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Патент USA US3050684

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Aug. 21, 1962
D. w. MOORE
3,050,674 .
PHASE REGULATED INVERTERS
7
Filed Aug. 9, 1960
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INVENTOR.
Aug. 21, 1962
D. w. MOORE
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3,050,674
PHASE REGULATED INVERTERS
Filed Aug. 9, ‘1960
3 Sheets-Sheet 2
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Aug. 21, 1962
D. w. MOORE
3,050,674
PHASE REGULATED INVERTERS
Filed Aug. 9, 1960
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3 Sheets-Sheet 3
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3,050,674
Patented Aug. 21, 1962
1
2
ent invention by plotting voltage magnitude as a function
3,050,674
PHASE REGULATED INVERTERS
Donald W. Moore, Los Angeles, Calif., assignor to Elec~
trosolids Corporation, Panorama City, Calif, a corpo
ration of California
Filed Aug. 9, 1960, Ser. No. 48,500
13 Claims. (Cl. 321—5)
of time;
FIGURE 2 shows a schematic diagram, partially in
block form, of a three channel embodiment of the present
invention to convert D.C. electricity into threephase A.C.
electricity;
nating current electricity and more particularly to fre
FIGURE 3 vectorially depicts the output voltage rela
tionships in the device of FIGURE 2;
FIGURE 4 shows a schematic diagram, partially in
block form, of a two-channel embodiment of the present
invention including transistorized circuitry suitable for
quency and phase regulated static inverter systems.
use in an inverter channel;
The present invention pertains to electronic devices for
converting direct current electricity into polyphase alter
FIGURE 5 vectorially depicts the output voltage rela
tionships in the device of FIGURE 4; and,
tricity for relatively high power applications. Static in 15 FIGURE 6 is a schematic diagram, partially in block
form, of a master oscillator ‘system embodiment of the
verter devices, i.e., those without an operational depend
present invention.
ence on relative mechanical movement between compo
The objects of the present invention are accomplished,
nent parts, usually achieve the desired high output ca
pability by generating an A.C. signal, splitting the signal
in the preferred embodiments, by providing a plurality of
into a desired output phase relationship and separately 20 single-phase static inverter channels, the outputs of which
Various devices have been developed to convert direct
current electricity into polyphase alternating current elec
amplifying the voltage of each phase. Adequate regula
tion of the frequency and magnitude of the output voltage
are combined in a desired polyphase A.C. con?guration.
Each inverter channel consists of an A.C. generator and
ampli?er stage driven thereby, together with any wave
of such devices can be readily accomplished and satis
shaping circuitry necessary to produce the desired sine
factory operation into a ?xed load at a ?xed power factor
can be obtained. However, at the present state of the art, 25 Wave voltage output. One channel is designated as the
master channel and its output is sampled to provide refer
there are no static inverter devices capable of providing
ence voltages for synchronizing the operation of the A.C.
adequate phase angle regulation to enable highly stable
voltage generator of each of the other channels. The
and el?cient operation into a varying load and/ or a
phase of the reference voltage fed to each of the other
changing power factor.
channels differs from that of the master channel output
vStatic inverter devices of the aforementioned type ordi
voltage in accordance with the desired output phase rela
narily contain circuitry to maintain the separate outputs
from the A.C. generator in ?xed phase relationship to
tionship. Hence, the reference voltage fed to each chan
each other as they are fed into the amplifying stages.
nel provides two reference standards; a frequency refer
ence and a phase reference. In addition, each of the
This type of phase regulation, however, does not automati
cally maintain the inverter output voltage in constant 35 other channels has a negative feedback loop which feeds
a portion of the output back to the A.C. voltage generator
phase relationship upon load variations resulting in a load
unbalance or a change in power factor, because such varia
tions can alter the amount of phase shifting in the am
for that channel to provide a phase feedback voltage.
This phase feedback voltage combines with the reference
voltage fed to that channel to form a resultant signal volt
signal voltages are maintained in the desired phase rela 40 age of {?xed frequency but of variable phase and ampli
tude. Therefore, the resultant signal voltage controls op
tionship there is no phase regulation of the inverter out
eration of the A.C. voltage generator to thereby maintain
put voltage.
the output voltage of that channel in frequency and in
It is therefore an object of the present invention to pro
pli?er stages. Hence, even though the ampli?er input
phase with the applied reference voltage.
vide improved static polyphase inverter systems.
‘It is another object of the present invention to provide 45 Thus, in normal operation and with a balanced load
and unity power factor, the phase feedback voltage in
improved frequency stabilized static polyphase inverter
each of the other channels will be 180° out of phase
systems.
with the reference voltage applied to that channel. The
It is a further object of the present invention to provide
resultant signal voltage will be exactly in phase with the
static polyphase inverter systems having effective output
phase regulation.
It is a still further object of the present invention to
applied reference voltage and will be of a magnitude
equal to the difference between the magnitudes of the
provide static polyph'ase inverter systems having both fre
quency and phase regulation.
reference voltage and the phase feedback voltage. Rele
output phase regulation in the presence of load variations
causing load unbalances.
peak magnitude of the applied reference voltage being
slightly greater than the peak magnitude of the applied
vant circuit parameters are selected so that, under the
It is a still further object of the present invention to 55 preceding speci?ed conditions of operation, the magni
tude of the resultant signal voltage approaches zero, the
provide static polyphase inverter systems having ef?cient
phase feedback voltage. Hence, the A.C. generator of
It is yet another object of the present invention to pro
vide static polyphase inverter systems having efficient 60 each of the other channels will be synchronized both in
frequency and in phase with the applied reference voltage
out-put phase regulation in the presence of load variations
derived from the output of the master channel. This
causing changes in power factor.
relationship is depicted graphically in FIGURE 1A of
It is still another object of the present invention to pro
the accompanying drawing, wherein the reference voltage
vide static polyphase inverter systems having e?icient out
put phase regulation in the presence of load variations 65 is shown by a solid line 7, the phase feedback voltage by
a dashed line 8, and the resultant signal voltage by a
causing load unbalance and changes in power factor.
dotted line 9.
Other objects and a fuller understanding of the inven
During operation should there occur a sudden phase
tion can be had from the following description and claims,
shift in the output voltage of a particular channel (other
taken in conjunction with the accompanying drawing, in
than the master channel) caused, for example, by a load
which:
70 unbalance or change in power factor, the phase feedback
FIGURES 1A and 1B graphically illustrate various volt
voltage of that particular channel will no longer be
age relationships developed during operation of the pres
exactly 180° out of phase with the reference voltage ap
3,050,674
3
reference voltage, will have changed in phase and magni
bodiment of transistorized circuitry is shown in FIGURE
4 of the accompanying drawing and will be discussed
hereinafter.
The channels 11, 12 and 13 terminate in output trans
tude as shown in FIGURE 1B of the accompanying
formers 21, 22 and 23, respectively, the primary windings
drawing.
Since the phase feedback voltage is a negative feedback
of which are not shown.
plied to that channel. Therefore the resultant signal
voltage applied to the A.C. generator of that channel,
although still in frequency synchronization with the
The transformers 21, 22 and
23 each have two secondary windings, designated as ?rst
output windings 24, 25 and 26, respectively, and second
voltage (with respect to the applied reference voltage)
output windings 27, 28 and 29, respectively. The ?rst
the phase shift of the resultant signal voltage will be in
the opposite direction from the phase shift of the channel 10 output winding 24 of transformer 21 is center-tapped with
the center tap 31 being connected to a point of common
output voltage as can be seen from the relative positions
of lines 7 and 3 in FIGURE 1B as compared with their
potential, i.e., ground.
respective positions in FIGURE 1A. A further study
of FIGURES 1A and 113 will show that the magnitude
of the resultant signal voltage will vary in accordance Y
Connected across the ?rst output winding 24 of trans
former 21 is a ?rst series RC phase shifting network
consisting of a resistor 32 and a capacitor 33 joined at a
with the amount of relative phase shift. In the particular
illustration of FIGURE 113 an approximate 45° phase
junction point 34. The orientation and the relative values
lag in the phase feedback voltage, dashed line 8, is seen
that an A.C. output voltage appearing between the junc
tion 34 and ground will have a phase relationship of 120°
with respect to an A.C. output voltage appearing across
the second output winding 27. The junction 34 is con
nected to a frequency sensitive point in the circuitry of
the A.C. generator 16 of channel 12 through an electrical
to have caused more than a 100 percent increase in the
magnitude of the resultant signal voltage, dotted line 9,
as well as an approximate 45° forward shift of the phase
thereof. Hence, the resultant signal voltage changes in
a compensating manner in response to phase changes in
the channel output voltage to control operation of the
A.C. voltage generator for that channel. This compen
sating change automatically brings the channel output
voltage back into phase synchronization with the applied
of the resistor 32 and the capacitor 33 are selected so
lead 35 and a phase reference resistor 36, to thereby com
plete the circuitry for application of the aforementioned
The phase regulation achieved
reference voltage to the A.C. voltage generator 16. One
end of the first output winding 25 of the channel 12 out
put transformer 22 is also connected to the aforemen
tioned frequency sensitive point in the circuitry of the
in this manner is particularly effective as, the greater the
amount of phase shift in a channel output voltage, the
phase feedback resistor 38, the other end of the output
greater is the magnitude of the corrective signal voltage
applied to the A.C. generator of that channel.
Winding 25 being grounded, to thereby complete the
circuitry to provide the aforementioned phase feedback
voltage.
reference voltage and thereby provides the desired out
put phase regulation.
If there should occur a sudden phase shift in the out
put voltage of the master channel, then the reference
voltage applied to each of the other channels will accord
ingly be changed in phase. The phase feedback voltage
for each channel will no longer be in exact 180° phase
relationship with the reference voltage applied to that
channel and the resultant signal voltage will change in
A.C. generator 16 through an electrical lead 37 and a
Also connected across the ?rst secondary Winding 24 of
the transformer 21 is a second series RC phase shifting
network consisting of a resistor 39 and a capacitor 41.
The orientation and relative values of the resistor 39 and
the capacitor 41 are selected so that an A.C. output volt
40 age appearing between their junction and ground will have
a compensating manner as hereinbefore explained with
a phase relationship of 240° with respect to an A.C. out
respect to changes in phase feedback voltage.
put voltage appearing across the second output winding
And,
similarly, the outputs of each of the other channels will
be then quickly brought into the desired phase relation
ship with the master channel output voltage to thereby
provide the desired efficient output phase regulation.
Referring now to FIGURE 2. of the drawing, there is
shown a preferred embodiment of the present invention
to produce a three-phase Y output of alternating current
27 and a phase relationship of 120° with respect to the
reference voltage appearing between the junction 34 and
ground. The reference voltage is picked off from the
junction between the resistor 39 and the capacitor 41 and
fed to the A.C. generator 18 of channel 13 through a
connecting lead 42 and a phase reference resistor 43.
One end of the ?rst output Winding 26 of the channel
electricity from a direct current input. The desired out
13 output transformer 26 is connected to the A.C. gen
put phase relationship is achieved by proper combination
of the outputs of three single-phase inverter channels
generally indicated by the reference numerals 11, 1‘2 and
13. Channel 11 consists of an A.C. voltage generator
erator 18 through an electrical lead‘ 44 and a phase feed
back resistor 45 to thereby complete the negative feedback
loop for channel 13. The resistance values of the re
sistors 43 and 45 are identical with those of the resistors
36 and 38, respectively, and other pertinent circuit pa
14 driving an ampli?er chain 15. Channel 11 forms the
master channel, the output of which controls the opera
rameters are selected so that the reference voltage and
tion of channels 12 and 13 in a manner to be hereinafter
described. Channel 12 consists of an A.C. voltage gen
the phase feedback voltage for channel 13 are of equal
magnitude with those fed to channel 12 to thereby in
erator 16 driving an ampli?er chain 17, and channel 13
sure equal sensitivities and response times for all channels.
consists of an A.C. voltage generator 18 driving an ampli 60
The relative magnitudes of the reference and phase
?er chain 19. The A.C. voltage generators 14, 16 and
feedback voltages are determined by the number of turns
18 are substantially identical, as are the ampli?er chains
in the ?rst output windings 24, 25 and 26 of the output
15, 17 and 19. The A.C. voltage generators may produce
transformers 21, 22 and 23, respectively. Correct rela
a sine wave output or any symmetrically shaped A.C.
tive phasing of these voltages is accomplished by con
voltage which can be shaped into a sine wave. The ampli
nection to the proper ends of the ?rst output windings of
?er chains perform any necessary waveshaping, amplify
transformers 21 and 22, in accordance with the orienta
the voltages to the desired magnitude and increase the
tion of ‘their respective windings with respect to the
power handling capabilities to the desired level. The
orientation of the ?rst output winding 24 of transformer
direct current input is obtained from a source of DC.
21.
The correct connections will result in negative feed
electricity not shown, in the form of operating voltages 70
back of the phase feedback voltage derived from the out
for the inverter channels. Circuitry suitable for use in
puts of channels 12 and 13. The junctions of resistors
the inverter channels 11, 12 and 13 to convert direct
36 and 38 and resistors 43 and 45 are summation points
current electricity to single-phase alternating current
at
which the reference and phase feedback voltages com
electricity is well known in the art and hence will not be
discussed in detail. However, a presently preferred em 75 bine to form the resultant signal voltages. In these sum
3,050,674
5
mation circuits the resistors '36, 38, 43 and 45 provide
isolation of the various voltage sources.
6
the output transformer secondary and by proper ?ltering
applied to the A.C. generators 16 and 18 are at their
minimum value under the operating conditions of a bal
anced load with unity power factor. Hence, the re
and attenuation of harmonics.
The output of the master channel 51 is sampled to pro
vide a reference voltage for synchronizing the operation
of the AC. generator of the channel 52 in the manner
hereinabove described during the discussion of the three
sistance values of the resistors 36, 38, 43 and 45, and the
turns ratios of the output transformers 21, 22 and 23‘
network, consisting of a resistor 59 and a capacitor 61,
As previously explained, the resultant signal voltages
channel embodiment of FIGURE 2. A phase shifting
are chosen so that under these operating conditions the
is connected across the ?rst output winding 56 of trans
peak magnitude of the reference voltage at each summa 10 former 55. The orientation and the relative values of the
tion point will be slightly greater than the peak magni
tude of the phase feedback voltage at that point. Only
resistor 59 and the capacitor 61 are selected so that an
A.C. output voltage appearing between their junction
a relatively small voltage diiferential is necessary to pro
vide a resultant signal voltage sui?cient to lock-in the
and‘ ground will have a phase relationship of 90° with
respect to an AC. output voltage appearing across the
AC. generators of the other channels under these ideal 15 second output winding 57 of transformer 55. The refer
operating conditions.
ence voltage is picked off from the junction between the
The second output secondary windings 2'7, 28 and 2§
resistor 59 and the capacitor 61 and fed to the sine wave
of the output transformers 21, 22 and 23, respectively,
oscillator of channel 52 through a connecting lead and a
are interconnected in the desired output phase relation
phase reference resistor 63.
ship, a V relationship in the illustrated embodiment.
A negative feedback loop is provided around the chan
The output of the master channel 11 is connected to an
nel 52 to provide the desired phase feedback voltage.
output terminal A through an electrical lead 46, the out
The output of channel 52 is sampled by a separate trans
put of channel 12 to an output terminal B through a
former 64 having its primary winding 65 connected across
lead 47, and the output of channel 13 to an output termi
the single secondary winding of the channel 52 output
nal C through a lead 48, the common Y connection is
transformer. Transformer 64 has two secondary wind
made from each of the output transformers to a terminal
ings, a ?rst secondary winding 66 and a second winding
labelled “neutral.” The voltage relationships between
these output terminals is vectorially depicted in FIG
67. The phase feedback voltage for channel 52 is ob
tained from the ?rst secondary winding 66 and fed to the
URE 3.
AC. generator for that channel through a connecting
Referring now to FIGURE 4, there is shown an adapta~ 30 lead 68 and a phase feedback resistor 69. The second
tion of the present invention for an inverter system pro
secondary Winding 67 of the transformer 63 samples the
viding a Scott-T output phase relationship. For a Scott-T
channel 52 output voltage for the DC. ampli?er which
output only two inverter channels, indicated generally by
controls the conduction time of the transistors in the pulse
the reference numerals 51 and 52, need be used. Channel
forming stage of that channel. The third output wind
51 is the master channel and is shown in block form to
ing 58 of the master channel output transformer 55 pro
consist of an AC. voltage generator 53 and an ampli?er
vides a sample of the master channel output voltage for
chain 54, terminating in an output transformer 55. The
the DC. ampli?er and pulse forming stage of the master
channel.
output transformer 55, the primary winding of which is
not shown, has three tapped secondary windings, a ?rst
The ends of the second output winding 57 of the master
output winding 56, a second output winding 57, and a 40 channel output transformer 55 are also connected to out
third output winding 58.
put terminals labelled “A” and “B.” The center tap of
The channel 52 is shown in schematic form and the
the second output winding 57 is connected to one end of
illustrated circuitry is a presently preferred transistorized
the single secondary winding of the channel 52 output
embodiment for all of the aforementioned inverter chan
transformer, the other end of the single secondary wind
nels (channels 11, 12 and 13 in FIGURE 2 and channel
ing being connected to an output terminal labelled‘ “C.”
51 in FIGURE 4). The various stages of the circuit are
The voltage relationships between these output terminals
indicated by vertical phantom lines and identi?ed by
captions appearing between the channels 51 and 52 which
is vectorially depicted in FIGURE 5.
Utilizing the presently preferred embodiment of tran
sistorized inverter channel circuitry shown in FIGURE 4
show the ampli?er chain to consist of a “pulse forming
stage,” a “driver stage,” and a “power stage.” The A.C. 50 a phase regulation response time of about 0.1 second was
generator is a push-pull sine wave oscillator, the output
obtained at an operating frequency of 400 cycles per
second.
of which is fed to the pulse forming stage. The function
of the pulse forming stage is to transform the sine wave
The preceding described embodiments of the present
input signal into a rectangular Wave having a pulse repe
invention are presently preferred because of their high
tition rate equal to the frequency of the applied sine wave 61 CH e?iciency and extreme effectiveness of regulation. How
signal, the duration of the rectangular pulses being varied
ever, other embodiments may occur to those skilled in the
in accordance with changes in the inverter load to thereby
art, as for example, an embodiment as shown in FIG
accomplish the desired regulation. The push-pull tran
URE 6. In such an embodiment, the advantages of the
sistors of the pulse forming stage are driven into satura
present invention are obtainable in a system, the e?i
tion to produce the desired rectangular waveshape, the 60 ciency and accuracy of regulation of which are not as
pulse duration being equal to the period of conduction of
great as in the preceding described embodiment. In
the transistors. The period of conduction of the tran
FIGURE 6 the inverter channels consist only of ampli?er
sistors is determined by variations in base bias, the base
chains 71, 72 and 73, all of the channels being driven by
bias being obtained from a DC. ampli?er controlled by
the inverter output voltage. Hence, the output from the 65 a single master A.C. generator 74-. The output of the
master A.C. generator provides the reference voltage,
pulse forming stage is a series of rectangular pulses that
hence there is no “master” channel, all three channels
vary in time duration with load but remain ?xed in
functioning in an identical manner. Each channel (am
amplitude and frequency.
pli?er chain) is provided with a negative feedback loop
The driver stage is a push~pull driver ampli?er in
to obtain the phase feedback voltage. The output of
which the transistors are driven hard into saturation dur
ampli?er chain 71 is sampled and fed back to its input
ing all of the conduction period, as determined by the
through a connecting lead 75 and a feedback resistor '76.
output from the pulse forming stage. The power stage
The output of ampli?er chain 72 is sampled and fed' back
utilizes push-pull power transistors also driven to satura
to its input through a connecting lead 77 and a feedback
tion, transistor current ?ow being steady during the con
duction time. Sine wave output is achieved by tuning of 75 resistor 78. And, in a similar manner, the output of
7
ampli?er chain 73 is sampled and fed back to its input
through a connecting lead 79 and feedback resistor 81.
The output of the master A.C. generator 74 is fed to
the input of the ampli?er chain 71 through a phase refer
ence resistor 82. The output of the master A.C. gener
ator 74 is also sampled by an R-C phase shifting net
less than the peak magnitude of the applied reference
voltage, the combination of said phase feedback voltage
with said reference voltage forming a resultant signal
voltage of ?xed frequency ‘but of variable phase and
amplitude to thereby control the operation of the A.C.
voltage generator for each of said other channels to main
tain the output voltage of that respective channel in fre
quency and in phase with the applied reference voltage;
orientation and relative values of which are selected so
output terminals; and output phasing means intercon
that an A.C. output voltage appearing between their junc
tion 85 and ground will have a phase relationship of 120° 10 necting said output coupling means of said inverter chan
nels with said output terminals in said predetermined
with respect to the A.C. output voltage of the master
output phase relationship.
A.C. generator 74. The reference voltage for channel
2. A multi-channel static inverter system for converting
72 is picked off from the junction 85 between the resistor
work comprising a resistor 83 and a capacitor 84, the
83 and capacitor 84 and fed to the ampli?er input
through a phase reference resistor 86. Similarly, a sec
ond R-C phase shifting network consisting of a capacitor
87 and a resistor 88 is connected to sample the output
of the master A.C. generator 74. The orientation and
relative values of the capacitor 86 and the resistor 87 are
selected so that an A.C. output voltage appearing between
their junction 89 and ground will have a phase relation
ship of 240° with respect to the A.C. output voltage of
master A.C. generator 74, and a phase relationship of
120° with respect to the reference voltage appearing be
tween the junction 85 and ground. The reference voltage
for ampli?er chain 73 is picked off from the junction 89
and fed to the ampli?er input through a phase reference
resistor 91. Hence, the resultant signal voltages applied
to the ampli?er chain inputs are a combination of refer
ence and phase feedback voltages. The resultant signal
voltage varies in a compensating manner in response to
phase changes in the channel output voltage to control
operation of the respective ampli?er chains to automati
cally maintain the channel output voltage in phase syn~
chronization with the applied reference voltage.
Although the present invention has been described with
electricity from a direct current source into polyphase
alternating current electricity of a predetermined output
phase relationship comprising, in combination: a master
single-phase inverter channel and at least one other single
phase inverter channel for connection to said D.C. source,
each of said channels including a generator of an A.C.
voltage of symmetrical waveshape and predetermined fre
quency and each of said channels also including an output
transformer with an output winding; frequency and phase
reference means interconnecting said output winding of
the master channel output transformer with a frequency
sensitive point in the A.C. voltage generators of said
other channels to provide a reference voltage to syn
chronize the A.C. voltage generators of said other chan
nels at the frequency of the master channel output volt
age, said reference means including phase shifting means
to determine the phase of the reference voltage applied
to each of the A.C. voltage generators of said other chan
nels in accordance with the predetermined output phase
relationship with respect to the output from said master
channel; negative feedback means interconnecting said out
put windings of the output transformers of each of said
a certain degree of particularity, it is understood that the
other channels with a frequency-sensitive point in the
respective A.C. voltage generator for that channel to
present disclosure has been made only by way of example
provide a phase feedback voltage to combine with the
and that numerous changes in the circuitry and the com
only three phase output con?gurations have been illus
reference voltage applied to that A.C. voltage generator,
the peak magnitude of said phase feedback voltage being
less than the peak magnitude of the applied reference volt
age, the combination of said phase feedback voltage with
said reference voltage forming a resultant signal voltage
trated, the present invention is adaptable for use with any
of ?xed frequency but of variable phase and amplitude to
desired polyphase con?guration, the number of inverter
channels required being determined by the number of
phases and their relative displacements.
tor for each of said other channels to maintain the out
bination and arrangement of parts may be resorted to
without departing from the spirit and the scope of the
invention as hereinafter claimed. For example, although
What is claimed is:
71. A multi-channel static inverter system for convert
ing electricity from a direct current source into polyphase
alternating current electricity of a predetermined output
phase relationship comprising, in combination: a master
single-phase inverter channel and at least one other
single-phase inverter channel for connection to said D.C.
source, each of said channels including a generator of an
A.C. voltage of symmetrical waveshape and predeter~
mined frequency, and each of said channels also including
thereby control the operation of the A.C. voltage genera
put voltage of that'respective channel in frequency and in
phase with the applied reference voltage; output ter
minals; and output phasing means interconnecting said
output windings of the output transformers of said in
verter channels with said output terminals in said prede
termined output phase relationship.
3. A multi-channel static inverter system for convert
ing electricity from a direct current source into three
phase alternating current electricity of a Scott-T output
phase relationship comprising, in combination: a master
single-phase inverter channel and one other single-phase
output coupling means; frequency and phase reference
inverter channel for connection to said D.C. source, each
means interconnecting said output coupling means of said
of said channels including a generator of an A.C. voltage
master channel with a frequency-sensitive point in the 60 of symmetrical waveshape and predetermined frequency,
A.C. voltage generators of said other channels to provide
and each of said channels also including an output trans~
a reference voltage to synchronize the A.C. voltage gen
former having an out-put Winding; frequency and phase
erators of said other channels at the frequency of the
reference means interconnecting said output winding of
master channel output voltage, said reference means in
the master channel output transformer with a frequency
cluding means for determining the phase of the reference
sensitive point in the A.C. voltage generator of said other
voltage applied to each of the A.C. voltage generators of
channel to provide a reference voltage to synchronize
said other channels in accordance with said predeter
the A.C. voltage generator of said other channel at the
mined output phase relationship with respect to the out
frequency of the master channel output voltage, said refer
put from said master channel; negative feedback means
ence means including phase shifting means to determine
interconnecting said output coupling means of each of 70 the phase of the reference voltage applied to the A.C.
said other channels with a frequency-sensitive point in the
voltage generator of said other channel in accordance
respective A.C. voltage generator for that channel to pro
with the‘ predetermined output phase relationship with re
vide a phase feedback voltage to combine with the refer
spect to the output from said master channel; negative
ence voltage applied to that A.C. voltage generator, the
feedback means interconnecting said output winding of
peak magnitude of said phase feedback voltage being 75 the output transformer of said other channel with a fre
3,050,674
It)
quency-sensitive point in the respective A.C. voltage gen
with the predetermined output phase relationship with
erator for that channel to provide a phase feedback volt
age to combine with the reference voltage applied to that
respect to the output from said master channel; negative
feedback means interconnecting the ?rst output winding
of the output transformer of each of said other channels
with a frequency-sensitive point in the respective A.C.
voltage generator for that channel to provide a phase
A.C. voltage generator, the peak magnitude of said phase
feedback voltage being less than the peak magnitude of
the applied reference voltage, the combination of said
phase feedback voltage with said reference voltage form
ing a resultant signal voltage of ?xed frequency but of
variable phase and amplitude to thereby control the opera
cs
feedback voltage to combine with the reference voltage
applied to that A.C. voltage generator, the peak magni
tude of said phase feedback voltage being less than the
peak magnitude of the applied reference voltage, the
combination of said phase feedback voltage with said
reference voltage forming a resultant signal voltage of
?xed frequency but of variable phase and amplitude to
thereby control the operation of the A.C. voltage genera
tion of the A.C. voltage generator for said other channel
to maintain the output voltage of that respective channel
in frequency and in phase with the applied reference volt
age; output terminals; and output phasing means inter
connecting said output coupling means of said inverter
channels with said output terminals in said Scott-T out 15 tor for each of said other channels to maintain the output
put phase relationship.
voltage of that respective channel in frequency and in
4. A multi-channel static inverter system for converting
phase with the applied reference voltage; output terminals;
electricity from a direct current source into three phase
and output phasing means interconnecting the second out
alternating current electricity of a Y output phase rela
put windings of the output transformers of said inverter
tionship comprising, in combination: a master single
channels with said output terminals in said predetermined
phase inverter channel and two other single-phase in
output phase relationship.
6. The device as de?ned in claim 5 wherein said phase
verter channels for connection to said D.C. source, each
of said channels including a generator of an A.C. volt
shifting means included in said reference means is con
age of symmetrical waveshape and predetermined fre
nected across the ?rst output winding of the master
quency, and each of said channels also including an out
channel output transformer with predetermined portions
of said phase shifting means being separately connected
put trans-former having an output Winding; frequency and
phase reference means interconnecting said output wind
ing of the master channel output transformer with a fre
through phase reference resistance means to the A.C.
voltage generators of said other channels.
quency-sensitive point in the A.C. voltage generators of
7. The device as de?ned in claim 5 wherein said nega
said other channels to provide a reference voltage to 30 tive feedback means includes feedback resistance means
synchronize the A.C. voltage generators of said other
connecting the ?rst output winding of the output trans
channels at the frequency of the master channel output
former of each of said other channels with the respective
voltage, said reference means including phase shifting
A.C. voltage generator for that channel.
means to determine the phase of the reference voltage
8. A mul-ti-channel static inverter system for convert
applied to each of the A.C. voltage generators of said 85 ing electricity from a direct current source into poly
phase alternating current electricity of a predetermined
other channels in accordance with the predetermined out
put phase relationship with respect to the output from
output phase relationship comprising, in combination: a
master single-phase inverter channel and at least one
said masterchannel; negative feedback means intercon
necting said output winding of the output transformer
other single-phase inverter channel for connection to said
of said other channels with a frequency-sensitive point 40 D.C. source, each of said channels including a generator
in the respective A.C. voltage generator for that chan
of an A.C. voltage of symmetrical wave shape and of
nel to provide a phasefeedback voltage to combine with
a predetermined frequency and an output transformer hav~
the reference voltage applied to that A.C. voltage genera
ing ?rst and second output windings, the ?rst output sec
tor, the peak magnitude of said phase feedback voltage be
ondary winding of the master channel output transformer
ing less than the peak magnitude of the applied reference
being center-tapped; frequency and phase reference means
voltage, the combination of said phase feedback voltage
including connection of the center tap of the master chan
with said reference voltage forming a resultant signal
nel output transformer ?rst output winding and one end
voltage of ?xed frequency ‘but of variable phase and am
of the ?rst output winding of the output transformer of
plitude to thereby control the operation of the A.C. volt
each of the other channels to a point of common po
age generator for each of said other channels to maintain 50 tential, the other end of said ?rst output winding of the
the output voltage of that respective channel in frequency
output transformer of each of said other channels being
connected to a frequency~sensitive point in the respective
and in phase with the applied reference voltage; output
A.C. voltage generator of that channel through negative
terminals; and output phasing means interconnecting said
output coupling means of said inverter channels with
‘feedback resistance means, and a series R-C phase shift
said output terminals in said Y output phase relationship. 55 ing network for each of said other channels, each of said
networks being connected across the ?rst output winding
5. A multi-channel static inverter system for convert
ing electricity from a direct current source into polyphase _
of the master channel output transformer, the junction
between the resistor and capacitor of the phase shifting
alternating current electricity of a predetermined output
phase relationship comprising, in combination: a master
network for each of said other channels being connected
single-phase inverter channel and at least one other single— 60 to a frequency-sensitive point in the A.C. voltage genera
tor of that respective channel through phase reference
phase inverter channel for connection to said D.C. source,
each of said channels including a generator of an A.C.
resistance means, the relative values and positions of the
resistor and capacitor in each phase shifting network
voltage of symmetrical waveshape and predetermined
being determined in accordance with said predetermined
frequency and each of said channels also including an
output phase relationship, the connections made to the ?rst
output transformer having ?rst and second output wind
output winding of the output transformer for each of
ings; frequency and phase reference means interconnect
said other channels. being phased in opposition to the
ing the ?rst output winding of said master channel out
connections made to the ?rst output winding of the master
put transformer with a frequency-sensitive point in the
A.C. voltage generators of said other channels to pro
channels output transformer; output terminals; and out
vide a reference voltage to synchronize the A.C. voltage 70 put phasing means interconnecting the second output wind
ings of the output transformers of said inverter channels
generators of said other channels at the frequency of
and said output terminals in said predetermined output
the master channel output voltage, said reference means
phase relationship.
including phase shifting means to determine the phase
9. A multi-channel static inverter system for convert
of the reference voltage applied to each of the A.C.
voltage generators of said other channels in accordance 75 ing electricity from a direct current source into polyphase
3,050,674c
il
12
alternating current electricity of a predetermined output
phase relationship comprising, in combination: a master
?ber chain of each of said channels to maintain the output
voltage of that respective channel in frequency and in
phase with the applied reference voltage; output ter
minals; and, output phasing means interconnecting said
output coupling means of said inverter channels with
said output terminals in said Scott-T output phase rela
A.C. generator for connection to said D.C. source to
provide an A.C. reference voltage of symmetrical wave
shape and predetermined frequency, said master A.C.
generator having out-put coupling means; a plurality of
single-phase converter channels, each of said channels
including an ampli?er chain for connection to said D.C.
source, said ampli?er chains having input coupling means
and output coupling means; frequency and phase refer
ence means interconnecting said master A.C. generator
output coupling means with the input coupling means
of each of said ampli?er chains to thereby provide each
of said ampli?er chains with said A.C. reference voltage,
said reference means including phase shifting means to
determine the phase of the reference voltage applied to
each of said ampli?er chains in accordance with said
predetermined output phase relationship; negative feed
tionship.
11. A multi-channel static inverter system for convert
ing electricity from a direct current source into three
phase alternating current electricity of a Y output phase
relationship comprising, in combination: a master A.C.
generator for connection to said D.C. source to provide
an A.C. reference voltage of symmetrical wave shape
and predetermined frequency, said master A.C. gener
ator having output coupling means; three single phase
inverter channels, each of said channels including an
ampli?er chain for connection to said DC. source, said
ampli?er chains having input coupling means and output
coupling means; frequency and phase reference means
of each of said ampli?er chains With the input coupling 20 interconnecting said master A.C. generator output cou
pling means with the input coupling means of each of said
means of that ‘respective ampli?er chain to provide a
ampli?er chains to provide each of said ampli?er chains
phase feedback voltage to combine with the reference
with said A.C. reference voltage, said reference means
voltage applied to that ampli?er chain, the combination
including phase shifting means to determine the phase
of said phase feedback voltage with said reference voltage
of the reference voltage applied to each of said ampli?er
forming a resultant signal voltage of ?xed frequency
chains in accordance with said Y output phase relation
but of variable phase and amplitude to thereby control
ship; negative feedback means interconnecting the output
the operation of the ampli?er chain of each of said
coupling means of each of said ampli?er chains with the
channels to maintain the output voltage of that respective
input coupling means of that respective ampli?er chain
channel in frequency and in phase with the applied refer
back means interconnecting the output coupling means
ence voltage; output terminals; and, output phasing means
interconnecting said output coupling means of said in
verter channels With said output terminals in said pre
determined output phase relationship.
10. A multi-channel static inverter system for convert
ing electricity from a direct current source into three
phase alternating current electricity of the Scott-T out
put phase relationship comprising, in combination: a
master A-C‘." generator for connection to said ~D.C. source
to provide a phase feedback voltage to combine with the
reference voltage applied to that ampli?er chain, the
combination of said phase feedback voltage with said
reference voltage forming a resultant signal voltage of
?xed frequency but of variable phase and amplitude to
thereby control the operation of the ampli?er chain of
each of said channels to maintain the output voltage of
that respective channel in frequency and in phase with
the applied reference voltage; output terminals; and, out
to provide an A.C. reference voltage of symmetrical wave
shape and predetermined frequency, said master A.C.
put phasing means interconnecting said output coupling
generator having output coupling means; two single phase
minals in said Y output phase relationship.
12. The device as‘ de?ned in claim 9 wherein said
inverter channels, each of said channels including an
means of ‘said inverter channels'with said output ter
phase shifting means included in said reference means
ampli?er chain ‘for connection to said D.C. sourcewsaid
is connected to the output coupling means of said A.C.
ampli?er chains having input coupling means and output
coupling means; frequency and phase reference means 45 master generator with predetermined portions of said
phase shifting means being separately connected through
interconnecting said master A.C. generator output cou
phase reference resistance means to the input coupling
pling means with the input coupling means of each of said
means of said ampli?er chains.
ampli?er chains to provide each of said ampli?er chains
with said A.C. reference voltage, said reference means
‘13. The device as de?ned in claim 9 wherein said
including phase shifting means to determine the phase 50 negative feedback means includes feedback resistance
means connecting the output coupling means of them
of the reference voltage applied to each of said ampli?er
chains in accordance with said Scott-T output phase
pli?er chain of each of said channels'with the respective
relationship; negative feedback means interconnecting
the output coupling means of each of said ampli?er
chains with the input coupling means of that respective
ampli?er chain to provide a phase feedback voltage to
combine with the reference voltage applied to that ampli
?er chain, the combination of said phase feedback volt
input coupling means for that ampli?er chain.
References Cited in the ?le of this patent
UNITED STATES PATENTS
2,567,410
Trousdale ___‘____.a_.___ Sept. 11, 1951
age with said reference voltage forming a resultant signal
2,575,600
Smith ________ __'_____ Nov. 20', 1951
voltage of ?xed frequency but of variable phase and 60
amplitude to thereby control the operation of the ampli
2,668,938
Henrich ____________ __ Feb. 9, 1954
2,827,576
Wohlers ___________ .._ Mar. 18, 1958
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