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Aug. 13, 1963
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‘
v
c. w. NIELSEN
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3,100,865
CONTROL SYSTEM FOR TAP CHANGING REGULATOR
Filed New 17. ‘1960
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7
,2 Sheets-Sheet 1
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.B?orrlfw e71).
I
C. W. NIELSEN
vAug. 13, 19.63
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- 3,100,865 v
CONTROL SYSTEM FOR TAP CHANGING REGULATOR
Filed Nov. 17. 196,0
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2 Sheeis-Sheet 2 '
PM 5
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AQLXl'oMw/y
United States Patent 0
l
1
rice‘
3,10%,865
Patented Aug. 13, 1963
2
and apparatus for transformers embodying'the present
.
3,100,865
._ invention;
a FIG. 2 is a schematic showing of the control system
‘
CONTROL SYSTEM FOR TAP CHANGING
'
REGULATOR
for synchronizing the tap changing mechanisms; and
‘FIGS. 3 through 5 are tables illustrating the sequence
‘Charles W. Nielsen, Eagle, Wis, assignor to Allis
(Jhalmers Manufacturing Company, Milwaukee, Wis.
of operation of the switches in the controlsystem of
Filed Nov. 17, 1960, Ser. No. 69,984
8 Claims. (Cl. 323-435)
FIG. 2.
'
I
The voltage regulating system illustrated in FIG. 1 is
This invention relates to a voltage regulating system
capable of operating through a range of zero to maxi
and in particular to a control system for a step type regu 10 mum voltage and comprises a coarse mechanism 11 and
lator having coarse and ?ne step mechanisms.
a ?ne mechanism 12 associated with an autotransformer
With increased use of electronic equipment in modern
13.
industrial processes, close control of operating voltages
has become extremely important. This is particularly
1
Coarse Step Mechanism
The autotransformer .13 comprises a core 15, an ex
true in electro-chemical industries where voltage recti?ers 15
citing winding 1‘6 and a coarse tapped series winding 17
are used to control electrolytic re?ning. 1In such applica
electrically and inductively connected to the exciting wind
tions the voltage applied to the recti?er must be closely
ing. in the particular embodiment, the coarse winding
controlled in ?ne steps in addition to coarse steps and
17
is in a bucking or substracting relationship with the
quite frequently available over a wide range.
exciting winding '16 and is divided into seven equal por
To achieve ?ne regulation over a wide range through 20
tions which are connected to circular arranged stationary
the use of mechanical tap changing regulators ?ne step
contacts1-8 on the coarse tap changing mechanism 11.
windings have been employed. A line step winding has
Rotatably coupled together are a pair of movable coarse
been connected between taps on the coarse step trans
contacts 21a and 21b which are positioned in a conven
former winding and, similar to the manner in which con
tional manner to make contact with the stationary con
tacts \are changed on the coarse winding, has a mechanical 25
tacts 18 of the coarse mechanism.
tap changing mechanism. In such a manner the voltage’
range between a pair of adjacent taps on the coarse wind
ing of the transformer can be divided into a number of
Fine Step Mechanism
The line step tap changing mechanism 12 which pro
?ner steps.
.
vides‘ small steps of voltage change is electrically con
In providing a voltage regulator with two mechanical 30 nected to the coarse mechanism 11 through a pair of
‘tap changing mechanisms synchronization of the two
leads connected to the pair of movable contacts 21a and
units is a major concern if a continuous uniform advance
21b on the coarse mechanism. Fine winding -23 may be
or decrease of voltage in ?ne steps is desired. It move—
wound on the same core 115 containing the exciting wind
ment of the contacts on the tapped winding of the coarse
ing and coarse winding; For the purpose of explaining
mechanism is not properly synchronized to the movement 35‘ the operation of the inventiomthe ?ne winding 23 should
of the contacts on the ?ne step winding, interruption of
’ be considered as being in a boosting or‘ additive relation
the load current will occur. Lack of synchronization
"ship with the coarse winding .17. However, if desired th
. would make it impossible to supply uniformly increasing
polarity‘of the line winding may be reversed.
.
?ne steps. if the contacts on thet?ne step winding start
In a conventional manner the ?ne winding is associated
40
_ on a second cycle without any movement of the contacts
with nine stationary contacts '25 arranged in a circular
‘on the coarse winding a sudden change in voltage equal
pattern. Thepotential across a pair of these contacts is,
to the potential across a pair of taps on the coarse mecha
' nism will occur. While synchronization could‘ be accom
plished by having an'operator stand by the regulator ready
to move the contacts on the coarse winding whenever
necessary, automation is Jmore‘ desirable.
in the particular embodiment, equal to % of the poten
tial across‘ a pair of adjacent coarse taps 18‘.
A second
45 pair of movable contacts 26a and 26b are positioned to
make cont-act with‘the stationary contacts '25 of the ?ne
winding. A preventive autotransformer 27 is connected
To automate
the mechanisms, expensive and'bulky mechanical cou
across the pair of movable contacts 26a and 26b on the
?ne winding in order to prevent short circuiting of a
“ Vpli'ngs have been used.
The invention described herein overcomes the disad 50 'eltappedv portion of the winding. Thus, the output'o-i the
vantages of expense, size and maintenance encountered . voltage regulating apparatus appears ‘across terminal 2-9
in the use of mechanical couplingssuch aslgearswthrough I " connected to the midpoint of ‘the preventive autotnans
a novel and unique arrangement of electrical switches.v
'forrner 27 andian' end 30‘ of the exciting winding 16.
Through a minimum number of switches arranged in a '
' During eachcoarse step the ?ne-mechanism movable con-j
predetermined fashion the ‘two tap changing mechanisms ‘ 55 tactsqrotate through a null cycle, providing 18 ?ne steps
are synchronized so that interruption of a load‘ current
numbered 71 through 88.
. l
and other undesirable occurrences are avoided.
<
Control
System
for
Fine
Step
Operation
‘
It is therefore one object of this invention to provide
‘a new and improved voltage regulating mechanism. .
‘With reference to FIG. 2, a control system 32 is pro
Another object of this invention is to provide a new and 60 vided for ‘synchronizing the ?ne and coarse mechanisms.
improved voltage regulating mechanismcapable of oper- . ~
ating over ‘a wide voltage "range in either coarse or ex
tremely. ?ne and uniform steps.
, .
‘
' A further object of this invention is? to provide a new
Thislsystem includes’ [a- pair of tap changing motors 34
and 35, one tor the coarse. mechanism 11 and theother.
, for the ?ne mechanism 12. A power supply 36 is pro
.vided_ forp driving
the _ two motors. The control system
p
which
includes
a
raise
circuit 39 and a lower circuit 39'
automatic electrical control system ‘for synchronizing a e5; may be designed to actuate the tap changing mechanisms
and improved voltage regulating mechanism having an
pair of tap changing mechanisms. .
v
‘ ‘in response to either manual or automatic‘ control, by
@means of a conventional sensing device. The sensing
above will be apparent from the following description I device has not been shown ‘for purposes of clarity and
when read in connection with the drawing ‘in which: '
70 may be any of a number of the devices designed to inter
yIObje‘cts and advantages other than those mentioned
FIG. 1 is a schematic showing of a tap changing‘system
pret voltage line conditions and provide an impulse to the
3,100,865
3
4
21a ‘and 21b bridge a pair of contacts 18. A pair of raise
input of the control system for the tap changing mech
and lower transfer switches 56 and 56’ which may be
anisms.
Connected to one side of powersupply 36 is switch 61
to which a pair of switches 42 and 42' are connected.
manually controlled are connected to switch B3». Switch '
57 is provided to enable the transfer switches to return
Switch 42 is closed to provide current to the motors in
to their normal positions on contacts 50a.
response to a‘ signal from the sensing device or manual
the transfer motor 51 which drives contacts 48a and 48b
Connected to
area pair of coarse and ?ne switches 58 and. 59‘.
Switches- 58 and 59 may be coupled to a manual con
trol which also operates ‘switch 61 and switch 60‘ con
‘to the raise and lower switches are corresponding sets of
raise switches B1, NBl, N132 and lower switches B1’, B2’ 10 nected to one ‘side of the power supply. Connected to
switch 60 are switches 63‘ and 63’, respectively, con
and NBI'. These switches open and close in response to
nected to the raise and lower windings of the coarse
the position 1-which the movable contacts 21a and 2112 on
motor 34. Switches 63 and 6-3" may be actuated by the.
the coarse mechanism assume. On the raise circuit 39,
switchesNBl and N132 close in response to nonbridging
same means that operates switches 56, 56' and 57.
' _ control indicating that a raise in‘ voltage is desired.
' a other switch 42’ closes upon a lower signal.
The
Connected
positions of the coarse, mechanism. By nonbnidgi-ng it 15
is’ means that both of the movable contacts 210: and 21b
of the coarse mechanismare on one tap contact 18.‘
Fine Step Operation
FIGS. 3, 4_ and 5 illustrate the sequence in which the
above described M switches close in response to the tap‘
The third switch B1 of the raisercircuit is closed in re
changing mechanisms. While explanations are directed
sponse to a bridging condition or, that is, when the pair
of movable contacts 21a and 2117 on the coarse mech v20 toward a raise operation, it is to be understood that the
lower operation functions in a reverse manner. On one
anism straddle two tap contacts 18. The lower circuit
axis of the table the M switches are set forth and on the
. 39’ includes a pair‘of bridging switches B1’ and B2’ and
other axis the eighteen positions (71-88 partially shown
one nonbridg-ing switch NBl'. One of several ways in
in FIG. 1) inwhich the ?ne tap changing mechanism
which these bridging and n-onbridging switches can be
made responsive to the positioning'of the coarse movable 25 26a and 26b assume are set forth. The shaded areas
indicate when a particular M switch is closed. Likewise,
‘ contacts 21a and 21b is to arrange them on a rotatable
FIGS. 4 and 5 show the sequence of switches 58 through
drum which is simultaneously driven with the coarse mov
Y61 and switches 56, 56', 57, 63, 63'.
A brief operation of the control system can be'readily
Connected between the bridging and. nonbridging
switches and raise and lower windings. 44, 44’, 45, 45' of 30 explained through reference to FIGS. 1, 2 and 'thethree
tables. With the particular type of illustrated windings,
the two drive motors 34 and35 is a setof motor switches
the pair of movable contacts 21a and 21b on the coarse
M which complete and interrupt current pathsto- the ?ne
able contacts.
mechanism are generally on a nonbridging position while
and coarse motors. Each of the lower and raise windings
the pair of contacts. 26a and 2612 on the ?ne winding ‘
in each of the motors has a pair of switches associated
with it. Thus, for the raise winding 44 of the coarse 35 produce ?ne step voltage changes through a sequence of
bridging and nonbridging positions. It will be observed
motor 34 switch M1 is connected to the coarse mecha
as the ?ne mechanism movable contacts move from non
nism bridging switchBl with switch M2 being connected
to- coarse mechanism nonbrid‘ging switch NB1. These
bridging position 87 to bridging position 88, the load cur- _
rent ?ows only through the leading coarse contact 21a.
motor switches M are responsive'to the positions 71
‘through 88of the movable contacts 26A and 26B of the 40 Thus, keeping in mind that the ?ne winding 23 is in
additive relationship with the coarse winding. 17,, it can
?ne mechanism. Again, this may be accomplished by ar
be seen that if the leading contact 21a of ‘the coarse
ranging the switches ona rotatable drum coupled to the
mechanism is still in a nonbridging position there will '
?nernotor 3'5.
bea sud-den drop of voltage when the ?ne contacts assume
'
Transfer Mechanism
position 88 instead of obtaining a ?ne increase in voltage.
45
I ' In the particular embodiment the output voltage may
If the various switches in the control system are arranged
‘be changed in 30*4'steps from 01% to 105.6% rated volt
in accordance to the sequence of FIGS. 3 through 5', the
age. However; torapidly increase the‘ output from one
above condition can be avoided. It is to be noted that
level, such as 25%v to a substantially greater level, such
.at position 84 of the ?ne mechanism, an additional switch ‘
as 75% a transfer mechanism 47v is provided. Inv FIG 1
M2 is closed. Assuming that the impulse from the sensing
- a pair'of movable transfer or bypass contacts 48a and 48b
device calls for an increase in voltage the closing of switch
are showniconnected between the coarse movable contacts
M2 causes an advance in the movable contacts 21a and
21a‘ and 21b‘ and the v?ne mechanism 12.v By moving
21b of_ the coarse mechanism. ‘.While the illustrated
' 'these‘bypass contacts from their ?ne position on stationary
coarse mechanism contacts B1, N131, etc., areall shown
contacts 50a‘ over to the coarse positions on’ stationary
contacts 50h with motor 51 the ?ne'mechanisrn' 12 and
55 in an open position it is to berecalled that half of these
switches \will always 'be closed since thexcoarse mech
"its preventive autotransformer 27 are bypassed. . ' A second’
anism contacts will either be in a bridging or nonbridging' '
7 larger preventive autotransformer 52M-becomes connected‘
to the coarse winding-17 and theco'arse mechanism‘ may . ,
now be operated through the entire voltage range in only '
. 32 steps-‘instead of the ?ne operation covering 304 steps. 60
normally in a nonbridging position. all of the nonbridging
In order that the load cnrrentis not interrupted. during
, to the raise winding 44 of the coarse mechanism motor 34.
movement of the bypass contacts 48a and 4% there must
‘be synchronization between the transfer mechanism,”
With the advance of the coarse mechanismfcontacts to
thebridging switches B1, B1’ and B2? close; In such a
manner the coarse motor is able to drive the coarse mech
Referring to FIG. ,2, a manual push button switch.‘ 54 is
nism?responsive switch M6. Switches M5 and'M6 may
'be’mounted'on the same'drum. containing theother M
.switchesp To synchronize the transfer .mechanism»with'
switches NB1., NB2 and NBl’ will be closed and, with
the additional closingfof switch M2, current is supplied .
a bridging- position, the nonbridging switches open andv
and both the ?ne and coarse mechanismsrll and 12.
‘connected between the raise and flower circuits, 39‘. and
39’ anda switch M5 ‘connectedto one sideof the power
,supply and responsive to the ?ne mechanism. Con~~
nected t-Q-one side of thepower supply is a ?nemecha
position. ‘Consequently, since the coarse mechanism is
anism only one step unlessotherwise called for. Thus,
with the closing of switch M2 at position 84 ofthe ?ne
mechanism the coarse mechanism movable contacts
76
advance well ‘before movement of; the ?ne mechanism
movable .contacts 26aand 261; into position 88.' ,Switch
M2 remains closed through positions 85 and 86 in order
the coarse mechanism switch B3 is connectedto switch
to vassure time for the coarse mechanism to move. With
the coarse; mechanism contacts 21a and’ 21b ‘now in a
‘,M3. Switch B3‘ is‘ closed when coarse movable contacts
bridging position and the ?ne mechanism contacts 26a ,
3,100,865
6
and 26b at position 88, current-?ows through the leading
position, switch so closes and current is supplied to the
contact 21a of the coarse mechanism; Likewise, this
coarse motor tor providing coarse steps.
leading contact 21a carries the load ‘current ‘as/the ?ne
?ne step operation the above procedure is reversed.
mechanism goes into position 71.
'
'
‘
But, as the ?ne mechanism continues to cycle'and move ’
into position 72, the load current is carried by the second
coarse movable contact 21b. Thus, it the second mov
able coarse contact Zlb is still in a bridging position there
will be a sudden drop in output voltage as the ?ne mech
To return to
Through the (above descnibed control system a compact
_ and dependable regulating unit is provided which may
operate in either. uniformly ?ne or coarse steps through an
extremely wide range. While only oneemb'odiment ‘of ‘
,the present invention has been illustrated and described,
it will be apparent to those skilled in the art thatmodi?ca
anism moves to position 72. This drop would be nearly 10 tions other than those shown'may be made Without de
equal to the potential across adjacent contacts 18 on the
panting'from the spirit {of the invention or ‘from the scope
coarse winding and is an undesirable condition. There
of the appended claims. For example, the illustrated
fore, there must be assurance that the second contact 215 ‘
moving switches may be replaced by static elements for
of the coarse mechanism moves into a nonbridging posi
controlling current flow without departing from the spirit
tion with the leading contact 21a prior to movement of 15 of the invention.
'
,
the ?ne mechanism into position 72‘ and subsequent to
Having now particularly described and ascertained the
leaving position 88.
'
As can be observed from the table in FIG. 3, switch ’
nature of my said invention ‘and the manner in which it
is to be performed, I declare that what I claim is:
M1, which is ‘connected to abridging coarse switch B1,
1. A wide range ?ne step voltage regulator comprising
closes when the ?ne mechanism reaches position 71. Upon 20 a coarse step tap changing unit and a ?ne step tap chang
closing of switch M1 current flows through the closed
ing uni-t mechanically independent of each other, each
bridging switch B1 and through the raise winding‘ 44 of
said unit having a winding with a plurality of taps with
the coarse motor, thereby obtaining an advance in the t‘ circular arranged stationary contacts connected thereto
second contact 21b. ‘With the coarse contacts now in
and a pair of movable contacts driven by a motor for
a nonbridging position, the ?ne mechanism continues onto 25 successively engaging said stationary contacts, said mov
position 72, etc. and a steady uniform voltage increase able contacts of said coarse unit being connected to the
is obtained.
,
.
_
tapped winding of said ?ne unit, and an electrical control’
With respect to switch M3 which is connected to the
system for synchronizing each said motor and said mov- '
raise winding 45 of the ?ne mechanism motor it will be
'able contacts in each'said unit comprising current limit
noted that this switch is open only at position 71 of the 30 ing means responsive to the positions of said movable
' ?ne mechanism. This switch further assures that as long
contacts relative to their respective stationary contacts
as the coarse mechanism contacts 21a and 21b are in a
whereby load current in said regulator is maintained
bridging position the ?ne mechanism will not be able
to advance farther than position 71' thereby assuring avoid
ance of load current interruption.
In a similar manner, svtu‘tch M4 also provides an addi
tional safeguard against load current interruption. It will
be noted that this switch is open only when the ?ne
mechanism is in'the position 87. Consequently, as long
as the coarse mechanism contacts are in a nonbridging
position, M4 prevents movement of the ?ne mechanism
from position 87 to position 88.
‘The function of the’second‘ nonbridging switch NB2 I
_ is to avoid overdriving the coarse mechanism. Thus, at
throughout cycling of said movable contacts by each said
motor.
35
'
'
2. A wide range ?ne step voltage regulator comprising
a coarse step tap changing unit and a ?ne step tap chang
ing unit, each said unit having a winding with a plurality
of taps with circular arranged stationary contacts con
nected thereto and a pair of movable contacts driven by a
motor for successively engaging said stationary contacts,
said movable contacts of said coarse unit being connected I
to the tapped winding of said ?ne unit, and an electrical
control system for synchronizing said movable contacts
in each said innit comprising switching means connected
positions 85 and 86'wl1enthe coarse mechanism is in a 45 between apowersupply and each said motor, said switch
bridging position with switch M2 closed, the‘hypothetical
ing means ‘being responsive to the positions of said mov
connection of switch M4‘ to the nonbridging switch NB];
able contactsrelative to their respective stationary contacts
i would cause'the coarse mechanism to continue moving as
Q whereby load current in said regulator is uninterrupted
“a current?ow would occur through switches B1, M3,
throughout cycling of said movable contacts by each said
M4 and M2 to the coarse raise winding ‘44. Likewise, 50
the particular arrangement of switches calls fora second
3. In combination with a wide'range ?ne step voltage .
bridging switch B2’ in the lowergcircuit to avoid over
‘regulatorhaving a coarse step tap changing unit and a
motor.
driving the coarse contacts 21a ‘and 21b through the
coarse lower winding 44'. I
V
'
'
'
'
i
?ne step‘tap changing‘unit, each said unit havinga wind
mg with a plurality of taps connected to circular arranged
55 stationary contacts and a pair of movable contacts driven
I Course Step ‘Operation
To operate the regulator through its 32 coarse steps,
by a motor for successively engaging said stationary con
‘ 'tacts, said movable contacts of said coarse unit being
bypassing the ?ne steps, switch 5415 closed. This runs
connected to the tapped winding of said ?ne unit, an
the ?ne mechanism contacts 26a and 26b to position 88
electrical
control system for synchronizing said movable
where switch M5 (normally closed) opens and auto~ 60 contacts comprising: a ?rst current limiting means con
matically stops the ?ne motor ‘and mechanism. A lever 7 nected to a power supply and responsive to bridging and
that may be mounted on the manual portion of the control
inonbridging positions of said coarse movable contacts;
panel of the regulator is then moved trom 1a normal posi ' land
a second current limiting means connected between
tion to either the ‘raiseor lower position causing either
said ?rst current limiting means and each said motor‘
switches 56 ‘and 63 or 56' and. 63.".to respectively simul
65 and responsive to the position of said ?ne movable con~
taneously close.- Inasmuch as switch 58 isal-ready closed" , tacts relative to said ?ne stationary contacts whereby load
current in said regulator is maintained ‘throughout cycling
transfer motor 511jand bypasscontact ~48a'movestoi'oon- ,
of said movable contacts by each said motor.
tact 50b‘, assuming an‘ intermediate position. Switch 611
1 4.‘ In combination with a wide range ?ne step‘ voltage
‘(see FIG. 4) current ?ows through winding: 165 ot' the
openswas it is also responsive to the positioning of the
transfer mechanism. Consequently, prevention of cur
regulator .‘having a coarse step tap changing unit and a
?ne step tap changing unit, each said‘ unit having a wind
ing with Ia-pluraliy of taps connected to circular arranged.
The transfer motor continuesto run and bypass sw-i-tcll
stationary contacts and a pair of movable contacts driven
48b moves to contact ‘50b, thus bypassing the ?ne mecha
by a motor for successively engaging said stationary con-'
With the transfer switches now in their coarse 75 'tacts, said movable contacts of said coarse unit being
rent to the ?ne mechanism is fully assured.
V
>
3,100,865
Y
@
,
connected'to the tapped winding of said ?ne unit, an elec- ‘
trical control system- for synchronizing said movable con
tacts comprising: a ?rst set ‘of switches connected to a
‘age steps and load current are maintained throughout
successive cycling of said ?ne movable contacts by said
?ne unit motor.
_
'
power supply and responsive to bridging and nonbridg
_ 7. In combination with tawide range" ?ne step voltage
.
ing positions ‘of said coarse'rnovable contacts; and a sec
ond set of switches connected between said ?rst switches
and each said motor and responsive to the position of
said ?ne movable contacts relative tosaid'?ne stationary
contact-s whereby said coarse movable contacts autos
matically advance from a nonbridging position to a 10
regulator having a coarse vstep-tap changing unit and a
bridging position upon said ?ne movable contacts reach
ing a predetermined ?ne stationary contact.
5. In combinationwith :a wide range ?ne step voltage
‘ regulator having a'coanse step tap changing unit and a ?ne
step tap changing unit, each said unit having a winding
?ne step tap changing unit, each said u'nithaving a wind
ing with a plunaility of taps connected to cincular arranged
stationary contacts and a pair of movable contacts driven
by ia-motor ‘for successively engaging said stationary con
tacts, said movable contacts‘ of ‘said coarse unit being
connected to the tapped winding of said ?ne unit,an elec
trical control system for synchronizing said movable con
tacts comprising: :a, ?rst set of switch carrying parallel
connected conductors connected to a power supply with 1a
portion thereof being conductive ‘only in response to v
bridging positions of said coans-e movable contacts the
with a plunality'of taps connected to circular arranged
remainder of said conductors being conductive only in
stationary contacts: and a motor driven. pair of movable
response to nonbridging positions or» said ‘coarse movable
contacts driven by a ‘motor for successively engaging said
contacts; each said motor having‘ a pair of windings with
stationary contacts, said movable contacts of said coarse
unit being connected to the tapped winding of said ?ne 20 each winding connected to ‘one each of said bridging and
nonbridging responsive conductors by two lot" a second set
unit, an electrical control system for-synchronizing said
of switch carrying conductors in series with said ?rst set
movable contacts comprising: a ?rst set of conductors
of conductors; said second set of conductors changing
connected to a power supply with a portion thereof being
from conductive to non-conductive in ‘response to the posi
conductive only in response to bridging positions of said
coarse movable contacts, the remainder of said conductors 25 tion of said ?ne movable contacts relative to said ?ne sta
tionary contacts whereby load current in said regulator
being‘conductive only in response to nonbridging positions
is maintained throughout successive cycles [of said ?ne
of said coarse movable contacts; each said motor having
movable contacts by said ?ne unit motor.
a, pairof windings with ‘each winding connected to one
v8. In combination with a wide range ?ne step voltage
each or said bridging and nonbridging 'responsive con
regulator having a coarse step tap changing unitand (a ?ne
ductors by two of a- second set of conductors; said second
step tap changing unit, each said unit having a winding
set of conductors changing from conductive to noncon
with a plurality of taps connectedto circular larnanged sta
ductive response to the position of said ?ne movable
tionary contacts and [a pair of movable contacts driven
contacts relative to said ?ne stationary contacts whereby
by a motor tor successively engaging said stationary con
Load current in said regulator is maintained throughout
‘ tacts, said movable contactswoi said coarse unit being con
cycling of said ?ne movable contacts by said ?ne unit
nected to the tapped winding of said ?ne unit through a
6. In combination with a wide range ?ne step voltage
pair of bypass switches, an electrical control system for
synchronizing ‘said tap changing motors comprising: 1a ?rst
regulator having a coarse step tap, changing unit ‘and a
?ne step tap changing unit, each said unit having a wind
set of switches connected to a power supply and respon~
ing with a plurality of taps connected to circular arranged 40 sive to bridgingand nonblridging positions of said coarse
movable contacts; a second set of switches connected be
stationary contacts and a pairv of movable contacts driven
tween said ?rst switches: and said motors and responsive
by a motor for successively-engaging said stationary con
to the position of said ‘?ne movable contacts'nellative to
tacts, said movable contacts ‘of said coanse unit being con
‘said ?ne stationary contacts whereby load currentin said
nected to. the tapped winding of said ?neunit, an elec
motor.
‘
.
j
'
-
' trioalcontnol system for synchronizing said movable con‘_ 4:5 regulator is maintained during ‘driving of said movable
tacts comprising: a ?rst set of switch carrying parallel
connected conductorsrconnected to -a power supply with a
contacts by said motors; a transfer mechanism having a
motor for driving said bypass switches; and switching
means connecting said transfer motor to said'power sup-s
portion thereof {being conductive [only .in response to
ply at a predetermined position-of said ?ne movable con
. bridging positions of said coarse movable contacts, the‘
tacts whereby load current is maintained throughout
remainder of said conductors being conductive only in 50
‘
cyclingof said movable contacts and operation of said
response tononbrid-ging positions of said coarse movable
contacts; each?said' motor having a pair of windings with
transfer mechanism. . ‘
eachwinding connected to one each of said bridging and
Q ' References Cited in ,the?le of‘this patent
“nonbrid-ging responsive conductors by two (of a second set 55
of ‘switch carryingconductors; said second set or con
ductors changing from conductive to noncondnctive in
response to the position of said ?ne movable contacts rela
tive to said ‘?ne’stationary contacts whereby uniform volt
UNITED'STATES PATENTS
2,480,589 > " McKenney ____.'.__p__.____. Aug. 30, 1949'
2,933,671
Prescott et al __________ __ Apr. 19‘, ‘1950
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