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ÈÁÍÍÍÍÁÈS
PHASE SHIFTING CIRCUIT
Filed may 9, 1944 ‘
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‘ :Patented ‘Novi’
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2,411,423 '
UNi'reo s’rArEs . PATENT ~ ori-*lcs
2,411,423
rmsnsmr'rmo cmcnrr
Heath It. Guptill, Washington, D. C., assignor to
, General Electric Company,
a corporation of__
New York
_ Application May 9, 1944, Serial No. 534,769
3
(01.'172-238)
connected directly to ground so that it is main
that source.
tained at the potential of the electrically inter
Vmediate connection 6 of winding I. The vari
u
My invention is oi' genera-l application in electron control and regulating systems, although it
is particularly adapted for use in connection with
the sweep circuit of the cathode ray tube. In
such applications, itis desirable. to control the
phase of the potential supplied to the sweep cir
cuit through` a' variation of substantially 360 elec
«Ítrical degrees in order to obtain optimum oper
ationoij such an apparatus.
It is an'obie’ct of my invention to provide a new
and improved electric phase shifting circuit.
It is a further` object off-my invention to pro
vide a new and improved electric kphase shifting
circuit of the static impedance type in which the
able contact II on resistor> I0 is likewise con
nected to the opposite terminal Ii‘of winding I.
through a variable resistance I4. The resistance
I 4 is shown as having‘a contact I5 adjustable in
position along the length ci the resistance to vary
’ the resistance
between contact II and
10 terminal ä. ‘ connected
.
` In the operation of the phase shifting circuit,
the two variable contacts I5 and," are moved in
a _certain sequence in order to obtain a phase shift
which progresses continuously in one direction
-15
without discontinuitiesv or reversals. This se
quence consists in starting the contact II at the
upper terminal of resistor I0 and contact I 5 at
output voltage may be varied through 360 elec- '
the lower 'terminal of resistance I4 so that the
resistance between output terminal I2 and ter
trical degrees relative to the input voltage.
minal 5 has a value of zero. The contact I5 is
ì
moved along resistance I4, changing this re
It is another object of~my invention to provide
an improved electric phase shifting circuit which
is simple in assembly and operation and which
sistance to a maximum value. This movement
~ oi' contact I5 produces o, shift in phase in the
requires only variable
v
resistances to obtain a - voltage of output terminals I2, I3 with respect
to the voltage across input terminals 4, 5 of
phase variation of 360 electrical degrees.
slightly less than 180 degrees. Thereafter, con
For a better understanding of my invention,
tact II is moved along resistor from its upper .
reference may be had to the following descrip.
terminal to its lower terminal toI 0produce
an ad-Á
tion taken in connection with the accompanying
ditional-` phase shift of between ten and twenty
drawing and its scope will be pointed out in the 30 degrees.
appended claims. Flg.x1 diagrammatically illus
strates an embodiment of my invention and Fig. 2 ,
illustrates a variable f resistance arrangement
which may be employed in the circuit of Fig. l,
Referring to Fig. 1, there is shown a phase shift 35
circuit `of the static impedance type which in
cludes a winding I across which is impressed an
alternating voltage. 'I'he winding I may be the
a transformer having a pri
. mary winding 2 connected to a source of alter
~
. The winding I is provided with
a pair of output terminals 4 and 5 and an elec
trically intermediate terminal 6 which is con
nected to ground so that the alternating poten
40
so the sequence may be
repeated. This particular order of adjusting the
variable elements in the phase-shifting circuit
produces a phase shift which progresses always
in the same direction. If the sequence is reversed,
tials appearing across the terminals 4 and 5 are 45. the phase shift is continuous in the opposite di
, rection. Any other desired sequence of opera
balanced with respect to ground.
'
Output terminal 4 of winding I is connected
to the common point 1 of a pair of reactance ele
ments comprising a iixed capacitance 8 and a
employed but the advan
tage of essentially constant-amplitude and es
sentially uniform phase shift is sacrificed.
fixed inductance 9 connected- in'series at their 50 In Fig. 2 there is shown a potentiometer ar
rangement which is particularly adapted for
use in the phase shifting circuit of Fig. -l. 'In
I0 is provided with a variable point or contact II
this ligure, elements corresponding to those in
which Is directly connected to an output terminal
the circuit of Fig. l are designated by corre
I2 of the phase shifting circuit. The other out
put terminal I3 of the phase shifting circuit is 55 spending reference numerals. The two resist
ance units I8. Il each have a value which is
opposite ends through a resistor I0. -The resistor
, a,41_1,4as
at an angle of 180°, or '1r radians, for X.> A poten
twice the value of the corresponding ~resistor
I4 shown in the circuit of'Fig. l.
tiometer having an approximately logarithmic
The points Y
taper approaches this function.
I8-’--2I correspond to the points indicated by
like reference numerals 'in Fig. 1. The resist
’
A of either of the contacts I I, I5 depends, of course,
ance units I 8, I1 are connected in parallel be
upon the particular values of resistances used
tween the equipotential points I8, I9 by means
for elements I0, I6, I‘I and the reactances of ele
ments 8; 8. Likewise, the change in amplitude
of conductor 22 of low resistance value to form
the inner resistance element of a potentiometer.
'I‘he two ends 20, 2I of resistance unit
l I0 have"
connected thereto similar conductors 23, -2I to
l
»The exact phase shift obtained by variation
of the output voltage depends upon the relative '
10 values of these _resistances and their magnitudes,
form the outer resistance element of a double
potentiometer arrangement. vAt a point oppo
site the point I8 on the inner potentiometer`
element, the conductors 23, 24 are terminated in' 15’
overlapping contact strips 25. 28, which form a
cross-over element in the outer potentiometer.
The variable contact points II, I5 are mechani
cally linked for uni-control operation. The re
sistances I8, I1 and III are so arranged in the
potentiometer that, as the contacts II, IB are 20
moved clockwise from the terminals I8, 25, first,
the eñective resistance value of resistors I6, Il
as >compared with the impedances of the react
ance elements of the circuit. In general, a sub
stantially uniform shift in phase may be obtained
with a variation in amplitude of less than-50 per
cent.
While I have shown a particular embodiment
of my invention, it will, of course, be under
stood that I do not wish to be hunted thereto
since various modiñcations may be made, and I‘
contemplate by the appended claims to cover
any such modifications as fall within the true
spirit and scope of my invention.
What I claim as new and desire to secure by
is varied-from a value of zero with respect to
Letters Patent of the United States is:
'
point I8 to a maximum value at point I8.
~1. In combination, a ' source of alternating
25
Throughout this motion, the value of resistance
>voltage having a pair of output terminals bal
I0 is unchanged, the contact I5 remaining elec
anced with respect to ground, a load connected
trically at the potential of point 2t. . Additional
between ground and one of said terminals
movement varies the- contact point il from the
Ácapacitance -end of resistor I@ to the inductance
' end. i. e., from terminal 20 to terminal 2i. .Ad
through a variable resistance, a pair of vreac
30 tances connected in seriesf through a resistor,
said reactances having a common point connect
`ditional clockwise movement of contacts II, I5
reduces the effective resistance value of resistors
ed to the other of said terminals, and means
connecting said load to a variable point of said
I1, It between points i8, I9 from a maximum
resistor.
value to zero value and completes a phase shift of
'
2. In combination, an alternating current cir
360 electrical degrees. Thereafter, the contact I i 35 cuit, apparatus for producing an alternating
moves across the contact strips 25, 2liv changing
voltage `variable in phase through 360 degrees
the contact Ii from the inductance end of the
relative tothe voltage of said circuit comprising
resistor It to its capacitance end, and preparing
a reactance element in said circuit having a pair
of terminals and an electrically intermediate
40
trical degrees.
'
,
connection, a- capacitance and an inductance
In the phase shift circuit described, in order
each having one terminal connected to one of
to obtain a shift in phase which varies substan
said terminals, a resistance connected between
tially uniformly with angular movement of the
the lopposite terminals of said capacitance and
the circuit for another phase shift of 360 elec
contacts Il, I5, resistors I6, I'I preferably may
be logarithmic in character, while resistor I0
preferably has a linear resistance characteristic.
The relation of the resistance between point I8
said inductance, an output circuit connected be-`
tween a.' variable point on said resistance and
said intermediate connection, and a variable re
sistance connected between said point and the
and the slider l5 to the angle of electrical phase -~
shift is represented by the following equation:
'
X
tang-gl)
where :
R=resistance between point I8 and slider I5
Xï--reactance of element 8 or 9
a=phase shift angle
other of said pair of terminals.
50
3. Inrcombination, an alternating current cir
cuit, apparatus for producing an alternating
voltage variable in phase relative to the voltage
of said alternating current circuit comprising a
winding energized from said circuit and having
55 a pair of terminal connections and an electrically
intermediate connection, a variable resistance a
connected between one of said terminals and
an output circuit, a resistance having a variable
point and connected between said variable _re-v
If the mechanical rotation of sliders II, I5 is
made equal to the electrical phase shift, for uni 60 sistance and said other terminal through a pairA
of serially connected reactances, and means con
form phase shift action, the resistance taper is
necting saidv output circuit to said electrically in
seen to be an inverse tangent or cotangent func
tion. This function is one which starts at zero
_for zero angle a, then increases at a constantly
.termediate connection.
increasing rate until it reaches an inñnite value 65.
.
,
_ '
HEATH R. GUPTILL.
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