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Патент USA US3082376

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March 19, 1963
R.
B . SANDERS I
3,082,366
MEANS FOR SPEED CONTROL OF A DIRECT CURRENT
MOTOR OPERATING FROM AN ALTERNATING
CURRENT SUPPLY SOURCE
Filed May 25, 1959
INVENTOR.
RICHARD B- SANDERS
BY
mw QLzW
HIS ATTORNEYS
United States Patent 0 "
CC
1
3,082,366
3,082,366
Patented Mar. 19, 1963
2
connection to an alternating current source, one of the
‘
MEANS FOR SPEED CONTROL OF A DIRECT CUR
RENT MOTOR OPERATING FROM AN ALTER
NATING CURRENT SUPPLY SOURCE
Richard B. Sanders, Albany, Cali?, assignor to L & B
Welding Equipment, Inc, a corporation of California
Filed May 25, 1959, Ser. No. 815,560
13 Claims. (Cl. 318-331)
leads, ‘15, is connected to one of the ?eld winding termi
nals 1 through a half-wave recti?er 19 of the metallic
type, while the other lead 17 connects directly to the re
maining ?eld winding terminal 3, whereby to provide
direct current for use in such ?eld winding.
In a somewhat similar manner, recti?ed voltage is ap
plied to the armature winding terminals 9 and 11, except
instead
utilizing a standard type metallic recti?er, I
My invention relates to motor control circuits and 10 employ aofgated
recti?er 21 having an anode 23, a cathode
more particularly to an adjustable constant speed con~
25, and a gate 27, the anode being connected to one of
trol circuit for a direct current motor operating from an
the leads 15 while the cathode is connected to one of
alternating current supply source.
the armature winding terminals 9, while the other arma
Such speed control circuits for electric motors have
ture winding terminal 11 is connected to the other lead 17.
heretofore, for the most part, utilized electron discharge 15' Recti?cation through this gated recti?er is controlled
devices, such as the gas ?lled tube known as the “thyra
in the present invention, in accordance with variations
tron” for example. Such devices, while they function
in back electromotive force of the motor when connected
well, can cause the controlling equipment to become
to the terminals provided therefor.
‘bulky by comparison with the apparatus to be controlled
Such control means comprises a direct current control
which may, by itself, be of limited or small size.
Such electron discharge devices further, require ?la
ments or heaters for the generation of electrons, and the
heating up of such ?laments or heaters, necessarily en
20 circuit from one of the leads 15 to the gate 27, such direct
current control circuit including a recti?er 31 and variable
resistance in series therewith, such resistance being pref~
erably in the form of a pair of resistors 33 and 35, the
tails a Warm up period to prepare the device for opera
former being variable and of the order of 5000 ohms, con
tion.
25 nected between the lead '15 and the recti?er v31 while the
Also, electron discharge devices such as the thyratron,
other resistor ‘35 may be of the ?xed type, connected’ be
introduce a voltage drop through the same of the order
tween the recti?er 31 and the gate 27 and of a value of
of ten volts and when functioning in the armature circuit
the order of 2300 ohms.
,
'
of amotor to be controlled, such drop in voltage lowers
circuit connected between the other lead 17
the motor speed proportionately unless the circuit is de 30 andA abranch
point 39 on ‘the direct current control circuit
signed to compensate for such drop in voltage.
between the recti?er 31 and the ?xed resistor 35, in
Among the objects of my invention are:
cludes
a resistor 41 of the order of 1800 ohms, shunted
(1) To provide a novel and improved control circuit
‘for an electric motor;
by a capacitor 43 having a value of the order of 8 micro
’farads. The values given are not critical but represent
(2) To provide a novel and improved control circuit 35 an embodiment of the invention as applied to a small
‘for a direct current motor operated from an alternating
motor of fractional horsepower utilized in driving the
current supply source;
I
electrode wire 45 in automatic and, semi-automatic
(3) To provide a novel and improved constant speed
welding.
'
'
control circuit for an electric motor operating from an
A gated recti?er 19 is a control device which will ?re
40
alternating current supply source;
and pass current when the gate current reaches a threshold
(4) To provide a novel and improved constant speed
value of the order of 15 millamperes, and will thereafter
motor control circuit requiring no electron discharge
continue to pass current until the voltage across it is
tubes;
(5) To provide a novel and improved motor speed
control apparatus occupying but a limited amount of
space;
brought to zero.
When power is derived ‘from a con
ventional alternating current supply source, as in the
45 vpresent instance, there will be 60 half cycles per second
during which current can ?ow through the gated recti?er.
(6) To provide a novel and improved motor speed con
' Accordingly there will be 60 cross-overs per second
trol circuit involving no Warm-up period;
through zero voltage, when extinguishment of current
(7) To provide a novel and improved motor speed con
will occur if current ?ow exists at the time of cross
trol circuit in which the voltage drop is negligible;
over. Whether such current flow through the gated
(8) To provide a novel and improved motor speed con 50 recti?er exists depends upon the value of the gate current
‘trol circuit of great sensitivity and high e?iciency;
at the start of each alternate half cycle, and this in turn
(9) To provide a novel and improved motor speed con
depends on two factors namely, the resistance in the gate
‘trol circuit having excellent load compensation; and
circuit, and the back electromotive force generated by
(10) To provide a novel and improved motor speed 55 the motor.
control circuit adapted to the control of electrode wire
Assume the motor 7 to be at a standstill and the ad—
‘feed in automatic and semi-automatic Welding equipment.
justable resistor 33 is gradually cut out until the threshold
Additional objects of my invention will be brought
value of gate current is reached. At this point, ?ring
out in the following description of a preferred embodi
occurs and alternate half cycles of current will begin to
ment of the same taken in conjunction with the a'ccorn~
?ow through the armature of the motor and start the
panying drawings wherein:
motor armature rotating, during the course of which the
The FIGURE is a circuit diagram depicting the motor
motor will pick up speed and generate an increasing ‘back
speed control circuit of the present invention as applied
electromotive force. Since the gate current was assumed
to the control of speed of a direct current motor of the
to be at threshold value, a small back electromotive force
shunt type, in feeding electrode wire in automatic or
65 "(low speed) will serve to reduce the value of the gate
. semi-automatic welding.
, Referring to the drawings for details of my invention
in its preferred form, the same provides a pair of termi
nals 1 and 3 for connection thereto of the ?eld winding
5 of a motor 7, and a second pair of terminals 9 and £11
current to a value just below the threshold value, as a
result of which, ?ring will not occur on the next alternate
half cycle and the motor armature will tend to “slow
down,” and such slowing down may continue for the
next few alternate half cycles su?icien-t to bring the
for the connection thereto of the armature winding 13 of 70 gate current ‘back to threshold value and cause the gated
such motor. ’Of a pair of leads 15 and 17 adapted for
recti?er to‘ again begin ?ring and supply current to the
8,082,366
motor armature, following which the motor will again
pick up speed to the point of developing a back electro
motive force su?icient to reduce the gate current again
to a point just below threshold value, and the cycle will
repeat itself.
'
'
While this may seem to indicate that the motor speed
will not remain constant but will vary considerably, it
must be remembered that all of this occurs within a
few cycles of alternating current which represents but
a fraction of a second, during which the gate current
and motor speed change only insigni?cantly.
By further reducing the value of resistance in the gate
circuit, a greater back electromotive force will have
to be developed by the motor to bring the gate current
down to a point just below its threshold value, and conse
quently the motor will have to reach a higher rate of
speed to accomplish this. While this may require a
few more alternating current cycle periods to accomplish,
4
a gate; and means for controlling recti?cation through
said gated recti?er in accordance with variations in back
electromotive force generated by said motor, said means
comprising a direct current control circuit from one of
said leads to said gate and including a recti?er, and means
for adjusting the amplitude of the resulting recti?ed cur
rent to said gate.
2. A motor control circuit comprising a motor having
a ?eld winding and an armature winding; a pair of leads
adapted for connection to an alternating current supply
source; means in circuit with said ?eld winding between
said leads for rectifying alternating current from such sup
ply source for energizing said ?eld winding; means in cir
cuit with said armature winding between said leads for
rectifying alternating current from such supply source for
energizing said armature winding, said means including
the anode and cathode of a gated solid state recti?er hav
ing an anode, a cathode and a gate; and means for con
trolling recti?cation through said gated recti?er in accord
the time interval involved will still consume but a frac
tion of a second and for all practical purposes, the speed 20 ance with variations in back electromotive force generated
by said motor, said means comprising a direct current
of the motor will be deemed constant at this new speed.
control circuit from one of said leads to said gate and
Accordingly, the variable resistance 33 in the gate
including a recti?er, and means for adjusting the ampli
circuit provides means ‘for adjusting the control current
tude of the resulting recti?ed current to said gate.
level and thus controlling the speed of the motor 7, and
whichever speed is selected, the speed of the motor will 25 3. A motor control circuit comprising a motor having
a ?eld winding and an armature winding; a pair of leads
for all practical purposes remain constant at that value.
adapted for connection to an alternating current supply
The same characteristics of the circuit, as described
source; means in circuit with said ?eld winding between
above, bring about very good load compensation in the
said leads for rectifying alternating current from such
operation of the circuit which results from the fact that
as a load is applied to the motor, such load will tend to 30 supply source for energiizng said ?eld winding; means in
circuit with said armature winding between said leads
slow down the rotational speed of the armature. As the
for rectifying alternating current from such supply source
armature tends to slow down, the back electromotive
for energizing said armature winding, said means includ
force generated by the motor begins to decrease thereby
ing the anode and cathode of a gated solid state recti?er
causing more current to ?ow in the gate circuit of the
recti?er which in turn causes the gated recti?er to ?re for 35 having an anode, a cathode and a gate; and means for
controlling recti?cation through said gated recti?er in ac
a greater number of alternate half cycles which in turn
cordance with variations in back electromotive force gen
tends to overcome the effect of the increase in load on
erated by said motor, said means comprising a direct cur
the motor armature and hold the speed of the motor
rent control circuit from one of said leads to said gate
constant.
In the application of the invention to automatic and 40 and including a recti?er and resistance in series there
with; and means for manually altering said resistances to
semi-automatic welding, the motor 7 will supply the
adjust the current level to said gate in said control circuit.
power for driving electrode wire 45 from a reel 47
4. A motor control circuit comprising a motor having
through a ?exible casing 49 to the work to be welded, and
a ?eld widing and an armature winding; a pair of’ leads
accordingly need only be of a fractional horse power
adapted for connection to an alternating current supply
rating of the order of 1/8 horsepower. ‘ The speed control
circuit, by reason of the fact that it requires no electron 45 source; means in circuit with said ?eld winding between
said leads for rectifying alternating current from such
tubes, may be assembled into a very small, light and
supply source for energizing said ?eld winding; said
compact unit of perhaps one tenth the size of a compar
means including a metallic type recti?er; means in cir
able unit utilizing electron discharge tubes. The com
cuit with said armature winding between said leads for
plete absence of ?laments or heaters eliminates the warm
up time formerly required when utilizing electron tubes, 50 rectifying alternating current from such supply source for
energizing said armature winding, said means including
and at the same time essentially eliminates the voltage
a gated recti?er having an anode, a cathode and a gate;
drop which occurs across such electron tubes when
and means for controlling recti?cation through said gated
functioning in a circuit.
recti?er in accordance with variations in back electromo~
It will be apparent that my invention ful?lls, all the
objects attributed thereto, and while I have disclosed 55 tive force generated by said motor, said means compris
the same in its preferred form as applied to automatic
ing a direct current control circuit from one of said leads ~
to said gate and including a recti?er and variable resist
ance in series therewith, and a branch circuit between said
other lead and a point on said direct current control cir
without departing from the underlying principles in
volved, and I accordingly do not desire to be limited in 60 cuit between said recti?er and a portion of said resistance.
5. A motor control circuit comprising a motor having
my protection to the speci?c details illustrated and de
a ?eld winding and an armature winding; a pair of leads
scribed except as may be necessitated by the appended
adapted for connection to an alternating current supply
claims.
source; means in circuit with said ?eld winding between
I claim:
1. A motor control circuit comprising a motor hav 65 said leads for rectifying alternating current from such
ing a ?eld winding and an armature winding; a pair of
supply source for energizing said ?eld winding; said means
leads adapted for connection to an alternating current
including a metallic type recti?er; means in circuit with
supply source; means in circuit with said ?eld winding
said armature winding between said leads for rectifying
between said leads for rectifyinng alternating current
alternating current from such supply source for energiz
from such supply source for energizing said ?eld wind 70 ing said armature winding, said means including a gated
ing; means in circuit with said armature winding be
recti?er having an anode, a cathode and a gate; and
tween said leads for rectifying alternating current from
means for controlling recti?cation through said gated rec
such supply source for energizing said armature wind
ti?er in accordance with variations in back electromotive
ing, said means including the anode and cathode of a
force generated by said motor, said means comprising a
75
gated solid state recti?er having an anode, a cathode and
and semi-automatic welding, it will be apparent that
the invention is subject to alteration and modification
8,082,366
5
direct current control circuit from one of said leads to said
gate and including av recti?er and variable resistance in
series therewith, and a branch circuit between said other
lead and a point on said direct current control circuit
between said recti?er and a portion of said resistance, said
branch circuit including a resistor and a condenser in
parallel therewith.
~
6. Apparatus for control of speed of a motor having a
?eld winding and an armature winding, said apparatus
6
9. Apparatus for control of speed of a motor having a
?eld winding and an armature winding, said apparatus
comprising a pair of ?eld winding terminals; a pair oat
armature vwinding'terminals; a pair of leads adapted for
connection to an alternating current supply source; means
in circuit with said pair of ?eld winding terminals for
rectifying alternating current from such supply source,
said means including .a metallic type recti?er to one of
comprising a pair of ?eld winding terminals; a pair of 10 said leads, a connection from the other side of said recti?er
to one of said ?eld winding terminals, and a connection
armature winding-terminals; a pair of leads adapted for
from the other of said ?eld winding terminals to the other
connection to an alternating current supply source; means
of said leads; means in circuit with said armature winding
in circuit with said pair of ?eld winding terminals for
vterminals for rectifying alternating current from such
rectifying alternating current from such supply source,
said means including a metallic type recti?er; means in 15 supply source, said means including a gated recti?er hav
ing an anode, a cathode, and a gate, a connection from
circuit with said armature winding terminals for rectify
said anode to one of said leads, a connection ‘from said
ing alternating current from such supply source, said
cathode to one of said armature winding terminals, and
means including a gated solid state recti?er having an
a
connection from said other armature winding terminal
anode, a cathode, and a gate, a connection from said
anode to one of said leads, a connection from said cath 20 to the other of said leads; and means for controlling
recti?cation through said gated recti?er in accordance
ode to one of said armature winding terminals, and a con
with
variations in back electromotive force of a motor
nection from said other armature winding terminal to
when connected to said terminals, said means comprising
the other of said leads; and means for adjusting the ampli
a direct current control circuit from one of said leads
tude of a direct current to said gate.
7. Apparatus for control of speed of a motor having a 25 to said gate and including a recti?er and variable resist
ance in series therewith, and a branch circuit ‘between said
?eld winding and an armature winding, said apparatus
other lead and a point on said direct current control cir
com-prising a pair of ?eld winding terminals; a pair of
cuit ‘between said recti?er and a portion ‘of said resistance,
armature winding terminals; a pair of leads adapted for
said
‘branch circuit including a resistor and a condenser in
connection to an alternating current supply source; means
parallel therewith.
,
in circuit with said pair of ?eld winding terminals [for 30
10. A motor control circuit comprising a motor having
rectifying ‘alternating current from such supply source,
a ?eld winding and :an armature winding; a pair of leads
said means including a metallic type recti?er; means in
circuit with said armature winding terminals for rectifying
adapted for connection to an alternating current supply
rectifying ‘alternating current from such supply source,
source; means in circuit with said ?eld winding between
winding terminals, and a connection from the other of
said ?eld winding terminals to the other of said leads;
means in circuit with said armature Winding terminals for
rectifying alternating current from such supply source, 60
rectifying alternating current from such supply source for
energizing said armature winding, said means including a
source; means in circuit with said ?eld winding between
alternating current from such supply source, said means
said
leads for rectifying alternating current from such
including a gated solid state recti?er having an anode, 35
supply
source for energizing said ?eld winding; means in
a cathode, and a gate, a connection from said anode to
circuit with said armature winding between said leads for
one of said leads, a connection from said cathode to one
rectifying alternating current from such supply source for
of said armature winding terminals, and a connection
energizing
said armature winding, said means including a
from said other armature winding terminal to the other
of said leads; and means for controlling recti?cation 40 gated solid state recti?er having an anode, a cathode and
a gate; and means for controlling recti?cation through
through said gated recti?er in accordance with variations
said
gated recti?er in accordance with variations in back
in back electromotive ‘force of a motor when connected
electrom-otive force generated by said motor, said means
to said terminals, said means comprising a direct current
comprising a direct current control circuit from one of
control circuit from one of said leads to said gate and
including a recti?er and an adjustable resistance in series 45 said leads to said gate and including a recti?er, said direct
current control circuit including a variable resistance, a
therewith.
recti?er and a further resistance connected all in series
8. Apparatus for control of speed of a motor having a
across said alternating current supply source, and a con~
?eld winding and an armature winding, said apparatus
nection from a point of said resistances to said gate.
comprising a pair of ?eld winding terminals; a pair of
11. A motor control circuit comprising a motor having
armature winding terminals; a pair of leads adapted for 50
a ?eld winding and an armature ‘win-ding; a pair of leads
connection to an alternating current supply source; means
adapted for connection to an alternating current supply
in circuit with said pair of ?eld winding terminals lfOI‘
said leads for rectifying alternating current from such
said means including a recti?er, a connection from one
side of said recti?er to one of said leads, a connection 55 supply source for energizing said ?eld Winding; means in
circuit with said armature winding between said leads for
from the other side of said recti?er to one of said v?eld
said means including a gated recti?er having an anode, a
cathode, and a gate, a connection ‘from said anode to one
of said leads, ‘a connection from said cathode to one of
gated solid state recti?er having an anode, a cathode and
a gate; and means for controlling recti?cation through
said gated recti?er in accordance with variations in back
electromotive force generated ‘by said motor, said means
comprising a direct current control circuit connected
across said current supply source from one of said leads
said armature winding terminals, and a connection from
said other armature winding terminal to the other of said 65 to said gate ‘and including a recti?er, said control circuit
including a variable voltage divider supplying variable
leads; and means ‘for controlling recti?cation through said
bias to said gate.
gated recti?er in accordance with variations in back elec
~12. A'circuit for controlling the speed of an electric
tromotive force of a motor when connected to said termi
motor
having an armature and ?eld winding fed from
nals, said means comprising a direct current control cir
a_ source of AC. voltage, comprising a variable ‘voltage
cuit from one of said leads to said gate ‘and including a
70 dlvider source connected across said source, a solid state
recti?er and resistance in series therewith, and a branch
controlled recti?er having an anode, a cathode, and a
circuit between said other lead and a point on said direct
gate, said recti?er having its cathode connected to one
current control circuit between said recti?er and a portion
end of said armature winding, the other end of said
of said resistance, said branch circuit including a resistor
armature Winding being connected to said source and said
and a condenser in parallel therewith.
.75 anode being connected to_ said source, and a diode and a
3,082,366
7
smoothing condenser connected in circuit with said volt
age divider and said gate, said voltage divider, diode, and
smoothing condenser providing a variable direct current
bias voltage to said gate.
a diode connected to said gate and to said variable volt
age divider for rendering said bias voltage unidirectional.
References Cited in the ?le of this patent
13. A motor ‘control circuit comprising a motor having
a ?eld winding and an armature winding adapted for
connection to a source of AC. voltage, a gated solid
state recti?er having an anode, a cathode, and a gate,
said anode and cathode being connected in series with
8
resistances being shun-ted by a smoothing condenser, and
UNITED STATES PATENTS
2,656,500
2,785,368
2,839,714
Dee ________________ __ Oct. 20, 1953
Elliot _____________ __ Mar. 12, 1957
Mueller ____________ __ June 17, 1958
‘Momberg et a1. ______ __ May 31, 1960
said armature winding across said source, said cathode 10 2,939,064
2,977,523
Cockrell ____________ __ Mar. 28, 1961
|being connected to one end of said armature winding,
and a source of controllable bias rvoltage for said gate,
OTHER REFERENCES
said source of controllable bias voltage including a vari
Pub1., Solid State Thyratron Switches Kilowatts,
able voltage divider connected across said supply and
including at least two resistances, at least one of said 15 Frenzel-Gutzueller, Electronics, March 28, 1958.
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