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‘Sept. 10, 1946.
’
'
' F. E. CREVER
ELECTRIC
2,407,476
CIRCUIT
'
Filed June 6, 1944
w“ Figl.
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Inventor:
Frederic-k E.Cr~ever~,
by
ri?e, Attorney.
-
Patented Sept. 10, 1943
25,407,476
UNITED STATES PATENT OFFICE
2,407,476
ELECTRIC omourr
Frederick E. ‘Crever, Scotia, N. Y., assignor to
General Electric Company, a corporation of
New York
Application June 6, 1944, Serial No. 538,933
1
8 Claims.
This invention relates to electric circuits and
more particularly to improvements in automatic
polyphase alternating-current regulating circuits.
It is often desirable to provide the main con
(Cl. 171-223)
2
line conductors I, 2 and 3 and to a common neu
tral point 8. The alternator 4 is provided with a
direct-current ?eld winding 9 which is energized
.by the armature voltage of a direct-current ex
citer Ill.
The excitation of the exciter I0 is controlled
by a bucking ?eld winding II which is energized
in accordance with the voltage of the main al
trol element of regulators for polyphase circuits
with polyphase voltage response and also with
line current response. The latter response is usu
ally for obtaining line drop compensation or cir
culating current compensation in case of parallel
ternating-current circuit in the manner which
operation. In accordance with a principal fea
will now be described.
ture of this invention there is provided a novel 10
Connected across the main alternating-current
and simple network fOr obtaining from a poly
circuit
is a T~connected potential transformer
phase circuit a single-phase voltage which is pro
I2, the primary of which has its main winding
portional to the positive phase sequence compo
I3 connected across conductors I and 2 and has
nent of the voltage of the polyphase circuit. This
single-phase voltage is in quadrature with the 15. the teaser winding I4 connected between line con
ductor 3 and the mid-point of main winding I3.
current in one of the lines of the polyphase cir
The voltage of teaser winding I 4 is, of course,
cuit at unity power factor of said circuit. This
.866 times the voltage of main winding I 3 so
network is made extremely sensitive to changes
in regulated voltage by means of a saturated re
actor, which, however, introduces a frequency
error.
In’ accordance with another feature of
that the voltages between the two terminals of
main winding I3 and the terminal of teaser wind
ing I4 are all equal and all displaced 120 degrees.
The secondary of potential transformer I2 dif
fers from the ordinary three-phase to two-phase
T-connected transformer in that the two phases
25 of the secondary do not have equal voltages and
and improved electric circuit.
the phase I5 which is excited by the teaser wind
Another object of the invention is to provide
ing I4 has twice the voltage of the phase I6
a new and improved symmetrical phase sequency
Which is excited by the main winding I3, and this
segregating network.
latter
half-voltage winding is connected to the
A further object of the invention is to provide
mid-point
of the full-voltage winding of the sec
a novel highly sensitive frequency compensated
ondary so as to form a T connection. Serially
positive phase sequence responsive regulator con
connected across the high-voltage secondary
trol circuit.
Winding
I5 are a resistor I1 and a reactor I8
An additional object of the invention is to pro
vide a new and improved automatic regulator 35 which have equal ohmic values at the normal fre
quency of themain circuit; that is to say, the
system.
reactance inohms of the reactor I8 is numerical
The invention will be better understood from
ly equal to the resistance in ohms of the resistor
the following description taken in connection with
ll. Consequently, the voltage between the junc
the accompanying drawing and its scope will be
tion point I9 of the resistor and the reactor and
pointed out in the appended claims.
.
40 the point 20 where the windings I5 and I6 are
In the drawing Fig. 1 is a diagrammatic illus
interconnected is equal to one-half the voltage
tration of an embodiment of the invention which
is provided with a pair of differentially-acting , of the winding I5 and is therefore equal to the
voltage of the winding I6. Thus, the voltage be
control windings and Fig. 2 is a modi?cation
tween
I9 and the free terminal of the
which provides a novel circuit for differentially 45 windingtheI6point
will be either twice the voltage of
energizing a single control winding.
the winding IE or will be zero, depending upon
Referring now to Fig. 1 of the accompanying
whether
the voltage between the points I9 and
drawing, which illustrates diagrammatically an
20 is in phase with or in phase opposition with
embodiment of the invention as applied to an
automatic three-phase generator voltage regu 50 the voltage of the winding It‘, and this depends
upon the phase rotation of the main circuit. The
lating system, there is shown therein a main
main
circuit is assumed to have 1—2—-3 phase
regulated three-phase alternating-current circuit
rotation and with this phase rotation the voltage
comprising conductors I, 2 and 3. This circuit
between the point I9 and the free terminal of
is energized by an alternator 4 having phase wind
the Winding I6 will be twice the voltage of the
ings 5, 6 and 7 connected respectively to the 55
the invention, novel frequency compensating
means is provided for the circuit.
An object of the invention is to provide a new
winding I 6 so that the voltage between these
2,407,476
it
points will be a measure of the positive phase se
quence voltage of the main circuit in that it wil
disappear for negative phase sequence voltages.
If the main circuit has the opposite phase rota
tion,
network will respond to the negative
resonant circuit connected across the resistor
ll. As shown, this consists of a capacitor 32
and a reactor 33 in the form of a step-up auto~
transformer. These devices are tuned to res
chance at the normal frequency of the system
so that they have extremely high net reactance
phase sequence voltage of the circuit.
and do not vaffect the operation of the circuit
Point IE5 is connected to one of the input ter
at normal frequency. However, if the frequency
minals of a full-wave recti?er 2i and the free
departs from normal, then the frequency corn
terminal of winding it is connected to the other
input terminal of the recti?er 2!. The direct 10 pensating circuit is no longer resonant and the
departure from resonance compensates for the
current output terminals of this recti?er are conchange in voltage held by the saturated reactor
nected to the bucking control field winding l l for
so that even though the reactor saturates at a
the eXciter It.
different voltage dependent upon the frequency,
The exciter it‘ is provided with a series wind~
ing 2?; which is sufficiently strong to cause it to 15 the primary voltage maintained is independent
of frequency. The action of the frequency com~
self-excite and build up to its ceiling voltage.
pensator produces no substantial shift in phase
However, before it can reach its ceiling voltage,
the output voltage of the positive phase se
the voltage of the alternator will reach a pre
quence network over an appreciable range or vari
1eterrnined normal value at which the ampere
ation in frequency.
turns of the bucking winding l i will be suf?cient
Hunting of the system is p ‘evented by an anti
ly strong to limit further increases in excitation
hunt control winding
for the exciter which
voltage of the exclter. The exciter is also
is energized through a stabilizing transformer 35
preferably a high-speed high-ampli?cation ma
whose pil
.' ing is connected across the
chine, such as an amplidyne which is provided
armature of the exciter. When desired, manual
with cross armature reaction excitation as de
control of the volt-age of the exciter, and hence of
scribed and claimed in Patent 2,227,992, granted
the alternator, may be obtained. by closing a
January 7, 1941, on a joint application of M. A.
switch
which connects the anti-hunt winding
Edwards and E. F. W. Alexanserson and assigned
across the armature of exciter it] through a
to the assignee of the present application.
In order to increase the sensitivity of the buck 30 manually operable rheostat El, thus providing
shunt ?eld rheostatic control.
ing ?eld circuit and also to decrease the peak
The operation of. most of the elements of Fig. 1
inverse voltage on rectifier 2i, capacitor 23 is
135 already been largely covered in connection
connected across bucking ?eld ll. Resistor 21’!
with the above description. In general, if the
has a high value and its purpose is to prevent
35 alternator and the exciter are being driven at
spurious oscillations.
rated speed by a suitable prime mover, or prime
The sensitivity of the regulator system is in
movers, and if the switch
is open, the system
creased by connecting a saturated reactor ‘25 in
will maintain the voltage of the output circuit
series with the input terminals of the recti?er
l, 2,
substantially constant at a value deter
2 I. The voltage drop through the impedance net
mined by the adjustment of the saturated reactor
work which supplies the rectifier 2| is reduced
25 for wide variations in load and power factor
to a minimum by means of a series capacitor
and for appreciable variations in speed. Thus,
2% so that the current in the winding H which
any decrease in voltage will cause the current
is supplied by the impedance network produces
in the bucking winding to decrease more rapidly,
a minimum amount of voltage drop in the cir—
that is, by a larger percentage, than the current
cuit through which it flows.
decreases in the boosting winding, thus decreas
A boosting ?eld winding 2'4 and recti?er 2:13,
ing the net bucking ampere-turns of the two ?eld
which is connected across the output of the posi
windings
allowing the series ezrciter to build
tive phase sequence network before it goes
up to a higher voltage and thus to restore the
through saturated reactor Eli, are interconnected
by wire 22 for the purpose of preventing polarity 5 O voltage of the main circuit to normal. Simi
larly, an increase in voltage of the main circuit
reversal. of the exciter and to supply additional
will increase the bucking ampere turns faster
speed of response in the boosting direction.
than it increases the boosting ampere turns so
The output voltage of the positive sequence
that there is a net increase in bucking ampere
network being in phase with the voltage of wind
turns and the voltage of the exciter is conse
ing
which in turn is in phase with the volt
quently reduced.
age of winding it, is in quadrature with the volt
The positive phase sequence response of the
age of phase l of the armature of the alterna
system insures that the action of the regulating
tor ll so that it will be in quadrature with the
system will be in the proper direction regardless
current in the line 3 at unity power factor oper
ation of the alternator it. Therefore, when a sim 60 of how unbalanced the voltages of the three
phase circuit are.
ple resistor to is connected in series with the
output of the positive phase sequence network
and current is circulated through it from a cur
rent transformer Si in line 3, the voltage drop
in the resistor 39 will be in quadrature with the
voltage of the positive phase sequence network
during unity power factor conditions. This volt
age will then add or subtract from the positive
phase sequence network voltage depending upon
whether the line current is leading or lagging
and thus circulating current compensation may
readily be obtained when the generator 4 oper
ates in parallel with other generators.
The control circuit is compensated for vari
ations in input frequency by means of a parallel
In the modification shown in Fig.
the opposed
?eld windings Z] and M of Fig. l are replaced
by a single control ?eld winding 38 which is
energized by a differential current obtained from
recti?er El and a recti?er 39 which is energized
from an auxiliary current source in the form
of a small alternator
The output terminals of
the rectifiers 2i and 39 are connected with addi
tive
cumulative polarity in a closed series cir
suit and the winding
is connected across this
circuit. As long as the output currents of the
two recti?ers 2! and 359 are equal, the control
winding 38 will be deenergized, but as soon as
the output currents of the recti?ers become un
2,407,476
5
6
equal, the controlwinding 33 will carry the dire
fercnce betWeenthe output currents of the two
fora-it isaimed in-the appended‘. claims to cover
recti?ers and this di?'erence current will ?ow
the-true,spiritand'scope of the invention;
all such changesand modi?cations as fallwithin
in opposite directions depending upon which rec
ti?er has the greater output current.
Current limiting resistors 4| and 42- are con
nected in the input side of the recti?er 39 and
in the common series circuit for the outputs of.
both recti?ers and also a smoothing reactor 43
is connected. in the latter circuit.
'
- /
What I .claim as new and desire to secure by
Letters Patent of the United States is:
1. A symmetrical phase sequence network
comprising, in combination, a T-connected trans~
former having a three-phase primary winding
and a two-phase secondary winding, one of the
10
phases of said secondary winding having half the
.Due to the extreme sensitivity of the circuit
voltage of the other and having one terminal
resulting from the saturation of the reactor 25,
thereofconnected tothe mid-point of said other
small variations in voltage of the alternator 4h
phase, a»resistor and an equal ohmic value re
will-have very little effect on the regulated out-put
actor-connected in series across said other sec
voltage of the main alternator 4.
15 ondary phase,» and output terminals connected
The operation of Fig. 2 is generally the same
respectively to the free terminal of the lower
as that of Fig. 1 in that the. circuit is so adjusted
voltage secondary phase and to they junction of
that, at normal voltage of the’ main alternator the
saidresistor and reactor.
~
>
'
l
difference in output currents of the recti?ers 2|
2. A symmetrical phase sequence network
and 39 will energize control winding 38 with the 20
comprising, in combination, a T-connected trans
proper amount of current to provide the neces
former having a three-phase primary winding
sary excitation for the main alternator.
If now
and a two-phase secondary winding, one of the
the alternator Voltage departs from this normal
phases of said secondary winding having half
value even slightly, there will be a relatively large
the voltage of the other and having one terminal
change in output current of the recti?er 2| thus 25 thereof connected to the mid-point of said other
causing a relatively large change in current in
phase, a resistor and an equal ohmic value re
the winding 38 and this change will be in such
actor connected in series across the higher volt
direction as to restore the voltage of the alter
age
secondary phase, output terminals connected
nator substantially to normal.
.
respectively to the free terminal of the low volt
In Fig. 2 the anti~hunting ?eld winding 34 of
age secondary phase and to the junction of said
the eXciter has been omitted and the secondary
resistor and reactor, and frequency compensating
Winding of the stabilizing transformer 35 has
means comprising a parallel resonant circuit con
been connected directly in series with the single
nected across said resistor.
differentially energized control winding 38 so
3. In combination, a polyphase alternating
that changes in voltage of the exciter will, by
current circuit, means for regulating the voltage
means of the stabilizing transformer 35, induce
of said circuit, a control element for said regu
voltages in the circuit of the winding 38 which
lating means, means including an impedance
are of such direction as to counteract the change
network for deriving from said circuit a single
in exciter voltage and thus prevent overshooting
phase voltage which is proportional to the posi
or hunting of the regulator system.
40 tive phase sequence voltage of said circuit and
When it is desired to control the voltage of the
which’ is in quadrature with one of the line cur
main alternator 4 manually, a switch 44 is moved
rents of said circuit at unity power factor, means
to the left, thus connecting the alternator 49 to
for vectorially adding to said single-phase volt
a recti?er 45 whose output terminals are con
age another single-phase voltage which corre
nected across the resistance of the manually op 45 sponds in phase and is proportional in magnitude
erated ?eld control rheostat 37. The switch 44
to said line current, and means for energizing
when moved to the left also connects the control
said control element in accordance with the vec
?eld winding 38 between the moving contact of
tor sum of said single-phase voltages.
the rheostat 3i and an intermediate point on a
voltage divider 493 which is connected across the
armature circuit of the exciter Ill. Thus, any
operation of the rheostat will cause a change in
energization of the control Winding 38 which in
turn will cause a change in the eXciter voltage
and this action Will continue until the change in
exciter voltage causes the voltage divider 46 to
produce a voltage substantially equal to the
changed voltage of the rheostat. In this manner
very stable operation of the manual voltage con
trol circuit is obtained.
In Fig. 2 the exciter has also been provided
with a conventional series winding 41 for provid
ing a predetermined amount of the excitation of
this machine. In some instances this series ?eld
winding can be so strong that it tends to saturate
the exciter and under these circumstances the 65
4. In combination, a polyphase alternating
current circuit, means for regulating the voltage
of said circuit, a control element for said regu
lating means, means including an impedance net
work for deriving from said circuit a'single-phase
Voltage which is proportional to the positive
phase sequence voltage of said circuit, means in
cluding a series saturated reactor for energizing
said control element in accordance with said sin
gle-phase voltage, and means for compensating
said network for the effect of frequency changes
on said saturable reactor.
5. In combination, an automatic electric reg
ulator, an electroresponsive control element
therefor, a pair of recti?ers having their output
terminals connected with cumulative polarity in
a closed series circuit, means for energizing said
recti?ers in such a manner that their relative
control winding 38 will normally act to hold the
energizations
Vary With variations in a regulated
voltage of the exciter down to the required value
quantity, and means for connecting said electro
corresponding to the normal voltage of the main
responsive control element across said circuit so
alternator 4.
70 as to be energized by the difference between the
While there have been shown and described
recti?er output currents.
particular embodiments of this invention, it will
6. In combination, an automatic electric regu
be obvious to those skilled in the art that various
lator, an electroresponsive control element there
changes and modi?cations can be made therein
for, a pair of recti?ers having their output termi
Without departing from the invention and, there 75 nals connected with cumulative polarity in a
2,407,476
closed series circuit, means for energizing one of
said recti?ers with a substantially constant al
ternating voltage, means for energizing the other
of said recti?ers with an alternating voltage
which varies in accordance with the magnitude CI
of a regulated quantity, and means for connect
ing said electroresponsive control element across
said circuit so as to be energized by the difference
between the recti?er output currents.
'7. In combination, a dynamo-electric machine, '
a ?eld winding for controlling the excitation of
said machine, a pair of recti?ers having their
output terminals connected with cumulative po
to variations in the voltage of said dynamo-elec
tric machine, and means for connecting said ?eld
winding across said circuit so as to be energized
by the di?erence between the recti?er output
currents.
8. In combination, a dynamo-electric machine,
a ?eld winding for controlling the excitation of
said machine, a pair of recti?ers having their out
put terminals connected with cumulative polarity
in a closed series circuit, means for energizing
said rectifiers in such a manner that their rela
tive energizations vary with variations in an op
erating condition of said machine, and means
for
connecting said field Winding across said cir
larity in a closed series circuit, means for ener
gizing one of said recti?ers with a substantially 15 cuit so as to be energized with the difference be
tween the recti?er output currents.
constant alternating voltage, means for energize
ing the other of said rectifiers with an alternat
ing voltage which varies non-linearly in response
FREDERICK E. CREVER.
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