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Патент USA US2504816

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April 18, 1950
.4
E. M. DAUGERT
2,504,812
SYNCHRONOUS MOTOR STARTING CONTROL
Filed Jan. 29, 1948
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l N V E N TO R
5777!, 130,-”,- M page/“f”,
v2, 5" z? , KTMWA
ATTORNEY
Patented Apr. 18, 1950
2,5t4,812
'UNITED STATES PATENT OFFICE
2,504,812
SYNCHRONOUS MOTOR STARTING
CONTROL
Emilian M. Daugcrt, Upper Darby, Pa“ assignor
to Westinghouse Electric Corporation, East
Pittsburgh, Pa, a corporation of Pennsylvania
1
Application January 29, 1948, Serial No. 5,076
5 Claims. (01. 318-—-176)
2
My invention relates to electric systems of con
a diagrammatic showing of an embodiment of my
trol for automatically starting, accelerating, syn~
chronizing and, in the event of pull-cut, resyn
chronizing synchronous motors.
It is Well known and usual practice to start a
synchronous motor as an induction motor on the
damper winding and at the balancing speed, the
maximum induction motor speed, to transfer the
motor from induction motor operation to syn
chronous motor operation by exciting the ?eld
H)
winding. Various automatice control systems are
well known in the art for this general purpose.
With most of such automatic starting control
systems, no provision is made to eliminate the
undesirable surge that is occasioned when the
?eld excitation is applied ‘and such application of
the ?eld excitation takes place, as is usually the
case, at an instant when the pole pieces are not
in the most favorable position with reference to
system of control.
In the drawing, M designates the synchronous
motor, the starting operation of which is to be
controlled. The energization of the motor ?eld
winding F is controlled by the ?eld contactor 23
and the connection of the motor M to the alter
nating-current buses l, H] and Hill is controlled
by the line contactor it.
The ?eld is provided with a discharge circuit
including a discharge resistor R1 and also the
primary winding P of the transformer T. This
transformer T through its secondary winding is
interconnected with a frequency relay HI and a.
pull-out relay P0. The frequency relay HI con
trols the deenergization of a control relay SGI
which in turn controls the deenergization of an
other control relay SGZ similar to the control
relay SGl.
the rotating magnetic flux produced by the alter 20 The characteristics of the frequency relay HI
in conjunction with the control relay SGI , which
nating current in the armature windings of the
has its coil shunted by an adjustable capacitor
motor.
I am aware that others have proposed to con
trol the instant of excitation of the synchronous
motor ?eld winding so as to obtain a maximum
pull-in torque, and, in consequence, also a mini
31, are so selected that the SGI relay will drop
out at a selected per cent slip of the synchronous
motor. The second control relay SGZ also being
provided with capacitor timing and being subject
to the drop out of control SGi drops out when a
given point on the pole pieces 01‘ the ?eld winding
of a given polarity holds a given position with
30 reference to a, point on the rotating wave of flux
load that is usually coupled to the motor.
in the armature or primary structure of the syn
Such prior art devices, however, were not ca
chronous motor.
pable of accurately, within a very few degrees,
The 5G5 relay through a set-up relay 8G3
selecting the correct angular position of the pole
controls the ?eld contactor 23 and thus controls
pieces with reference to the rotating flux and the
35 the excitation of the ?eld winding F with direct
structure of the armature Winding.
current.
It is, therefore, a broad object of my invention
A more accurate understanding of my inven
to provide for e?ectively controlling the time of
tion can very likely be had by a study of a typical
excitation of the ?eld winding with reference to
starting cycle.
mum of the electrical surge of current in the
armature winding and also a minimum of mech
anieal shock to the motor and the mechanical
the rotating ?ux in the stator.
Another object of my invention is the accurate
selection of the time of energization of the ?eld
winding to obtain maximum pull-in torque at
synchronization of the motor.
It is an important and somewhat more speci?c -~
object of my invention to select a particular point
of a particular slip cycle of a synchronous motor
for the excitation of the ?eld windings with direct
current in such a, manner as to provide a given
polarity 0n given pairs of alternate poles.
The objects hereinbefore stated are merely il
lustrative of the objects of my invention. Many
other objects and advantages will become more
apparent from a study of the following speci?ca
tion and the drawing in which the single ?gure is
Assuming that the alternating-current buses
i, it, and Hill are energized and the source of
direct current for the ?eld is also available and
it is desired to start the motor, then the attendant
actuates the starting push button A, whereupon a
vcircuit is established from bus I through con
ductor 2., the ‘stop pushbutton 3, the start push
button t. the actuating coil 5 of the low voltage
‘relay 3, contact ‘l of the incomplete sequence time
relay R, conductors 3 and 9 to the alternating
current bus I ii. The low voltage relay t‘ holds
itself in through-contacts ll, and through-con
tacts l2 energizes conductor ,IE. Energization of
conductors l6 and 5; thus provides alternating
current potential to the full-wave recti?er it to
thus supply the buses IS‘and lt‘with direct-cur
2,504,812
3
4
rent energy. Energization of conductors it and
5% also establishes a circuit for the line contactor
cuit is established from bus I8 through the back
contacts 42 of the pull-out relay PO, contacts 43,
14 by the circuit from conductor :8 through coil
I3 and conductor is to conductor a.
‘ti ._
actuating coil M of the time limit relay 36 to the
bus
The time limit relay 35 holds itself in
of the line contactor it closes the contacts 21?, 28
and 5.9 to connect the primary or armature winde
ing of the motor to the alternatingecurrent buses
i, it, and its to thus start the motor on its
through the closure of contacts 8% and its ener
gized or actuated position is thus independent of
the position of contacts 43.
The operation of the control relays 6G! and
damper winding as an induction motor.
S012 causes the opening of the contacts 58 and £9.
The energization of buses i8 and it with direct 10 From this operation, it will be apparent that the
control relay
having actuating coil 55, can
current establishes a circuit from conductor 58
only become energized when both contacts 43 and
through actuating coil 2B of the time limit relay
‘22 and back contacts 25 on the ?eld contactor 2'5
1555 are closed and contacts 56 are closed. At the
to the bus 59. The time limit contactor 22 al
most instantly closes its contacts 25 to thus enere
giZe the motor of the incomplete sequence tim
time the time limit relay 36 picks up to close
contact
contacts at and t9 are, 01‘ course, open.
When the synchronous motor has attained very
ing relay R.
near its balancing speed which may be from 95
I
the ?eld which includes the resistor Bi and @011
to 97% of the synchronous speed, the frequency
relay HI drops out to open contacts 33 to deemergize the coil as. The contacts as may even chat
tel‘ once or twice, but the adjustment of the
tacts til and the transformer primary winding
capacitor 3‘? is such that the control relay SG!
P. The transformer secondary winding S supplies
energization for the frequency relay HI through
drops out at a selected per cent slip, as, for in
stance, a 3 % slip. When the frequency relay drops
While the motor M is accelerating as an induc
tion motor, an alternating current induced in the
?eld winding F traverses the discharge circuit of
the recti?er 3i and the actuating coil 32. This : out, contacts 35 are also opened, and an instant
later, when contacts .45 open, the circuit for the
relay, since it is thus energized by a pulsating di
actuating coil at of the control relay SGZ is in
rect current where the pulsations have a free
terrupted. The adjustment of capacitor M with
quency proportional to the per cent slip, will start
reference to the coil 49 is such that the control
to vibrate when the time periods between succes
sive direct-current pulsations are suf?ciently long _-_;,_ relay 5G2 drops out with just the delay to close
contacts £9 when a given point on the pole piece
to cause the armature of the frequency relay to
of the synchronous motor of a given polarity holds
drop.
a given position with reference to a given point
At the instant of starting, the current in coil
32 causes the HI relay to pick up to close the con
tacts 33 and 38.
By this operation a circuit is '»
established from the direct-current bus I 8 through
contact 33, actuating coil 34, back contact 35 of
the time limit relay 36 to the bus vl9. The closure
of the contact 33 ‘establishes a, circuit from con
ductor or bus l8 through contacts 38, contacts 39
of the time limit relay 3%, actuating‘ coil {in of the
control relay SG2 to the bus [9. A capacitor 3'!
shunts the actuating coil .34 and a similar capaci
tor ill shunts the actuating coil til. These two re.
lays SGI and SGZ are similar in every respect,
except that the adjustment of the capacitors may
be and usually will be different, since these relays
will be required to operate in di?erent time inter
vals by the capacitor timing these capacitors
provide.
The control relay SGI holds itself in through
contacts 4,5 but the control relay SGE does not
hold itself in directly by its own action but is
held in by the closure of both the contacts at on
the control relay SGI and the contacts 4? on the
‘control relay 8G2. It is thus apparent that the
sequence of operation must of necessity be, ?rst,
control relay SGl
second, control relay SGZ.
Further, the control relay SGi holds itself in
during vibration of the frequency relay HI, by
reason of the capacitor timing .01" the capacitor
3.‘? cQnnectcd in shuntrelaticn to. the/c0334. until
the c-pen circuit time at contacts 33 ,issui?ciently
lens t0 cause SCH tc .drep 911t
,on the rotating wave of ?ux ‘in the armature
winding. From this, it is apparent that contact
4%) controls the energization of the actuating coil
Si or" the set-up relay SCI-3 at a time When the
rotating structure of the motor holds the above
mentioned position with reference to the rotating
40 ?eld.
Operation of the set-up relay SGS closes the
contacts 53, whereupon the actuating coil 52 of
the ?eld contactor 23 is energized. Operation of
the ?eld contactor causes the closing of contacts
54 and 55 and an instant later the opening of con
tacts
Operation of the ?eld contactor also
closes the contacts 56 to connect the actuating coil
57 of the pull-out relay to the secondary of the
transformer T. The time constants of both the
?eld contactor 23 and the seteup relay 8G3 are
extremely small, but can be accurately selected
so that, when the ?eld contactor 23 eventually
closes, the contacts 54 and 55 to energize the ?eld
winding F with direct current, the energization
will take place at an instant when the pole pieces
hold such a position With reference to the rotat
ing flux in the armature structure that the motor
pulls in with maximum pull-in torque.
Even with the most favorable synchronizing
conditions, some current surge is produced in the
held winding and it may happen that such cur
suf?cient
rent surgetoincause
the the
evil opening
51 cf theof pull-out
contactsrelay
'22 and
Thecontrel relay 8G2 has a similar capacitor 6.5.5 the ?eeing of contacts 6! and 62- ‘The time delay
ef the time limit relay 3.6, hewevel’, is eu?lciest
timing circuit built is. not directly subject to
to prevent opening ef'contaets 59 until sincere:
any
capacitor
timing'4!from
connected
the frequency
in. shuntrelay
relation
?le-11d
to coil
nizetien is complete Of course after the we
elironization is cemelete. no current will ?ew in
4%
ergized the
until
capacitor
SGE drops
and coil
to remove
At bethremai'n
the by-pass 70 the actuating e011 5'! and, in consequence. the cen
beets
willremain closed.' '
contacts
from across theirequency relay con»
In the event of loss of synchronous operation
tacts 351. It is thus apparent that the sequence
of the meter, by reason .Of overload 01“ for any
of operation must of necessity be, ?rst, SG! con
other reason that may cause a pulbout. a cure
trol relay and then, second, SGZ control relay.
After operation of the control relay 5?}2, a Q11‘? 7t rent surge is Produced in the @1151 of the pull-.
2,504,812
5
out relay and, in consequence, contacts 42 are
opened to deenergize the time limit relay 3B
which thus opens the contacts 59. Opening of
contacts 5!] causes the opening of contacts 53
for the circuit of the actuating coil of the ?eld
contactor and as a result, the direct-current ex
citation is removed from the ?eld winding F.
The motor thus again operates as an induction
relay for effecting the operation of the ?eld
»
contactor.
2. In a synchronous motor starting control
scheme of the type described, the combination
of a synchronous motor having an armature, or
primary, winding and a ?eld winding, a plu
rality of terminal leads normally energized with
alternating current, a pair of terminal leads
motor to instantly establish the conditions for
normally energized with direct current, a con
resynchronization. The closure of contacts BI 10 tactor for connecting the armature Winding to
and 62 again effects the energization of the con
the terminals energized with alternating current,
trol relays SG! and SG! in the order named.
a ?eld contactor for connecting the ?eld wind
An instant after the surge of current has ceased
ing to the terminals energized with direct cur
through the actuating coil 57, contacts 33 and 38
rent, and a control system for controlling the op
are closed by the frequency relay. The ener 15 eration of the ?eld contactor, said control sys
gizaticn of the control relays SGi and SGZ
tem comprising, an energized control circuit, a
thereafter is independent of the pull-out torque.
control relay connected to the control circuit and
Synchronization, therefore, proceeds in exactly
having switch contacts to be operated thereby
the same manner after a pull-out, as during
and having a coil and a capacitor of a given
starting of the motor from rest.
20 selected capacity connected in parallel to the
coil to accurately select, by capacitor timing,
While I have shown and described but a single
the instant of operation of the relay after the
embodiment of my invention, I realize that
coil and capacitor are deenergized, a frequency
others, particularly after having had the bene
relay, switching means operable by said fre
?t of the teachings of my invention, may devise
similar systems of control for the same general 25 quency relay for deenergizing said control relay
by operation of said switching means to discon
purpose. I, therefore, do not wish to be limited
nect said control relay from said control circuit,
to the details of the particular showing of my
said frequency relay being interconnected with
invention.
the ?eld winding to be energized with the alter
I claim as my invention:
1. In a synchronous motor starting control 30 nating current induced in the ?eld winding while
said motor is operating as an induction motor
scheme of the type described, the combination
during starting, the combined characteristics of
of a synchronous motor having an armature, or
the control relay and frequency relay being such
primary, winding and a ?eld winding, a plu
that the control relay functions at an instant
rality of terminal leads normally energized with
when
the motor operates at a selected slip, and
alternating current, a pair of terminal leads
a second control relay similar to the ?rst con
normally energized with direct current,
con
trolled in its connection to the control circuit by
tactor for connecting the armature windingv to
the
switch contacts and having its capacitor
the terminals energized with alternating cur
timing so adjusted that the second control relay
rent, a ?eld contactor for connecting the ?eld
winding to the terminals energized with direct 40 will operate with sufficient delay after the open
ing of the switch contacts to thus effect the op
current, and a control system for controlling the
eration of the ?eld contactor at an instant when
operation of the ?eld contactor, said control
the ?eld winding holds a selected angular posi
system comprising an energized control circuit,
tion with reference to the rotating flux in the
a frequency relay interconnected with the ?eld
armature winding.
Winding to be energized with the alternating
3. In
synchronous motor starting control
current induced in said ?eld winding while said
scheme of the type described, the combination
motor operates as an induction motor during
of a synchronous motor having an armature, or
starting, switching means operable by said fre
primary, winding and a ?eld winding, a plurality
quency relay, a control relay, having switch con
tacts and having a coil and having a capacitor
of terminal leads normally energized with alter
connected in parallel to said coil to accurately se
nating current, a pair of terminal leads normally
lect, by capacitor timing, the instant of operation
energized with direct current, a contactor for
of the relay after the coil and capacitor are de
connecting the armature winding to the terminals
energized by the opening of said switching means
energized with alternating current, a ?eld con
by the operation of the frequency relay, the ad
tactor for connecting the ?eld winding to the
justment of the capacitor and the operating
terminals energized with direct current, and a
characteristics of the frequency relay as it opens
control system for controlling the operation of
said switching means for longer and longer in
the ?eld contactor, said control system compris~
tervals of time as the motor approaches synchro
ing, an energized control circuit, a control relay
(it)
nous speed being so selected that the control
relay operates at an instant when the motor is
at a selected per cent of synchronous speed, a
second control relay similar to the ?rst con
trolled in its operation by the interconnection
e?'ected with said control circuit by the posi
tion of the switch contacts operated by the ?rst
control relay, the capacitor of the second con
trol relay being so adjusted with reference to
the coil of the second control relay that the
second control relay operates with sufficient
delay after the closing of said switch contacts
that a given pole of the synchronous motor holds
a given position with reference to a given point
on the rotating flux wave in the armature wind
ing, and means operable by the second control "i
connected to the control circuit having switch
contacts operated thereby and having a coil and
a capacitor of a given selected capacity con
nected in parallel to the coil to accurately select,
by capacitor timing, the instant of operation ‘of
the relay after the coil and capacitor are de
energized, a frequency relay, switching means
operable by said frequency relay for deenergizing
said control relay by operation of said switching
means to disconnect said control relay'from said
control circuit, said frequency relay being in
terconnected with the ?eld Winding to be ener
gized with the alternating current induced in the
?eld winding while said motor is operating as an
induction motor during starting, the combined
2,604,812
8
0
characteristics of the control relay and frequency
relay being such that the control relay functions
second control relay for effecting the operation
of the ?eld contactor.
at an instant when the motor operates at a se
lected slip, a set-up relay having a swi;
for
connecting the field contactor to the c' trol
5. In a synchronous motor starting control
scheme of the type described, the combination
circuit to thus effect the operation of ti
contacts-r and a second control relay si
'
of a synchronous motor having an armature, or
primary, winding and a ?eld winding, a plurality
of terminal leads normally energized with alter
d
to
the ?rst controlled 1 its connection to
con
trol circuit by the said switch contacts and hav
nating current, a pair of terminal leads nor
and thus the held contactor at an instant when
and a control system for controlling the opera
mally energized with direct current, a contactor
ing its capacitor timing so adjusted that the 10 for connecting the armature winding to the
second control relay will ope‘ate with s1; rcient
terminals energized with alternating current, a
delay after the opening of the switch contacts to
?eld contactor for connecting the ?eld winding
thus effect the operation of the set~up relay
to the terminals energized with direct current,
a given ,
nt on a given pole piece carrying a
tion of the ?eld contactor, said control system
?eld w rdn‘r'
a given position with
ence to a b.iven point on a rotating in}; wave in
comprising, an energized control circuit, a con—
trol relay connected to the control circuit having
switch contacts operated thereby and having a
the armature winding.
4. In a synchronous motor starting control
vscheme of the type described, the combination of
coil and a capacitor of a given selected capacity
' a
a synchronous motor having an
rreature, or
a hold winding, a plural
primar", winding
of terminal
ris normally energized "'vlth alter
nating current, a pair of terminal leads no
ily
energized with direct current, a contactor for
connecting the armature winding to the t
tor are dcenergized, a frequency relay, switching
means operable by the frequency relay whereby
said frequency relay upon drop-out disconnects
-
the control relay from the control circuit and
thus deenergizes the coil and capacitor of the
control. relay, said frequency relay having a coil,
and rectifier connected in series therewith, con
nected to the ?eld winding whereby the coil of
nals energized with alternating current, 21, held
cont-actor for connecting the field winding to
the terminals energized with direct c'crre‘
connected in parallel to the coil to accurately
select, by capacitor timing, the instant of opera
tion of the control relay after the coil and capaci
'
a control system for controlling the
of the ?eld contactor, said control -
the frequency relay is energized by pulsations
prising, an energized control circuit, a control
relay connected to the control circu ' having
of direct current the frequency of which varies
with the per cent slip, the characteristics of the
switch contacts operated thereby and having
control relay and frequency relay combination
a coil and a capacitor of a given selected capacity
being so selected that the control relay drops out
connected in parallel to the coil to accurately
select, by capacitor timing, the instant of opera»
tion of the control relay after the coil and capaci
tor
deenergized, a frequency relay, switching
means operable by the frequency relay whereby
said frequency relay upon drop-out disconnects
the control
from the control circuit and
thus deenergizes the coil and capacitor of the
control relay, said frequency relay having a coil,
at a selected low per cent slip, and a second con—
trol relay similar to the ?rst having its coil and
capacitor deenergized by the drop-out and thus
the opening of said switch contacts of the ?rst
control relay, the capacitor timing of the second
control relay being so adjusted that the second
control relay drops out with just the right time
delay after opening of the switch contacts that
the ?eld Winding and rotating flux in the arma
ture winding have a selected angular relation,
and means responsive to the drop-out of the
second control relay for effecting the operation
and rectifier connected in series therewith, con
nected to the ?eld winding whereby the coil of
the frequency relay is energized by pulsations of
direct c rrent the frequency of which varies with
the per cent slip, the characteristics of the con
trol relay and frequency relay combination being
so selectedthat the control relay drops out at a
selected low per cent slip, and a second control
relay
to the ?rst having its coil and ca
pacitor controlled in its connection to the con
trol circuit by the said switch contacts and hav
of the ?eld contactor, and a pull-out relay con
(Li $1
nected to the ?eld winding by the field contactor,
said pull-out relay being energized upon loss of
synchronism of the motor to reset the system of
control to resynchronize the motor.
EMILIAN M. DAUGE T.
REFERENCES CITED
ing its capacitor timing so adjusted that the
The following references are of record in the
second control relay will operate with a sufficient
file of this patent:
delay after the opening of the switch contacts
UNITED STATES PATENTS
that the field winding and rotating flux in the
armature winding have a selected angular rela 60 Number
Name
Date
tion, and means responsive to the drop-out of the
Heumann et a1. ____ June 28, 1948
2,444,253
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