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. 17, 1946.
J. G. AIVY
2,412,888
CONTROL SYSTEM
Filed June 14, 1944
2 Sheets-Sheet 1
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WITNESSES:
INVENTOR
. 17, 1946.
2,412,888
J. G. lvY
_
CONTROL SYSTEM
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Filed June 14, 1944
2 Sheets-Sheet 2
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INVENTOR
Jae 614g'.
BY
Mâíîìámu'w
ATTORNEY
‘
Patented Dee. 17, 1946
2,412,888
UNITED STATES PATENT orticaCONTROL SYSTEM
Joe G. Ivy, Forest Hills, Pa., assignor to Westing
house Electric Corporation, East Pittsburgh,
Pa., a corporation of Pennsylvania
Application June 14, 1944, Serial No. 540,267
8 Claims. (Cl. 172-239)
1
n
My invention relates to control system of the
variable voltage type and particularly to systems
containing an auxiliary regulating generator for
hereinafter called the “regulating generator” has
but is al-so distinguished by increased accuracy
' voltage” variable in accordance with the speed or
a saturation characteristic so that it generates
`an appreciable armature voltage only when its
limiting the load current of a motor to be con
field excitation exceeds a given finite magnitude.
trolled, systems and generators of this kind being 5 The regulating generator has a, field winding ex
disclosed in my copending applications Serial No.
cited in dependence upon the load current of the
496,596, filed July 29,1943, and Serial No. 532,975,
motor to be controlled and is provided with other
filed April 27, 1944, both assigned to the assignee
field exciting means also referred to hereinafter.
of the present application.
I further equip the system with operator-con
An object oi’ my invention is to provide a con 10 trolled circuit means which provide an adjustable
trol system of the type just referred to that pro
“pattern voltage” and also with automaticallyA
duces not only a load limiting regulating effect,
operating circuit means which provide a “control
and speed as regards its response vto changes in '
Voltage of the motor to be controlled. These dii
ierent circuit means are connected with each
the control adjustment selected by the attendant,
While being free of appreciable hunting even at
a high rate oi change of the control adjustments.
Another object of my invention, with reference
other and with the above-mentioned other neld
exciting means of both auxiliary generators so as
to produce in each of them a component field
to hoists, particularly mine hoists, is to provide
excitation in dependence upon the differential
a hoist control system in which the torque of 20 Value of the pattern and control voltages.
the hoist motor and hence the stress on the ropes
According to another feature of my invention,
and other mechanical hoisting equipment are
the above-mentioned differential value of pattern
automatically limited due to control characteris
tics inherent in the electrlcalcontrol system, and
voltage and control voltage is formed electrically
by superimposing both on a single electric circuit
in which the hoisting speed is va function of the 25 and impressing the resultant differential voltage
on a single iield winding of the two auxiliary
selected controller position regardless of the
amount of load, thus reducing the degree of at
tention and skill for operating the hoist, for in
generators, respectively.
These and other objects of my invention will
stance, When landing a cage or pulling a skip into
be apparent from the following description of the
the dumping horns.
30
embodiment represented in the drawings, in
Still another aim of my invention is to achieve
which:
~
the above-mentioned objects with the aid of aux
Figure 1 is the circuit diagram of a mine hoist
design and operative in accordance with my
i iliary generators which have a minimum number
of field windings and low iield heating, and it is
also intended to reduce undesirable transients apt .
to be caused by inductive couplings (transformer
effects) between diüerent magnetically linked
field windings.
'
Having these objects in mind, and in accord
ance with the invention, I control the field excita
tion oi' a main generator of a variable voltage
System with the aid of two interconnected aux
armature and hence, in contrast to a "separately
j excited” winding, derives its excitation from the
'
Figs. 2 and 3 are explanatory diagrams relating
to the same system;
Fig. 4 is a partial view of a regulating generator
used in the system of Fig. 1, the ñgure represent
ing one of the pole structures of this generator;
40
Fig. 5 is a partial circuit diagram of a second
iliary generators. One of these auxiliary gen
erators, hereinafter called the “control generator”
has a “self-excited” field winding, rated or kad v45
justed to just sustain the armature voltage, and
other field exciting means operating as described
hereafter. (When referring to a “self-excited”
winding in this specification, I use this term for
designating a field winding which is shunt or
series connected to the appertaining generator
invention;
control system according to the invention; and
Fig, 6 is the circuit diagram of a third control
-system also relating to a hoist drive.
Referring to the hoist control system shown in
Fig. 1, the hoisting equipment proper is schemati
cally indicated at l and includes a hoisting drum
whose shaft 2 is mechanically connected to the
armature I0 of a driving motor HM. The motor
has a separately excited field Winding Il and
a series-connected compensating winding I2.
Winding Il is connected through a rheostat RI
with a suitable direct current source of substan
electric energy generated in the armature of the
tially constant voltage, here represented by an '
same machine.) 'I'he other auxiliary generator, 55 exciter generator EX having an armature 50, two
aaiases
stat R7.
_.
The amature i@ of the hoist motor HM is con
nected in load circuit Ai> with the armature 2@
of a main generator MG which forms .the current
source of circuit Ai. The main generator MG
4
operator. This voltage„hereinaft_er referred .to
iield windings 5l and 52, and an adjusting rheo- ’
as the “pattern voltage,” is derived from the ex
.citer mains Iii> and Y through reversing switch
means RS and a potentiometric control device
C0 whose resistor is denoted by R3.
The reversing `switch RS, as illustrated, has
'two movable contacts il and ifi, each cooperat
has a main field winding 2i connected in a con
ing with two stationary contacts i2, ‘i3 and it, ‘i3
trol circuit A2 whose current source is formed by
respectively. In one position of switch RS, con
the armature 33 of a control generator CG. A
resistor R2 is series-arranged in circúit A2. Nu 10 tact ’il is in engagement with contact l2, andl
contact lll with contact i5 in order to energize
meral ‘22 denotes a compensating or interpole
the hoist motor HM for operation in the hoisting
winding ofthe main generator MG. .
direction In its other position, »the reversing
The control generator CG has three iield wind
switch RS connects movable contacts ‘il and ‘M
the voltage impressed on the main generator ñeld 15 with stationary contacts 'i3 and i6, respectively,
for controlling the hoist motor to operate in the
winding 2|. The resultant energization of ñeld
lowering direction. The control device CO is
winding 2| determines the voltage- and current
preferably designed like a customary master con
supplied by` .the main generator armature 2@
` trollër, while vthe reversing switch RS and its
through circuit Al to the hoist motor HM, .there
by controlling the torque and speed of the hoist 20 contacts are Ypreferably formed by electromag
ings 3|, 32, and 33 which cooperate in controlling
neticfcontactors which are controlled in accord
ance with the selected hoist or lower position
ing equipment driven by the motor HM.
'
The change of current in circuit -A2 is deter- .
lof the master controller. Since the particular
design of the operator-actuated control elements,
control generator CG. Field Winding 32 is self 25 here represented by CO and RS, is not essential
for the invention proper, and as such, need not '
energized and serves to amplify the control eil’ect.
involve novelty over the known master control
While the connection of winding 32 in circuit A2
1ers, the simpliñed illustration in Fig. 1 has been
is shown as a series arrangement, a shunt wind
chosen for the sake of convenience and clarity.
ing may be used instead. Winding 33 remains
mined by the _excitation of field winding 3|, here-l
inafter called the “pattern field winding” of the
substantially deenergized as long as the load cur
rent in circuit AI remains <below a given limit, but
when energized by the action of a regulating gen-_
erator RG to be described hereinafter, acts in
opposition to ñeld winding 3|. That is, when
30
The other voltage source of the control circuit Y
of .windings 3| and 4| »serves to impose on this
circuit a‘component voltage, hereinafter called .
the “control voltage,” that varies automatically
in accordance with the speed of the hoist motor
, winding 33 is excited, its ampere turns diminish 35 HM. In the embodiment of Fig. 1, the source
of. .this voltage consists of a pilot generator PG
. the resultant field effective on the armature 30 ,
whose iield winding 6I obtains constant excita
of> control generator CG. This function .takes
Vtion lfrom exciter mains X and Y through an
place when the load is positive, that is when HM
adjusting rheostat R8, while its amature 60 is
acts as a drive and MG as a generator.. The-ar
rows shown in Fig. 1 adjacent to-windings 3| and 40 driven by,the motor shaft 2 and hence generates
a voltage proportional to the armature speed. '
33, respectively, to indicate the directional rela
The pattern voltage and control voltage coun
tionship of the fields-induced by these windings
teract each other so that the resultant voltage
refer to the just-mentioned operating conditions.
impressed on the control field windings 3| and 4 I,
Under overhauling load conditions', HM will act
as a generator and MG as a motor. The system 45 or the Voltage drop across either, corresponds to
will then still be operative to limit current, but
the ñeld of winding 33 is thenoperative in the
same sense as winding 3| and hence assist 4rather
than buck the iield of the latter.
.
'I'he regulating generator RG has its amature
40 connected to'ñeld winding 33 of control gen
erator CG through a. rheostat Rßwhose adjust
the differential value of these two component volt
ages. Consequently, when the speed o-f the hoist
motor HM corresponds exactly tc the setting of`A ^
lthe master controller, the electrically established
50 voltage differential is zero so that both field wind
ings 3| and 4I are deenergized. When the motor
speed departs from the value set by the motor
ment-need not be changed during the operation . controller, a. positive or negative differential volt- ».
~age appears and causes the iield winding 3| of
of the system. Generator RG has Itwo 'cumula
.tively acting ñeld windings 4| and 45 as indi 55 control generator CG to change the field excita
tion of the main generator MG in the direction
cated by the respective arrows in Fig. 1. Field
required for correcting the discrepancy. This
winding 45, hereinafter called .the “regulating
speed regulating eiîect is extremely sensitive due
field winding” is excited in accordance with the
to the action of the self-energized iield winding 32
load current in the motor circuit A| and to this
end connected across the interpole and com 60 which feeds a small portion of the control gen
erator output power back into the control gen
pensating winding 22 of main generator MG.
erator as excitation to produce still more output.
The armatures of generators MG, CG, RG, and
EX are driven at substantially constant speed,_ The self-excited field is just suii‘icient to sustain
the generated voltage. Hence,'the action of the
for instance, as shown in Fig. l, by means of a
constant speed motor MI driving a common shaft 65 control generator is always under the control of
one or more of the separately excited ñeld vwind
3 of armatures 20 and 30, and another constant
ings 3| and 33. Stating this another way, the re
speed motor M2 driving a shaft 4 common to
sistance of the external control circuit A2 is ad
armatures 40 and 50. _
Justed relative to the self-excited iield excitation
The above-mentioned control iield windings 3|
and 4| of the auxiliary generators CG and RG, 70 so that the machine CG operates near, or pref
variable voltage sources.> One of these sources
imposes on the circuit a constant voltage whose
erably on, its air gap line.
As stated above, the field winding 33 is deener
gized under normalload conditions but modifies
the voltage of circuit A2, thus producing a limit
magnitude and direction are adjustable by »the
ing effect on vthe load current in circuit Al, when
respectively, are both connected to a control cir
cuit which isenergized from two independently
2,412,888
5
this current tends to exceed a safe limit. In order
to accomplish this action, the regulating genera
tor RG is given a special characteristic similar to
that shown in Fig. 2. This characteristic differs `
Y from that of conventional machines by having an
extended low voltage or zero voltage interval be
tween points E and F which are both displaced
from the zero point 0 by fixed amounts of excita
tion.
.
the correcting effect required of the current limit
winding 33 of generator CG, in order to properly
limit the current, will be less because the control
voltage of the pilot generator PG Willcancel a
greater portion of pattern voltage and does not
have to buck down as many ampere turns from
winding 3i as was previously -necessary due to the
larger difference between pattern voltage and con
trol voltage. The iield winding 4I of generator
A characteristic of’this type can be obtained 10 RG is now eil'ective to produce this desired adjust
by providing the field poles of the generator with
ment in excitation of the current limit winding
a saturable magnetic shunt as exempliiled by
33. That is, since the just-'mentioned differential
Fig. 4.
’
~
value of control and pattern voltages is also effec
In Fig. 4, numerals l, Il, and 80 denote the
'tive in field winding Il, the resultant field excita
shaft, armature, and stator frame, respectively, of
tion of generator RG and hence the current limi‘
the regulating generator. The pole structure
ing effect of winding 33 are automatically reduced
comprises a base portion 8| in good magnetic con
tact with the stator frame, and a pole shoe por
tion 82 adjacent to the armature. The main pole
portion 83 is shunted by a saturable ilux path 85 20
and contains an air gap, or a shim 84 of high mag
netic reluctance, for instance of brass. The wind
ings of the generator are arranged on the main
pole portion 83.
_
'I’he air gap or shim at the top of the main pole
position carries both the armature exciting ñux
and the shunt flux, and hence does not iniluence
the division of ñux. It primarily determines the
1 spacing F-E of the zero voltage interval as well
as the slope of the characteristic beyond points F 30
and E according to the diagram of Fig. 2. Be
cause of this gap or shim, substantially all iiux
ilows through the shunt, since the reluctance of'
this path is low, and almost no flux is forced
across the air gap into the armature to generate 35
voltage, as long as the resultant ileld excitation
is insuñicient to saturate the shunt path. The
shunt 85 is so proportioned that it saturates at an
excitation corresponding to points F and E of Fig.
2 and then becomes unable to carry appreciably 40
more ilux. Consequently, upon saturation of the
shunt, an increasing field excitation forces ilux
across the air gap into the armature so that now
a voltage is generated. The action, after the
shunt has been saturated, is similar to that of a 45
conventional mach/ine.
Y
Due to the fact that ampere turns from the
in the right amount to maintain the same arma
ture current in hoist motor HM. It is this si
multaneous occurrence, and its corrective eñect.
of the regulating action of the speed-dependent
and operator-adjusted voltages in both generators
CG and RG that decreases the tendency of hunt
ing, and thus increases the accuracy, reliability`
and permissible speed of control.
The control is completely reversible by actuat
ing the switch RS and, when reversed, will limit
regeneration in the same manner as described
above with respect to current limitation.
Fig. 3 shows a theoretical speed torque charac
teristic I of a motor controlled by such a system.
Curve T represents a test curve as obtainable, for
instance, by point-to-point static loading. Any
transient overshooting of the current limit can
be kept in the order of 10% or less even on the
>severe test of plugging.
The advantages of this system of control in
clude:
.
-
-l. Better performance due to a closer approach
to the ideal speed torque characteristic;
2. Less maintenance, due to the elimination of
contactors and excessive commutating cur- l
rents in the motors and generators;
3. Increased life oi the mechanical hoist parts,
’ due to less abuse from high torque (or cur
rent) peaks;
' 4. Great reliability, since the control system is
the magnetic shunt, the generator output voltage
based on proven designs of D.-C. equipment
and is substantially free from mechanically
is controlled in response to the armature current 50
(and hence torque) of the hoist motor HM. As a
to introduce sources of failure;
- regulating field winding 45 are used for saturatìng
sensitive measuring or control devices apt
'
result, the above-mentioned action between the
control ñelds and the current limiting field of the
5. A small number of separate iield windings in
voltage during normal steady-state operation of
RG are controlled in dependence upon the diiîer
the auxiliary generators and, consequently,
a low heat development in these generators
control generator CG is not effective before the
and a reduced possibility of disturbances due
magnetic shunt on the regulating generator RG is 55
to inductive coupling between field wind
saturated, and this saturation occurs only when
ings.
the load current of the hoist motor has exceeded
a safe limit value. The control ñeld winding li
As explained in the foregoing, it is essential for
does not saturate the shunt because the pattern
the invention that the ñeld excitations of the con
voltage equals, and thus balances out, the control
trol generator CG and of the regulating generator
the hoist motor. The transient departure from
yentlal value of two component voltages, one (pat
zero of this control ñeld occurring during periods
tern voltage) being adjusted at will by the oper
of changing speed is alone insuñicient to saturate
ator with the aid of the master controller, while
the shunt although these transient field effects are 65 the other component voltage (control voltage).
operative to produce the regulatory anti-hunting .
varies substantially in -accordance with the speed
action mentioned presently.
of the motor to be controlled. While in the em
Assume, for instance, that the operator initiates
bodiment of Fig. l the speed indicating voltage is
a control operation by advancing the master
produced by a pilot generator PG, there are other
switch toward the full speed position and that this 70 means available for producing a component volt
is done so rapidly that the limiting-current would
age representative of the motor speed. The mod
be exceeded except for the action of the generator
ification shown in Fig. 5 serves to exemplify one oi
RG. When, under such conditions, the hoist
these other possibilities.
‘
motor HM approaches full speed and the voltage ”
The system represented by Fig. 5 is partially
of the main generator MG approaches maximum, 75
identicalwith that of Fig. 1 and hence illustratedV
2,412,888
only to the extent necessary to indicate its dif
ferences. Th'e main difference lies in the fact that
the speed responsive -control voltage is not pro
duced by a pilot generator but is derived by po
vtentiom'etric means from the load circuit of the
hoist motor HM. To this end. a potentiometer
rheostat R9 is connected across the armature it)
of the hoist motor. The adjustment of this rheo
stat need not be changed during the operation of
of pattern voltage and control voltage. The pat
tern field winding 3l of -control generator CG is
resultant field excitation of windings 3i and Sli so
in effect a shunt connected self-energized wind
through a calibrating rheostat R8 with the master
controller/ and the pilot' generator so that it is
excited in accordance with the differential valuev
also connected with the master controller and
pilot generator so as to obtain likewisea com-`
ponent excitation in accordance with the just=
mentioned differential voltage value. The arma
the'hoist. The armature voltage is substa'ntially 10 ture d@ of the regulating generator RG is con-,
proportional to the motor speed. Hence, the volt
nected between pilot generator- PG and pattern
age drop between points t3 and ed in Fig. 5 is sub
field winding 3l. Under normal operating con
stantially a measure of the motor speed. The ter
ditions, the output voltage of the regulator arma
minal points t@ and ed in Fig.,5 correspond to
ture il@ is negligible. Under overload conditions,
the similarly indicated points in Fig. 1, and the 15 however, this output voltage reduces theresultant
circuit of the master controller and of ñeld wind
differential voltage across .winding 3l., and hence
ings .3l and ¿il isotherwise exactly as shown in
reduces the excitation of the control generator
Fig. 1, with the exception that anv additional ñeld ' CG, thus imposing thereon a current limiting ef
winding 3d is placed on the control generatorCG
fect similar to the one obtained magnetically in
and connected, through a resistor Rd', across the 20 the system of Fig. 1. Winding ¿il of generator RG,
main generator winding 22 in order to correct the
in the circuit connectionaccording to Fig. 6, is
that it corresponds more accurately to the speed
ing. It is preferably so rated relative to the re
of motor HM. The operation of the system rep
sistance of the armature circuit of this generator
resented by Fig. 5 is otherwise substantially the 25 that the generator operates on its air gap line.
same as described above in'connection with Fig. 1.
As exemplified in the foregoing, it is possible
Referring once more to Fig. i, it will be
to lmodify control systems according to my in
remembered that the output voltage of the regu- '
lating generator RG, under operating conditions
vention as regards several- of its details without
vdeparting from its spirit and its essential features
where a current limitation in the load circuit of 30 as set forth in the appended claims.
the motor HM is desired, causes the current limit
Iclaim as my invention:
'
ing field winding 33 of the control generator CG to
1. A variable voltage drive comprising, a motor,
buck by its ampere turns those of the field wind
a main generator having an armature circuit
ing 3i. în other words, the regulating efîect of
connected to said motor and a main generator
generator RG in the system of Fig. 1 functions by 35 field winding for controlling the voltage of said
circuit, an amplifying control generator for ener‘
imposing a subtractive magnetic eñect on thel
field excitation of the control regulator CG. Ac
cording to another feature of my invention, how
ever, it is also possible to have the, E. M: F.’s pro
' gizing said main generator ñeld winding having a
current limiting ñeld winding and a control ñeld‘
winding, operator-controlled circuit vmeans for
duced by the differential effect of the pattern 40 providing an adjustable pattern voltage, speed
voltage and control voltage 'and by the output
voltageof the regulating generator, respectively,
responsive circuit means for providing a control
voltage variable substantially in accordance with -
act directly upon each other so that a single field
the speed of said motor, said operator-controlled
winding in generator CG may take the place of
circuit means and said speed-responsive circuit
both windings 3l and 33. A modiñcation of this 45 means 'being connected with eachother and with i
type is represented in Fig. 6.y
said control field winding so as to energize said
The hoist control system according to Fig. 6 is
latter windingin accordance with the differential
partially identical with that of Fig. 1, as is ap
value of said pattern and control voltages, a regu
parent from the use of the same reference char
lating generator having saturably shunted field
acters in both ñgures for corresponding elements. 50 poles so as to generate an output‘voltage only
The hoist motor HM is energized by a main gen
when the excitation of said ñeld poles exceeds
erator MG and has a separately excited field
a given value, means connecting said regulating
winding I I connected by an adjusting rheostat Rl
generator with said armature circuit for provid
to the mains X and _Y of a suitable direct-current
ing field excitation for said regulating generator
source of substantially constant voltage. The 55 in dependence upon the load current in said
separately excited field winding ll of the main
armature circuit, said regulating generator being
generator MG is energized by a control generator
connected to said current limiting ñeld Winding >
CG which, in contrast to _the system of Fig. 1. has
so as to impress said output voltage on the latter
only two field windings, one being a self-excited
in order to linut said load current when said load
or feedback winding, denoted by 32,' while the,
current tends to exceed a safe limit value.
_
other winding, denoted by 3|, is energized by a re
2. A variable voltage drive comprising, a motor,
sultant voltage is composed as follows:
_
An operator-actuated master controller CO, in
cluding a reversing switch RS, serves to provide
a selective pattern voltage. A pilot generator PG
mounted on the shaft 2 of hoist motor HM, as in
the system of Fig. l, provides a speed responsive
control voltage. A regulating generator RG hav
ing its regulating i‘leld winding 45 energized
through a rheostat R5 in accordance with the 70
load current of the hoist motor, also as described
more in detail in connection with Fig. 1, produces
an armature output voltage only when the load
current exceeds a given maximum. The winding
di of the regulating generator RG is connected 75
a main generator having an armature circuit
connected to said motor and a main generator
field winding for controlling the. voltage of said
circuit, an amplifying control generator disposedl
for energizing said‘main generator field winding
and having a current limiting ñeld winding and
a control vf-leld winding, a regulating generator
having saturably shunted. field poles so as to
generate voltage only when _the excitation of said
field poles exceeds a given Value, said regulating
generator being held-controlled by said armature
circuit and connected to said Acurrent limiting
field winding so as to impress on the latter said
voltage when the load current in said armature
annees
,
circuit exceeds a desired maximum value, a con
trol field winding on said regulating generator,
i
l0
»
winding and separately excited ñeld winding
means, a regulating 'generator having saturably
operator-controlled circuit means for providing
shunted ñeld poles for generating abruptly in
creasing regulating voltage in dependence upon
‘ an adjustable pattern voltage, circuit means for
providing a control voltage variable substantially
the passing of its field excitation through a shunt
in -accordance with the speed of said motor, said
saturating value and being provided with ñeld
former and said latter circuit means being con
winding means and having a regulating iield
winding connected with said circuit for provid»
ing excitation in accordance with the load cur
rent of said motor, operator-controlled circuit
nected with each other and with said two con
trol iield windings so as to energize them simul
taneously in accordance with the differential
value of said pattern and control voltages.
3. A variable voltage drive comprising, a motor,
means for providing an adjustable pattern
voltage, circuit means for providing a control
a main generator having an armature circuit con
nected to said motor and a main generator field
voltage variable substantially in accordance with
the speed of said motor, said former and said
latter circuit means being connected with each
other and with said field winding means of said
control generator as well as with said field wind
having a current limiting ?eld winding and a
ing means of said regulating generator so as to
control ñeld winding, a regulating generator hav
ing saturably shunted field poles so as to generate 20 energize said respective ñeld winding means
winding for controlling the voltage of said cir
cuit, an amplifying control generator disposed for
energizing said main generator ñeld winding and
15
simultaneously in accordance with the differen
tial value of said pattern and control voltages,
and said ñeid winding means of said control
generator being also connected with said regu
voltage only when the excitation of said field
poles exceeds a given value, said regulating
generator being held-controlled by said> arma
ture circuit and connected to said current limit
ing ñeld winding so as to impress on the latter 25 lating generator so that the resultant ñeld ex
citation of said control generator is modiñed due
said voltage when the load current in said circuit
to
said regulating voltage when said load curren
exceeds a given maximum limit, a control ñeld
exceeds a desired maximum value.
‘
winding on said regulating generator, operator
6. A variable voltage drive comprising, a motor,
controlled circuit means for providing an adjust
able pattern voltage, and >a pilot generator 30
mechanically connected with said motor for pro
viding a control voltage variable substantially iny .
accordance with the motor speed, said circuit
means and said pilot generator being connected 35
~with each other and with said two control ñeld
windings so as toV energize them simultaneously
in accordance with the diiîerential value of said
pattern and control voltages.
.4. A variable voltage drive comprising, a motor, 40
a. main generator having an armature circuit
connected. to said motor and a main generator
ñeld winding for controlling the voltage of said
circuit; an amplifying control generator disposed
for energizing said main generator i'leld winding
and having a current limiting field winding. and a
control ñeld winding, a regulating generator hav
ing saturably shunted field poles so as to generate
'voltage only when the excitation of said ’?leld
poles exceeds a given value, said regulating gen
. erator being deliri-controlled ‘by said armature
circuit and connected 'to said current lini'ìing
a main generator having an armature circuit con»
nected to said motor and a main generator field
winding for controlling the voltage of said cir
cuit, a control generator disposed for energizing
said main generator ñeld winding and having a
self-excited voltage-sustaining ileld winding and
a current limiting ñeld Winding and a control
field Winding, operator-controlled circuit means
for providing an adjustable pattern voltage, cir
cuit means for providing a control voltage
variable substantially in accordance with the
speed of said motor, said former and said latter
circuit means being connected with each other
and with said control field winding so as to
energize it in accordance with the differential
value of said pattern and control voltages, a
regulating generator having saturably shunted
ñeld poles for generating abruptly increasing
output voltage in dependence upon the passing
or its :field excitation through a shunt-saturating
value and being connected with said current
limiting ñelrl winding so as to impress said outn
put voltage thereon ier reducing the resultant
field winding so as to impress on ‘the latter said
control generator when
voltage when the load current in said circuit ex 55 ûeld excitation of
the
load
current
of
said
motor exceeds a desired
ceeds a desired maximum value, a control deld
maximum value, and circuit means connected to
Winding on said regulating generator, operator
said armature circuit for supplying :iield excita-v
controlled circuit means for providing an ad
justable pattern voltage, and voltage measuring
circuit means connected with said armature cir
cuit for providing a control voltage variable sub
stantially in accordance with the motor speed,
tion to said regulating generator in dependence
60 upon said load current.
7. A variable voltage drive comprising, a motor,
a main generator having an armature circuit con
nected to said motor and a main generator iìeld
said former and said latter circuit means being
winding for controlling the voltage of said cir
connected with each other and with said two con-l
cuit, an amplifying control generator disposed
65
trol ñeld windings so as to energize them in ac
cordance with the diiîerential value of said pat
tern and control voltages.
`
for energizing said main generator iield winding
and having a self-excited voltage-sustaining iield
winding and a current limiting field winding and
5. >A variable voltage drive comprising, a drive
a control ñeld winding, a regulating generator
motor, a main generator having an armature>
having saturabli7 shunted iield poles for generat
70
circuit connected to said motor and a main gen
ing abruptly increasing output voltage in de
erator field winding for controlling the voltage
pendence upon the passing of its ñeld excitation
through a shunt-saturating value and being con
energizing said main generator field winding and A nected with said current limiting ileld winding,
having» a self-excited voltage-sustaining ilèld 75 said regulating generator having a control iield
of said circuit, a control generator disposed for
2,412,888
>
il
.
«
'
l2
saturably shunted ñeld poles -for generating ab
ruptly increasing> regulating voltage in de
pendence upon the passing of its ñcld excitation
winding and a regulating ñeld winding. operator
controlled circuit means for providing an adjust
able pattern voltage, circuit means for providing
a control voltage variable substantially in ac
field windings so as to energize them in accord
through a shunt-saturating value and being pro
vided with ñeld winding >means and having a
regulating ñeld winding connected with said cir
cuit for providing excitation in -accordance with
the load current of said motor, operator-con
ance with the diiîerential value of said pattern
-trolled circuit means for providing an adjustable
cordance with the speed of said motor, said
former and said latter circuit means being con
nected with each other and withsaid two control
pattern voltage and circuit means for providing
a control voltage variable substantially in ac
cordance with the speed of said motor, said
and control voltages, circuit means connected
with said regulating winding for energizing it in
dependence upon the load current of said motor
so that said current limiting winding is energized
only when said load current exceeds a predeter
mined maximum limit, and said current limiting
iield winding being arranged to act in opposition
to said control ñeld winding of said control gen
15
former and said latter circuit means being con
nected with each other and with said iield wind
ing means of said control generator as well as
with said ñeld winding means of said regulating
t generator so as to energize said respective iield
winding means simultaneously by a resultant
erator so that said output voltage causes said
voltage corresponding to the diiîerential value of
current limiting ileld winding to reduce the re
sultant field excitation of said control generator, 20 said pattern and control voltages, and said ñeld
winding means of said control generator being
8. A variablevoltage drive comprising. a drive
also connected with said regulating generator so
' motor, a main generator having an armature cir
that the resultant ñeld excitation of said control
_cuit connected to said motor and a main gen- ‘
generator is reduced due to said regulating `
erator iield winding for controlling the voltage
of said circuit, a control generator for energizing 26 voltage when said load current exceeds a given
maximum value.
said main generator ñeld winding having ñeld '
JOE G. IVY.
winding means, a regulating generator having
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