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Патент USA US2406429

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Aug- 27, 1946.
‘J. R. MAHONEY
2,406,429
ELECTRONIC CONTROL SYSTEM
Filed NOV. 20, 1943
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INVENTOR
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BY
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Aug. 27, 1946-
J. R. MAHONEY
2,406,429
ELECTRONIC CONTROL SYSTEM I
Filed Nov. 20, 1945
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INVENTOR
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Patented Aug. 2?, 1946
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UNITED STATES PATEN'EOFFICE
2,406,429
ELECTRONIC CONTROL SYSTEM
John R. Mahoney, Pittsburgh, Pa, assignor to
Westinghouse Electric Corporation, East Pitts
burgh, Pa., a corporation of Pennsylvania
1
Application November 20, 1943, Serial No. 511,087
10 Claims. (Cl. 171—119)
This invention relates to an electronic control
system and has particular relation to a system
such as is employed in resistance welding in which
current is supplied from an alternating potential
source to a load under the control of electric
discharge valves.
In resistance welding apparatus constructed in
accordance with the teachings of the prior art,
2
control circuit which includes means for com
pensating for fluctuations in the source potential.
In the Smith circuit, the welding current is con
trolled by a pair of inversely connected ignitrons
which are rendered conductive alternately in suc
cessive half-periods of the source at an instant
in each half-period, known as the ?ring point,
selected according to the welding heat desired.
a pair of inversely connected ignitrons are in
To compensate for fluctuations in the eifective
terposed between an alternating-current source 10 value of the source potential, the control means
and the welding transformer for controlling the
for the ignitrons includes means responsive to
flow of current to the transformer. For each
the source potential to advance the ?ring point
Weld the ignitro-ns are rendered conductive al
of the ignitrons for a decrease in the source po
ternately in successive half periods of the source
tential to supply current over a greater portion
by suitable control circuits during a predeter 15 of a half-period and thereby to avoid the cor
mined interval of time which is measured in
responding decrease in welding heat. For in
terms of half periods of the source. To control
creases in the effective value of the source poten
the amount of energy supplied to the welding
tial, the firing point is, of course, delayed, ‘In
transformer and thus to control the welding
any case, the amount of variation in the posi
heat, the control circuits are arranged to cause 20 tion of the ?ring point depends upon the amount
each ignitron to become conductive at an in
of variation in the source potential.
stant in a half period preselected by the oper
The Smith apparatus operates quite satisfac
ator in accordance with the requirements of the
torily to maintain the welding heat within lim
material to be welded. In this manner, a pre
its suitable for many welding operations even
selected number of spaced current impulses is
though the source potential may ?uctuate. How
supplied to the welding transformer.
ever, it has been found that the limits are not
It is well known that in many welding oper
sui?ciently close for some of the welding oper
ations, the maintenance of a proper welding heat
ations which require extremely accurate heat
is essential. If too much heat is provided, the
control.
material is burned. On the other hand, if too
It is, accordingly, an object of my invention to
little heat is provided, the material is not prop
provide a new and improved control system for
erly fused. However, in the usual power system
resistance welding apparatus in which the weld
employed for resistance welding, the effective
ing heat is maintained within narrow limits even
value of the source potential is subject to nu
though the effective value of the source potential
merous fluctuations as the result of such condi
may fluctuate.
tions as a widely varying load or a lack of ca
More generally, it is an object of my invention
pacity of the system. It is apparent that when
to provide an improved apparatus for supplying
the effective value of the source potential de
a preselected number of spaced current impulses
creases, the eifective value of the current con
from a source of potential to a load in which
ducted to the transformer and, therefore, the 40 variations in the effective value of the current
welding heat, decreases. Conversely, when the
source potential increases, the welding heat in
creases. It follows that to maintain the welding
heat substantially constant, it is necessary to
supplied in response to variations in the effective
value of the source potential is avoided.
Another object of my invention is to provide
apparatus for supplying spaced current impulses
compensate for fluctuations in the source poten 45 from a source of alternating potential to a load
tial.
in which a predetermined amount of energy is
Since changes or ?uctuations of the source po
supplied to the load by each of the impulses re
tential may occur with considerable rapidity, it
gardless of ?uctuations in the effective value of
is impossible to compensate for the ?uctuations
the source potential.
by manual adjustment of the control circuits. 50
My invention arises from a realization that the
In the copending application of Clyde E. Smith
amount of compensation in the nature of a vari
Serial No. 443,987, ?led May 21, 1942, and as
ation or shifting of the ?ring point of the ig
signed to the assignee of the present invention,
nitrons which is necessary for a given variation
‘which application issued as United States Patent
No. 2,374,044 on April 17, 1945, is described a 55 in the effective value of the source potential, dif
fers for different heat settings and differs for the
2,406,429
o
is
same heat setting with different power factor
conditions. That this is true may be understood
A
a third direct-current potential which varies in
magnitude in accordance with variations in the
eifective value of the source potential. Thus, the
from a consideration of the operation of the sup
ratio of the variation of the instant in a half
ply circuit under different conditions. For a low
heat, an ignitron is fired late in. a half~period Li period in which an ignitron becomes conductive
to the source potential variation is varied in ac
of the source potential. A drop in the effective
cordance with the adjustment of the phase prese
value of the source potential then requires an ad
lecting means with the ratio increasing for ad
vancing of the ?ring point by a certain amount
justments of the phase preselecting means from
to increase the effective value of the current sup
a setting for an instant late in a half-period
plied and thereby maintain the heat constant.
toward a setting for an instant early in a half
For a high heat, an ignitron is ?red early in a
half-period. However, with the source potential
having the usual sinusoidal wave form, a drop in
the effective value of the source potential requires
an advancing of the ?ring point by an amount
greater than that required under low heat condi_
tions to maintain the heat constant. For exarn~
ple, with a 20% heat setting, a 10% decrease in
source potential causes a 10% decrease in cur
rent supplied which amounts to a 2% decrease in
current with respect to the maximum steady state
current at 100% heat setting and the original
source potential. Likewise with a 50% heat set
ting, a 10% decrease in source potential causes a
10% decrease in current supplied but the decrease
amounts to a 5% decrease in current with respect
to the maximum steady state current at 100%
heat setting and the original source potential, To
compensate for a 5% decrease requires an ad
vancing of the ?ring point by a greater amount
than that necessary to compensate for a 2%
decrease.
I have also found that it is necessary to con_
sider the power factor of the load in determin
ing the amount of compensation necessary. For
a 100% power factor and an 80% heat setting, an
ignitron is rendered conductive at a given in
stant in a half-period of the source potential.
However, for a different power factor, such as a
215% power factor, and the same 80% heat setting.
an ignitron is rendered conductive at a different
instant later in a half-period of the source po
tential to deliver 80% of the available current.
However, for a 20% heat setting an ignitron must
be rendered conductive at approximately the
period and’ with the rate of increase adjusted in
accordance with the power factor of the load.
The novel features that I consider character
istic of my invention are set forth with particu
larity in the claims, the invention itself, however,
both‘ as to its organization and its method of op
eration, together with additional objects and ad
vantages thereof, will best be understood from
the following description of a speci?c embodiment
when read in connection with the accompanying
drawings, in which:
Figure l is a schematic diagram illustrating a
speci?c embodiment of my invention; and
Figs. 2 and 3 are curves illustrating the opera
tion of the circuit of Fig. 1.
In the apparatus as shown in the drawings, a
pair of welding electrodes 3 and 5 engage the
material "i to be welded and are connected across
the secondary 9 of a welding transformer I l. The
primary 53 of the welding transformer is supplied
with power from a source of alternating current
potential it‘ through a pair of inversely-con
nected ignitrons ill and iii. A. pair of electric
devices at and 23, preferably thyra
trons, which are hereinafter designated as ?ring
valves, are arranged to control the ignition of the
ignitrons ll and i0. respectively.
The ignition
circuit for one of the ignitrons ll extends from
one
2d of the source i5 through a conductor
the anode
and cathode 29 of the ?ring valve
2!», the igniter 3i and cathode 33 of the ignitron
ii and the primary !3 of the welding transformer
' to the other side 34.! of the source l5.
The igni
tion circuit of the other ignitron 19 may be traced
from the other side 36 of the source It through
same instant in a half-period with any power fac
the primary E3 of the welding transformer, a con
tor under which the rsual welding apparatus is
ductor
the anode
and cathode 39 of the
operated. It follows that the possible ?ring point
?ring
valve
23,
the
igniter
Ill and cathode 43 of
positions over the entire range of heat control
settingsfrom 190% heat to 20% heat includes a 50 the ignitron Hi to side 24 of the source l5.
It is to be noted that the anode 21 of ?ring
smaller portion of a half~period for a low power
valve 2! is always of the same polarity as the an
factor than for a high power factor. Consequenh
ode Iih of the corresponding ignitron Ill, and the
ly, the ratio of the variation of the instant of ?r
anode
of ?ring valve 27; is of the same polarity
ing of the ignitrons for compensation to the
source potential variation must not only increase 55 as the anode d1 of ignitron iii. Thus, when a
?ring valve becomes conductive, ignition of the
for adjustments of the heat control selecting
corresponding ignitron is eifectcd. When an ig
means from a setting for an instant late in a half
nitron becomes conductive, the ignition circuit
period toward a setting for an instant early in
through the corresponding ?ring valve is short
a half-period, but. in addition, the rate of in
circuited by the discharge path through the ig
crease must be adjusted to be greater for loads
nitron, and the ?ring valve is rendered non-con
having lower power factors than for loads having
ductive. The ignitron then becomes non-con
higher power factors.
ductive at the end of the half-period of the source
In accordance with my invention, each ignitron
potential in. which it was ignited.
is rendered conductive while its anode is positive,
The control electrodes 49 and 5! of the ?ring
when a control potential in a control circuit 13%
valves 2! and 23 are interconnected through their
comes more positive than a predetermined criti
corresponding grid resistors 53 and 55 and con
cal potential. The control potential comprises a
ductor 57. The cathodes 29 and 39 of the ?ring
?rst periodically pulsating potential having a pre
valves are also interconnected through three re
selected phase displacement relative to the source
potential, each of the pulsations of said ?rst po 70 sistors 523, M, 63. A gaseous discharge recti?er
tube 05 is connected across the ?rst and second
tential having a sloping wave front with a slope
resistors 59 and 6| and a second gaseous dis
which is non-uniform over the length of said
charge recti?er tube ST is connected across the
front, a second direct-current potential of a mag
second and third resistors BI and 63. The ?rst
nitude depending upon both the particular phase
displacement selected and the power factor, and 75 recti?er tube ‘65 is arranged to conduct current
5
2,406,429
away from the junction point of the ?rst and
second resistors 59 and GI and the second recti
?er tube 51 is arranged to conduct current away
from the junction point of the second and third
resistors BI and 63. This arrangement is more
particularly described in the copending applica
6
allel with the recti?er I0 I, potentiometer I03, and
capacitor I65. Thus, when the start valve 53 is
conductive, the terminal of the resistor 8| which
is connected to the cathode 99 of the start valve
becomes positive with respect to the center tap
‘I3 of the divider ‘II. As a result, the control
electrodes 49 and 5| of the ?ring valves become
less negative with respect to their cathodes 29
and 39.
as United States Patent No. 2,363,305 on Novem 10
The control circuit of the start valve 93 may
ber 21, 1944. As will be explained hereinafter,
be traced from its grid I51 through a grid re
a control potential is impressed between the con
sistor I59 and resistors III and 32 to the oath
trol electrodes 49 and 5I of the ?ring valves and
ode 59. A direct current biasing potential is im
tion of Donald P. Faulk, Serial No. 463,989, ?led
October 30, 1942, and assigned to the assignee of
the present invention, which application issued
a center tap 69 on the second resistor 6| to con
pressed across the resistor 82 from an auxiliary
trol the conductivity of the ignitrons. The three 15 source H3 and is of such polarity as to tend to
resistors 59, 6| and 63 interconnecting the oath
maintain the start valve 93 non-conductive. A
odes 29 and 39 of the ?ring valves are also con
potential impulse is periodically impressed across
nected across the source I5 through the igniters
3| and M and cathodes 33 and 43 of the ignitrons
I‘! and I9. Consequently, an alternating poten
tial in phase with the source appears across these
resistors. When the potential across the resis
tors 59, 5| and 63 is of such polarity that the
cathode connected end of the ?rst resistor 59 is
the resistor III through an impulse transformer
H5 energized from the alternating current
20 source I5 through a phase-shifting circuit Ill.
The phase-shifting circuit III is adjusted so that
the potential impulse is impressed across the re
sistor III at the beginning of a period of the al
ternating current source. The potential impulse
negative, meaning that the anode 27 of ?ring
across the resistor MI is su?‘icient to counteract
valve 2| is positive, the ?rst recti?er I55 becomes 25 the biasing potential across the resistor 82.
conductive to short-circuit the ?rst and second
Thus, when the push-button switch 9'! is closed,
resistors 59 and GI. It follows that the control
the start valve 93 is rendered conductive by the
potential impressed between the control elec
next succeeding potential impulse across the re
trodes 49 and 5I of the firing valves and the cen
sistor III.
ter tap 69 of the second resistor 5i is then effec 30
Current flowing through the start valve 93
tively impressed directly between the control
charges the capacitor IE5 at a rate determined
electrode 49 and cathode 29 of the ?ring valve
by the setting of the potentiometer I93 in series
2!. Similarly, when the cathode connected end
of the third resistor 63 is negative, meaning that
the anode 37 of ?ring valve 23 is positive, the
second recti?er Ii'I becomes conductive to short
circuit the second and third resistors ‘SI and 53
and the control potential is effectively impressed
between the control electrode 5| and cathode 39
of the second ?ring valve 23. Interference with
the shape of the wave form of the control poten
tial by the alternating potential across the three
resistors is thus avoided.
The remainder of the circuit shown in Fig. 1
is arranged to produce the control potential and
includes a voltage divider ‘II energized from the
source I5 through an auxiliary transformer ‘I3, a
full wave recti?er ‘I5 and ?ltering elements 11.
An intermediate tap 19 on the divider ‘II is con
nected to the center tap 69 on the second resis
tor 6i interconnecting the cathodes 29 and 39 of
the ?ring valves 2! and 23. The negative termi
nal of the divider ‘II is connected to the control
electrodes 49 and ‘SI of the ?ring valves 2! and
23 in a circuit extending from the negative ter
minal through four resistors 8|, 82, 93, 84 to an
adjustable tap 85 on a potentiometer I31 and from
the end terminal 89 of the potentiometer through
another resistor BI, the conductor 51, and the
corresponding grid resistors 53 and 55 to the
control electrodes. The potential originally ap
pearing between the intermediate tap "i9 on the
divider "II and the negative terminal thereof is
su?icient to maintain the ?ring valves non-con
ductive regardless of the other potentials in the
control circuit.
An electric discharge valve 93, preferably a
thyratron, has its anode 95 connected through a
push-button switch 91 to the positive terminal
of the divider ‘II. The valve 93 is designated as
a “start” valve and its cathode 49 is connected
through a recti?er IIlI, a potentiometer I93, and
a capacitor I95 to the negative terminal of the
divider ‘II. The resistor 8| is connected in par
therewith. The capacitor I95 is also connected
in the control circuit of another electric discharge
device I I9, preferably a thyratron, which is des
ignated a “stop” valve. The anode I2I of the
stop valve H9 is also connected to the positive
terminal of the divider ‘II through the push—but~
ton switch 9?. The cathode I23 of the stop valve
is connected to another intermediate tap I25
on the divider ‘II.
The control circuit of the stop valve H9 may
then be traced from the grid I21 through the
grid resistor I3I, the capacitor I95 to the nega
tive terminal of divider ‘II and from the interme
diate tap I25 to the cathode I23. The potential
appearing between the intermediate tap I25 and
the negative terminal of the divider ‘II normally
50 maintains the stop valve non-conductive. How
ever, a predetermined interval of time after the
start valve 93 becomes conductive, as determined
by the setting of the potentiometer I33, the po
tential across the capacitor I85 rises to a value
55 suf?cient to counteract the biasing potential in
the control circuit of the stop valve I I3 to render
it conductive. Upon the stop valve I I 9 becoming
conductive, the intermediate tap I25 is connected
through the stop valve to the positive terminal
60 of the divider and the intermediate tap ‘I9 con
nected to the cathodes 29 and 39 of the ?ring
valves again becomes positive with respect to the
control electrodes 49 and 5!. The start and stop
valve circuits are explained in detail in Patent
65 No. 2,220,151 issued to Finn I-I. Gulliksen on No
vember 5, 1940 and assigned to the assignee of
the present invention.
A second phase shifting circuit I33 is energized
from the alternating-current source I5 by an aux
70 iliary transformer I35. A reactance I31 and a
resistor I 39 are connected in series across the
end terminals of the secondary I4I of the trans
former I35. The reactance I31 and the resistor
I 39 both have an intermediate tap I 43 and I45,
7,5 respectively. A heat control potentiometer I41,
2,406,429
7
another resistor I49, and a variable resistor I5I
are connected in series between the intermediate
tap I45 on the resistor I39 and the intermediate
tap I43 on the reactance I31. A full-wave recti
?er unit I53 has one of its input terminals I55 (.71
connected to a center tap I51 on the secondary
MI, and the other input terminal I59 connected to
the adjustable tap I6I of the potentiometer I41.
The output terminals of the recti?er I53 are con
nected across the third resistor 83 in the circuit
between the negative terminal of the divider H
and the control electrodes 49 and 5I of the ?ring
valves.
Thus, a potential is impressed across the third
resistor 83 which has the wave form of a full
wave recti?ed alternating potential inverted with
respect to the control electrodes 49 and 5I and
displaced in phase relative to the source poten
8
but its magnitude varies with variations in the
magnitude of the alternating source potential.
The potential across the second divider I95 is de
rived from a three-phase rectifying system I91
energized from the source I5 through a pair of
auxiliary transformers I99 and 20L The primary
and secondary windings of the transformers I99
and 29I are connected in a well-known manner
to deliver three-phase alternating potential to the
rectifying system. A small ?lter capacitor 293
is connected across divider I95 so that the re—
sultant potential appearing between the grid and
cathode of device I14 is only varied to any ap
preciable degreee when the effective value of the
source potential varies.
As the grid-cathode potential of the vacuum
discharge device I14 increases, the resistivity of
the device to the flow of current increases. The
current flowing through the resistor 9I in series
tial. The amount of phase displacement is de
with the device I14 then decreases as does the
termined by the position of the adjustable tap
potential developed thereacross by that current.
IBI on the potentiometer I41 and the setting of
It is then apparent that the potential across the
the variable resistor I5I. A scale I63 is provided
resistor 9| varies in accordance with the poten
alongside the variable resistor I5I to permit set
tial across potentiometer I95 and, therefore, in
ting thereof in accordance with the power factor
of the load. Another scale IE5 is provided along 25 accordance with the source potential. However,
because of the ampli?cation effected through de
side the potentiometer I41 to permit setting of the
vice I153 a slight change in the effective value of
adjustable tap I6l thereof in accordance with the
the source potential produces a comparatively
welding heat desired.
large change in the direct current potential on
Another auxiliary transformer I51 has its pri
resistor 9|. The polarity of the potential across
mary I69 connected between an end terminal of
resistor 9I tends to make the control electrodes
the potentiometer I41 connected to tap I45 on
99 and El of the ?ring valves positive. However,
resistor I39 and the adjustable tap I5I of the
it is to be noted that an increase in the source
potentiometer. The potential appearing across
potential acts through resistor 9| to make the
the secondary ill of the auxiliary transformer
control electrodes less positive and a decrease
is recti?ed and ?ltered by a recti?er unit I13 and
impressed across the fourth resistor 84 in the cir
cuit between the negative terminal of the divider
TI and the control electrodes 49 and 5| of the
?ring valves. The potential across the fourth re
sistor 84, therefore, is a direct current potential
which varies in accordance with the setting of
the heat control potentiometer I41. It is to be
noted that for the same heat control setting of
in the source potential makes the control elec
trodes more positive.
potentiometer I41, different potentials appear
The operation of the apparatus may be more
readily understood by reference to Figs. 2 and 3
with respect to the circuit of Fig. 1. In Fig. 3,
the anode potential of one ?ring valve is shown
by the dotted curve 294, and the anode potential
of the other ?ring valve is shown by the solid
line curve 295.
across the fourth resistor 84 for different settings
of the variable resistor I5I in series with the heat
valves is represented by curve 291.
control potentiometer.
The fourth resistor SI and the potentiometer
81 in the control circuit of the ?ring valves are
also part of a voltage compensating circuit I12. '
A vacuum discharged device 114 and resistor 9|
are connected in series across the end terminals
of the potentiometer 81. A substantially constant
direct current potential is impressed across the
potentiometer 81 which is derived from the alter- r»
nating source I5 through a voltage regulator I18,
an auxiliary transformer I19, a recti?er I8I and
several ?ltering elements I83, I85, I81 and I89.
The voltage regulator I18 shown in the drawings
is the well-known type manufactured by the
Raytheon Manufacturing Company, although
any suitable regulator may be used. The purpose
of the regulator is to prevent the potential across
potentiometer 81 from varying with ?uctuations
in the source.
The vacuum device I111 is of the type whose
resistivity varies in accordance with variations
in the magnitude of the potential impressed be
tween its grid I15 and cathode I11, an R. C. A.
2A3 tube being satisfactory. The grid I 15 is con;
nected through a grid resistor I9I to an inter
mediate tap I93 on another voltage divider I95
whose positive terminal is connected to the oath
ode I11. A direct current potential is also im
pressed across the second voltage divider I95
“Originally the control potential for the ?ring
To initiate
a welding operation, the push-button switch 91
is closed manually. The start valve 93 then be
comes conductive when the next potential im
pulse is impressed across the resistor III in its
control circuit. When the start valve 93 be
comes conductive, the sum of the continuous po
tentials in the control circuit of the ?ring valves
becomes less negative. As a result, the control
potential is raised to the position shown as curve
291'. In this position, the control potential curve
291’ rises above the critical potential of the ?rst
?ring valve, which for the purposes of simplicity
is assumed to be zero, at a point 299 in each half
period of the source in which the anode of the
?rst ?ring valve is positive. Likewise the con
trol potential rises above the critical potential
of the second ?ring valve at a point 2I I in each
half period of the source in which the anode of
the second ?ring valve is positive. As each ?r
ing valve becomes conductive, the corresponding
ignitron becomes conductive to conduct current
to the welding transformer.
The phase position of the points 299 and ‘M I
is the same with respect to the corresponding
half-period and is determined by the setting of
the variable resistor I5I and the heat control
potentiometer I41 of the phase shifting circuit
E33. The variable resistor I5I is set in accord
ance with the power factor of the load so that for
2,406,429
9
a 100% heat setting of the potentiometer I41, the
?ring valves are rendered conductive at the be
ginning of the positive half-period of the cur
rent regardless of the power factor. The poten
tiometer I4‘! may, of course, be set for different
heats, each of which is a given percentage of the
available current.
10
by rendering the valve conductive at a phase
point of 135° shown in Fig. 2 as point 229. Con-.
sequently, the lower end of the potentiometer M1
is always employed for the 20% heat setting, and
the line representing the positions of the control
potential peaks for various heat settings with
normal source potential always passes through
In Fig. 2, the anode potential of one of the
the point 239. In other words, changing the
?ring Valves is represented by a solid line curve
power factor setting of the variable resistor l5!
2l3. Let it be assumed that the power factor is 10 selects the angle of the line of peaks and chang
100% so that the current curve tends to follow
ing the heat setting of the potentiometer selects
the source potential curve. Then for a given
the particular point along the line of peaks at
heat setting, which may be high, the control po
which the control potential peak is to be lo
tential may be represented by another solid line
cated. In this manner, a variation in source po
curve 295. Assuming that the critical potential
tential is compensated by a variation in the po
of the ?ring valve is zero, the control potential
sition of the ?ring point with due regard to the
causes the valve to be rendered conductive at
power factor and heat control setting. Thus, in
the point 216. Should the source potential de~
the present case, the line of peaks falls along
crease, as represented by the dotted line curve
line 24 I.
213a, the circuit I12 increases the direct-cur 20 A predetermined time interval after the ?ring
rent component of the control potential by an
of the start valve 93, the capacitor E05 in the con
amount illustrated as ill. Consequently, the
trol circuit of the stop valve I I9 becomes charged
control potential is raised to the position repre
suf?ciently to render the stop valve conductive.
sented by the second dotted line curve 255a and
When the stop valve becomes conductive, the
the valve becomes conductive at point 22!. Be
sum of the continuous potentials in the control
cause of the slope of the wave front of the control
circuit of the ?ring valves again becomes highly
potential curve, the ?ring point of a ?ring valve
negative to prevent the control potential curve
is advanced by an amount represented by 223.
from rising above the critical potential of the
Of course, if the source potential should increase,
valve.
Thus, further conductivity by the ig
the control potential curve would be lowered so
nitrons I‘! and I9 is prevented. The push-button
that the ?ring point of the valve would be de
switch 91 may then be released, whereupon a
layed by an amount necessary to compensate for
back contactor 243 thereon is closed to complete
the reduced potential.
a discharge circuit for the capacitor, Hi5. An
If the heat setting is then changed to a posi
other welding operation may thereafter be ini
tion corresponding to 20% heat with the anode
tiated by reclosing the push-button switch 91.
potential represented by curve Zlt’, the direct
Although I have shown and described a spe
current component of the control potential is
ci?c' embodiment of my invention, I am fully
lowered by an amount illustrated by 225, and at
aware that many modi?cations thereof are pos
the same time the phase position of the pulsat
sible without departing from the spirit of the in
ing component is shifted to the right. As a re 40
vention. My invention, therefore, is not intend
sult, the control potential now assumes the posi
ed to be restricted to the speci?c embodiment
tion represented by curve 2 51). It is to be noted
shown.
that with the same power factor setting, but with
I claim as my invention:
various heat settings, the peak of the control
1. For use in controlling the supply of current
potential curve will follow along the line 227.
from a source of alternating potential to a load,
With the 29% heat setting, the ?ring valve is
the combination comprising electric valve means
rendered conductive at the point 229. Should
of
the arc-like type interposed in circuit be
the source potential decrease to the position of
tween said source and load, and control means
the dotted line curve Zita, the control potential
is raised by the same amount as in the case of 50 for rendering said valve means conductive in suc
cessive half-periods of said source potential in
the higher heat setting to curve 215a. However,
because the slope of the wave front of the control
cluding manually adjustable means for preselect
ing the instant in a half-period at which said
valve means is normally rendered conductive,
point is only advanced from point 228 to point
23!! by an amount 23! which‘ is less than the 55 means for varying said instant in a half-period
in accordance with variations in the effective
amount of advance 223 of the firing point in the
value of said source potential, and means for
case of the higher heat setting. As previously
varying the ratio of the variation of said instant
pointed out, the compensation required with a
to the source potential variation in accordance
low heat setting is much less than with a high
with the adjustment of said preselecting means
heat setting, and, consequently, the ?ring point
and with the power factor of said load.
need not be advanced to the same extent.
2. For use in controlling the supply of cur
If the power factor of the load is not 100%
rent from a source of alternating potential to a
but is something less so that the current assumes
load, the combination comprising electric valve
the variable
position represented
resistor i5| by
is set
thetodot~dash
correspond
line with
means of the arc-like type interposed in circuit
65 between said source and load, and control means
the power factor. Then with the same high heat
for rendering said valve means conductive in
setting as in the original case, the control po
successive half-periods of said source potential
tential is represented by curve 2!
‘and rises
including manually adjustable means for prese
above the critical potential at the point 235. If
lecting the instant in a half-period at which said
the source potential is then lowered to Zita, the
control potential is raised to the dotted curve 70 valve means is normally rendered conductive,
means for varying said instant in a half-period
2i5e and the ?ring point is advanced from point
in accordance with variations in the effective
235 to point 231 by an amount 238.
value
of said source potential, means for varying
It has been found that regardless of the power
the ratio of the variation of said instant to the
_ factor of the load, a 20% heat may be obtained 75
source potential variation in accordance with the
potential increases with respect to time, the ?ring
2,406,429
11
12
adjustment of said preselecting means with said
ratio increasing for adjustments of said prese
direct current control potential of a magnitude
lecting means from a setting for an instant late
in a half-period toward a setting for an instant
ment selected.
6. For use in controlling the supply of current
from a source of periodically pulsating potential
to a load, the combination comprising electric
valve means of the arc-like type interposed in
circuit between said source and load, control
dependent upon the particular phase displace
early in a half-period, and means for adjusting
the rate of increase of said ratio for loads hav
ing different power factors.
3. For use in controlling the supply of current
means for said valve means, said valve means be
from a source of periodically pulsating potential
to a load, the combination comprising electric 10 ing adapted to be rendered conductive in a period
of said source potential upon the application to
valve means or" the arc-like type interposed in
said control means of a potential greater than a
circuit ‘between said source and load, control
predetermined critical value, means for applying
means for said valve means, said valve means be~
to said control means a second periodically pul
ing adapted to be rendered conductive in a pe
sating control potential of the same periodicity
riod of said source potential upon the applica
but having a preselected phase displacement rela
tion to said control means of a potential greater
tive to said source potential, each of the pulsa
than a predetermined critical value, means for
tions of said second potential having a sloping
applying to said control means a second period
wave front with the degree of slope with respect
ically pulsating control potential of the same pe
to time increasing over the length of said front,
riodicity but having a preselected phase displacemeans for applying to said control means a third
ment relative to said source potential, each of the
direct-current control potential of a magnitude
pulsations of said second potential having a slop
determined by the particular phase displacement
ing Wave front with a slope which is non-uniform
selected with the magnitude decreasing with an
over the length of said front, means for applying
to said control means a third direct-current con
25 increase in displacement, and means for also ap
trol potential of a magnitude depending upon the
plying to said control means a fourth direct-cur
particular phase displacement selected, and
rent control potential which varies in magnitude
in accordance with variations in the effective
value of said source potential.
fourth direct-current control potential which
‘7. For use in controlling the supply of current
varies in magnitude in accordance with variations 30
from a source of periodically pulsating potential
in the effective value of said source potential.
to a load, the combination comprising electric
4. For use in controlling the supply of current
valve means of the arc-like type interposed in cir
from a source of periodically pulsating potential
cuit between said source and load, control means
to a load, the combination comprising electric
valve means of the arc-like type interposed in 35 for said valve means, said valve means being
adapted to be rendered conductive in a period of
circuit between said source and load, control
said source potential upon the application to said
means for said valve means, said valve means be
means for also applying to said control means a
control means of a potential greater than a pre—
ing adapted to be rendered conductive in a pe
determined critical value, means for applying to
riod of said source potential upon the applica
tion to said control means of a potential greater 40 said control means a second periodically pulsating
control potential of the same periodicity but hav
than a predetermined critical value, means ‘for
ing a preselected phase displacement relative to
applying to said control means a second periodi
said source potential, each of the pulsations of
cally pulsating control potential of the same pe
said second potential having a sloping wave front
riodicity but having a preselected phase dis
placement relative to said source potential, each 45 with a slope which is non-uniform over the length
of said front, means for applying to said control
of the pulsations of said second potential having
‘means a third direct-current control potential in
a sloping wave front with the degree of slope with
respect to time increasing over
length of said
front, means for applying to said control means
a third direct-current control potential of a mag
nitude depending upon the particular phase dis
placement selected, and means for also applying
to said control means a fourth direct-current con
cluding means for adjusting the magnitude there
of in accordance with both the power factor of
the load and the particular phase displacement
selected, and means for also applying to said con
trol means a fourth direct-current control po
tential which varies in magnitude in accordance
with variations in the effective value of said
trol potential which varies in magnitude in ac
source potential.
cordance with variations in the effective value of
said source potential.
8. For use in controlling the supply of current
from a source of alternating potential to a load,
5. For use in controlling the supply of current
from a source of alternating potential to a load,
the combination comprising electric valve means
of the arc-like type interposed in circuit between
the combination~ comprising electric valve means
of the arc-like type interposed in circuit between 60 said source and load, control means for said valve
means, said valve means being adapted to be ren
said source and load, control means for said valve
dered conductive in a half-period of said source
means, said valve means being adapted to be ren
potential upon the application of said control
dered conductive in a half-period of said source
means of a potential greater than a predeter
potential upon the application to said control
means of a potential greater than a predeter
mined critical value, means for applying to said
control means a second control potential having
mined critical value, means for applying to said
control means a second control potential having
the wave form of an inverted, full-Wave recti?ed,
alternating potential of the same frequency but
the wave form of an inverted, full~wave recti?ed,
alternating potential of the same frequency but
having a preselected phase displacement rela
tive to said source potential, means for applying
to said control means a third direct-current con
trol potential which varies with. variations
the
effective value of said source potential, and means
for also applying to said control means a fourth,
having a preselected phase displacement relative
to said source potential, means for applying to
said control means a third direct-current control
potential which varies with variations in the ef
fective value of said source potential, and means
for also applying to said control means a fourth
direct-current potential including means for ad
2,406,429
13
justing the magnitude thereof in accordance with
both the power factor of the load and the par
ticular phase displacement selected.
9. For use in controlling the supply of current
from a source of periodically-pulsating potential
to a load, the combination comprising electric
valve means of the arc-like type interposed in cir_
cuit between said source and load, control means
for said valve means, said valve means being
adapted to be rendered conductive in a period of
said source potential upon the application to said
14
tude increasing with an increase in power factor
and decreasing with an increase in phase dis
placement, and means for also applying to said
control means a fourth direct current control
potential which varies in magnitude in accord
ance with variations in the effective value of said
source potential.
10. For use in controlling the supply of current
from a source of alternating potential to a load,
the combination comprising electric valve means
of the arc-like type interposed in circuit between
control means of a potential greater than a pre
said source and load, and control means for ren
determined critical value, means for applying to
dering said valve means conductive in successive
said control means a second periodically pulsat
half-periods of said source potential including
ing control potential of the same periodicity but 15 manually adjustable means for preselecting the
having a preselected phase displacement relative
instant in a half -period at which said valve means
to said source potential, each of the pulsations of
is normally rendered conductive, means for vary
said second potential having a sloping wave front
ing said instant in a half-period in accordance
with the degree of slope with respect to time in
with variations in the effective value of said
creasing over the length of said front, means for 20 source potential, and means responsive to adjust
applying to said control means a third direct~
ment of said preselecting means for varying the
current control potential including means for ad
ratio of the variation of said instant to the source
justing the magnitude thereof in accordance with
potential variation in accordance with such ad
both the power factor of the load and the particu
justment and with the power factor of said load.
lar phase displacement selected with the magni 25
JOHN R. MAHONEY.
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