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Патент USA US2111423

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March 15, 1938.
Filed April 8,‘ 1936
F735. l . .
p N
Raiph D Given,
is Atborne‘y.
Patented 7 Mar. 15, 1938
Ralph D. Given, lLeamington, England, assignor
to General Electric Company, a corporation of
New York
. Application April 8, 1936, Serial No. 73,317
In Great Britain October 22, 1935
3 Claims. (oi. 171-119)
My invention relates to speed regulation and
more particularly to the speed regulation of
electric‘ motors and motor generator sets although
not limited to such machines.
An object of the present invention is to pro
vide improved means for preventing an electric
motor from overspeeding.~~ ' '
For a better understanding of my invention,
together with otheri’and further objects thereof,
reference is had to the‘following description
taken in connection with the accompanying
drawing and its scope will be pointed out in the
rheostat will drive it in the opposite direction
so as to weaken the ?eld it of motor I until
the speed rises su?ciently and the engagement
between contacts 6 and 8 is broken. These con
tacts may therefore be referred to as the “raise”
in the event of the load on the motor i being
reduced suddenly by a large amount, the rheo
stat it may not respond rapidly enough to pre
vent the speed of the motor I and consequently
the speed of the alternator 2 from rising to a
appended claims.
point on the curve beyond b and if the point 0
were passed the relay would behave in the same
In the accompanying drawing, Fig. l is a
diagram of the circuit of one form of my inven
manner as between points a and 31 since the
current value would be the same as at some 15
tion, Fig. 2 is a curve showing the speed-current
point between a and p.
characteristic of the controlcircuit, and Figs.
3 and 4 illustrate modi?ed applications.
5, however, would be the opposite to that required
for correct speed regulation and the motor speed
l I have shown my invention as applied
to a direct current shunt wound motor 5, the
speed‘ of which is to be regulated within close
limits. Directly coupled to the motor l is a small
alternator 2 connected in a circuit containing
necessary condition for the speed to be brought N) 0
back to its correct value is that once the speed
rises beyond point p the rheostat i
strengthen the field it for all speeds above 12.
a capacitor 3, an inductive-reactance I.‘- and a
25 relay 5. The relation between the current and
speed of the alternator is shown in Fig. 2. the
shape of the curve being due to the capacitor,
reactance and‘resistance in the alt ""nator cir~
cuit, the peak value b of current ccc
lng when
30 the circuit is in resonance.
The wo
ng range
may be taken to lie between the poi
and p
‘on the curve and it is obvious from the steepness
The effect of the relay
would not be returned to the correct value. The
To effect this I provide a centrifugal switch
53 w ich remains closed for all speeds above go
or if desired above I? or c. The chest of this
centrifugal switch is to. short circuit contacts ii
and ‘i and so cause rhecst‘ ‘i to l§8€p strength
ening ‘the ?eld
for al‘’; speeds above the setting
When the s, eed has been brought
e speed for which the switch
is set
at the read aticn. is again taken over
of the curve between these two pen .s '
ition is not limited
comparatively large change in omit-”
35 tained with a small change in speed,
rest or went motors 35
the condition needed for close speed log
tor the speed
The relay ii, which is operated by the
‘ in the alteiniator, circuit, makes contact l
a moving contact 6 and a stationary cont ct
‘ by the con
;ig. 3 is illus
40 ‘contact
‘i’ when point
8 whenis the
a with
is reached.
a station
motor l is provided with a main ?eld t5 and an
auxiliary ?eld iii and in the circuit of the aux
iliary ?eld a motor-operated rheostat l i is
45 connected.
When contacts 6 and _'l are in engagement due
to a rise in the speed of motor i, current is
supplied from'a supply circuit l2 to the motor
of the rheostat I I and the ?eld I0 is strengthened
50 thereby reducing the speed of motor I until the
connection between contacts 6 and ‘I is broken.
These contacts may therefore be referred to as
the “lower” contacts. If, on the other hand,
the speed of the motor I falls the contact 6
66 will engage contact 8 and the motor of, the
g current com
or which is varied by
moving the brushes 55.
stat ti driven
a sma
place of the rheo
motor this motor is
‘utilized to drive the brush gear. In the event
of the contacts of relay 5 not being suitable for
carrying the current for operating the small
motor the ‘relay 5 may control suitable con
tactors iii and ii’ capable of carrying the full
motor current. To prevent positively any inter
ference by the relay 5 with the action of the
speed responsive switch I3 I provide this switch
with a set of normally closed contacts IS in
series with the “raise” contact 8 so that when
switch l3 operates, the circuit through the raise 55
contact is'opened independently of the relay 5.
x As shown in Fig. 4, this invention may also be
means having a variable operating character
istic which is to be regulated within relatively
used for holding the frequency ot a turbo , close limits, means for producing an alternating
altemator II, or an alternator driven by any ‘potential whose frequency is a function of the
prime mover, within close limits. In this case the value of said characteristic, a resonant circuit
small alternator 2 may be dispensed with and connected to be energized by said alternating
the tuned circuit may be supplied from the main potential, said resonant circuit having both values
alternating current supply which is to be regu
of frequency corresponding to the regulated limits
lated. The rheostat II is replaced by conven
tional mechanism operating on the ordinary
of said variable characteristic on the-same ‘side
of its resonant peak and below the resonant fre
speed governor gear.
quency thereof, means controlled by said resonant
While I have shown and described what I at , circuit for regulating the value of said character
present consider the preferred embodiment of my istic in both directions, said means being rela
invention, it will be obvious to those skilled in the tively slow acting compared with the maximum
15 art that various changes and modi?cations may speed at which said characteristic is capable of
be made without departing from my invention,
and I, therefore, aim in the appended claims to
varying inherently whereby the resonant peak of
said resonant circuit is subject to being passed‘
cover all such changes and modi?cations as fall
within the true spirit and scope of my invention.
What I claim as new and desire to secure by
Letters Patent of the United States, is:
circuit controlled regulating means reversing its ,
to such an extent as to result ‘in said resonant
directions of regulation of said characteristic, 20
and separate protective control means responsive
to such abnormal conditions for restoring said
characteristic to values to which said regulating
means responds in the normal and correct di
1. In combination, rotating apparatus, means
driven by said apparatus for producing an alter
nating current whose frequency is proportional to
25 the speed of said apparatus, a resonant circuit rection.
connected to said source of alternating current,’
3. In combination, apparatus having a variable
electro-responsive means connected to be con
operating characteristic to be regulated, regulat
trolledlby said resonant circuit, said electro-re
ing means responsive to a function of said char
sponsive means having a set of contacts which acteristic for increasing said characteristic when
30 close when the frequency of said source of alter
it falls below a predetermined value and decreas
nating current is slightly below the frequency ing it when it rises above a predetermined value,
causing the resonant peak in said resonant cir
said regulating means reversing its regulating
cuit and having another set of contacts which effect when said characteristic exceeds one of
close when the frequency of said circuit is below its normally regulated predetermined limits by a
35 the frequency at which the ?rst set of contacts predetermined amount, said reversing being to
close, a reversible electric motor whose direction such an extent that said regulating means pod
of operation is controlled by said contacts, means tively causes saidwharacteristic further to exceed
controlled by said motor for regulating the speed said one of its regulated limits, and auxiliary
of said rotating apparatus, and a centrifugal protective means responsive to said character
switch operative to complete a circuit between istic exceeding said one of its regulated limits by
the ?rst mentioned set of contacts on said electro
said predetermined amount for positively restor
responsive device when the speed of said rotat
ing said characteristic to a value at which said
ing apparatus substantially exceeds the speed cor
regulating means operates in the proper direction
responding tothe frequency at which said con
to maintain said characteristic within said pre
tacts are adapted to be closed by said electro
determined regulated limits.
responsive device.
2. In an automatic regulating arrangement,
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