Heteropolar machine for demodulating polyphase voltages interfering among themselves

A demodulator for the demodulation of polyphase voltages of n phases, interfering among themselves which constitute a system of polyphase pseudo-sinusoidal voltages modulated in amplitude to a pulsation .epsilon., in order to obtain a system of polyphase voltages of pulsation .epsilon.. The demodulator is preferably formed by n heteropolar synchronous rotating polyphase machines and includes n stators of n phases, fed by n systems of polyphase pseudo-sinusoidal voltages modulated in amplitude to a pulsation .epsilon., and of the form ##EQU1## in which i represents the index of the group of voltages and varies from 1 to n, and p represents the index of phase of the group of voltages and varies from 1 to n. Mounted for rotation with the n stators are n wound rotors, each including magnetic circuits made up of a low loss material and capable of passing an alternating magnetic flux without damping, each rotor having the same number of poles as the corresponding stator. Slip-rings that rotate with the rotors and stationary brushes are provided to collect n systems of polyphase voltages of pulsation .epsilon. from the n rotors.

BACKGROUND OF THE INVENTION 
This invention pertains to a demodulator applicable to the demodulation of 
polyphase voltages of n phases, interfering among themselves, and which 
create a system of polyphase pseudo-sinusoidal voltages, modulated in 
amplitude to a pulsation .epsilon., in order to obtain a system of 
polyphase voltages of pulsation .epsilon.. 
The interference between two sinusoidal voltages of frequency f.sub.1, 
f.sub.2 or pulsation .omega..sub.1, .omega..sub.2, (where .omega..sub.1 
=.omega..sub.2= 2.pi.f.sub.2 and .omega..sub.2 =2.pi.f.sub.2 and of 
different amplitudes U.sub.1, U.sub.2, is a well known phenomenon, 
currently used in radio, in the technique of synchroscopes, of 
transmitters, etc. 
This phenomenon may be summarized by the following equation: 
EQU U(t)=U.sub.1 sin .omega..sub.1 t+U.sub.2 sin .omega..sub.2 t=2U.sub.o 
cos(.epsilon.t) sin (.omega.t)+2e sin (.epsilon.t) cos (.omega.t) (1) 
in which 
.omega..sub.1 =.omega.+.epsilon. 
and 
U.sub.1 =U.sub.o +e 
.omega..sub.2 =.omega.-.epsilon. 
U.sub.2 =U.sub.o -e 
with .omega.: average pulsation and U.sub.o =average voltage of the 
component sinusoidal voltages. 
Of course, if two systems of polyphase voltages are placed in series, phase 
to phase, the result is the production of n voltages U.sub.p analogous to 
the preceding one and within the same envelope, but staggered between 
themselves by 2.pi./n, n being the number of phases of each system, such 
that: 
##EQU2## 
in which p may take all the values from 1 to n. 
Further, if the differential voltage e=0, that is if U.sub.1 =U.sub.2 
=U.sub.o, the resulting voltage u(t)=2U.sub.o cos .epsilon.t sin .omega.t 
may be described as a pseudo-sinusoidal voltage of pulsation, .omega., and 
variable amplitude 2U.sub.o cos .epsilon.t. The same is true for the 
voltages resulting from the two polyphase systems placed in series, phase 
to phase, and previously described. 
In addition, considering n groups of n voltages resulting from the two 
polyphase systems of the kind previously described, and if in each case 
there is performed circular permutations of the phases of the second 
polyphase system in relation to the first, the result is n groups of 
voltages with the general characteristics of those of the first group, but 
the respective envelopes of which are staggered between themselves. The n 
groups of polyphase voltages U.sub.ip, may be expressed as: 
##EQU3## 
in which i represents the index of the group of voltages and varies from 1 
to n, and p represents the index of phase in a group of voltages and 
varies from 1 to n. 
For example for triphase systems, the 3 resulting voltages (U.sub.a.sbsb.1, 
U.sub.a.sbsb.2, U.sub.a.sbsb.3), (U.sub.b.sbsb.1, U.sub.b.sbsb.2, 
U.sub.b.sbsb.3), and U.sub.c.sbsb.1, U.sub.c.sbsb.2, U.sub.c.sbsb.3) form 
three "pseudo-sinusoidal" systems, with variable amplitudes respectively 
equal to U.sub.A.sbsb.o =2U.sub.o cos .epsilon.t, 
##EQU4## 
This invention has as an object to provide new appropriate means for using 
this "pulsating" phenomenon, in particular, to produce a system of 
polyphase voltages with a given, constant or variable, frequency f, and 
corresponding to the modulation in amplitude of the component voltages of 
the said systems of polyphase voltages of the kind described in equation 
above. 
U.S. patent application Ser. No. 33,957 filed on Apr. 27, 1979 in the name 
of the same applicant entitled "Demodulator of polyphase voltages 
interfering among themselves", concerns a demodulator of the kind 
mentioned previously and which comprises a rotating polyphase machine, 
including basically: (a) n armatures at n phases connected between 
themselves by a common yoke made up of a low loss material and fed by n 
systems of polyphase pseudo-sinusoidal voltages modulated in amplitude to 
a pulsation .epsilon., (b) a rotor freely rotating, including n circuits 
connected by a common magnetic axle, made up, in its useful parts, of a 
low loss magnetic material, and (c) n static coils, concentric with the 
axis of the magnetic axle and at the terminals of which n systems of 
polyphase voltages of pulsation .epsilon. are collected, which rotating 
machine is such that each of the n magnetic circuits of the rotor bears a 
number of polar masses equal to the number of pairs of poles on the 
corresponding armature, and that the relative geometric keyings of the 
homologous phases of the n armatures of the stator are identical to the 
relative longitudinal keyings of the polar masses of the rotor. 
Such a demodulator permits the realization of machines, the size and weight 
of which are relatively small compared to the speeds of rotation which may 
be very high. However, in such a demodulator, it is important to create 
altogether a common frame made up of low loss material and a rotor with a 
common magnetic axle to allow the closing of the lines of the magnetic 
field. These requirements, in some cases, may turn out to be a hindrance 
to the extent that they prevent the use of elements from entirely 
classical electric machines. 
This invention aims precisely at permitting the creation of a demodulator 
of simple design and at a relatively small cost starting from elements of 
rotating machines especially easy to manufacture from known techniques, in 
particular, those applied to synchronous machines. These and other goals 
are met in accordance with the invention by a demodulator applicable to 
the demodulation of polyphase pseudo-sinusoidal voltages modulated in 
amplitude to a pulsation .epsilon., in order to obtain a system of 
polyphase voltages of pulsation .epsilon. by employing a complex of n 
polyphase synchronous heteropolar rotating machines including n stators at 
n phases fed by n systems of polyphase pseudo-sinusoidal voltages, 
modulated in amplitude to a pulsation .epsilon., and of the form 
##EQU5## 
in which i represents the group index of the voltages and varies from 1 to 
n and p represents the phase index of the group of voltages and varies 
from 1 to n. Mounted for rotation within the n stators are n wound rotors 
each including magnetic circuits made up of a low loss magnetic material 
and capable of passing a magnetic alternating flux without damping, each 
rotor having the same number of poles as the corresponding stator. 
Means to collect from the n rotors, n systems of polyphase voltages of 
pulsation .epsilon. are also provided. 
The means for collecting the n systems of polyphase voltages of pulsation 
.epsilon. from the n rotors may be readily provided by means of a 
slip-ring integral with the rotors and fixed brushes contacting the 
slip-rings. 
Thus, in a demodulator according to the invention, there is no need to have 
a frame and a common axle made up of a low loss material and capable of 
permitting the passage of a magnetic flux since the machine according to 
the invention is of a heteropolar kind. In addition, with the exception of 
using a foliated rotor capable of permitting the passage of an alternating 
flux, the demodulator according to the invention permits the use of 
techniques used with synchronous machines. 
According to a specific embodiment of the invention, the n stators 
associated with their rotors constitute n similar synchronous heteropolar 
machines, mechanically independent. Thus, for example, for a demodulator 
of the triphase kind, it is enough to associate three synchronous 
heteropolar machines meeting the conditions which have been mentioned 
previously, and fed by means of three systems of triphase 
pseudo-sinusoidal voltages, modulated in amplitude to a pulsation 
.epsilon., and conforming to the equations (3), to collect on each of the 
rotor windings a system of pseudo-triphase voltages conforming to the 
equations (4). 
According to another embodiment of the invention, the n stators associated 
to the n corresponding coiled rotors are mounted on the same frame and the 
n magnetic circuits of the rotors are supported by a common axle. This 
embodiment results in a compact machine in which the number of bearings is 
reduced, and in which the number of slip-rings may also be reduced 
eventually to the number of magnetic circuits of the rotor plus one, each 
rotor winding being associated with an independent slip-ring and also to a 
slip-ring common to the n rotor windings and serving as a neutral. 
Other objects, characteristics and advantages of the invention will be 
better understood upon reading the following detailed description of 
specific forms of the invention, given only as non-limitating examples, 
with reference to the attached drawings.

DETAILED DESCRIPTION 
FIGS. 1a-1c provide sectional diagrams of a triphase demodulator according 
to the invention. The illustrated demodulator is structured for a three 
phase system but it will be appreciated that the principles of the 
invention are applicable to other electrical systems as well. 
Referring to FIGS. 1a-1c, the embodiment of the demodulator there shown 
includes three triphase armatures 11, 12, and 13 each including three 
phases A.sub.1, A.sub.2, and A.sub.3, respectively for the armature 11 
(FIG. 1a), B.sub.1, B.sub.2, and B.sub.3 for armature 12 (FIG. 1b), and 
C.sub.1, C.sub.2, and C.sub.3 for armature 13 (FIG. 1c). 
The phases (A.sub.1, A.sub.2, A.sub.3), (B.sub.1, B.sub.2, B.sub.3), and 
(C.sub.1, C.sub.2, C.sub.3) of the armatures 11, 12, and 13 are 
respectively fed by the resulting voltages (U.sub.a.sbsb.1, 
U.sub.a.sbsb.2, U.sub.a.sbsb.3), (U.sub.b.sbsb.1, U.sub.b.sbsb.2, 
U.sub.b.sbsb.3), and (U.sub.c.sbsb.1, U.sub.c.sbsb.2, U.sub.c.sbsb.3) 
previously described and provided by a pulsating generator such as the 
generator described, for example, in U.S. patent application Ser. No. 
33,955 filed under the name of the same applicant, and entitled "Pulsating 
generator for the production of systems of polyphase voltages of 
interference". 
Each stator or armature 11, 12, and 13 may be in its structure, strictly 
similar to a stator of a classical triphase synchronous motor. Each 
armature 11, 12, and 13 works together with a respective coiled rotor 21, 
22, and 23 each provided with windings 31, 32, and 33, respectively. While 
FIGS. 1a, 1b and 1c, by way of example, show magnetic circuits of bipolar 
or quadripolar rotor construction with jutting poles, it should be 
understood however, that the invention is also applicable to magnetic 
circuits of multipolar rotor including an even number of jutting poles. 
Moreover, smooth rotors are particularly advantageous when the speeds 
involved are high. 
Each rotor 21, 22, and 23 is made up of low loss foliated material in order 
to permit the passage of alternating flux. It should be noted that the 
need for passing alternating flux makes it imperative to use rotors 
without damping circuits, that is without short circuited windings or full 
or partial squirrel-cage windings. 
The windings 31, 32, and 33 work together with a set of slip-rings 41 to 
43, 40a to 40c and brushes 51 to 53, 50a to 50c which permit the 
collection of the systems of triphase voltages U.sub.A, U.sub.B, and 
U.sub.C of frequency f=.pi./2 corresponding to the equations (4). Each 
winding 31, 32, and 33 is connected to a slip-ring 41, 42, and 43 
respectively corresponding to a phase A, B, and C, respectively, and to a 
slip-ring 40a, 40b, and 40c respectively corresponding to the neutral N. 
The brushes 51 to 53, and 50a to 50c work together with the slip-rings 41 
to 43 and 40a to 40c in the classical manner, to collect the systems of 
demodulated triphase voltages produced. 
The operation of the demodulator, according to the invention, is as 
follows. Each stator 11, 12, and 13 is fed by a triphase voltage, the 
carrier of which is a voltage with a pulsation .omega., modulated in 
amplitude to a pulsation .epsilon.. The voltages generate, in the airgap 
of each synchronous machine 11, 21; 12, 22; and 13, 23, a magnetic flux 
rotating at an angular velocity .omega. (in the case where the machine is 
bipolar) and of an amplitude which varies sinusoidally at the pulsation 
.epsilon.. This flux drives the rotor at a speed .omega., in the manner of 
a synchronous motor with variable reluctance running without any load. The 
variation of amplitude of the rotating flux, in relation to the time, 
induces in the rotor windings a sinusoidal voltage having the same 
pulsation .epsilon. as the pulsation of the modulation of the input 
voltages. To the extent that the three similar complexes 11, 21; 12, 22; 
and 13, 23 are fed in the above described manner, and that the relative 
phases of the three modulations are staggered by 2.pi./3, that is where 
the alternating flux produced by each of the three armatures 11, 12 and 13 
are of respective values 
##EQU6## 
the three rotor windings are the center of a system of triphase voltages 
of pulsation which are collected by means of the systems of slip-rings 41 
to 43, 40a to 40c and of brushes 51 to 53, 50a to 50c. 
According to one embodiment, the three elementary synchronous machines 11, 
21; 12, 22; and 13, 23 which constitute the demodulator are mechanically 
independent and form three distinct units. Thus, it is easy to realize a 
demodulator according to the invention starting from three synchronous 
heteropolar quasi standard machines, the rotors alone being especially 
conceived for transmitting alternating flux, and consequently being made 
up of foliated material and without any damping. 
Another embodiment is represented in FIG. 2 wherein like reference numbers 
have been used to designate like elements described previously in 
connection with FIG. 1. It can be seen in FIG. 2 that three elementary 
synchronous machines are associated within a common frame 10. In this 
embodiment, the three magnetic circuits of rotor 21, 22, and 23 are 
supported by a common axle 24. The number of bearings is also reduced 
since the two end bearings 61 and 62 are sufficient for the whole of the 
machine. In addition, the "integrated" setting of the magnetic circuits of 
rotor permits to use eventually only three or four slip-rings 40-43. As 
shown in FIG. 2, the creation of a common connection serving as neutral, 
for the three rotor windings 31, 32, and 33 permits to use a common system 
slip-ring 40 brush 50 for the neutral while the systems of slip-rings 41, 
42, and 43 and brushes 51, 52, and 53 are similar to the general case 
shown on FIG. 1, but are re-grouped at one end of the axle 24. 
While in the compact frame of FIG. 2 the magnetic circuits of rotor 21, 22, 
and 23 must indeed be foliated and capable of passing an alternating flux, 
the frame 10 does not come into play for the transmission of the magnetic 
flux and does not need to be made up of a low loss material. 
Of course various modifications and additions may be made, by one skilled 
in the art to which the invention pertains, to the settings that have been 
described only as non-limitating examples, without departing from the 
scope of the invention as set forth in the attached claims. Thus, for 
example, in the case of an "integrated" setting for the magnetic rotor 
circuits, the number of slip-rings and brushes may be strictly equal to 
the n number of rotors and stators, or equal to n+1, as previously 
described, in the case where the neutral is taken from a slip-ring common 
to the n rotor windings.