONTROL OF DIRECT CURRENT ELECTRIC MOTORS
Filed June 24, 1935
‘
ZSheets-Sheet 2
ImwrOR'
Giuseppe M. Postal-1:11
ATTORNEY
Patented Sept. 22, 1936
2,055,304
UNITED STATES PATENT OFFICE
2,055,304
CONTROL OF DIRECT
(gémmivr ELECTRIC
MOT O
Giuseppe Massimo Pestarini, Sheffield, England
Application June 24, 1933, Serial No. 677,522
In Great Britain July 27, 1932
12 Claims. (Cl. 171-123)
This invention relates to the control of direct
current electric motors and has for its object to controlled motors and the actual electromotive
provide improved arrangements for connecting to force developed by them. If, however, the open
the supply line direct current motor equipments ing and closing of the switch has to occur very fre
which are operated in connection with a rotary quently the current and mechanical shocks re
sulting from the sudden closure of a switch con
direct current transformer hereinafter referred to necting the machines to a circuit of compara
as a metadyne transformer.
tively high voltage, such, for example, as 3000
A metadvne transformer is a rotary machine volts, will result in damage to the machines. It
somewhat similar in construction to a direct cur
is, therefore, desirable to provide means whereby
10 rent dynamo electric machine in that it has an
the voltage on either side of the switch may be
brought to the same value before closure of the 10
switch takes place so as to prevent suddent varia
tion in the current occurring at the time of clo
armature with windings and a commutator
(sometimes more than one commutator) and a
stator, generally with salient poles, within which
the armature rotates. In the simplest form two
sure.
15 pairs of brushes are arranged to make contact
With this object in view according to the pres
with the commutator, one pair ‘of which form
the primary brushes by which current is led into
and out of the armature from a source of direct ,
current supply, the other pair forming the sec
ondary brushes by which the current generated
in the armature is led to one or more consumption
or load circuits. In some cases more than two
pairs of brushes are provided. The rotor is ro
tated in the magnetic ?eld due to the currents
2g
circulating in the rotor windings, and the action
of the machine is such that the current ?owing in
the consumption or load circuit or circuits is
maintained at a substantially constant value irre
spective of the resistance within limits of said
30 consumption or load circuit. The stator affords
a return path of low magnetic reluctance for the
?ux which is set up by the rotor currents. rll'he
stator is usually provided with various windings
by which magnetic ?uxes are set up which regu~
35 late the electrical and mechanical performance
of the machines.
For a fuller description of metadyne trans
formers reference is directed to the speci?cations
of French Patents No. 547,855, dated 25th Feb
ruary 1922, No. 623,438, dated 27th January 1926,
and No. 637,946, dated 25th November 1926. A.
description of the general construction and op
eration of metadyne transformers, generators and
motors treated mathematically in considerable
detail will also be found in a paper entitled “Es
quisse sur la Metadyne” by G. M. Pestarini in the
Bulletin Scienti?que A. I. M. No. 4 April 1931 oi’
50
l'Association des Ingénieurs Electricians, pub
plished by the Institut Electrotechnique Monte
?ore, Liege.
With a motor and metadyne transformer equip
ment such as above indicated the metadyne trans
former must be started into rotation and brought
up to its normal speed by some means, for exam
ple by a motor connected across the supply mains
or other auxiliary driving machine, and its pri
mary circuit must be connected to the supply line.
This may be done through a switch or circuit in
terrupter which must be closed whatever may be
60 the actual connections of the metadyne with the
ent invention means are provided for develop
ing a counter electromotive force in the meta
dyne which shall be substantially equal to the
voltage of the supply line. This may be done in
several ways.
In one method according to the invention the
20 "
stator of the metadyne transformer may be fur
nished with windings to which a current is sup
plied before the main circuit is closed and the
current in which induces a magnetic flux in the
rotor core in such a direction that, due to the ro~
tation of the rotor, an electromotive force in a
sense opposing that of the main supply is de
veloped at the primary brushes of the machine
without any circulation of current taking place
in the secondary circuit.
In a second method the windings on the stator
are such as will induce a ?ux in the rotor core in.
a direction whereby when the rotor is rotating
an electromotive force is developed at the sec
ondary brushes. If the circuit between the sec~ .
ondary brushes is closed a current will circulate
through the rotor windings by which a magnetic
flux will be induced in the core such that the ro~
tation of the rotor will develop an electromotive 4t)
force between the primary brushes as in the ?rst
arrangement, but independent of the connection
of the primary brush set to an external source
of electrical power supply. However the second
method is usually preferred as fewer ampere
turns are required on the stator to produce the
necessary electromotive force between the pri
mary brushes.
The two methods just described may in some
cases be combined, in which case the stator 60
winding must be arranged both to induce im
mediately a counter electromotive force direct
between the primary brushes and also to cause a
current to circulate in. the secondary circuit
through the rotor windings the. magnetic ?ux
due to which current develops an electromotive '
force between the primary brushes. The sum of
these two electromotive forces are together ar
ranged to be substantially equal to the line volt
age.
2
2,055,304
It is a common plan in connection with
switches'or circuit interrupters employed with
high voltages to provide an impedance shunting
the switch contacts so that the apparatus to be
connected to a high voltage line is first connected
‘ through the impedance so that the current will
gradually increase without surges or peaks from
zero to that normally transmitted through the
switch, after which the switch may be closed.
An advantageous arrangement according to
the present invention consists in combining one
or other of the methods above described with this
last mentioned arrangement of a reactance for
which purpose the reactance may_be constituted
15 by an external choke coil or an additional wind
ing on the stator of the metadyne.
Afterlthe counter electromotive force has been
made equal to the line voltage by one of the
methods above indicated a balancing relay which
W is operated by a di?erence in voltage at the two
contacts of the switch or circuit breaker may be
employed for closing or permitting the closure of
the switch, or such a relay may be employed to
give an indication that the voltages on the two
sides of the switch’ are the same, whereupon the
switch may be closed by hand or otherwise, or
the counter electromotive force may be meas
ured by an instrument-connected between the
ground and the primary brush which is joined
80 to the switch and when this is substantially equal
to the line voltage the switch may be closed,
either by the instrument or a relay, or man
ually or otherwise.
‘ In another arrangement the switch is closed
a
a predetermined time after the stator windings
have been energized, the time being so chosen
and the stator at 2. The primary brushes are
shown at 3 and 1i, and the secondary brushes at
5 and 6. The primary brush 3 is arranged to be
connected through a main switch indicated by
two lines in the conventional manner at l to a
trolley line T, and the primary brush it is ar
ranged to be connected to ground G. In the ma
jority of the ?gures the load in the secondary
circuit is indicated as’ comprising two motors 8
and a connected between the brushes 3‘ and S 10
and t and 5 respectively in the well known ?g
tire-8 connection, but in Figs. 6 and 8 the load,
also indicated as being two motors 8 and 9, is
shown as being connected to the secondary
brushes 5 and 6 in the Well known cross-connec
tion. An auxiliary driving means for starting
up the rotor is shown at 27 in Figs. 1, 2, 3, 4, 5
and 6.
v
.
Referring now to Fig. 1 the polar projections
it, H of. the stator are provided with windings 20
l2, l3 adapted to be connected through a switch
It to the source of supply T and ground G. vAs
suming that the main switch ‘I is open if switch It
is closed the polar projections l0 and H of the
stator will be excited in such a manner as to pro 25
duce a magnetic ?uxv parallel with the line a.
This magnetic flux can be considered as a result
of two components, one in line with the primary
brushes, that is to say parallel with the line b,
and the other in line with the secondary brushes, 30
that is to say parallel with the line c. If the
rotor I is rotating the conductors thereon with
which it is wound cut the magnetic ?eld in line
with the component 0 and an electromotive force
is thereby produced at the primary brushes 3 and
4, and the direction of rotation and the direc
as to enable the counter electromotive force to - tion of the current in the windings l2 and it
- is so chosen that the electromotive force thus
rise to the requisite value.‘
produced is opposed to the electromotive force
In the arrangements above described it is as
sumed that the armature is revolving, otherwise between the source of supply T and ground G
40. there will be no cutting of ,?ux by rotor con
when the switch ‘I is closed. In other words, the
potential of. the primary brush 3 is raised above
ductors. Where, however, the starting reactance that
of the primary brush 4 independent of .the
is constituted wholly or partly by winding on
connection of the primary brush set to an ex
the metadyne stator the metadyne may be con
ternal source of electrical power supply. The 45
45 nected to the line when at rest if said stator ampere turns on the polar projections l0 and H,
winding is arranged so that when a current cir
culates in said winding a torque is exerted on and the number of conductors in the rotor and
the metadyne rotor. It will be easily seen that other factors, are so determined that when the
as soon as the rotor begins to revolve a counter rotor attains the desired normal speed of rota
electromotive force at the primary brushes will tion the potential of the primary brush 3 equals 60
50 be
developed which will gradually increase as the the potential of the supply line T. The main
speed of the rotor increases until when the latter switch ‘I can then be closed without any danger
of surges or other undesirable occurrences, where
has'reached the desired normal speed, the coun
ter electromotive force is substantially equal after the switch it can be opened and the meta- '
dyne remains connected to the source of. supply. 55
55 to the line voltages and independent of the con
nection of the primary brush set to an external With regard to the magnetic flux component par
source of electrical power supply, whereupon the allel with the line b, it will be found on consid
metadyne transformer may be connected direct eration that, assuming the same direction of ro
to the circuit and the stator winding (with the tation and direction of current, the potentials at
the brushes 3 and 6 will be the same and conse 60
starting
resistance if present) cut out.
so, The reactance
or resistance may be gradually quently no current will be caused to circulate in
the secondary circuit through the electric motor
reduced in value by any suitable means, for ex
ample by electromagnetic switches in a similar 8, and similarly the potentials between the
manner to that commonly employed for reducing brushes d and 5 will be the same so that no cur
the accelerating resistance in the armature cir~ rent will 'be caused to circulate in the circuit con 65
_
cuit when starting a direct current electric motor taining the electric motor 9.
Referring now. to Fig. 2, the general arrange
or by means of a rotary switch similar to a direct
ments are very similar .to those indicated in Fig. 1,
current motor starter.
1
The invention'will now be further described but in place of the coils I2 and I3 on the stator
poles l0 and II the stator polar projections I5 70
70 with reference to the accompanying drawings and lBare wound with coils I1 and I8 connected,
which are electrical diagrams illustrating by way
of example methods of carrying out the same in between the source of supply T and ground G _
.through aswitch IS. The e?ect of the stator coils
practice.
In all the ?gures a one-cycle machine is shown. is lac-produce a magnetic flux parallel with the
‘The rotor 01 the transformer is indicated-at‘ l line (2 which ‘can be considered as being made up 754
9,055,804
oi’ components in the lines o and b, and assuming
that the rotor i is rotating in the same direction
as before, the magnetic flux components parallel
_ with the line b will be found to produce an elec
tromotive force between the secondary brushes
t and t, which will result in current circulating
through the external secondary circuit contain
ing the motors ,8 and a. This current circulating
in the rotor windings will produce a magnetic
flux in the direction or”. the line 0, which mag-é
neticv?ux together with that_ in this direction
forming one of the components of the magnetic
?u'x lll'lllie d is cut by the rotating conductors and
produces an electromotive force between the
brushes 3 and ll in such a direction that the po
tentialor” the brush 8 will be raised to that of the
line T, whereupon the main switch ‘i can be
closed, connecting the machine to the line.
The proceeding. illustrated by Fig. 2 is better
than the proceeding illustrated by Fig. l; in fact,
the ?ux created in the metadyne is due to the
rotor ampere turns, and the stator is relatively
smaller than the stator of a dynamo; therefore
if the same ?ux must be created by a stator wind
ing a much larger amount of energy is required,
particularly if. the total flux has to be created
by only one pair of polar segments. Thus the
energy required by the proceeding illustrated by
l is much higher than that required by the
proceeding illustrated by Fig. 2, and when the
line voltage happens to be high the proceeding
illustrated by Fig. 1 does not entirely prevent a
shock, where with the proceeding 01? Fig. 2 the
connection to the line is very smooth, the sec=
ondary current circulating in the right direction
even before the connection to the supply.
in Fig. 3 the arrangements of Fig. 2 are super»
posed on those of Fig. i, that is to say windings
are provided on all the polar projections, namely
it and i i‘, and i6 and it. The conditions here
ina'oove described with reference to Figs. 1 and 2
will he simultaneously produced with the result
that an elcctromotive force will be produced be
tween the brushes ii and ii which willenable the
switch l to be closed and the metadyne safely
connected to the line. The windings i2, :18, ill
and i may be connected in series through a
switch 8 9 between the supply line l and ground G
as shown.
‘in Fig. 1i the circuit through the primary
brushes 3 and ii can be connected direct between
the supply line T and ground G through an im
pedance 2t and switch 2i which form a shunt to
the contacts of . the main switch ll. As is well
known in such case the switch it can be closed
so that the machine will ‘be connected to the line
through the impedance 2E, whereupon the cur
rent will gradually increase without surges or
peaks from zero to that normally transmitted
through the switch 'l by gradually reducing the
value of the impedance so, after which the switch
'i' can be closed without detriment, leaving the
metadyne transformer connected to the source
of supply. The arrangements shown in Fig. 4
are not intended to be independently claimed, but
are shown in order to aid the easy comprehension
of the further description.
Referring to Fig. 5 the arrangement of stator
windings, namely the coils i2, i3, i1 and it}, is
similar to that shown in Fig. 3, but the circuit of
said coils is connected through the switch 22 so
as to form a shunt to the contacts of the main
switch 1. The stator coils therefore form an im~
pedance which has similar effects to the imped
Consequently when the switch
‘in once 20 in Fig. 4.
3
22 is closed the conditions obtaining in Fig. 3 are
produced with the addition of the impedance
effect described with reference to Fig. 4 thereby
enabling the switch ‘l to be closed without dis
turbance. No further description of the opera
tion of the arrangements in this ?gure is deemed
necessary in view of the earlier description 05.’
Fig. 3.
In Fig. 6 the arrangements of Fig. 2 are repro
duced, but the motors t and 9 are connected in flit
the well known cross-connection between the sec
ondary brushes s and t instead oi’ in the figure-i3
connection as shown in Fig. 2.
Fig. 7 shows arrangements similar to those oi’
Fig. 5 with the addition of an adjustable impede
ance
This impedance is similar to the im
pedance 2c in
a and is provided with switches
25, 25, 253, by. which it can be gradually reduced
to zero as the speed of the machine increases to
the desired normal‘speed.
In Fig. 8 arrangements similar to those of F g. 7
are provided, but the secondary circuit containing
the motors i3 and 9 is connected between the
brushes 5 and 6 in the well known cross-connec
tion instead of in the figure-8 connection. in
view or" the explanations given of the earlier fig
ures of the drawings it is deemed unnecessary to
explain further the operation and working of the
arrangements of Figs. 1-}, 7 and 8.
The machines shown in the diagrams are one
cycle machines that is to say the same disposition
of electrical elements and magnetic elements re
curs only once in progressing through one com
plete turn round the rotor in the air gap between
the rotor and stator. In this case there are
four polar projections and the primary and sec
ondary brushes are located at the‘ ends oi diame
ters at right angles to each other. The invention
is however applicable to multl-cycle machines
and is not limited to the simple one-cycle ma 4:0
chine which is illustrated.
I claim:
l. An electrical system including a transformer
metadyne having a stator and a rotor provided
with windings and. a commutator connected
thereto, means including a primary brush set as
sociated with said commutator for providing a
primary circuit through said rotor, means includ
ing a secondary brush set associated with said
commutator and arranged in electrical duadra» 50
ture relation with said primary brush set for pro
viding a secondary circuit through said rotor, at
source of direct-current supply, means for con~
nesting said source of direct-current supply across
said primary brush set, a low-resistance load cir 55.
cuit, means for connecting said low-resistance
load circuit across two of said brushes and in
cluding at least one of the brushes of said second
ary brush set to provide an external secondary
circuit, and means including a winding on said 60
stator arranged to produce an electromotive force
in said rotor secondary circuit and utilizing said
external secondary circuit to complete an elec
tric current carrying circuit for producing a coun
ter-electromotive force in said rotor primary cir 65
cuit balancing the voltage of said direct-current
source of supply, said last mentioned means be
ing independent of the connection of said primary
brush set to said source of direct current supply.
2. An electrical system including a transformer 70
metadyne having a stator and a rotor provided
with windings and a commutator connected there
to, means including a primary brush set associ
ated with said commutator for providing a pri
mary circuit through said rotor, means including 75
Q,
' _
accuses
a secondary brush set associated with said com- - rent source of supply, said last mentioned means
mutator and arranged in electrical quadrature
relation with said primary brush set for providing
a secondary circuit through said rotor, a source or
direct-current supply, means for connecting said
source of direct-current supply across said pri
mary brush set, a low-resistance load circuit,
means for connecting said low-resistance load cir
cult to at least one or tnebrushes of said second=
W ary brush set to provide an external secondary
circuit, and means including a winding on said
stator connected across said direct-current source
of supply arranged to produce an electromotive
force in said rotor secondary circuit and utilizing
16 said external secondary circuit to complete an
electric current carrying circuit for producing a
counter-electromotive force in said rotor primary
circuit balancing the voltage of said direct-cur
rent source of supply, said last mentioned means
being independent of the connection of said pri
mary brush set to said source of direct current
supply.
3. An electrical system including a transformer
metadyne having a stator and a rotor provided
with windings and a commutator connected there=
to, means including a primary brush set essoci=
ated with said commutator for provding a primary
circuit through said rotor, means including a
secondary brush set associated with said commaon
will
tater and arranged in electrical quadrature rela=
tion with said primary brush set for providing a
secondary circuit through said rotor, a direct~
current source of supply, means for connecting
said source of direct-current supply across said
85 primary brush set, a low-resistance load circuit,
means for connecting said low-resistance load
circuit to at least one of the brushes of said sec»
ondary brush set to provide an external secondary
circuit, and means including a. winding on said
stator connected in series with said primary
brush set across said direct-current source of sup»
ply arranged to produce an electromotive force in
being independent or the connection of said pri
mary brush set to said source or direct current
supply°
'
5. An electrical system including a transformer
metadyne having a stator and a rotor provided
with windings and a commutator connected
thereto, means including a primary brush set
associated with said commutator for providing a
primary circuit through said rotor, means in W
cluding a secondary brush set associated with
said commutator and arranged in electrical
quadrature relation with said primary brush set
for providing a secondary circuit through said
rotor, a source of direct-current supply, means 155
for connecting said source of direct-current sup
ply across said primary brush set, a low-=resist
ance load circuit, means for connecting said low
resistance load circuit across a primary and a
secondary brush of sad brush sets/to provide
an external secondary circuit, a winding on said
stator arranged to produce a component oi’ coun=
tereleetromotive force in said rotor primary cir»
cult, and means including a second winding on
said stator arranged to produce an electrornotlve 25
force in said rotor secondary circuit and utilizing
said external secondary circuit to complete an
electric current carrying circuit to produce a
second component of counterelectromotive force
in said rotor primary circuit in the same direc=
time as the component oi’ counterelectromotive ,
force produced by said ?rst mentioned stator
win! ring for balancing the voltage of said dircct~=
current source of supply.
6. An electrical system including a transformer
metadyne having a stator and rotor provided
with windings and a commutator connected
thereto, means including a primary brush set
associated with said commutator for providing
a primary circuit through said rotor, means in
eluding a secondary brush set associated with
said commutator and arranged in electrical
said rotor secondary circuit and utilizing said ex- ' quadrature relation with said primary brush set
ternai secondary circuit to complete an electric for providing a secondary circuit through said
rotor, a source of direct-current supply, means
current carrying circuit for producing a counter
electromotive force in said rotor primary circuit for connecting said source of direct-current sup=
balancing the voltage of said direct-current source ply across said primary brush set, a low-resist
of supply, said last mentioned means being inde-’' ance load circuit, means for connecting said
pendent of the connection of said primary brush low-resistance load circuit across‘said secondary
' brush set to provide an external secondary cir
iii? set to said source of direct current supply.
4. An electrical system including a transformer cuit, a winding on said stator arranged to pro
metadyne having a stator and a rotor provided duce a component of counterelectromotive force
with windings and a commutator connected in said rotor primary circuit, and means includ
thereto, means including a primary brush set ing a second winding on said stator arranged
associated with said commutator for providing to produce an electromotive force in said rotor
secondary circuit and utilizing said external sec
a primary circuit through said rotor, means in
cluding a secondary brush set associated with ondary circuit to complete an electric current
said commutator and arranged in electrical carrying circuit to produce a second component
quadrature relation with said primary brush set of counterelectromotive force in said rotor pri
so for providing a secondary circuit- through said mary circuit in the same direction as the com-l
ponent of counterelectromotive force produced
rotor, a source of direct-current supply, current
by
said ?rst mentioned stator winding for bal
limiting devices, means for connecting said
ancing the voltage of said direct-current source
source of direct-current supply across said pri
of supply.
mary brush set in series with said current-limit
7. An electrical system including a transformer
65 ing devices, a low-resistance load circuit, means
for connecting said low-resistance load circuit metadyne having a stator and a rotor provided
to at least one of the brushes of said secondary with windings and a commutator connected
thereto, means including a primary brush set
brush set to provide an external secondary cir
cuit, and means including a winding on said associated with said commutator for providing a
70 stator arranged to produce an electromotive primary circuit through said rotor, means in
force in said rotor secondary circuit and utilizing cluding a secondary brush set associated with
said external secondary circuit to complete an said commutator and arranged in electrical
electric current carrying circuit for producing a quadrature relation with said primary brush set
counterelectromotive force in said rotor primary for providing a secondary circuit through said
rotor, a source of direct-current supply, means
75 circuit balancing the voltage of said direct-cur
45
50
60
65
70
75
2,055,304
for connecting said source of direct-current sup
ply across said primary brush set, a low-resist
ance load circuit, means for connecting said low
resistance load circuit across a primary and a
secondary brush oi said brush sets to provide
an external secondary circuit, and means in
cluding a winding on ‘said stator connected across
said source of direct-current supply arranged to
5
provided with windings and a commutator con
nected thereto, means including a primary brush
set associated with said commutator for provid
ing a primary circuit through said rotor, means
including a secondary brush set associated with
said commutator and arranged in electrical quad
rature relation with said primary brush set for
providing a secondary circuit through said rotor,
produce an electromotive force in said rotor sec- ‘ a source of direct-current supply, means for con
ondary circuit and utilizing said external second=
ary circuit to complete an electric current carry
ing circuit for producing a counterelectromotive
force in said rotor primary circuit balancing the
voltage of said direct-current source of supply.
8. An electrical system including a transformer
metadyne having a stator and a rotor provided
with windings and ‘a commutator connected,
thereto, means including a primary brush set
associated with said commutator for providing
20 a primary circuit through said rotor, means in
cluding a secondary brush set associated with.
said commutator and arranged in electrical
quadrature relation with said primary brush set
for providing a secondary circuit through said
15
25 rotor, a source of direct-current supply, means
for connecting said source of direct-current sup»
ply across said primary brush set, a low-resist
ance load circuit, means for connecting said low
resistance load circuit across said secondary
30 brush set to provide an external secondary cir
cuit, and means including a winding on said
stator connected across said source of direct
current supply arranged to produce an electro
motive force in said rotor secondary circuit and
85 utilizing said external secondary circuit to com
plete an electric current carrying circuit for pro
ducing a counterelectromotive force in said rotor
across said direct-current source of supply ar
rangedto produce an electromotive force in said
rotor secondary circuit and utilizing said external
secondary circuit to complete an electric current 20
carrying circuit for producing a counter-electro
motive force in said rotor primary circuit balanc
ing the voltage of said direct-current source of
supply, said last mentioned means being inde
pendent of the connection of said primary brush
set to said source of direct current supply.
11. An electrical system including a trans
former metadyne having a stator and a rotor
provided with windings and a commutator con
nected thereto, a primary brush set associated
with said commutator, a secondary brush set
associated with said commutator and arranged
in electrical quadrature relation with said
primary brush set, a source of direct-current
supply, means for connecting said source of
direct-current supply across said primary brush
set, a low-resistance load circuit, means for con
primary circuit balancing the voltage of said
necting said low-resistance load circuit across a
direct-current source of supply, said last men;
tioned means being independent of the connec
tion of said primary brush set to said source of
primary and a secondary brush of said brush sets,
direct-current supply.
_
9. An electrical system including a transformer
metadyne having a stator and a rotor provided
with windings and a commutator connected
thereto, means including a primary brush set
associated with said commutator for providing
a primary circuit through said rotor, means in
cluding a secondary brush set associated with said
50 commutator and arranged in electrical quad
rature relation with said primary brush set for
providing a secondary circuit through said rotor,
a source of direct-current supply, means for con
necting said source of direct-current supply
e
necting said source of direct-current supply 10
across said primary brush set, a low-resistance
load circuit, means for connecting said low-re—
sistance load circuit across said secondary brush
set to provide an external secondary circuit, and
means including a winding on said stator con 15
nected in series with said primary brush set
across said primary-brush set, a low-resistance
load circuit, means for connecting said low
resistance load circuit across a primary and a
secondary brush of said brush sets to provide an
external secondary circuit, and means including a
60 winding on said stator connected in series with‘
said primary brush set across said direct-currerit
source of supply arranged to produce an electro
motive force in said rotor secondary circuit and
utilizing said external‘ secondary circuit to com
65 plete an electric current carrying circuit for pro
, ducing a counter-electromotive force in said
and means including a winding on said stator
connected in series with said primary .brush set
across said direct-current source of supply and
utilizing the ampere turns on said rotor for pro
ducing a counter-electromotive force on said
rotor balancing the voltage of said direct-current
source of supply, said lastementioned means in
cluding a current-limiting device in series with
said stator winding.
12. An electrical system including a trans
former metadyne having a stator and a rotor 60
prcvidedwith windings and a commutator con
nected thereto, a primary brush set associated
with said commutator, a secondary brush set
associated with said commutator and arranged
in electrical quadrature relation with said
primary brush set, a source of direct-current sup
ply, means for connecting said source oi.’ direct
current supply across said primary brush set, a
low-resistance load circuit, means for connecting
said low=resistance load circuit across said
secondary brush set, and means including a wind
ing on said stator connected in series with said
primary brush set across said direct-current
source of supply and utilizing the ampere turns
on said rotor for producing a counter-electro
motive force on said rotor balancing the voltage
rotor primary circuit balancing the voltage of
said direct-current source’ of supply.
of said direct-current source of supply, said last- ‘
mentioned means including a current-limiting
10. An electrical system including a trans
former metadyne having a stator and a rotor
device in series with said stator winding.
GI‘USEPPE MASSIMO PES'I‘ARINI.
70
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