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Патент USA US2405708

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Aug, 13, 1946.
Filed D90. 27, 1943
GEORGES Oar/mow”
Patented Aug. 13, 1946
Georges Ogurkowski, Zug, Schonbuhl, Switzer
land, assignor to Landis &- GyrgA. G., a body
corporate of Switzerland
Application December 27, 1943-, SerialYNo. 515,788
1115 Switzerland December 11, 1942.
2 Claims’. (C1. 1-72-4581).
oftheaudio-irequency generator, said voltage be
ing proportional to the mechanical’ brake moment
ofthe; generator. This voltage is in phase with
Arrangement for speedmpmpounding of a three
phcise generator-cascade as prime mover 0 1" an
asynchronous‘ audio-frequency generator
the line voltage and is transmitted as the regu
Devices for remote tariff control with audio
frequent control Currents superimposed; on the
lating voltage through the frequency converter
over to the rotor circuitrof the asynchronous m0
network require exact constancy of 'the control
tor toexert a driving moment therein. The mag
frequency. The special reason for this resides
nitude of this driving moment is such that the
in the fact that the blocking elements preventing
sum of the torques developedin all the three ma
the energy at the checking places from leaving the l0 chines by the load of the eaudiorfrequency genera
line to be controlled possessan exceedingly sharp ' tor is asvnear to zerovasipossiblep
The nature of theinvention will be understood
resonance curve. Another reason for the high
constancy of the controlfrequoncylioslihllhe félir1Y’Di‘ohounoe‘d’selectivity‘ of the reoeiyer relays in
‘ ‘
from the following speci?cation taken’ with the
accompanying drawing in which one embodiment
15 is illustrated byway of; example.
As prime‘ mover for the audio-frequency gen: '
erators a combination‘ of; a. three-phase, asyn:
In the drawing, the numeral I denotes an asyn
chronous motor driving across a shaft 2 on the
chronous motor and a special machineis-particur
one hand a frequency converter 31 and‘ on the
larly convenient, this machine impressing onto
other hand‘an audio-frequency generator 4; The
the rotor of theasynchronous motor anadditional 20 system is fed; through a network‘ 5; In the stator
regulating’ voltage ‘of slip vfrequency. This special
circuit of the asynchronous motor there is a
machine consists/of a frequency convertor! thatris
av D. "C. armature with slip ring connections ro-
switch ‘I. From network 5 a lead goes across a
speed regulating transformer 8_ and the second
tating in a coil-less stator. Preferably, ‘however,
ary winding of the compound transformer [5 over
this frequency OQIIVBYtQI' would: be RT°Yid€d with 25 tothe slip rings 9 of the frequency convertor 3.
a compensating winding‘onthe'stator havingv for
A compensating winding l I of the frequency con
its- duty to nullify the, ?eld establisheduby. the-r0—
vertor 3'lies on the one hand oncollector H!‘ of
tor currentsinthe armature. Thus, for enorsib
the frequency. convertor and; on the other hand,
hog-the frequency collvel‘tor, would. be necessary
across aline I2, on slip rings l3'of the asynchron
only the transmitter. capatity, ,<Er.reger1eistung.>., 3° ous motor I.
so that thewhole arrangement ‘may then be. conNumeral 4 designates. anaudio-frequency gen
trolled without any‘ substantial; loss of- energy. ' erator driven through the shaft‘ 2. The ' audio
There is, howeverrah 013390131011. ‘59.; this driving
method in that the drop in sneedtherebyensuine
frequency generator 4 is'put on network 5 across
a switch‘ [4 and a. series-transformer’ i5. The
between_no-1oad andrfullload isexactlyiequivar 35 stabilizedaudioefrequency,voltageisderiyedfrom
lent to’ that of a normal motor, Asinthe nature
of things a frequencyvariationisinvolvedithor?r
the slip rings [6 of the audio-frequency genera
tor 4 and carried?to a network IT.
with which naturally is of thesame order asthe
The effect of the known arrangement is as fol
slipped number of‘revolutions'i. e., about 374%,,
care must be taken‘either to’ nullify completely 40
this: drop in speedfor to compound it‘ by an. ar.rangement whatsoever. This phenomenon; pro(111.688 aparticularly,disagreeableye?cctwith the
Synchronous selection methodiin which Short 1m.pulses‘ of, say 0.3 s. duration_ are pickediip. '
Aocording t0 the invention, With systomsvusing
On the shaft ‘2 of the/asynchronous motor I ‘ a
frequency convertorv 3 rides, being compensated
or not according to requirement. The convertor
has for its duty toconveyto the asynchronous
motor the regulating voltage. E4 oifslip frequency.
45 This permits regulation of the number of revolu
tions over a speci?ed range when the adjustable
an, asynohl‘oholls audio-frequency generator.‘ for
voltage E3 with the network frequency is conveyed
producing’ the audio-frequency, the’ additional
to the slip rings 9 through the speed regulating
regulatingvoltageis no longer derived‘fromthe
transformer 8. If;thev voltage E3=0, We. obtain
stator circuit of theasynohronous motor. butis a 50 the normal speed characteristic of the asyn
function of the exciting currentofthe'drifven auchronousmotor. If E3 possesses a declared value
die-frequency generator so that speed ‘variations
so that E4. counteracts the induced rotor voltage,
are entirely nulli?ed. Thiscanbe accomplisht‘.1
the resultis the characteristic sub-synchronous
vbyv providing means, which generates: a dvoltaggi
operation. If E4 acts in the opposite way so that
from vthe powercomponent oflthaeirciting current
65 Ehiactsinphase with the induced rotor voltage
The capacity balance of the asynchronous
audio-frequency generator with negligible losses
the result is the characteristic hyper-synchronous
operation. But with the mechanical load of the
machines there always follows between no-load
and full load a certain drop in speed An, which
in its essentials is determined by the total ohmic
resistance of the rotor circuit of the asynchronous
Substantially different therefrom appears the
effect of compounding by the compound trans
former I5. In prior art, the additional regulat 10
ing voltage E3’ is produced by the stator current
may be simply represented as follows, if 1121 de
notes the number of the primary windings on the
stator, 202 the number of the secondary windings
on the rotor, ¢ the flux per pole-pair, grthe E.
M. F. induced per phase in the stator, and 6% the
E. M. F. induced per phase in the rotor:
of the asynchronous motor _I, and hence is de-,
pendent on slip. Closer contemplations, however, .
show that a full compounding with normal means
is impossible. The compound transformer l5 as
well as the frequency convertor 3 become bulky
and expensive, even if a substantial drop of speed
is allowed for.
It should be noted that only the component of
f “As further, by ignoring the magnetizing current
g2 wi
the regulating voltage lying in phase with the 20
rotor voltage of the asynchronous motor has for
6.54", f1
The secondary real power taken up by the cone
sumer emanates consequently only partially from.
the mechanical output Wm of the shaft. The:
its effect a change of speed, as the ohmic com
ponent of the rotor current alone develops torque.
The reactive component of the regulating voltage
other part W1 is derived from the network byway .
sets up more or less wattless currents at the 25 of transformer and we get thus for the mechani»
cally led real power
stator end of the asynchronous motor without,
however, affecting the torque or the number of
revolutions. ‘In practice, this sharp separation
does not occur; rather does the reactive compo
nent of the regulating voltage, too, act to provide 30
speed-regulating in a certain range of the load.
inversely, in other load ranges, the watt or active
component of the regulating voltage also acts
If by means of high-speed regulators, &c, meas
as phase-compensating upon the stator current
ures are taken to keep constant the primary fre
however, are not taken into consideration here
the active component of the primary exciting
current is proportional to the mechanical moment
of the generator.
The above summarized properties of the asyn
chronous audio-frequency generator are applied
of the asynchronous motor. ‘ These phenomena, 35 quency, f1, the primary voltage E1 and the me
chanical speed am, this distinctly signifies that
as being immaterial.
To make the invention well understood a some
what closer reference to certain properties of the
asynchronous audio-frequency generator must be
made. It is known that every induction machine
represents a universal transformer liable to be
modified as voltage-, phase- or frequency con
vertor, so that thereby a higher frequency may
likewise be attained. For this purpose a standard
induction machine is utilized bearing multipolar
three-phase windings on its stator and rotor. If
it is intended to derive higher frequency currents
from the rotor, it has to be driven contrariwise
to the stator rotary ?eld.
Suppose now f1 be the frequency of the exciting 50
voltage, f2 the frequency of the produced audio
frequency voltage, and p the pole-pair number
of the machine, then i2 is determined by the rela
tive speed of rotary ?eld and rotor Winding, viz:
w2=w1+wm; L;;£2=2%f1+73r_75‘§fz=f1+%§
for producing that voltage which as additional
regulating voltage brings forward the required
action in the asynchronous motor I .
This con
sists in the fact that by the aforementioned reg
ulating voltage a starting moment is exerted in
the asynchronous motor which is exactly equal
in magnitude to the brake moment ensuing by the
load of the audio-frequency generator. " As in
this event the sum of all the torques developed
by the load, no variation of speed occurs.
According to this invention, in this exciter cir
cuit, however, there is now the series-transformer
l5 which conveys to the slip rings 9 the addi
tional regulating voltage E3 which depends no
longer on the stator current of the asynchronous
motor, but upon the exciting current of the audio
frequency generator 4. According to what pre
cedes the latter is driven against its rotary ?eld
and produces at the slip ring end E6 the audio
For a 18-polar machine (11:9) would be for in
stance: f2=500 cycles per second with 12:3000
60 frequent voltage E5 of the frequency f2 which is
R. P. M. and f1=50 cycles per second.
conveyed to the consumers. Further, by the aid
The slip of the generator is thereby seen to be
of the speed-regulating transformer 8 any sub
as follows. Let m be the synchronous number of
or hyper-synchronous number of revolutions may
revolutions with the frequency ii, that is to say
the slip is then
be set within the regulating range given by the
voltage E3.
With unloaded audio-frequency generator the
voltage E3’=0; the no-load speed being deter
mined by the speed-regulating transformer 8
and as n=—n,,,s=
may1 02"1m6 0
79 +
alone.‘ As soon as a voltage arises on the second
70 ary end of theeseries-transformer l5 (i. e., upon
excitation of the audio-frequency generator 4),
for f1=50 cycles per second and fz=500 cycles‘ per
second so that s=10%.
the additional regulating voltage appears at a
de?nite amount according to the load and lumps
' ' together WithEs tothe exciting voltage E3" of the
75 frequency convertor. Thereby, as with sub-syn
chronous operation in general, the voltage E3 will
chronous selection method. Another feature ap
provide for itself alone a rotor voltage E4 which
pears in that the reactive component in the con
trol current J1 does not affect the regulation or,
if it does, extremely small in amount, It may,
counteracts the rotor voltage of the asynchronous
motor. E3’ has then to be so set as to counteract
the pressure E3.
for instance, be highly possible that the audio
frequency generator has to give off quite an ap
The operation may still be disclosed by a con
crete example. Let switch 14 ?rst be open and
preciable inductive audio-frequency power which,
. E1=500 V=const., f1=50 cycles per second=const.
naturally, is derived in part from the exciting
Assume further the turns ratio of the windings
current, i. e., from the network. This reactive
between stator and rotor of the asynchronous 10 component, however, merely causes a phase shift
motor be "11:1:1, and the no-load speed sub
of the stator current in the driving motor.
synchronously set at 10% by means of the voltage
Obviously, in lieu of the current transformer
E3. The rotor voltage is then E4m=50 volts. At
15 any other device may be employed which sup
plies a potential in phase and proportional to the
no-load, too, the voltage of the frequency con
vertor E4FUE50 volts being put against the pres 15 watt component of the current J1, say induction
sure Emit, so that actually only a slight voltage
regulators, adjustable ring transformers, networks
consisting of resistances, inductivities and capaci
difference remains effectual in the rotor circuit
ties, thermionic valve ampli?ers, separate exciters
which provides the necessary current for the
for the frequency convertor, automatic or high
torque of the losses to be covered. As EtEEs,
hence must also>E3=E3", as at the outset E3'=0, 20 speed regulators, 8:0. I
consequently E3250 volts. The resistance in the
Furthermore, it is immaterial whether the fre
quency convertor be provided with a compensa
rotor circuit is now supposed to be so that the
asynchronous motor considered by itself develops
tion coil or not. In the case of a compensated
frequency converter it must merely be taken into
the full torque with a slip of s:3%, for which a
rotor voltage of 0.03-500=15 volts is required in 25 account that this likewise develops a torque, thus
modifying the working conditions insofar as the
order to produce the rotor current in the rotor
sum of the torques for all the three machines has
to be equal to zero.
Assume now the switch I4 be closed and the
Having now particularly described and ascer
audio-frequency generator thereby excited so that
the audio-frequency energy ?ows across I‘! to the 30 tained the nature of my said invention and in
what manner the same is to be performed, I de
consumer, which, let us say, puts up such a re
clare that what I claim is:
sistance that by considering the energy ?owing
1. A frequency converting system comprising a
via M the full torque is set up on the shaft, which
three-phase induction motor and a three-phase
in this case must be of the same magnitude as
the driving or starting moment of the motor with 35 induction generator driven thereby, said motor
and generator having rotor windings and stator
a slip of s=3%. According to the above pre
windings, means for exciting the stator windings
requisite a current flows thereby in the stator of
of said motor and generator at one frequency, the
the audio-frequency generator whose active com
ponent should be J1,,,=2.6 A. On the secondary
generator rotor being driven against the rotat
end of the current transformer |5—Which for 40 ing ?eld produced by excitation of the stator
windings, a frequency converter connected to be
adjusting the phase may consist of an induction
driven by said motor, said converter having stator
and rotor windings, means for exciting the rotor
winding of said converter at said one frequency,
the voltage E3, so that on the slip rings 9 of the
frequency convertor a further potential E3"=35 45 means for feeding slip frequency potentials in
duced in said converter rotor winding to said
volts comes into action, By this E4 is momen
motor rotor winding, said converter exciting po
tarily reduced to 35 volts. Consequently an excess
tential being just large enough to provide a
of voltage of 15 volts occurs at once in the rotor,
which according to what precedes, supplies the
counter E. M. F. in the motor rotor so that power
rotor current for the full torque of the asynchro 50 loss due to slip frequency is minimized, means for
deriving a potential proportional to the generator
nous motor.
exciting power, and means for applying said po
One salient feature of the invention resides in
the fact that for producing the control va1ue—~in
tential to said frequency converter, said potential
deriving means being so arranged that said last
this case of the regulating voltage E3'—no slip
is required, that is to say the tripping of the 55 named potential is opposed to the excitation po
tential of said frequency converter and is so pro
driving moment ensues directly from the driven
portioned that as the generator load varies the
end, i. e. from the audio-frequency generator.
counter E. M, F. applied to the winding of the
Hence it is possible to set up an ideal shunt char
motor rotor varies inversely to maintain a con
acteristic without having to fear instabilities, A
further advantage is that the starting moment 60 stant slip speed in the motor.
occurs instantaneously with the brake moment.
2. The system of claim 1 wherein the means
for deriving a potential comprises a transformer
Apart from short transient effects the regulating
performance happens momentarily. Consequent
whose primary winding is in the generator ex
ly the arrangement appears suitable also for ob
citing circuit, and whose secondary winding is in
jects which are liable to load jerks between 0 and 65 the exciting circuit of the frequency converter.
full load, say remote control plants on the syn
regulator-a voltage E3’=15 volts is thereby sup
posed to be produced being in counter-phase with
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