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Патент USA US2125792

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Aug- 2, 1938-
Filed Jan. 50, 1937
Fig. l.
2 Sheets-Sheet 1
by 56/62/16.
Aug. 2, 1938.
- 2,125,792
Filed Jan. 30, 1937
2 Sheets-Sheet 2.
Inventor :
5 eq] amin \Mdo?es,
by )émwé/Jwwz
Patentet'fAug. 2, 1938v
Benjamin W. Jones, Schenectady, N. Y., assignor
to General Electric Company, a corporation of
New York
Application January 30, 1937, Serial No. 123,217
8 Claims. (Cl. 172—179)
This invention relates to control systems, more
particularly to systems for controlling the opera
motor operation. In other words, it is desirable
that all the motor armature resistance shall be
tion of electric motors, and it has for an object
shunted, thereby to produce the most effective
braking and thus, even with increasing load, to
the provision of a simple, reliable, and improved
5 system of this character.
Still more particularly, the invention relates to
motor control systems in which the driving motor
is required to drive light loads and also heavy
loads which at times may overhaul the motor,
10 and a further object of this invention is the
provision of means for safely controlling the
motor under these conditions.
In hoist installations, there has been a demand
for‘ ever increasing speeds of lowering an empty
15 hook, together with good safe regulation in brak
ing the load for loads that overhaul the motor.
For example, there have been demands for empty
hook lowering speeds ranging from 150% to 250%
of normal running speed, togetherwith safe regu
20 lation for loads that are of such magnitude as
to overhaul the motor. Stated in other words, a
limit the speed to a safe value. Accordingly, a
further object of this invention is the provision
of means for producing a moderately steep speed
torque characteristic in the power lowering quad
rant of motor operation and a fairly ?at speed
torque characteristic in the dynamic braking
lowering quadrant of motor operation.
In carrying the invention into e?ect in one
form thereof, a plurality of, resistors are con
nected in the motor armature circuit, and means
are provided for shunting these resistors, to
gether with means for preventing the shunting
of one of the resistors during motoring opera
tion in one direction, and for shunting this re
sistor when the load overhauis the motor. In the
case of a motor operating a hoist for driving any
load acted upon by gravity, these means also
fairly ?at maximum speed-torque curve for the , provide for shunting this resistor when the motor
motor is very desirable for this type of installa
is hoisting the load, thereby to provide for maxi
tion. However, certain difficulties are encoun
mum torque output of the motor.
g5 tered in obtaining this desired operating char
For a better and more complete understanding
acteristic. Motor speeds of this order are nat
of the invention, reference should now be had to
urally obtained with the motor operating with a the following speci?cation and to the accom
very weak ?eld. Controllers for such installa
panying drawings, in which Fig. 1 is a diagram
tions are usually arranged to insert resistance in matical illustration of an embodiment of the
30 the field circuit and to‘ shunt resistance in the invention; Fig. 2 is a simpli?ed diagrammatical
armature circuit in predetermined steps. When illustration in “across the line form” of the em
a motor is operating'with a ?eld weakened suffi
bodiment of Fig. 1; and Fig. 3 is a chart of curves
ciently to produce speeds greatly in excess of representing operating characteristics of the mo
normal running speed, it is in a very unstable tor, which serve to explain the invention.
3;, operating condition, and shunting the last sec
Referring now to the drawings, a motor l0,
tion of armature resistance under this condition such for example, as a motor utilized to drive a
is very likely to produce bad commutation and hoist, is supplied from a suitable source repre
even to produce such a surge of current as to sented by the supply lines il, l2. The motor In
result in "?ashover”.
_ It is therefore desirable to maintain a section
of the armature resistance in circuit when the
‘motor is lowering a load and operating as a
motor. This produces a much steeper speed
torque curve in the power lowering quadrant of
45 the motor operation, but does eliminate the
is illustrated as a series type motor having a
series field winding l3 and a commutating ?eld
Winding l4.
Means are provided for controlling the direc
tion of rotation of the motor.
These means are
illustrated as a multipoint reversing type master
switch l5, and a pair of switching devices i6, 11
danger described in the foregoing.
under the control of the master switch. The
However, if the load actually 'overhauls the‘ positions on the right-hand side of the master
motor, a steep speed-torque characteristic would ' switch are referred to as the hoistingypositionsr
be very undesirable, because the speed might rise and when the master switch is operated to these
so quickly to a dangerous value, resulting in dam
positions, the switching device l6, referred to as 50
age to the motor and to the apparatus with which the hoisting contactcr, is closed to connect the
the motor is associated. Under thiscondition of armature of the motor ill to the source for rota
operation, it is desired that the‘maximum speed
tion in a direction to hoist the load. Similarly,
torque curve of the'motor shall be as ?at as the positions on the left-hand side of the master
55 possible in the dynamic braking quadrant of 'switch are the lowering positions and when the
master switch is operated to these positions, the
contactor 26, conductor 44 through operating coil
lowering contactor I1 is closed to connect the
motor ll to the source for rotation in a direc
tion to lower the load.
Suitable current limiting means illustrated as
a plurality of resistors i8, i9, and 20 are included
in the armature circuit oi! the motor ior con
of contactor 21 to the negative side of the source.
Contactor 21 in closing opens its normally closed
interlock to interrupt the energizing circuit 0!
the contactor 24 previously traced through these
interlocks, and, accordingly, contactor 24 is again
operated to its open position in which it is illus
trated. In the closed position oi the contactor
21, an energizing circuit is completed for con
motor. For the purpose of varying the ?eld ex
tactor 28 that is traced from the power conductor 10
22, and 23 are included in the field circuit 01' the ' 38 to the conductor 44, as previously, and thence
trolling the acceleration and deceleration of the
motor, and the shunting of these resistors is under vthrough conductor 44a, segments l5; and ISL oi
the control of the electromagnetic contactors 2|, ‘the master switch, conductor 44b, interlock con
tacts of contactor 21, normally closed contacts of
2!, and 28, respectively.
relay 32, and operating coil of contactor 28 to 15
Contactors 21 and 28 serve to control the shunt
ing of resistors I8 and I9, respectively. A resistor the negative side of the supply source. Contactor
29 is at times in the ?eld circuit of the motor
and at other times in the armature circuit, de
pending upon Whether its controlling contactor Jill
20 is open or closed.
theA contactor
relay 21 provides
‘.21. This
relay ‘voltage
is ordinarily
by a spring or by gravity", to complete
nainic braking ci cult for the armatur
loop lily‘
of motor
it, con»
Justed to close its contactav on 25% of nor“
i0 that may he s
‘to extend from
in of he motor ti'lrougli trolley W
line volts. iii relay 32 having its operating cc“
of dynamic
4?, dynamic
braking inciting
25 connected across the resistors Ill and, it o -
operates with interlock contacts 21'; oi" contact-or
21 to control the energization and operation oi
'contactor 28.
In order to prevent the relay 32 from energia
and closing the contactor 28 when the motor
i0 is accelerating in the lowering direction, means
are provided tor energizing the relay 32 anti
causing it to open its contacts when the motor is
accelerating in the lowering direction, and for
35 preventing the relay 32 from opening its contact-t
it the load should overhaul the motor, These
means are illustrated as a recti?er
in therecti?er
circuit may
or the
he operating
of any suitable
coil of relay
e loot it
40 is preferably of ‘the plate
contact t
such, for example, as the welldmowo copper
hauled by its load in the lowering Clio "t
when it is driving the load in the hoist“ ”
With the I‘.
this camp‘
from “to
of the sol '
an ant
Likewise, con
and its enei'giringciim L .i
tend from the conductor ill 0
75 through segment i512. conductor
it, and thence through series field it and coin
mutating field H to the opposite terminal of the
motor armature. Thus the apparatus and ele
ments are in the positions described in the fore
going, and the master switch it”: is in the of‘! posi
tion when the pilot switch 3% is closed.
Movement of the master switch it: ‘to the ?rst
lowering position completes an energizing circuit
for the operating coil. oi’ contactor till which ex‘
tenols from the power conductor
oi‘ the master ,
switch ‘through segment I50 and cooperating
?nger, and, thence by conductors iil'ancl t2, and
operating coil oi contactoi" Hill to the negative side
the source, ?ontactor till closes in rear:
its circuit
of recti?er.
that it passes
so connected
is driving its lead in the lowering dire
n and
does not
current when it is
28 closes in response to energization and shunts
the resistor IQ. The contacts of dynamic brak
ing contactor 45 are normally held closed either
partially completes the
oi‘ motor
is conilpleteci
coil oi contactor M» the is traced
the operating
contactor 28, resistors 29 and 2!! to the negative
side of the supply source.
Thus it will be noted that themotor is con
nected to the line with the resistor 2iiv in the
armature circuit and the resistors 20 and 28 in
the field circuit. Under these conditions, the
motor begins to accelerate, and its performance
\_ is represented by the characteristic curve 83 of
‘Fig. 3.
10 ’ It will be understood that it is usual practice ~
terlocks of contactor 25 (in the closed position
thereof), and operating coil of contactor 30 to
the opposite side of the supply source. Contactor
30 closes its contacts in response to energization
and connects the resistor 29 in parallel with re
sistor 20, and at the same time, it connects the
?eld winding i3 to the negative sides l2 of the
supply source through the resistors 23 and 22
without passing through resistor 20, so that the
motor is now connected to the line in a straight 10
for the operator to throw the master switch
quicklyfrom the off position to the maximum
shunt connection, and the motor performances
speed position. However, this operation is de
Contactor 30 in closing completes an energizing
circuit for accelerating relay 3|. This circuit is
traced from the terminals ills of the motor arma 15
ture through conductors 46 and 41, resistor 48,
conductor ‘Ii , operating coil of relay 3|, conductor
scribed as taking place step by step so that the
15 operation may be more readily visualized and
0n the second point, of the master switch, the
energizing circuit of contactor 28 is interrupted
at the segments l 51, P51. of the master switch, and
20 the contactor opens its contact and inserts the re
will be in accordance with the curve ‘iii of Fig. 3.
12, interlock contacts of relay 30, and thence by
conductors 13 and 14 to the common terminal of
resistors 22 and 23, and thence through resistor
sistor IS in the armature circuit of the motor. 23 to the opposite motor terminal. Relay 3i 20
Under this condition, the performance of the mo
closes its contact under the in?uence of the coun
tor, that is to say, its speed-torque characteristic, ter voltage of .the motor to complete an energiz
is represented by the curve 64 of Fig. 3. When 'ing circuit for contactor 21, provided that the
25 resistor is is inserted in the motor circuit, a volt
motor speed has become sufficiently high. The 25
age dro‘p appears across this resistor which causes
energizing ‘circuit for contactor 21 is readily
current to flow through the operating coil of re
traced from‘ power conductor 36 of the master
lay 32. This voltage drop is oi such a polarity switch through segment l5g and co-operating
that current will ?ow through the recti?er ‘33. ?nger, thence through conductor 15 and contacts
30 The circuit is traced from the right-hand or posi
of relay 3i, and thence through conductor 44
tive side of the resistor i 9 through the contacts and the coil of contactor 2'! to the negative side 30
of contactor 2?, thence through conductor 65, op 7 of the supply source. As a result, contactor 21
erating coil of relay 32 and conductor 66, recti?er closes its main contacts and shunts the resistor
33 to the left-hand or negative terminal of the
IS in the armature circuit of the motor, thereby
35 resistor. As a result of its energization, relay 32 vcausing it to increase its speed. Under this‘ con
opens its contacts and further interrupts the en
dition, the motor performance will be in accord 35
ergizing circuit of contactor 28 so that it cannot
be reclosed as long as current flows through the
resistor IS in the direction from right to left; or
40 in‘ other words, as long as the motor is operating
‘ as a motor in the lowering direction.
ance with the speed-torque curve ‘iii of Fig. 3.
In the closed position of contactor 21, its in
terlock contact 21s interrupts the energizing cir
cuit of contactor 24. The coil of contactor 22 is
short-circuited by a resistance 11, and accord
ingly, this contact will open its contacts with a
On the third point of the master switch, the
energizing circuit for the'operating coil of con Y slight time delay. Contactor 2i in opening its
tactor 21 is interrupted. This energizing circuit contacts inserts the resistor 2i in the ?eld cir
45 was previously traced through the segment i5: cuit oi’ the motor and this produces further accel
of the master switch and the interlock contacts eration of the motor in accordance with the char
of contactor 26.- Contaotor 21 opens its contacts acteristic curve 18 of Fig. 3.
and inserts the resistor i8 in the armature circuit
When contactor 2'! closed its contacts, its upper
of the motor, and the motor continues to accel-' interlock contacts» also closed, thereby partially to
50 erate its load in accordance with the speed-torque complete an energizing circuitfor the operating
characteristic represented by the curve 81' of Fig. coil of contactor 28. However, since the energiz
3. Contactor 21 in opening, recloses its lower ing circuit for contactor 28 is maintained open at
interlock contacts 21a to re-establish the ener
the contacts of relay 32 as long as the motor is
gizing circuit for the operating coil of contactor driving its load in the lowering direction, con
56 24. Contactor 24 closes in response to energize
tactor 28 remains open and the resistor i9 re
mains in the armature circuit of the motor. At
On the fourth point of the master switch, the this time the motor i0 is operating with a very
energizing circuit for the operating coil of con- ' weak ?eld because the resistors 2!, 22, and 23 are
tactor 26 is interrupted. at the segment [5b of all connected in series in the ?eld circuit. If the
60 the master switch, and the contactor opens its . resistor is in the armature circuit of the motor
contacts and inserts the resistor 23 in the field cir
could he short-circuited at this time, the motor
suit of the motor. This causes the motor to ac
performance would be in accordance with the
celerate further in accordance with the char
speed-torque curve 19 of Fig. 3. It may now be
acteristic represented by the curve 68 of Fig. 4.
assumed that at the present point in the opera
As the master switch passes to its ?fth posi
tion, the speed and torque of the motor are repre
tion, the energizing circuit for the operating coil sented bythe point 80 on the speed-torque char
of contactor 25 is interrupted at the segment I51 acteristic 18. Now it will be observed that if the
oi’ the master switch, and as a result, contactor resistor IS in the armature circuit of the motor
25 opens its contacts and inserts resistor 22 in should be short-circuited at this point in the op
70 the field circuit/of the motor._ At ‘the same time eration, the performance of the motor would be
an energizing circuit is completed for the operat— suddenly transferred from the point 80 on the
ing coil of contactor 30. This circuit is readily characteristic curve 18 to a point 8| on the char
traced from the power conductor 36 of the master acteristic curve 19. The point 8| on the curve 19
switch through segments iEd and co-operating
75 ?ngers, thence by conductor 69 through upper in
is readily seen to represent» a torque speed of ap
proximately 200%, and since torque and current
8. A motor control system for hoists and the
to shunt said resistor during motoring operation > like in which the motor drives the load and at
and to provide for operation of said contactor to times is overhauled thereby comprising a plu
shunt said resistor when the motor load becomes rality of resistors in the motor armature circuit,
prevent said relay from actuating said contactor
a plurality of contactors each for shunting a
7. A motor control system for hoists and the
like in which the motor drives the load and at
times is overhauled thereby comprising a reversi
ble type masterlswitch operable to hoisting and
to lowering positions for controlling the direction
of rotation of said motor, a plurality of resistors
in the armature circuit of said motor, a corre
sponding plurality of contactors controlled by
said master switch for shunting said resistors in
succession, and means responsive to motoring
operation of said motor in the lowering direction
for preventing one of said contactors from shunt
ing its corresponding resistor and responsive to
overhauling operation and to motoring opera
tion in the hoisting direction for effecting opera_
tion of said contac'tor to shunt said correspond
ing resistor.
corresponding one of said resistors, a multi-posi
tion reversing type master switch for controlling
the operation of said contactors in sequence to
shunt said resistors, and means responsive to the
direction of current flow in the armature cir 10
cuit of said motor for preventing operation of one
of said contactors from shunting its correspond
ing resistor during motoring operation in the
lowering direction and providing for shunting
said resistor when said motor is overhauled by its
load and during motoring operation in the hoist
ing direction said means comprising a rectifier
connected across a portion of said armature re
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