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Патент USA US2394111

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Feb. 5, 1946.
w. SCH’AELCHLIN ETAL
2,394,111
CONTROL SYSTEMS
Filed Sept. 28, 1944
WITNESSES;
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INVENTORS
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ATTORN EY
2,394,111
Patented Feb. 5, 1946
UNITED ‘STATES PATENT OFFICE *
Walter Sohaelchlin, Pittsburgh, and Earl 11.
Hornbarger, Edgewood, Pa... assignors to West
inghouse Electric Corporation, East Pittsburgh,
Pa., a corporation of Pennsylvania
Application September 28, 1944, Serial No. 558,160
6 Claims.
(Cl. 172-179)
This invention relates, generally, to an electric
drive and, more particularly, to an electric drive
embodying an electric motor and which includes
means for reversing the direction of rotation of
the motor.
parent from a study of the following disclosure
when considered in conjunction with the accom
panying drawing, in which the single ?gure there
of illustrates a reversible electric drive embody
ing the principles of this invention.
Referring now to the drawing, the reversible
electric drive therein illustrated comprises gen
drives space limitations are such that standard
erally a direct-current motor M which is re
reversing equipment will not fit into the allowed
versely operable, a. reversing switch generally‘
space. It is also frequently required that the
motor be entirely disconnected from the line when 10 designated RS for establishing reversing connec
tions for the motor armature, forward and re
the system is stopped. Ordinarily in a reversible
versing push buttons respectively designated FWD
electric drive in which‘ the motor is to be discon
and REV which selectively energize the forward
nected from the line at a minimum there is re
and reversing solenoids F and R of the reversing
quired one main line contactor and a pair of two
pole mechanically interlocked contactors for re 15 switch, an accelerating relay designated A which
controls the starting cycle of the motor M and
versing the connections to the motor armature.
in addition initiates an energizing circuit for the
A compact design is obtainable by utilizing, in
coil of the main line contactor, which contactor
place of the reversing'contactors, an electromag
is designated MC, and as the ?nal general cone
netically operated switch which is maintained in
either of its two operative positions with the 20 troi element the main line contactor MC which
establishes energizing circuits for the motor.
actuating coils thereof deenergized. Such‘ a re-v
The motor M, as illustrated, comprises a pair
versing controller differs from conventional ar
of field windings, one a shunt field winding desig
rangements in that the reversing elements are
nated SHF and the other a series iield winding
always in one or the other of the two operating
positions. In other words, the controller is always 25 designated SRF. While two field windings have
been shown for this motor it will, of course, be
positioned for either forward or reverse operation
understood that any suitable ?eld winding ar
of the motor and the motor will start as soon as a
rangement may be utilized. For example, the
the line contactor closes. Thus suitable provision
motor may be a series motor or av shunt motor
should be made to prevent closing of the ‘main
line contactor until the reversing switch or con 30 depending upon the operating characteristics
which are desired. The armature winding of
troller is in the desired position. _
'
the motor M is connected through either the for
A principal object of this invention is to provide
In certain applications of reversible electric
a reversible electric drive which is inherently com
pact in design and simple in operation.
' Another object of this invention is to provide
a reversible electric drive which utilizes a simple
reversing switch operable to either of its two posi
tions, in which the reversing switch automatically
assumes its correct forward or reverse position
before the motor is connected to the line.
Another object of this invention is to provide
a reversible electric drive in which low voltage
' ward or reversing elements of the reversing switch
and the contacts MCI and M03, across the ener
gizing buses BI and B2. When the reversing
switch is in the position indicated in the drawing,
that is the forward position, the contact mem
bers F3 and F4, thereof establish connections to
energize the motor armature in a direction with
40 respect to the motor ?eld system such that the
motor will operate in a forward direction. The
contact members F2 operate in conjunction with
the front contacts of the forward push button and
protection is provided.
Another object of this invention isto provide a 45 the back contacts M04 to connect the coil of the
accelerating relay A across the main line buses.
reversible electric drive in which. the reversing
The contact members Fl, when closed, provide an
switch‘ or controller is operated only to effect re
energizing circuit for the coil of the forward
versing of the direction of rotation of the motor
solenoid, in conjunction with the contacts API
and is not energized and therefore does not func
of the anti-plugging relay AP and the contacts
tion during starting of the motor in the same
50 M02 when the forward push button is depressed,
direction as last operated.
to effect operation of the reversing switch to its
Another object of this invention is to provide
forward position. This circuit may not be com
an electric drive of the character mentioned in
pleted if a voltage appears across the motor arma
which the motor must be deenergized before a
ture terminals of sumcient magnitude to oper
reversing cycle can be initiated.
Other objects and advantages will become an 55 atimz the anti-plugging relay. The contacts M02.
2
2,894,111
when the main line contactor is operated, also
The main line contactor immediately picks up.
open this energizing circuit. For reverse opera
tion of the motor the contact members RI and
closing its contact members MCI and MCI and
immediately starts the motor in the forward
R4 reversely energize the motor armature and
direction. At this time the contacts M04 open
thus cause the motor to operate in the reverse
and deenergize the coil of the relay A. This
direction. The contact members R2, when closed,
relay now drops out and shunts the starting re
like the contact members F2, form part of an
sistor from the motor circuit. The contact mem
energizing circuit for the coil or the accelerating
bers MCB close before the relay A drops out and
relay A. The contact members RI form part of
maintain the coil of the main line contactor
an energizing circuit for the coil or the reversing 10 energized. Since the contact members MCZ have
solenoid R.
-'
opened, the energizing circuit for the coil of the
The accelerating relay A controls the starting
reverse solenoid is opened at this point. This
cycle of the motor at'its contact members Al
actuation of the reversing push button may not
which shunt the starting resistor SR. This relay
complete an energizing circuit for the reverse
picks up once the reversing switch is in its cor 15 coil. After the motor armature voltage builds up
rect position and opens theshunt circuit around
the anti-plugging relay AP is operated, thus open
the starting resistor at its contacts Al. Thus
ing its contact members API also in the ener
gizing circuit for the forward and reverse sole
starting resistor is connected in series with the
noids. 'By reason of these expedients the motor
armature winding and the series field circuit ‘to 20 may not be suddenly reversed in its direction of
thus limit the armature currents within permis~
operation by operation of either the forward or
sible values. This is desirable in the case of a.
reverse push button. To accomplish reversing of
motor which is permanently connected to the a
the motor it is necessary to press the stop button
load which it drives since under this condition
and deenergize the main line contactor. When
the motor armature currents at very low speeds 25 the main line contactor is deenergized its con
and high torque may be excessively high. The
tact members MC2 close. If these contacts alone
accelerating relay at its contact members A2 also
maintained the energizing circuit for the forward
forms part of an energizing circuit for the coil
and reversing solenoids open, it would be possible
of the main line contactor. Thus this contactor
immediately upon deenergization oi the main line
may not be closed to energize the motor until the 30 contactor to initiate a reversing cycle or the
when the motor accelerates irom zero speed, the
accelerating relay has operated. Likewise, the
accelerating relay may not be operated, as here
inbei’ore noted, until the reversing switch is in
motor. This is prevented, however, by the anti
plugging relay which will not drop out until the
motor armature terminal voltage has decreased
its correct position depending upon which of the
forward and reverse push buttons is depressed.
rThe main line contactor at its contacts MCI
and M63 energizes the motor circuits. Its con
tact members M62 open the energizing circuit
for the coils of the forward and reverse solenoids
which comprise part of the-reversing switch.
The Contact members M64 open the energizing
circuit for the accelerating relay thus causing
it to drop out shortly after the main line con
tector operates. Thus the resistor SR is inserted
in the motor circuit for a short interval Just
sufficient to bring the motor from zero speed
up to some higher speed, and then is shunted
to permit the motor to accelerate over the rest‘
of its speed range. The contact members M05
in conjunction with the stop push button, so
designated in the drawing, form an energizing
circuit for the coil of the main line contactor
to keep this coil energized when the contact
members A? open.
The operation of the system is as follows. If
to a fairly low level, at which level a reversing
35 cycle may be initiated without damage to the
motor.
I! it had been desired to start the motor in
the reverse direction with the reversing switch
in the forward position, the reversing push but
40 ton would have been depressed, immediately en
ergizing the coil or the reversing solenoid in a
circuit through the stop push button and the
forward and reverse push buttons which includes,
the contacts RI, AP! and M02. The magnetic
45 forces acting on the core of the reversing solenoid
accelerate the reversing switch to the right. This
immediately opens the contacts Rl to deenergize
the coil R. The assembly, however, by reason
oi its inertia, moves to its extreme reverse posi
50 tion and closes the contacts R2, R3 and R4. The
contacts R2 energize the coil of the accelerating
relay A and the contacts R3 and R4 establish
reversed armature connections for the motor to
operate the motor in its reverse direction. The
55 main line contactor now closes to start the motor
direction, the forward push button is depressed.
and deenergize the accelerating relay.
Since the reversing switch operates only dur
This establishes an energizing circuit for the coil
ing periods when the motor circuits are deen~
it is desired. to operate the motor in a forward
of the accelerating relay since the reversing
ergized its contacts do not interrupt energized
switch is in its forward position, which begins 60 circuits. This relay may therefore be of fairly
at the bus Bi and includes the stop push button,
small capacity, thus lending itself to small
the back contacts of the reversing push button,
physical design. Further, the coils of the re
the front contacts of the forward push button,
versing solenoids are only intermittently en
the contact members F2 now closed, the coil of
ergized and are deenergized by contacts within
the accelerating relay and the contact members 65 the reversing switch itself. The coils may thus
MC4 to the bus B2. This accelerating relay thus
be intermittently rated. In controllers which
picks up and opens its contact members Al to
would be reversed very infrequently the revers
insert the starting resistor in the motor circuit
ing switch illustrated in the drawing would re
and closes its contact members A2 to complete
ceive correspondingly infrequent operation. In
an energizing circuit for the coil of the main 70 the case of contactor-type reversing controllers
line contactor which includes the stop push
the reversing devices would open and close every
button, the back contacts of the reversing push
time the motor was started.
button, the front contacts of the forward push
The reversing switch, as illustrated in the
button, the contacts F2, the contacts A2 and the
drawing, is schematically shown for the sake of
coil of the main line contactor to the bus B2.
simplicity and it should be understood that any
asaaui
physical arrangementoi' parts for this switch
3
tionthereoi'to eitherof two positionsupon sep
arate encrgization thereof, means for selectively
which embody the principles illustrated may be
utilized. One form of such ‘switch which has
been found satisfactory and which is not affectedv
energizing said pair of coils, a relay for energiz
ing the contactor, means forming a’ part of said
by shock involves a cam shaft and a pair of sepa
switch for energizing said relay when said switch
rate switch units operated in the alternate posi
isinthepositionselectedbysaidmeansforse
tions of the cam shaft. The‘cam shaft is op
erated to its two positions by means of two small
' lectively energizing said coils; means forming a
- part of said contactor for deenergizing' said relay _
electromagnetic elements which are mechanical
ly linked thereto..
Theforegoingdisclosure andtheshowingmade
1o vwhen said contactor is energized and operated,
a resistor connected ineseries with said motor,
'andmeansformingapartoisaidrelaynormally
inthedrawingaremerelyillustrativeofthe
shuntingsaidresistorwhensaidrelayisdeen
principlesofthisinventionandarenottohein
terpretedinalimitingsense. Theonlyiimita
ergized
tionsaretobedeterminedfromthescopeoi'ths
motor, a contactor for
appended claims.
switch having a pair of coils tor effecting opera
tion thereof to either of two positions upon sep
arate energization thereof, means for selectively
energizing said pair of cells, a relay for energiz
5. In. an electric drive, the combination ‘of, a ‘
‘
motor, acontactor forenergisingthe motor, av
relayhavingapairofcoilsforactuatingsaidre
lay to either ortwo positions depending upon
whichlcoil is energized, means for selectively en-v
erginngsaidpairofooimsaidrelaybeingeifec
tiveineaehofitstwopositionstoeifectrevers
thereof under in?uence of said energized coil.
2. In an electric drive, the combination of, a
motonmeans for energizing the motor, revers
20
the motor, a -
lngthe contactor, means i'orminga part of said
switch i'orv energizing said relay when said switch.
isinthepositionselectedbysaidmeansforse
lectively energizing said coils, means forming a
' part of said contactor for deenergizing said relay
when said contactor is energized and operated,
a resistor connected vin series with said motor,
means forming a part of said relay normally
shuntingsaidresistorwhensaidrelayisdeenr
ergiaed,andmeans for preventing
tion of,
"eitherofsaidpairofcoilsaslong-assaidmotor
is energized.
-
v
8. In an electric drive, the combination of, a
motor, a contactor for
the motor, a
switchhavingapairofcoilsforeilectingop'era
3‘ tionthereoftoeitheroftwopositionsuponsepa
rate energization thereof, means for selectively
energizingsaidpairofcoils,arelayfor energiz
lnsthecontactonmeansformingapartofsaid
switchforenergizingsaidrelaywhensaidswitch
“isinthepositionselectedbysaidmeansforsr
-lectivelyenergizingsaidcoils,meansforminga
partofsaidcontactorfordsaidrelay'
when said contactor is energized and operated, a
resistor connected in series with said motor,
“meansforminga‘pu'tofsaidrelaynormaily
.shuntingsaidresistorwhen saidrelayisadeen
ergined,andareiayaccordingtothe
_ motor voltage and having contacts which main
taintheenergizingcircuitsforsaidpairofeoils'
openaslongasthemotor‘voltsgeisabovea
determinedvalue.
>
v
,
‘s
"WALTER SCHAEICHLIN.
EARLEHORNBARGER,
‘
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