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Патент USA US2407121

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Sept 39 1946.
2,407,121
F. H.OWINTER
FIELD CONTROL SYSTEM FOR SYNCHRONOUS MACHINES
Filed‘ Nov. 27, 1945
by
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F?» wdw,
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Patented Sept. 3, 1946
2,407,121
UNITED
STATES
PATENT 7 OFFICE
2,407,121
FIELD CONTROL SYSTEM FOR
SYNCHRQNOUS MACHINES
Fred H. Winter, Schenectady, N. Y., assignor to
General Electric Company, a corporation of
New York
Application November 27, 1943, Serial No. 511,974
10 Claims. (Cl. 171-—118)
1
2
My invention relates to ?eld control systems
The synchronous motor 5 is also provided with
a ?eld winding 5, which is arranged to be con
for synchronous machines and particularly to a
system, for effecting the application of ?eld ex
nected across a suitable source of excitation 6
citation to a synchronous motor so that it can
when a two-position ?eld switch 1 is in one of its
synchronize its maximum load during a single 5 positions and across the terminals of a suitable
slip cycle, thereby preventing the objectionable
?eld discharge resistor 8 when the ?eld switch
succession of current and torque ?uctuations
‘I is in its other position.
which occur when a synchronous motor is operat
In accordance with the preferred embodiment
ing out of step, and for effecting a quick removal
of my invention shown in the drawing, the ?eld
of ?eld excitation when the motor falls out of
switch ‘i comprises a movable member 9, shown
step.
,
as a hinged armature of suitable magnetic ma
,
One object of my invention is to provide an
improved arrangement of apparatus whereby the
automatic application and removal of ?eld ex
citation are e?ected by a single movable device.
Another object of my invention is to provide an
improved arrangement of apparatus for eliecting
terial, which is normally biased toward the open
position of the switch by means of a spring it
so that the armature closes the magnetic circuit
or a U-shaped electromagnet II. A second U
shaped electromagnet I2 is so positioned relative
to the armature 9 that when the electromagnet I2
is energized it opposes the bias of the spring IE)
the application of ?eld excitation to a synchro
nous machine which is simple in construction,
cheap to manufacture and easily adjusted so as
to effect the application of ?eld excitation at the
and the force exerted by the electromagnet II.
Therefore, when the force of the electromagnet
most desirable point in the slip cycle.
I
by the spring Ill and the electromagnet II, the
A further object of my invention is to provide
an improved arrangement of apparatus for quick~
1y effecting the removal of ?eld excitation from a
magnet II and toward the electromagnet I2,
thereby increasing the reluctance of the electro
synchronous machine as soonas the motor starts
to fall out of step.
magnet H and decreasing the reluctance of the
electromagnet I2. A third electromagnet I3 is
My invention will be better understood from
the following description when taken in connec
also so located that when it is energized it tends to
hold the movable member 9 in the position to
which it is arranged to be moved when the force
of the electromagnet I2 predominates over the
combined forces of the electromagnet I I and the
tion with the accompanying drawing, the single
?gure of which diagrammatically illustrates a
synchronous mot-or starting system embodying my
invention, and the scope of my invention will be
pointed out in the appended claims.
Referring to the drawing, I represents a syn
chronous motor having an armature winding 2,
which is arranged to be connected to a suitable
alternating current supply circuit 3 by means of a
switch 4, which may be of any suitable type, ex
amples of which are well known in the art. While
I have shown a manually controlled line switch 4
for connecting the armature winding 2 to the al
ternat'ng current supply circuit 3, it is obvious
that any suitable automatic means may be em
ployed for controlling the connections between
the armature winding 2 and the supply circuit 3.
Furthermore, in order to simplify the disclosure,
I have shown an arrangement in which the motor
is started as an induction motor by having the
I2 predominates over the combined forces exerted
movable member t moves away from the electro
biasing spring It, which position is the closed po
sition of the ?eld switch ‘i.
The electromagnet I I is provided with an ener
gizing winding !5, which is connected across a
portion of the discharge resistor 8. A unidirec
tional current conducting device such as a half
wave recti?er I6 of any suitable type is connected
in series with the winding I5 so that it is ener
gized only by alternate half cycles of the slip
frequency current that flows through the ?eld
winding 5 and the discharge resistor 8 when the
motor is operating subsynchronously during the
starting operation thereof. In order to prevent
the flux in the magnetic circuit of the electro
magnet It during each of the half cycles of in
duced field current that do not ?ow through the
winding I5 from decreasing to a sufficiently low
value to allow the movable member 9 to be moved
to the switch closed position by the force exerted
normal voltage of the alternating current supply
circuit applied directly to the armature winding
of the motor, but it will be obvious that any other
by the electromagnet I2 until the slip frequency
well-known arrangement may be employed for
starting the motor from rest and accelerating
has decreased below a predetermined value, the
it to approximately synchronous speed.
55 electromagnet II is also provided with a short
2,407,121
3
4
circuited winding ll around a portion of its mag
netic circuit.
The electromagnet I2 is provided with an ener
gizing winding I8, which is arranged to be con
of slip to a suf?ciently low value to allow enough
current to flow through the energizing winding
l5 to maintain the movable member in the switch
open position. Preferably, this condenser 28 is
connected in parallel with the adjustable resistor
nected to a suitable direct current source 19 when
21, and a loading resistor 29 is connected in par
both the ?eld switch ‘I is open so that its auxiliary
allel with the series connected half-wave recti?er
contacts 20 are closed and the line switch 4 is
l6 and the energizing winding l5. This con~
closed so that its auxiliary contacts 2| are closed.
denser 28 also serves to advance the phase of the
As shown in the drawing, the direct current
source I9 is a full-wave recti?er, the input cir 10 current through the energizing winding l5 rela
tive to the current in the ?eld winding 5 so that
cuit of which is connected across one phase of
the operation of the ?eld switch ‘I is initiated
prior to the point in the cycle of induced ?eld
current where the current in the negative direc
closed and the output circuit of which is con
nected across the winding l8 when the auxiliary 15 tion reaches zero, which is substantially the op
the alternating current supply circuit 3 when the
auxiliary contacts 2| of the line switch 4 are
contacts 20 of the ?eld switch ‘I are closed. The
electromagnet I2 is also provided with a short
circuited winding 22 around a portion of its mag—
netic circuit so that when the energizing winding
[8 is deenergized a short time delay elapses be
fore the flux in the magnetic circuit of the elec
tromagnet l2 can decrease to a su?‘iciently low
value to allow the biasing spring Hi to move the
tirnum point during the slip cycle for applying
?eld excitation to the motor.
'
The operation of the embodiment of my inven
tion shown in the drawing is as follows: When it
is desired to start the motor I, the line switch 4
is closed so that the full voltage of the supply
circuit 3 is applied to the armature winding 2
to start the motor from rest and accelerate it
to approximately synchronous speed. During the
movable member 9 away from the electromagnet
starting operation of the motor, the ?eld switch
l2 and toward the open position of the ?eld switch
1 is in the position shown so that the ?eld dis
in which the movable member 9 is shown in the
charge resistor 8 is connected across the ter
drawing. This time delay is made long enough to
minals of the ?eld winding 5. The closing of the
allow the electromagnet 13 to become energized
auxiliary contacts 2| on the line switch 4 con
and hold the movable member 9 in its switch
nects the input terminals of the full-wave recti
closed position against the bias of the spring ii).
?er 19 across two of the phase conductors of the
The electromagnet l3 has an energizing winding
supply circuit 3 so that the energizing winding
24, a portion of which, in the particular embodi
I8 of the electrom-agnet l2 is energized by the
ment shown in the drawing, is connected in series
output voltage of the recti?er l9. However, be
with the direct current source of excitation 6 and
fore the electromagnet l2 can exert enough
the ?eld winding 5 when the ?eld switch is closed.
force to move the movable member 9 to the switch
vA suitable condenser 25 is connected across the
closed position, the energizing winding l5 of the
end terminals of the Winding 24 so that when only
electromagnet II is suf?ciently energized by a
direct current is ?owing in the ?eld circuit, only
portion of the induced ?eld current in the ?eld
a portion of the winding 24 is energized by this
direct current, but when the ?eld switch 1 is 40 winding 5 to exert in conjunction with the spring
it enough force to maintain the movable mem
closed and the motor is operating out of syn
ber in the switch open position.
chronism so that slip frequency current flows
As is well known by those skilled in the art,
through the ?eld winding 5 and the source of
when the motor I is operating subsynchronously,
excitation 6 connected thereto, slip frequency cur
a voltage of slip frequency is induced in the ?eld
rent simultaneously ?ows in opposite directions
winding 5, and this voltage causes a current of
through the two portions of the winding 24 so
slip frequency to ?ow through the ?eld winding
as to decrease the flux in the magnetic circuit of
the electromagnet l3 quickly to a low enough
5 and the discharge resistor 8. Also, a portion
of this induced ?eld current ?ows through the
value to allow the biasing spring I 0 to restore the
movable member 9 to the switch open position SD branch circuit which includes the resistor 21 and
the condenser 28 in parallel and the resistor 29,
irrespective of the value of direct current excita
and when the current in the branch circuit is in
tion that may be ?owing in the ?eld winding prior
a predetermined direction, a portion of the branch
to the machine falling out of step.
current also ?ows through the half -wave recti?er
In order to adjust the slip at which the ?eld
l6 and the energizing winding I5 of the electro
switch 1 closes, I provide suitable means, such
magnet I I. The electric constants of this branch
as an adjustable resistor 21, in series with the
circuit are so designed that at high slips the
half-wave recti?er IE and the energizing winding
magnitude of the current that ?ows through the
l5 of the electromagnet l I for varying the amount
energizing winding [5 during alternate half cycles
of the total induced ?eld current that flows
through the energizing winding l5 during alter (A) is sufficient to maintain the member 9 in the
nate cycles of each slip cycle. Since the operat~
switch open position. Also, due to the condenser
28, the current in the branch circuit and through
ing winding l5 contains considerable inductance
the energizing winding I5 is advanced in phase
and the discharge resistor 8 is substantially non
with respect to the main induced ?eld current so
inductive, the impedance of the branch circuit
including the adjustable resistor 27 and the ener (3.3 that it decreases to zero before the induced cur
rent in the ?eld winding 5 does.
gizing winding 15 may be so high when the slip
Until the motor I reaches a predetermined
frequency is high that, at the instant of starting,
speed near synchronous speed, the frequency and
su?icient current may not ?ow through the ener
gizing winding l5 to maintain the movable mem
magnitude of the induced ?eld current are such
ber 9 in the switch open position against the
that the combined forces of the spring l0 and the
force exerted by the electromagnet 12. There
electromagnet l l predominate over the force ex
fore, I provide a suitable condenser 28 in series
erted on the movable member 9 by the electro
in the branch circuit which includes the ener
niagnet [2. When, however, the motor reaches
gizing winding l5 of the electromagnet H so as
a predetermined speed, the frequency of the pul
to reduce the inductance thereof at high values ' sating current through the winding 5 is low
2,407,121
5
6
enough so that the half cycle of slip frequency
current which does not flow through the winding
switch open position, an electromagnet associ
ated with said member so as to exert thereon a
force in a direction to maintain said member in
the switch open position and having an energiz
ing winding, means controlled by said movable
I 5 is su?iciently long to allow the pull of the elec
tromagnet I I to decrease to such a low value that
the force of the electromagnet I2 predominates
and causes the movable member 9 to move to the
switch closed position. The ?eld winding 5 is
thereby disconnected from the ?eld discharge re
sistor 8 and is connected. in series with the wind
ing 24 of the electromagnet I3 and the auxiliary 10
member for connecting said energizing winding in
contacts SI on the line switch 4 to the source of
excitation 6 so that the motor I is pulled into syn
ber from the switch open position to the switch
closed position and having an energizing wind—
chronism. The opening of the auxiliary contacts
26 on the ?eld switch ‘I interrupts the energizing
circuit of the winding I8 of the electromagnet I2,
but the short-circuited winding 22 delays the de
ing, a source of direct current, means controlled
circuit with said ?eld winding when said member
in the switch open position, a second electro
magnet associated with said member so as to exert
thereon a force in a direction to move said mem
by said member for effecting the energization of
said last mentioned energizing winding from said
source of direct current when said member is in
the switch open position, and a third electro
magnet associated with said member so as to ex
ert thereon a force in a direction to maintain
magnetization of the electromagnet I2 for a su?‘l
cient length of time to allow the electroinagnet
I3 to become su?iciently energized to hold the
?eld switch ‘I in its closed position. Therefore, 20 said member in the switch closed position and
as long as the ?eldwinding 5 is supplied only with
having an energizing winding, and means con
normal excitation current from the source of ex»
trolled by said member for connecting said last
citation Ii, the ?eld switch ‘I is held in its closed
mentioned winding in series with said ?eld wind
position by the electromagnet I3.
ing and said source of excitation when said mem
In case the motor is pulled out of step for any
ber is in the switch closed position.
reason, the induced ?eld current of slip frequency
2. For use with a synchronous motor having an
during half of each slip cycle is in opposition to
armature winding and a ?eld winding, means for
the direct current supplied by the source of ex
supplying alternating current to said armature
citation 6 so that during the ?rst slip cycle the
winding, and a source of excitation for said ?eld
electromagnet I3 is deenergized su?iciently to al
Winding, a device for controlling the connection
low the spring ill to move the member 9 to the
open switch position. While, in some cases, when
the normal exciting current is low reiative to the
induced ?eld current, the desired demagnetiza
tion of the electromagnet i3 can be effected dur
between said source and said ?eld winding com
prising a movable armature member having a
switch closed position and a switch open posi;
tion, means normally biasing said member to the
switch open position, means dependent upon the
frequency of the current induced in said ?eld
ing the ?rst slip cycle without a condenser being
connected across the winding 24, I ?nd that more
winding when said motor is operating subsyn
chronously with the ?eld winding disconnected
positive results are obtained by connecting such
a condenser across the winding 24 and preferably
across the winding so that the direct current ex~
citation current ?ows through only a portion
ill
thereof, preferably one-half.
The opening of the ?eld switch ‘I in response
to the motor pulling out of step restores the start
ing ?eld circuit connections of the motor so that
as soon as the motor is again running at the
proper subsynchronous speed the ?eld switch ‘I is
again automatically closed in the manner hereto
fore described to pull the motor into synchronism.
It will be observed that by merely adjusting - .
the rheostat 2? the subsynchronous speed at
which the ?eld switch ‘I closes can be varied and
by varying the size of the condenser 28 the excita
tion can be applied at the most favorable point
in the slip cycle of induced ?eld current.
While I have, in accordance with the patent
from said source for effecting the movement of
said member from the switch open position to the
switch closed position against the force exerted by
said biasing means, an electromagnet associated
with said member so as to exert thereon a force
in a direction to maintain said member in the
switch closed position and having an energizing
winding, and means controlled by said member‘
for connecting said energizing winding in series
with said ?eld winding and said source of excita
tion when said member is in the switch closed
position.
3. For use with a synchronous motor having
an armature winding and a ?eld winding, means
for supplying alternating current to said arma
ture winding, and a source of excitation for said
statutes, shown and described my invention as
applied to a particular system and as embodying
?eld winding, a device for controlling the con~
nection between said source and said ?eld wind
ing comprising a movable armature member hav
various
ing a switch closed position and a switch open
devices
diagrammatically
indicated,
position, means normally biasing said member to
changes and modi?cations will be obvious to
those skilled in the art, and I therefore aim in (it) the switch open position, means dependent upon
the appended claims to cover all such changes
the frequency of the current induced in said ?eld
and modi?cations as fall within the true spirit
winding when said motor is operating subsyn
and scope or‘ my invention.
chronously with the ?eld winding disconnected
What I claim as new and desire to secure by (5-5 from said source for effecting the movement of
Letters Patent of the United States:
said member from the switch open position to
1. For use with a synchronous motor having an
the switch closed position against the force ex
armature winding and a ?eld winding, means for
supplying alternating current to said armature
winding, and a source of excitation for said ?eld
inding, a device for controlling the connection
between said source and said ?eld winding com
prising a, movable armature member having a
switch closed position and a switch open posi
tion, means normally biasing said member to the
erted by said biasing means, an electromagnet
associated with said member so as to exert
thereon a force in a direction to maintain said
member in the switch closed position and having
an energizing winding, means controlled by said
member for connecting said energizing winding
in series with said ?eld winding and
source
of excitation when said member is in the ‘switch
2,407,121
7
8
closed position, and a condenser connected in
wave recti?er connected in series with said en
ergizing winding, a condenser connected in series
with said energizing winding, an adjustable re
sistor connected in parallel with said condenser,
‘and a ?xed resistor connected in parallel with
said series connected half-wave recti?er and en
parallel with said energizing winding.
4. For use with a synchronous motor having
an armature winding and a ?eld winding, means
for supplying alternating current to said arma
ture winding, and a source of excitation for said
ergizing winding.
?eld winding, a device for controlling the con
7. For use with a synchronous motor having a
nection between said source and said ?eld wind
ing comprising a movable armature member hav
?eld winding and a source of excitation connected
ing a switch closed position and a switch open 10 to said ?eld winding, a device for controlling the
position, means normally biasing said member
connection of said source to said ?eld winding and
to the switch open position, mean-s dependent
the disconnection of said source from said ?eld
winding comprising a movable armature mem
said
upon ?eld
the winding
frequency
when
of the
said current
motor isinduced
operating
ber having a switch closed position and a switch
subsynchronously ‘with the ?eld winding disco-1%
open position, means normally biasing said mem
nected from said source for eifecting the move
ber to the switch open position, means compris
ment of said member from the switch open po
ing a ?rst electromagnet for e?ecting the move
sition to the switch closed position against the
ment of said member from the switch open posi
force exerted by said biasing means, an electro
tion to the switch closed position against the
magnet associated with said member so as to 20 force exerted by said biasing means, a second
exert thereon a force in a direction to maintain
electromagnet associated with said member so as
said member in the switch closed position and
to exert thereon a force in a direction to main
having an energizing winding, means controlled
tain said member in the switch closed position,
by said member for connecting a portion of said
an energizing winding for said second electro
last mentioned winding in series with said ?eld 25 magnet connected in series with said source and
winding and said source of excitation when said
?eld winding, and a condenser connected in par
member is in the switch closed position, and a
allel with said energizing winding.
condenser connected across the terminals of said
8. For use with a synchronous motor having a
last mentioned winding.
?eld winding and a source of excitation connected
5. For use with a synchronous motor having
to said ?eld winding, a device for controlling the
an armature winding and a ?eld winding, an al~
connection of said source to said ?eld winding and
ternating current supply circuit, means for con
the disconnection of said source from said ?eld
necting said armature winding to said circuit,
winding comprising a movable armature member
and a source of excitation for said ?eld winding,
having a switch closed position and a switch open
a device for controlling the connection between 35 position, means normally biasing said member to
said source and said ?eld winding comprising a
the switch open position, means comprising a ?rst
movable armature member having a switch
electromagnet responsive to the fraquency in
closed position and a switch open position, means
duced in said ?eld winding when said motor is
normally biasing said member to the switch open
operating subsynchronously with said ?eld wind
position, an electromagnet associated with said 40 ing disconnected from said source for effecting
member so as to exert thereon a force in a di—
the movement of said member from the switch
rection to maintain said member in the switch
open to the switch closed position against the
open position and having an energizing winding;
force exerted by said biasing means, a second
means controlled by said movable member for
electromagnet associated with said member so as
connecting said energizing winding in circuit
to exert thereon a force in a direction to main
with. said ?eld winding when said member is in
tain said member in the switch closed position,
the switch open position, a second electromagnet
a winding on said second electromagnet having a
associated with said member so as to exert
portion thereof connected in series with said
thereon a force in a direction to move said mem
source and ?eld winding, and a condenser con
ber from the switch open position to the switch 50 nected in parallel with said energizing winding.
closed position and having an energizing wind
9. For use with a synchronous motor having
ing, a full-wave recti?er, means controlled by
an armature winding and a ?eld winding, an al
said connecting means for connecting the input
ternating current supply circuit, means for con
circuit of said recti?er to said alternating cur_
necting said armature winding to said circuit, and
rent supply circuit, means controlled .by said
a source of excitation for said ?eld winding, a de
member for effecting the connection of the out
vice
for controlling the connection between said
put circuit of said recti?er to said last men
source and said ?eld winding comprising a mov
tioned energizing winding when said member is
‘able armature member having a switch closed
in the switch open position, and a third electro
magnet associated with said member so as to 60 position and a switch open position, means nor
mally biasing said member to the switch open
exert thereon a force in a direction to maintain
position, an electromagnet associated with said
said member in the switch closed position and
member so as to exert thereon a force in a direc
having an energizing winding, and means con
tion to maintain said member in the switch open
trolled by said member for connecting said last
position and having an energizing winding, a uni
mentioned winding in series with said ?eld wind~
ing and said source of excitation when said mem
directional current conducting device, means
ber is in the switch closed position.
controlled by said movable member for connect
6. For use with a synchronous motor having a
ing said energizing winding in series with said
?eld winding, a ?eld discharge resistor connected
?eld winding and said unidirectional current con
to said ?eld winding, and a source of excitation,
ducting device, a second electromagnet associated
a device for controlling the connection of said
with said member so as to exert thereon a force
source to said ?eld winding comprising an elec
in a direction to move said member from the
tromagnet having a short-circuited winding and
switch open to the switch closed position and hav
an energizing winding connected in a branch cir
ing an energizing winding, and means for ener
cuit around a portion of said resistor, a half
gizing said last mentioned energizing winding
2,407,121
10
position and having an energizing winding, a
unidirectonal current conducting device, means
controlled by said movable member for connect
10. For use with a synchronous motor having
ing said energizing winding in with said ?eld
an armature winding and a ?eld winding, an
alternating current supply circuit, means for con CH Winding and said unidirectional current conduct
ing device, a second electromagnet associated With
necting said armature winding to said circuit, and
while said connecting means is connecting said
armature winding to said supply circuit.
a source of excitation for said ?eld winding, a
‘said member so as to exert thereon a force in a
device for controlling the connection between said
direction to move said member from the switch
open to the switch closed position and having an
energizing Winding, and means for energizing said
last mentioned energizing winding while said con
necting means is connecting said armature wind
ing to said supply circuit and said member is in
the switch open position.
FRED H. WINTER.
source and said ?eld winding comprising a mov
able armature member having a switch closed '
position and a switch open position, means nor
mally biasing said member to the switch open
position, an electromagnet associated with said
member so as to exert thereon a force in a direc
tion to maintain said member in the switch open
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