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Патент USA US2134880

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Nov. 1, 193-8.
T. E. MCDOWELL ET AL
SELF EXCITING ALTERNA‘TING CURRENT MACHINE
2,134,380
'
Filed Aug. 16, 1955
d .
M
Patented Nov. 1, 1938
2,134,880
UNITED STATES 7 PATENT OFFICE
2,134,880
‘SELF-EXCITING ALTERNATING CURRENT
MACHINE
Thomas E. McDowell, Oak Park. and “MG.
Howard, Chicago, Ill., assignors to The Pyle
National Company, Oliicago, 111., a corporation
of New Jersey
Application August 16, 1935, Serial No. 36,454
3 Claims. (Cl. 171-223)
The present invention relates in general to al
oxide type of recti?er, it has been found that
ternating current machines, such as generators, aper
recti?er of the copper sulphide type, such as a
and is more particularly concerned with the pro
vision of improved means for excitation of the
5 ?eld coils of the machine.
»
The present invention is particularly ‘adapted
for use in connection with train lighting systems,
and is of special utility for the furnishing of
power for the head light of the locomotive. On
the other hand, it will be'appreciated by ‘those
skilled in the art that it may, with equal facility,
be utilized for other purposes where the genera
tion of electricity is required, and moreover, al
though the invention is disclosed as being em
Ll bodied in a single phase generator, it is contem- .
plated that the principlesv of the invention may
likewise be ‘embodied in apparatus adapted for
multi-phase operation.
Generators for use in connection with train
20
lighting systems, particularly for furnishing
power ‘to the locomotive headlight, are con
structed to'operate at a relatively high frequency,
for example, 400 cycles, and generate at normal
operation a line voltage of around 32 volts. Gen
erators so constructed are comparatively small
and do not take up a great deal of space.
30
This
feature is of particular importance in train light
ing systems. Moreover, for many reasons, it has
been found desirable to use alternating‘current
in this connection rather than direct current
which necessitated the replacement of brushes,
cupric sulphide recti?er or one having similar
characteristics, has many desirable features.
This type of recti?er is of smaller size, lower cost, '
is capable of operation through a wider range
of ambient temperatures, and has the inherent ~‘
advantage of being self healing when the copper
sulphide ?lm is punctured.
In attempting to use the copper sulphide type
of recti?er, it was found that the recti?er would
operate at good e?iciency at comparatively low
frequencies such as 60 cycles, but that when it
was operated at the normal operating frequency
of the generators, such as used in connection 15
with train lighting systems, namely 400 cycles, the
e?lciency of the recti?er would be decreased when ,
an inductive load such as the ?eld of the gener
ator was applied to the recti?er output circuit.
The present invention therefore resides in the 20
.general application of this compact lower cost
recti?er to alternating current generators and
especially to the type utilized in connection with
railway lighting equipment, whereby self excita
tion and desirable operating advantages are se 25'
cured.
,
In accordance with the principal features of the
invention, it is proposed to provide an alternat
ing currentgenerator of any one of the three
well known .types, namely, the inductor type, the 30'
type having a rotating armature, or the rotating
etc., whereas in the case of alternating current,_ ?eld type. In whichever type is used, the direct
it is possible to use the inductor type generators, current ?eld coils may comprise a main ?eld and
thus doing away with any brushes whatever. It an auxiliary ?eld for compound operation, and
has heretofore been proposed, in order to make recti?ers of the copper sulphide type or other 35
the alternating current generator as simple as type having similar characteristics as are utilized
possible and eliminate the use of auxiliary equip
for individually exciting the main and auxiliary
ment such as direct current exciters for the ?eld ?elds from the alternating current delivery cir
winding, to utilize a recti?er suchas the copper cult of the generator. One of these ?elds, as for
40 oxide type to excite the direct current ?eld wind
example, the main ?eld, may be excited from
ings of the generators, which in the case of the such a recti?er connected directly across the de 40’
inductor type is. arranged to build up from re
livery circuit. It is preferred to excite the auxil
sidual.
.
Although the copper oxide recti?er has been
)
found to be very well suited for this purpose on
account of its instantaneous operation assoon
as the generator is started, it, however, possesses
the inherent disadvantage of being relatively
large and requiring a substantial amount of space
50 for its mounting. Moreover, the satisfactory op
eration of this recti?er is limited to a relatively
narrow temperature range, and there have been
- installations where the recti?ershas ceased to
function at low temperatures.
In seeking to
65 overcome the inherent disadvantages of the cop-.
iary ?eld from a similar recti?er which has its
input circuit connected to the secondary of a.
transformer having its primary connected in se 45
ries in the delivery circuit of the generator, so
that the auxiliary ?eld will be excited in accord
ance with the .?ow of current or load on the de
livery circuit of ‘the generator.
In order that the load on each recti?er may 60
be of substantially unity power factor, it is pro
posed to insert condensers across the respective
?eld windings. Moreover, the operation of the
recti?ers is also improved if condensers are in
serted across the input circuit of the rsctiflers.
55
2
2,184,880
An additional feature resides in the provision
of means for automatically applying full line
voltage to the recti?er which is utilized for ex
citing the main ?eld winding, when the generator
is being started up and is operating on residual,
and thereafter, function in such a manner as to
apply less than full line voltage to the recti?er
as the generator comes up to normal speed and
full voltage at normal frequency. This is dis
10 closed as being accomplished by the use of a
choke coil which is inserted in the supply circuit
to the recti?er. This choke coil, as is well known
in the art, will have an increasing potential drop
across its terminals as the frequency of the volt
16 age applied thereto and the recti?ed current is
increased.
Other objects and features of the invention
will more fully appear from the following de
through conductors 25 and 28 to the auxiliary
?eld windings I2-l2.
-
Asv in the case of recti?er II, the recti?er 24
is likewise improved in e?lciency by inserting a
condenser 21 across the input circuit of the recti
?er, and a condenser 28 across thev output circuit
of the recti?er.
~
In the drawing and description, recti?ers have
been disclosed and described as being of the full
wave type. It is contemplated, however, that the
invention is not to be limited to the use of full
wave recti?cation, but that half-wave recti?ca
accompanying drawing, which illustrates a pre
tion might be used with equal facility, if desired.
From the foregoing description, it will be ap
parent that the present invention provides im 15
proved means for exciting the ?elds of alter
nating current machines, which makes use of
low cost, small size rectifying elements of the
copper sulphide type; which is so arranged that
the recti?ers operate at substantially unity power 20
ferred embodiment thereof and in which:
factor with the result that high efficiency is at
tailed description, taken in connection with the
The drawing diagrammatically illustrates an
tained; and wherein the impressed voltage of
embodiment of the invention in connection with
the main field recti?er is automatically controlled
so that line voltage is applied at the time of start
a compound alternating current generator of
the self exciting type.
‘As shown on the drawing:
In the disclosed embodiment of the invention,
the generator armature winding is shown as be
ing connected to an alternating current delivery
circuit II! which may be connected to any de
sired load, such as a headlight of a locomo
tive etc.
In the present disclosure, the generator is pro
vided with main direct current ?eld coils ll--II
and auxiliary compound windings embodying
?eld coils l2-l2. Although a compound gen
erator has been chosen to illustrate the present
invention, it will be readily apparent that the
invention may be utilized for generators operat
ing with shunt characteristics.
The main'?eld winding H is excited from a
bridge recti?er of the cold type having copper
sulphide elements, the output circuit of this rec
ti?er being connected to the ?eld windings by
45 means of conductors I4 and I5. One side of the
input circuit of this recti?er is connected by con
ductor 15 to one side of the delivery circuit, and
the other side of the input circuit of this recti
?er is connected through a choke coil IT to the
other side of the delivery circuit. While a choke
coil has been disclosed in this instance; it has
been found that a resistance may be utilizedin
stead, and that a resistance under these circum
stances gives quite acceptable operation.
The operation of this recti?er is also found to
be improved by inserting a capacitance such as
a condenser it across the delivery circuit at the
terminals of the generator windings and a con—
ing the generator and less than normal operating 25
voltage is applied when the generator has come
up to normal operation with normal speed, volt
age and frequency.
_
Now, it is of course to be understood that al
though we have described in detail a single em
bodiment of ‘our invention, the invention is not
to be thus limited, but only insofar as de?ned
by the scope and spirit of the appended claims.
We claim as our invention:
1. In combination, an alternator having an
armature and a ?eld winding, and recti?er means
to supply said ?eld winding with an exciting cur
rent, said recti?er means comprising a plurality
of rectifying elements arranged in a bridge‘ type
circuit formation with one pair of apices con 40
nected to said armature in series with a reactor I
and with the other pair of apices connected to
said ?eld winding, a ?rst capacitor means con;
nected bridging said one pair of apices and a
second capacitor means connected bridging said
other pair of apices, said reactor being arranged _
to selectively affect control of current through
said recti?er as the voltage of the alternator
varies with speed and ?eld current.
2. In combination, an alternator having an ar
mature and a ?eld winding, and recti?er means
to supply said ?eld winding with exciting cur
rent, said recti?er means comprising a plurality
of rectifying elements arranged in a bridge type
circuit formation with one pair of apices con 65
nected to said armature and with the other pair
of apices connected to said ?eld winding, a ?rst
capacitor means connected bridging said one pair
denser is across the input terminals of the bridge
of apices and a second capacitor means con
recti?er, as well as a condenser 20 across the ?eld
nected bridging said other pair of apices, and
means interposed in series with said one pair
windings. These condensers counteract the in
ductive reactances of the respective windings and of apices to automatically control current there
through' as the voltage of the alternator varies
result in operation of the recti?er at substan
under the combined in?uences of speed and ?eld ,
tially unity power factor and consequently great
er e?lciency. Moreover,__ these condensers also excitation.
3. In combination, an alternator having an ar
tend to smooth out the ‘ripple in the recti?ed
mature and a ?rst ?eld winding and a second
exciting current.v
For the auxiliary winding 12 which is utilized ?eld winding, means to supply said ?rst ?eld
for compounding the ?eld excitation in response winding with exciting current, said means com
prising recti?er elements arranged in a bridge 70
70 to load changes on the delivery circuit, a trans
former 2| is connected with its primary in series ~ type circuit formation with one pair of apices
connected to said armature and with the other
in the delivery circuit and its secondary con
nected through conductors 22 and 23 to the pair of apices connected to said ?rst ?eld wind
supply terminals of the bridge recti?er 24. The ing, a ?rst capacitor means connected bridging
output terminals of this recti?er are connected said one pair of apices and a second capacitor 1‘
3
means connected bridging said other pair 0!
apices, means interposed in series between said
armature and said one pair of apices to selec
tively a?ect current flow through said recti?er
as the voltage of the alternator varies under the
combined in?uences of speed and ?eld excitation,
means to supply said second ?eld winding with
exciting current, said means comprising a series
transformer having its primary in series with a
10 load output wire and having its secondary con
nected to a ?rst pair of apices of a bridge cirg
cult formation of a plurality of recti?er ele
ments, the second pair of apices of said bridge
circuit being connected to said second ?eld wind
ing, a third capacitor means connected bridging 5
said ?rst pair of apices and a fourth capacitor
means connected bridging said second pair 0!
apices.
THOMAS E. MCDOWELL.
JOHN G. HOWARD.
10"
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