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2,424,255
Patented July 22, 1947
UNITED STATES PATENT OFFICE
2,424,255
CONTROL SYSTEM FOR ELECTRIC HOISTS
Walter Schaelchlin and Kurt Mahnke, Forest
Hills, Pa., assignors to Westinghouse Electric
Corporation, East Pittsburgh, Pa., a corpora—
tion of Pennsylvania
Application August 10, 1945, Serial No. 610,128
'7 Claims. (Cl. 172-152)
1
Our invention relates to electric hoist control
systems and especially to systems for controlling
the operation of marine winches.
Winch controllers are now available in which a
load-responsive ?eld ?uttering relay is series-con
nected in the armature circuit of the winch motor
and controls a resistor in a separately excited mo
tor ?eld circuit so as to weaken the ?eld when the
the master switch has reached the position 01
highest lowering speed. The motor is thus per
mitted to pass from motoring to overhauling con
dition if the hook load is su?iciently large. The
- current in the load-responsive relay coil may then
increase to further maintain the relay in the ?eld
strengthening position.
The invention is exempli?ed by the embodi
ment of a winch control system described here
motor load current decreases below a given value.
Due to this function of the relay, the motor, 10 inafter in conjunction with the drawing in which:
Figure 1 represents a circuit diagram of the
when lowering a light or empty hook, will run
system;
at increased speed which is desirable for fast
Fig. 2 is a typical speed torque characteristic
cargo handling.
as
occurring due to the invention when the mas
Controllers with such a relay, however, require
experienced and cautions handling and may oth 15' ter switch is rapidly placed in the position of
erwise cause damage and danger because a mo
highest lowering speeds; while
,
Fig. 3, for comparison, shows a speed—torque
mentary overspeed is apt to occur if the operator
diagram
typical of the condition obtaining in
moves the master switch too rapidly to the high
control systems with a ?eld ?uttering relay of
speed lowering position. This is due to the fact
that during the transition from motoring to over 20 the known type referred to in the foregoing.
Referring to Figure 1, numeral 1 denotes a
hauling the motor load current is low and hence
drum for accommodating the hawser of a hoist or
the ?eld relay caused to provide a minimum ?eld.
winch. A friction brake 2 is provided for stop
As a result, the motor has the tendency to accel
ping the drum. This brake is mechanically set
erate quickly to an extreme lowering speed before
by
means of a spring and has a magnet core 3
the ?eld relay becomes effective to strengthen the 25
which releases the brake when energized from
motor ?eld and to then reduce the speed.
the mains LI and L2 of a suitable direct-cur
It is an object of our invention to provide a
rent source. The hawser drum is geared to the
hoist control system, applicable for winches, which
armature of a winch motor WM which has a self
while being provided with a load-responsive ?eld
control relay in order to afford the advantage 30 excited ?eld winding 5 and a separately excited
?eld winding 6. Winding 5 is designed for oper
of the above-mentioned known controllers, is free
ation either in series of shunt connection depend
of the tendency to run temporarily at overspeed
ing upon the control condition of the system,
when lowering a light hook and thus eliminates
while winding 6 is connected to the above-men
the danger or the necessity of special skill in
85 tioned mains LI and L2 through a resistor ‘I
herent in the known systems.
under control by the contact 8 of a load relay
According to our invention, a load relay of the
LR. Relay LR has a current coil 9 connected in
non-?uttering type for controlling the resistance
the circuit of armature 4 and is also provided
of the separately excited motor ?eld is provided
with a voltage coil 10 which acts‘together with
with two control coils of which one is series-con
the current winding 9 on the same relay armature
nected in the armature circuit of the motor while
and receives excitation from the mains LI and L2
the other coil is controlled in dependence upon
under control by a master switch MS. Relay LR
the position of the master switch so that the relay
has a delayed dropout. In the illustrated em
is caused to maintain a strong motor ?eld in all
bodiment, the delay is obtained by means of a
lowering positions of the master switch with the
short-circuited winding which is magnetically as
exception of the position for highest lowering
sociated with the relay armature.
speed. Consequently, the ?eld remains strong
Several resistors denoted by H, l2, I3, M, iii and
during the interval of control movement of the
I6 are connected with the motor circuits under
master switch regardless of the speed with which
control by several relays denoted by IM, 2M,
the switch is operated and regardless of the mag
3M, 4M, IA, 2A, 3A, 4A, and DB, respectively.
nitude of the motor load current flowing during
Relay IM has a contact l‘l actuated by a control
that interval. Only after the switch has reached
coil [8. Relay 2M has its contact [9 controlled
the positive of highest lowering speed is the load
by a coil 20. Relay 3M has a main contact 2|
responsive coil of the relay effective to cause
and an interlock contact 22 actuated by a con
either the maintenance of the strong ?eld or a
trol coil 23. Relay 4M has also a main contact
55
reduction in ?eld strength depending upon the
24 and an interlock contact 25, both actuated by
value of the load current.
a coil 26. Relays IM, 2M, 3M and 4M control
According to another feature of our invention,
the
direction of current flow through the arma
we provide the load-responsive‘?eld relay with
ture 4 of the winch motor and also the connec
timing means in order to delay the weakening
tion of ?eld winding 5 as regards its series or
of the motor ?eld for a short interval of time after 60
2,424,255
3
parallel arrangement relative to the armature 4.
Relays IA, 2A, 3A and 4A control the acceler
ation characteristic of the motor by shorting the
resistors I3 through 55 sequentially, thereby in
creasing the current in the motor armature 4.
Associated with the control coils 34 and 36 of
the relays 3A and 4A are two timing relays IT
4
contact I9. Relay DB picks up because its coil
42 lies in parallel to coil 23 of relay 3M. Hence,
contact 4| opens and disconnects the dynamic
braking resistor I2. Relay |A picks up in cir
cuit LI, 5|, 50, 49, etc. The closure of contact 2|
in relay 3M causes coil 3 to release the friction
brake 2. Armature 4 and ?eld winding 5 of mo
tor WM are now energized in series connection
and ET. Relay IT has two contacts 3'1 and 51
controlled by a coil
and relay 2T has two
in the circuit LI, 2|, 21, I4, I5, I6, 5, 4, I1, L2,
contacts 39 and 58 controlled by a coil 49.
10 with resistor II connected at I9 in shunt rela
Relay DB has a contact 4| which, when closed,
tion to the armature 4. In other words, the re
connects resistor I2 across armature 4 for dy
sistors I4, I5 and I6 are now effective in series
namic braking. Coil 42 of relay DB is excited
connection
with ?eld winding 5 and armature 4
in all positions of the master switch MS with
and the voltage across the armature 4 is lowered
the exception of the off position so that the brak~
by resistor II. As a result, the motor is ener
ing resistor I2 is effective only when the control 15 gized
for operation in the hoisting direction and
system is set for stopping the winch. An inter
lock contact 43- in relay DB is disposed in the
coil circuit of relay 4M and prevents relay 4M
for development of lowest hoisting effort.
On second point hoisting of switch MS, the
above-mentioned control conditions are main
from being energized in the off position of the
20 tained with the exception that relay 2M drops out
master switch.
due to the interruption of its coil circuit. Con
All above-mentioned relays of the control sys
tact
I9 opens and disconnects the shunt resistor
tem receive excitation from mains LI and L2 un
II for operation at increased speed or torque.
der control by the master switch MS and through
On third point hoist, relay 2A picks up through
a connection which extends through the contacts
25
LI,
3|, 5|, 54, 49, etc., and short~circuits the re
44 and 45 of a low voltage relay LV whose con=
trol coil is denoted by 46.
>
The coil circuits of the above-mentioned relays
sistor I4 at contact 29 while opening the inter
lock contact 30. Timing relay IT drops out with
are connected to the contact ?ngers, such as those
delay and closes its contact 51, thereby preparing
denoted by 41, of the master switch MS. The
switch has a number of contact segments denoted
by 48 through 55, respectively, and in the illus
a circuit for coil 34 of relay 3A.
2T picks up through LI, 33, 31, 49, 49 etc. The
tem is in operative condition and the ?eld wind
at 32 for a further increase in hoisting speed or
Timing relay
closure of contact 29 in relay 2A completes a
short circuit for resistor I4 and hence causes a
trated example has ?ve selective hoisting posi~
further increase in hoisting speed or torque.
tions and five selective lowering positions.
On point four hoist, relay 3A comes in through
When the mains LI and L2 are excited by the 35
circuit LI, 34, 51, 5|, etc., and shorts resistor I5
closure of a main switch (not illustrated) , the sys
torque. Time relay 2T drops out due to the in
terruption of its coil circuit at 33, and closes
contact 58 with delay, thereby preparing the coil
as the master switch is in the illustrated o? po
sition due to the fact that contact 2| of relay 3M, 40. circuit for relay 4A.
On point ?ve hoist, relay 4A picks up through
which controls the supply of load current and
LI, 3B, 58, 55, 5|, etc., and shorts resistor I6 at
?eld current to the motor, is in the open posi
contact 35 for maximum hoisting speed.
tion. Since the excitation of the brake releasing
When returning the master switch to the oil’
coil 3 is also controlled by contact 2| of relay 3M,
- position, the above-mentioned control steps are
the brake remains set. The closure of the main
performed substantially in the reverse sequence.
switch, however, has the effect of energizing coil
The performance of the control system during
46 of relay LV in the circuit LI, 45, 48, L2 and
lowering operations is as follows:
closes a self-holding circuit at contact 44. Con
Starting with the illustrated off position, the
sequently, when thereafter the master switch is 50. positioning of switch MS on point one lower has
turned out of the off position, relay LV stays
the e?ect of energizing coil 20 of relay 2M in the
picked up through contact 44 as long as the volt
circuit LI, 20, 53, 52, 45, 44, L2. Contact I9 is
age between mains LI and L2 remains su?iciently
closed so that the shunt resistor II is effective.
high. In the case of voltage failure, relay LV
Relay 3M is energized through LI, 23, 53, 52, etc.,
drops out and can be reset only by returning
~ so that the brake 2 is released. Relay DB picks
switch MS to the off position. With relay LV in
up and opens its contact 4| because its coil 42
the picked up condition, the current for energiz
is energized in parallel to coil 23 of relay 3M.
ing all other relays is supplied from main LI
Relay 4M comes in through LI, 26, 42, 53, etc., and
through contacts 44 and 45 and thence through
opens contact 4|. Relay 2A picks up in circuit
either segment 49 or 52 of switch MS, provided 60
LI, 3|, 53, etc., and short resistor I4 at contact
the switch is in any of its hoisting or lowering
ing 6 of motor WM is energized, while armature 4
and ?eld winding 5 remain deenergized as long
positions. Consequently, when during the oper
ation of the winch the relay LV drops out due
to voltage failure, all other relays are deenergized
so that the motor is stopped and the brake 2 put
in operation.
When, starting from the illustrated off posi
tion, the master switch MS is turned into the
first hoisting position, the following operations
take place. Relay 3M picks up in circuit LI, 23,
59, 49, 45, 44, L2, and closes contacts 2| and 22.
Relay IM picks up in circuit LI, 22, 25, I8, 49, 45,
44, L2, and closes contact I1. Timing relay IT
picks up in circuit LI, 30, 38, 49, etc. Relay 2M
picks up through L2, 29, 50, 49, etc., and closes
29. Relay 3A picks up through LI, 34, 39, 54, 53,
etc., and shorts resistor I5. Relay 4A comes in
over LI, 35, 58, 55, 54, 53, etc., and shorts re
sistor I6. The armature circuit of motor WM is
now closed through LI, 2 I, 24, 9, 4, ||, I9, L2, and
the ?eld winding 5 is connected in parallel to the
armature 4 through contacts 35 and 24. The mo
tor is now energized for low speed lowering op
eration with resistors I4, I5 and I6 short-cir
cuited and the armature energized in series con
nection with resistors II and I3 by a current
Whose direction is opposite to that effective dur
ing the above-mentioned hoisting operations.
The armature current flows through coil 9 of the
load relay LR, However, this coil is rendered in
2,424,255
effective due to the fact that coil II) of the same
relay is energized in all lowering positions except
the ?fth and causes relay LR to close contact 8.
thus placing increased excitation on the sepa
rately excited ?eld winding 6 in order to reduce
the motor speed accordingly.
One second point lower, relay 4A drops out
teristic with the diagram according to Fig. 3 will
elucidate the new performance and advantages of
the present invention. According to Fig. 3, which
it will be remembered refers to a load-responsive
?eld weakening relay that is not dependent on
the position of the master switch, the speed torque
characteristic F’ for point 5 lowering under
transient acceleration conditions extend from
and opens contact 35. Resistor I6 is inserted
point QI through points Q2 and Q3 to the ?nal
in the circuit of ?eld winding 5 and weakens the
10 load point Q4. Due to the fact that the motor
?eld in order to increase the lower speed.
load current is low during the transition between
On third point lower, relay IA picks up in cir
motoring and overhauling, the load-responsive re
cuit LI, 28, 53, etc., and closes contact 21,
lay does not respond, so that the separately ex
thereby short-circuiting the resistor I3. Relay
cited motor ?eld remains weak and causes the
3A drops out and opens contact 32, thereby in
serting the resistor I5 in the circuit of ?eld wind 15 motor to accelerate rapidly to a temporary over
speed which is reduced only after the load cur
ing 5 for a further weakening of the ?eld excita
rent reaches a su?icient magnitude. This re
tion.
duction occurs at point Q3 in Fig. 3. The re
On the fourth'point lower, relay 2A ‘drops out
sponse of the relay has the effect of causing the
and. increases the resistance in the motor ?eld
circuit by adding the resistor I4. As mentioned, 20 motor to thereafter run at a lower speed in ac
cordance with point Q4. It thus will be seen that,
the relay LR stays in during all above-mentioned
when the master controller is turned from off to
lowering operations.
?fth point lower at excessive speed, the motor
On ?fth point lower, relay IA drops out and
may develop a temporary overspeed which leads
adds resistor IS in series with ?eld winding 5 of
the motor. At the same time, the circuit of coil 25 to overstress, jerky operation and may entail clan~
ger to the operating crew. In systems according
I0 is interrupted at contact 48 so that relay LR
to the invention, these disadvantages are fully
is now free to respond to the condition of coil
eliminated and the motor condition remains al
9. However, the effect of coil I0 vanishes with
ways under safe control regardless of the speed
delay. Hence, contact 8 remains closed for an
additional interval of time and maintains full 30 with which the master switch is actuated. For
the sake of completness, Figs. 2 and 3 indicate also
excitation on ?eld winding 6. This permits the
the speed torque characteristic occurring at
motor to pass from motoring to overhauling con
steady state operation, i. e., under steady condi
dition in cases where the load on the hook is
tions, the characteristics extend also along curves
su?iciently high. In such cases, the current
in coil 9 will increase and maintain the relay 35 F or F’ except that they then follow the lines G
or G’ between points P2, P3 and points Q2, Q3
LR closed before the latter has time todrop out
respectively.
and to produce a weak ?eld condition. If the load
It will be understood by those skilled in the
on the hook is insufficient to cause an overhaul
art that control systems according to the inven
ing condition, the current in coil 9 remains too
tion may be modi?ed as to details without de
low for closing the contact 8 upon the expiration
parting from the principal and essential features
of the above-mentioned timing interval. Conse
of the invention. For instance, while we have
quently, relay LR will then drop out and insert
shown an embodiment in which the voltage coil
the resistor ‘I in the circuit of ?eld winding 6,
of the load-responsive relay is energized directly
thereby weakening the ?eld excitation of the mo—
through a contact of the master switch, it is
tor in order to increase the lowering speed.
readily possible to tie this voltage coil up with
The performance of the load relay will be more
one of the other relays of the system. For in
fully understood from the following reference to
stance, the relay IA, as illustrated in the draw
the schematic diagrams in Figs. 2 and 3. Both
ing, can be made to pick up during points one
diagrams show a typical speed torque character
'
through
four lower of the master switch, and
istic as occurring when moving the master switch
the coil ID of the load relay LR can be energized
set rapidly from off to ?fth point lowering. The
together with the coil of relay IA or it may be
diagram, according to Fig. 2, exempli?es condi
energized by a contact actuated by relay IA.
tions obtaining in a system which is designed and
These
and other possibilities of modifying the
operative in accordance with the invention and
as described in the foregoing in conjunction with 55 invention are not illustrated in the drawing be
cause they will be obvious to those skilled in the
Fig. 1. The diagram of Fig. 3, in comparison, rep
art.
resents a typical speed torque characteristic as
We claim as our invention:
occurring in a system of the known type men
1. A hoist control system, comprising a hoist
tioned previously in this speci?cation,
The transient speed torque conditions occurring 60 motor, control means connected to said motor
and including a master switch having a plurality
during the acceleration of the winch motor in a
of hoisting and lowering positions for causing
system according to Fig. 1 when a load is low
said motor to operate at different speeds in the
ered with the master controller quickly moved to
hoisting
and lowering directions respectively, cir
point 5, lower, are typi?ed by the curve F in Fig.
cuit means for providing controllable ?eld excita
2. Starting at point PI, the lowering speed in
tion for said motor, a relay disposed for con
creases at a declining motor torque. When the
trolling
said circuit means to increase and de
hook load is sufficient to produce overhauling
crease said ?eld excitation and having two con
torque, the load relay LR will stay in, as men
trol coils, one of said coils being connected to
tioned previously, so that the ?eld winding 8 of
said motor so as to respond to the load current
70
the motor continues to receive full excitation. In
of
said motor in order to provide increased ?eld
this case, the characteristic will continue steadily
excitation when said current exceeds a given
through points P2 and P3 to the ?nal operating
point P4 depending upon the magnitude of the
load.
magnitude, said other coil being connected with
said control means so as to provide increased
A comparison of the above-described charac 75 ?eld excitation when said master switch is in
2,424,255
7
position for lowering speeds and decreased ?eld
excitation when said switch is in a position for
high lowering speed.
8
5. A hoist control system, comprising a hoist
motor having an armature circuit and a shunt
?eld circuit, control means connected to said ar
mature circuit and including a master switch hav
2. A hoist control system, comprising a hoist
motor having
armature circuit and a shunt Cl ing a plurality of hoisting and lowering posi
?eld circuit, control means connected to said
tions for causing said motor to operate at differ
armature circuit and including a master switch
ent speeds in the hoisting and lowering directions
having a plurality of hoisting and lowering po
sitions for causing said motor to operate at dif
ferent speeds in the hoisting and lowering direc
tions respectively, resistance means disposed in
said ?eld circuit, an electromagnetic relay having
contact means connected with said resistance
means for controlling the ?eld excitation of said
respectively, resistance means disposed in said
?eld circuit, an electromagnetic relay having con
tact means connected with said resistance means
for controlling the ?eld excitation of said motor,
said relay having two coils for controlling said
contact means, one of said coils being connected
with said armature circuit in order to respond to
motor, said relay having two coils for controlling 15 the load current of said motor so as to provide in
said contact means, one of said coils being con
nected with said armature circuit in order to re
spond to the load current of said motor so as to
creased ?eld excitation when said current exceeds
a given magnitude, said other coil being con
nected to said control means in order to be ener
provide increased ?eld excitation when said cur“
gized in dependence upon the position of said
rent exceeds a given magnitude, said other coil 20 master switch so as to provide increased ?eld ex
being connected with said control means so as
citation in all lowering positions of said switch
to provide increased ?eld excitation when said
except the position for highest lowering speed,
master switch is in position for low lowering
and timing means associated with said relay for
speeds and decreased ?eld excitation when said
delaying the change from increased to decreased
switch is in a position for high lowering speed.
3. A hoist control system, comprising a com
pound hoist motor having an armature circuit
and a shunt ?eld circuit, control means connected
to said armature circuit and including a master
?eld excitation a given interval of time after said
switch is placed into said position for highest low
ering speed.
6. A hoist control system, comprising a hoist
motor having an armature circuit and a sepa
switch having a. plurality of hoisting and lowering 30
rately excited ?eld circuit, means disposed for
controlling the excitation of said ?eld circuit and
different speeds in the hoisting and lowering di
connected with said armature circuit to strength
rections respectively, resistance means disposed
positions for causing said motor to operate at
in said shunt ?eld circuit, a relay having two con
en said excitation when the load current in said
trol coils and being disposed for controlling said 35 armature circuit exceeds a given magnitude, op
erator-actuated master control means connected
resistance means to vary the ?eld excitation of
to said motor for causing it to selectively operate
said motor, one of said coils being connected with
at different hoisting and lowering speeds, and
said armature circuit in order to respond to the
means under control by said master control means
to render said load responsive control means in
40 effective when said master controller is set for
ceeds a given magnitude, said other coil being
lowering with the exception of the setting for
connected to said control means in order to be
highest lowering speed.
load current of said motor so as to provide in
creased ?eld excitation when said current ex
energized in dependence upon the position of said
7. A control system for wi ches, comprising a
master switch so as to provide increased ?eld
winch
motor having an armature circuit and a
excitation in all lowering positions of said switch 45
Li. A hoist control system, comprising a motor,
separately excited ?eld circuit, resistance means
disposed in said ?eld circuit, an electromagnetic
magnitude, said other coil being connected with
switch contacts and said armature circuit for
position for high lowering speed, and timing
highest lowering speed in order to permit said
except the position for highest lowering speed.
relay disposed for controlling said resistance
control means connected to said motor and hav
means and having two control coils, one of said
ing a master switch with a plurality of positions
for controlling said motor to operate at different 50 coils being connected with said armature circuit
in: order to respond to the load current of said
speeds for hoisting and lowering respectively, cir
motor so as to provide increased ?eld excitation
cuit means for providing adjustable ?eld excita
when said current exceeds a given magnitude,
tion for said motor, a relay having two coils for
control means comprising a selective multi-posi
controlling said circuit means, one of said coils
being connected with said motor so as to respond 65 tion master switch having contacts adjustable
into a plurality of hoisting and lowering posi
to the motor load current in order to provide high
tions and relay means disposed between said
?eld excitation when said current exceeds a given
causing said motor to operate at different selec
said control means in order to be energized in de
pendence upon the position of said master switch 60 tive hoisting and lowering speeds, said other coil
of said relay being also connected to said switch
so as to provide high ?eld excitation when said
contacts so as to be energized when said switch is
switch is in a position for low lowering speeds
placed in any lowering position except the one .for
and low ?eld excitation when said switch is in a
means associated with said relay for delaying the 65 load-responsive coil to cause an increase in ?eld
excitation during lowering operations only in said
change from high to low ?eld excitation for a
highest speed lowering position of said switch.
given interval after said switch is placed into said
position for high lowering speed.
WALTER SCI-IAELCHLIN.
KURT MAHNKE.
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