Note: Descriptions are shown in the official language in which they were submitted.
212~766
Case 907
A GENEE~ATING SET
The present invention relates to a generating set for
supplying electrical energy at a first voltage that is an
a.c. voltage having a set effective value and a set
frequency, comprising a motor and a generator mechanically
coupled to said motor to produce said electrical energy.
Such a generating set is obviously intended to supply
electrical energy to a consuming device of any kind, which
will simply hereinafter be termed llthe consuming device~
The output a.c. voltage of a known generating set, i.e.
the voltage it supplies to the consuming device, is
directly made up of the voltage produced by the generator
of the generating set.
The frequency of this output voltage must of course
be as constant as possible regardless of the electrical
power that is absorbed by the consuming device and that
the generating set is required to supply.
The generator of a known generating set must
therefore practically be a generator of the synchronous
type, i.e. a generator that produces a voltage having a
frequency proportional to the rotational speed of its
rotor, and this rotational speed must be adjusted to a
constant value such that this frequency will have the
required value.
The rotor being mechanically coupled to the output
shaft of the generating set's motor, it is obviously the
rotational speed of the motor that has to be set at a
constant value.
Thus, for instance, in a generating set having a
bipolar generator whose rotor is directly coupled to the
output shaft of the motor, the latter's rotational speed
must be set at 3 000 rpm for the frequency of the
generating set~s output voltage to be 50 Hz, regardless of
how much electrical power is being absorbed by the
consuming device.
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AS iS well known, it is difficult accurately to set
the rotational speed of a motor, in particular of an
internal combustion engine such as that generally used in
a generating set, during rapid variations of the
mechanical power the motor is required to supply.
But, in a generating set, this mechanical power
obviously depends on the electrical power that is absorbed
by the consuming device, which power may vary in a very
short time between a low or even zero value, and a high
value or even the value of the maximum power that can be
supplied by the generating set, or conversely.
~ uring such variations in the power absorbed by the
consuming device, the rotational speed of a known
generating set~s motor, and hence the frequency of the
latter's output voltage, cannot therefore in practice be
kept at the required constant value.
Variations in the frequency of a generating set's
output voltage caused by variations in its motor~s speed
can be attenuated, but not completely eliminated, by
fitting an inertia flywheel on the shaft that connects the
motor to the generator. But such a flywheel suffers from
the drawback of being a heavy and bulky component.
The effective value of a generating set~s output
voltage must also remain constant regardless of the
electrical power that is absorbed by the consuming device.
To adjust this output voltage, use is generally made
in a known generating set of a generator having a rotor
fitted with so-called excitation windings and of a
suitable circuit for modifying the current flowing in
these excitation windings in dependence on the electrical
power absorbed by the consuming device.
But upon a rapid change of this electrical power, the
current flowing in the excitation windings varies only
relatively slowly because, in particular, of the windings~
inductivity thereby causing the value of the voltage
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supplied by the generator and hence of the output voltage
of the generating set to vary.
The voltage supplied by the generator being moreover
dependent on the rotational speed of the latter~s rotor,
the variation of this voltage upon a change in the power
absorbed by the consuming device is further worsened by
the rotational speed's variation that occurs at that time
as mentioned earlier.
In short, neither the value nor the frequency of the
voltage supplied by a known generating set remain constant
upon a change in the electrical power absorbed by the
consuming device it supplies.
An object of the invention is therefore to provide a
generating set that does not suffer from these drawbacks, -~
i.e. a generating set supplying an a.c. voltage having an w
effective value and a frequency that are constant even
with large and/or rapid variations of the electrical power
absorbed by the consuming device it supplies.
This object is achieved by the claimed generating --~
set, that is intended to supply electrical energy at a
first voltage that is an a.c. voltage having a set
effective value and a set frequency, which comprises a
motor and a generator mechanically coupled to said motor
to produce said electrical energy, and which is
characterized in that said generator is arranged to ` -
produce said electrical energy at a second voltage, and in
that it comprises a first converter electrically coupled
to said generator to convert said second voltage into a
third voltage that is a d.c. voltage having a constant
value, a rechargeable source of electrical energy coupled
in parallel with said first converter, and a second
converter electrically coupled to said first converter and
to said rechargeable source of electrical energy to
produce said first voltage from said third voltage.
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other objects and advantages of the invention will
become apparent from the following description with
reference to the accompanying drawings in which :
Figure 1 illustrates diagrammatically and by way of
non-limiting example an embodiment of the generating set
according to the invention;
Figure 2 is a graph illustrating the mechanical power
supplied by a motor in dependence on its speed of
rotation;
Figure 3 is a table summarizing the operation of a
circuit of the Figure 1 generating set;
Figure 4 illustrates the variation in relation to
time of some signals measured in the Figure 1 generating
set;
Figure 5 illustrates diagrammatically and by way of
non-limiting example another embodiment of the generating
set according to the invention;
Figures 6, 7 and 8 diagrammatically illustrate
various ways of using the Figure 5 generating set;
Figure 9 illustrates diagrammatically and again by
way of non-limiting example a further embodiment of the
generating set according to the invention; and
Figure 10 diagrammatically illustrates a rechargeable
source of electrical energy that can be used in a
generating set according to the invention.
The generating set according to the present invention
and illustrated diagrammatically and by way of non-
limiting example in Figure 1, generally referenced 1, is
intended to produce electrical energy in the form of an
a.c. voltage V1 having an effective value U1 and a
frequency fl.
This electrical energy is intended to supply a
consuming device, of any kind, that is represented in a
very diagrammatic manner in Figure 1 with reference 2.
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AS Will hereinafter be made clear, the a.c. voltage
vl may, depending on the way the generating set 1 is
constructed, be monophase or polyphase, e.g. three-phase.
The output terminals of the generating set 1, whose
number will of course depend on the number of phases of
voltage V1 and to which the terminals of consuming device
2 are connected, have not been shown separately and are
collectively referenced S.
The generating set 1 comprises a motor 3 which, in
the present example, is an petrol engine supplied by a
carburettor that is not shown separately.
The position of the carburettor~s butterfly valve,
which determines the flow and the composition of the fuel
and air mixture being fed to engine 3 and hence the
mechanical power being supplied by the latter at each of
its speeds of rotation, is controlled by the value of an
electric adjustment signal SM, in a manner hereinafter
described, via a control circuit 4.
Control circuit 4 will not be described in detail as
it can be constructed without difficulty in several
different ways by a specialist who knows the various
functions it is required to fulfill, which functions will
be discussed later. A man of the art will readily realize
that this control circuit 4 may be constructed to
advantage by, for example, combining a microcomputer with
suitable interface circuits and by programming this
microcomputer to perform the reguired functions.
The generating set 1 further comprises an electrical
energy generator 5 having, in conventional manner, a
stator and a rotor that ar,e not shown separately. The
rotor of generator 5 is directly connected to the output
shaft of motor 3 by a mechanical linkage symbolized by a
double line.
Generator 5 may be any one of the several types of
well-known generators that produce electrical energy in
monophase or polyphase a.c. voltage form in response to
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rotation of its rotor in relation to its stator, and will
therefore not be described in greater detail.
The a.c. voltage produced by generator 5 is
identified in Figure 1 by reference V2 and its effective
value and frequency will respectively be referenced U2 and
f2.
As will hereinafter become evident, the number of
phases of voltage V2 may very well be different from that
of voltage V1. Moreover, the effective value U2 and the
frequency f2 of voltage V2 are variable and generally
different from the effective value U1 and of the frequency
fl of voltage V1. -
The output terminals of generator 5 across which -
voltage V2 appears and whose number obviously depends on
the number of voltage v2~s phases have not been shown
separately and are collectively referenced 5.1.
The generating set 1 also comprises a first converter
circuit 6 having a number of first terminals equal to that
of generator 5's terminals 5.1, each connected to one of
the latter. The first terminals of converter 6 have not
been shown separately either and are collectively
referenced 6.1. ~ -
Converter 6 further comprises second terminals, two
in number, which have not been shown separately either and
which are referenced 6.2.
It should be noted here that each of the various -
electrical connections between the elements of the
generating set 1 described above or that will be described ~-
below is only symbolized in Figure 1 by a single line,
even when it consists of several conductive wires as is
obviously the case, for example, with the connection
between generator 5 and converter 6.
For a better understanding of Figure 1, the
connections which, as will be seen later, serve to
transfer electrical energy have been symbolized by lines
that are thicker than those which, as will also be seen
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later, serve to transmit control, adjustment or
measurement signals.
The above-mentioned converter 6 is arranged to
produce a d.c. voltage V3 across its terminals 6.2 in
response to the a.c. voltage V2 it receives from generator
5 when the latter is driven by motor 3. Converter 6 is
moreover so arranged that the value U3 of voltage V3 is
constant regardless of the effective value of voltage V2
which, as will be seen later on, may vary considerably.
Additionally, converter 6 is arranged to regulate the
electrical power it supplies to the components that are
connected thereto and which will be described below in
dependence on the value of an adjustment signal SC it
receives from control circuit 4.
In the present example and for a reason that will be
made clear further on, signal SC can assume two distinct
values SCO and SC1 in circumstances that will also be
described further on. Further, converter 6 is arranged to
transmit no electrical power at its outputs 6.2 when
signal SC has its value SCO and to transmit at its outputs
6.2 all of the electrical power it receives from generator
5 when signal SC has its value SC1.
A converter like converter 6 is a circuit that is
well-known to specialists and will therefore not be
described in detail.
Suffice it to say that such a converter generally
comprises a voltage stabilizer that produces the desired
d.c. voltage from a rectified and possibly filtered
voltage supplied by a rectifier which receives the a.c.
voltage that is applied to the converter, even when the
peak value of the rectified voltage is less than the value
that the the d.c. voltage is required to have.
The generating set 1 further comprises a rechargeable
source of electrical energy, referenced 7, i.e. a device
able to store and to give back a certain amount of
electrical energy under d.c. voltage. Source 7 has a pair
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of terminals, collectively referenced 7.1, which are
connected each to one of the output terminals 6.2 of
converter 6. Source 7 is moreover so arranged that the
voltage V4 it produces across its terminals 7.1 when the
latter are not connected to the terminals 6.2 of converter
6 will be at least substantially equal to the voltage V3
produced by the latter.
When the terminals 7.1 of source 7 and the terminals
6.2 of converter 6 are connected, voltages V3 and V4 are
of course exactly equal.
- It will be assumed, in the present example, that
source 7 consists of a battery of conventional
accumulators such as lead or cadmium-nickel accumulators.
It should however be noted that source 7 may also be
differently constructed as in the example described
further on.
The generating set 1 moreover comprises a monitoring
circuit 8 which is connected to source 7 and arranged to
supply to control circuit 4 a measurement signal SQ
representative of the state of charge of source 7, i.e. of
the amount of electrical energy available in the latter.
It will be assumed, in the present example, that signal SQ
has a maximal value SQ1 when source 7 is fully charged,
and decreases at the same time as source 7 discharges.
Monitoring circuit 8 and its connections with source
7 will not be described in detail as they can be made in
various ways well known to specialists. Suffice it to say
here that such a monitoring circuit generally includes at
least two circuits that supply measurement signals which
are respectively representative of the voltage across the
terminals of the source with which it is associated and of
the charging or discharging current of the latter, and
possibly circuits that supply measurement signals which
are representative of other parameters of the source such
as its temperature or its age, i.e. the time that has
elapsed since it was first put into operation. Such a
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monitoring circuit also of course includes a computing
circuit able to produce the signal that is representative
of the state of the source to which it is connected in
dependence on the various above-mentioned measurement
signals.
The generating set 1 furthermore comprises a second
converter circuit, referenced 9.
Converter 9 has a pair of input terminals
collectively referenced 9.1, each connected to one of the
terminals 6.2 of converter 6, and output terminals
collectively referenced 9.2. The output terminals 9.2 are
equal in number to the output terminals S of the
generating set 1 and are each connected to one of the
latter via a measurement circuit 10 that will be described
further on.
Converter 9 serves to produce the output a.c. voltage
vl of the generating set 1 from the d.c. voltage V3.
Converter 9 is thus a circuit of the same kind as the
circuits commonly termed inverters which are well known
and will therefore not be described here in detail.
Suffice it to say that an inverter is a circuit
intended to produce an a.c. voltage, which may be
monophase or multiphase, from a d.c. voltage, the peak
value of the a.c. voltage being at most equal to the value
of the d.c. voltage. To this end, an inverter includes in
particular electronic elements such as transistors and
thyristors whose number and connection depend on the
monophase or polyphase nature of the a.c. voltage it is
required to produce. Additionally, each of the electronic
elements is controlled by a signal formed of periodic
pulses having a width that varies along a sinusoidal
function. The various sinusoidal functions defining these
pulse widths all have the same amplitude and same
frequency, which respectively define the effective value
and the frequency of the a.c. voltage produced by the
inverter, but which are phase-shifted in relation to one
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another by an amount which also depends on the monophase
or multiphase nature of this a.c. voltage.
In the generating set 1, the various signals for
controlling the electronic elements of the inverter
constituting converter 9 are permanently produced by
control circuit 4 with the result that converter 9 also
operates permanently. So as not unduly to clutter up the
drawing, all of the connections through which these
control signals are transmitted from control circuit 4 to
converter 9 have only been represented by a single line.
Also, so as not unnecessarily to complicate the following -
description, all of these control signals will simply be
termed the control signal of converter 9 and will be
referenced SD.
The generating set 1 additionally comprises two
measurement circuits respectively referenced 10 and 11. --
Measurement circuit 10 is disposed between the output
terminals 9.2 of converter 9 and the output terminals S of
the generating set 1, and is arranged to supply to control
circuit 4 a measurement signal SP representative of the
electrical power supplied by the generating set 1 to the
consuming device 2, which is obviously identical to the
electrical power absorbed by the latter. These two powers
being identical, they will hereinafter both be referenced
Pe. -- -
Measurement circuit 10 is moreover so arranged that
the voltage V1 supplied by converter 9 is applied without
modification to the output terminals S of the generating
set 1.
Measurement circuit 10 will not be described in
detail as it can be constructed in various ways well known
to specialists. Suffice it to say here that circuit 10 ~
may include a pair of circuits that supply measurement ~ ;
signals that are respectively representative of the
effective value of the voltage V1 and of the current
absorbed by the consuming device 2, as well as the
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11
computing circuit that is necessary for producing the
signal SP is response to these measurement signals.
Measurement circuit 11 has input terminals that are
connected in the present example to the terminals 5.1 of
generator 5, and is arranged to supply to the control
circuit 4 a measurement signal SR that is representative
of the rotational speed of the rotor of generator 5 and
hence of the rotational speed of motor 3. This rotational
speed will hereinafter be referenced R.
Measurement circuit 11 will not be described in
detail either as it can be constructed in various ways
well known to specialists. It will be assumed, in the
present example, that circuit 11 is arranged for signal SR
to depend on the frequency f2 of voltage V2, which
frequency is of course proportional to the rotational
speed R of the rotor of generator 5 and of motor 3.
It should be noted that, if needed, protection means
against any overcurrent consisting for instance of fuses
or cut-outs may be provided between the measurement
circuit 10 and the output terminals S of the generating
circuit 1. Such protection means have not been shown as
they have no direct bearing on the present invention.
As will be described in detail further on, the
electrical power Pe that is absorbed by the consuming
device 2 when the generating set 1 is operating is
generally supplied, in mechanical power form, by motor 3.
This mechanical power, hereinafter referenced Pm, is
transformed into electrical power by the generator 5 and
transmitted to the consuming device 2 via converters 6 and
.:
Part of the mechanical power Pm supplied by motor 3
is dissipated by generator 5 upon being transformed into
electrical power, and part of the latter is dissipated by
converters 6 and 9 upon being transmitted to the consuming
device 2.
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12
The power dissipated in generator 5 and in converters
6 and 9 is however generally low compared to the
electrical power Pe supplied by the generating set 1 and
will be neglected in the following detailed description of
the operation of the generating set 1, as the man of the
art will realise without difficulty how to dimension the
various components of the generating set 1 to take into
account, if necessary, this dissipated power.
Figure 2 diagrammatically illustrates the well-known
variation of the mechanical power Pm supplied by motor 3
as a function of its rotational speed R for three
different values SM0, SM1 and SM2 of signal SM. In the
present example, the value SM0 is that for which the
butterfly-valve of the carburettor of motor 3 is fully
closed or, in other words, is in the position generally
known as the idling position. When signal SM has this
value SM0, motor 3 thus hardly supplies any mechanical
power, whatever may be its rotational speed. Similarly,
the value SM1 is that for which the butterfly-valve of the
carburettor of motor 3 is fully open, i.e. the position in
which motor 3 supplies, at each of its rotational speeds,
the maximum power it can supply at this speed. Finally,
the value SM2 is that for which the butterfly-valve is in
a position such that motor 3 supplies, at each of its
rotational speeds, a defined fraction of the maximum power
it can supply at this speed. It will be assumed that this
defined fraction is equal to 80% in the present example.
For a reason which will be made clear later on, the
above-mentioned measurement circuits 10 and 11 are so
arranged that signals SP and SR are of the same kind. For
example, each of these signals SP and SR may consist of an
electrical voltage. Further, measurement circuits 10 and
11 are so arranged that, whatever may be the electrical
power Pe that is absorbed by the consuming device 2,
signals SP and SR will be equal when signal SM has the
above-defined value SM2 and when motor 3 rotates at the
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13
speed at which the mechanical power Pm it supplies is
equal to this electrical power Pe.
Moreover, control circuit 4 is arranged for signal SM
to have value SM0 when signal SP is less than signal SR
and value SMl when signal SP is greater than signal SR,
and, when signals SP and SR are equal, for signal SM to
have value SM2 if signal SQ is equal to SQl and value SMl
if signal SQ is less than SQl. Control circuit 4 is
further arranged for signal SC to have its value SCl when
signal SP is less than or equal to signal SR and its value
SC0 when signal SP is greater than signal SR.
This operation of control circuit 4 is summarised in
the Figure 3 table.
The operation of the generating set 1 will hereafter
be described by starting at an arbitrary instant when the
electrical power Pe absorbed by the consuming device 2 has
a value Pel other than zero, less than the maximum
electric power the generating set 1 can supply and having
remained unchanged for a certain length of time. It will -~
also be assumed that, at that same instant, source 7 is
fully charged and that signal SQ thus has its value SQl.
Under these conditions and as will be made clear
later on, motor 3 rotates at speed Rl for which signal SR
has a value SRl equal to the value SPl of signal S
corresponding to the value Pel of electrical power Pe. -;
Signal SM thus has value SM2 and motor 3 supplies a
power Pml equal, on the one hand, to this electrical power
Pel and, on the other hand, to 80% of the maximum
mechanical power Pml' it can supply at speed Rl.
The electrical power produced by generator 5 thus
also has value Pel.
Moreover, signal SC has value SCl, with the result
that converter 6 transmits to converter 9 all of the
electrical power Pel it receives from generator 5. As
converter 9 operates permanently, this electrical power
Pel is therefore fully transmitted to user device 2.
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1~
It should be noted that, in this situation, the
rotational speed R of motor 3 does not vary since the
mechanical power Pml it produces is equal to that which is
absorbed by generator 5 to produce the electrical power
Pel, and since tne driving torque supplied by motor 3
is therefore equal to the braking torque created by
generator 5.
The generating group 1 is thus in a stable situation
which remains unchanged as long as the electrical power Pe
that is absorbed by consuming device 2 remains constant.
Let us now consider a case where the electrical power
Pe that is absorbed by consuming device 2, after having
remained at value Pel for a certain length of time,
abruptly diminishes and takes on a new value Pe2 other
than zero.
Signal SP then takes on a new value SP2 less than the
previous value SP1. Control circuit 4 thus gives to
signal SM value SM0 at which the butterfly-valve of the
carburettor of motor 3 is in its idling position, but
continues to give to signal SC value SC1.
Motor 3 thus practically supplies no mechanical power
but continues to rotate, at a decreasing speed, in
response to its kinetic energy and to that of generator 5.
The latter thus continues to supply electrical power and
since signal SC has value SC1 this electrical power is
equal to the electrical power Pe2 that is absorbed by
consuming device 2.
When the rotational speed R of motor 3 reaches value
R2 at which value SR2 of signal SR is equal to the new
value SP2 of signal SP, control circuit 4 gives back to
signal SM value SM2.
The mechanical power Pm2 that motor 3 then supplies
is thus again equal to 80% of its maximum mechanical power
Pm2', and this mechanical power Pm2 is moreover equal to
the electrical power Pe2 absorbed by consuming device 2
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since the value SR2 of signal SR is equal to the value SP2
of signal SP.
The generating set 1 is thus again in a stable
position which only differs from the previous one as
regards the values of the rotational speed R of motor 3,
of the mechanical power Pm it supplies, and of the
electrical power that is produced by generator 5 and which
is transmitted to consuming device 2 via converters 6
and 9.
This situation remains unchanged as long as the value
of this electrical power Pe remains constant and equal to
Pe2.
Let us now consider a case where the electrical power
Pe that is absorbed by consuming device 2 abruptly
increases after having remained at value Pe2 for a certain
length of time and takes a new value Pe3.
Signal SP then takes on a new value SP3 greater than
the previous value SP2. The control circuit 4 thus gives
to signal SM value SM1 at which the butterfly-valve of the
carburettor of motor 3 is fully open.
Simultaneously, control circuit 4 gives to signal SC
its value SCO at which converter 6 no longer supplies any
electrical power at all.
The electrical power supplied by generator 5 thus
also becomes zero, as also the braking torque exerted by
generator 5 on motor 3. All of the mechanical power
supplied by motor 3 is thus now available to accelerate
the latter and the rotor of generator 5.
As converter 6 no longer supplies electrical power,
the electrical power Pe3 that is absorbed by consuming
device 2 is now supplied by source 7. The latter thus
discharges and the value of signal SQ decreases and drops
to less than SQ1.
When the rotational speed R of motor 3 reaches value
R3 at which the value SR3 of signal SR is equal to the
value SP3 of signal SP, control circuit 4 gives back to
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212476fi
16
signal SC its value SCl but still maintains signal SM at
its maximum value SMl, as signal SQ is less than SQl.
Under these conditions, motor 3 supplies its maximum
mechanical power Pm3' and generator 5 supplies an
electrical power equal to this mechanical power Pm3' and
greater than the value Pe3 of the electrical power Pe that
is absorbed by consuming device 2.
The difference between power Pm3', which is also the
power that is supplied by converter 6 since signal SC has
its value SCl, and power Pe3 that is absorbed by consuming
device 2 is absorbed by source 7. In this connection, it
will be recalled that source 7 is constituted in the
present example by a battery of conventional accumulators,
which battery is partially discharged at this instant as
stated earlier.
As the terminals 7.1 of source 7 are linked directly
to the output terminals 6.2 of converter 6, source 7
recharges itself under d.c. voltage, i.e. voltage V3, and
the current it absorbs during charging progressively
decreases as the amount of electrical energy it contains
increases.
This reduction in the current being absorbed by
source 7 results in a decrease of the mechanical power
having to be supplied by motor 3 and in a tendency for the
rotational speed R of motor 3 and the value of signal SR
to increase.
But as soon as the value of signal SR exceeds the
value SP3 of signal SP, control circuit 4 gives back to
signal SM value SMO with the result that the mechanical
power Pm supplied by motor 3 almost drops to zero and its
rotational speed R decreases. When the value of signal SR
again reaches value SR3 egual to value SP3, control
circuit 4 gives back value SMl to signal SM and motor 3
again starts supplying its maximum power Pm3~.
This process is repeated several times but since the
current being absorbed by source 7 continues to decrease
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17
the ratio between the length of time during which motor 3
supplies its maximum power Pm3' and the length of time
during which it only supplies almost zero power decreases,
with the result that the average mechanical power supplied
by motor 3 progressively diminishes.
When source 7 is fully recharged, signal SQ again
reaches value SQl. Control circuit 4 then gives back to
signal SM its value SN2 when motor 3 rotates at speed R3
and the value SR3 of signal SR hence equals the value SP3
of signal SP.
The mechanical power Pm3 that motor 3 then supplies
is therefore again equal to 80% of its maximum mechanical
power Pm3', and this mechanical power Pm3 moreover equals
the electrical power Pe3 that is absorbed by consuming
device 2 since the value SR3 of signal SR equals the value
SP3 of signal SP.
This situation remains unchanged as long as the
electrical power Pe that is absorbed by consuming device 2
does not vary and remains equal to Pe3.
A process similar to one of those just described
obviously takes place whenever the electrical power Pe
that is absorbed by consuming device 2 changes.
Figure 4 diagrammatically illustrates the evolution
of the various processes described above in relation to
time t.
In Figure 4, graph a) shows by means of a continuous
line the electrical power Pe that is absorbed by consuming
device 2 and the corresponding signal SP and also shows by
means of a broken line the signal SR representative of the
rotational speed R of motor 3. As explained earlier,
signals SR and SP only differ for very short spaces of
time that follow each change in the value of the
electrical power Pe. That is why the broken line
representing signal SR is only visible in those parts of
graph a) corresponding to these time spaces.
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18
Graphs b) to e) of Figure 4 respectively represent
the values of signal SM, of the mechanical power Pm
supplied by motor 3, of signal SC and of signal SQ.
It should be noted that the variations of signal SR
and of the mechanical power Pm are generally not linear as
has been shown for purposes of simplification.
The various elements of the generating set 1 and in
particular control circuit 4 may of course be so arranged
that the generating set 1 will operate in a manner other
than that just described.
For instance, control circuit 4 may be so arranged
that, when the electrical power Pe being absorbed by
consuming device 2 increases, signal SC does not take its
value SCO as in the above-described example but another
fixed value such that converter 6 may carry on working,
while at the same time limiting the electrical power it
transmits from its inputs 6.1 to its outputs 6.2 to a
value other than zero set by this value of signal SC.
This limited electrical power is obviously produced by
generator 5, so that the mechanical power supplied by
motor 3 no longer exclusively serves to accelerate the
latter and the rotor of generator 5, a part of this
mechanical power still being converted into electrical
power by generator 5. During this acceleration, source 7
is only required to supply that part of the electrical
power Pe being absorbed by consuming device 2 which is no
longer supplied by converter 6.
It is thus possible in such a case to so dimension
source 7 that the maximum amount of electrical energy it
must be able to store may be less than in the example
described with reference to Figure 4, thereby lowering its
cost price.
In a case similar to that just described, the value
given to signal SC by control circuit 4 may not be fixed
but depend on the value of the increase in the electrical
power Pe that is absorbed by consuming device 2.
.,' : : '
,"'
--- 212~766 : -
19 ,.
It will thus be seen that each variation in the
electrical power Pe absorbed by consuming device 2 causes
a variation in the rotational speed R of motor 3 and of
generator 5, and hence a variation in the effective value
U2 and in the frequency f2 of the a.c. voltage V2 produced
by the latter.
But it will also be seen that these variations in the
effective value U2 and in the frequency f2 of voltage V2
have no effect on the effective value U1 and on the
frequency fl of voltage V1 produced by the generating set
1 since the effective value Ul and the frequency fl only
depend on the value U3 of the d.c. voltage V3, which is
constant, and on the characteristics of the signal SD
controlling converter 9, which are determined by control
circuit 4 independently of the effective value U2 and of
the frequency f2 of volta~e V2.
~ his property of the generating set 1 is a great
advantage of the latter in relation to the known
generating sets.
It wili further be seen that the effective value U1
and the frequency fl of voltage V1 may be chosen quite
freely since it suffices to so arrange control circuit 4
that signal SD for controlling converter 9 will have the
required characteristics. It is even possible to so
arrange control circuit 4 that these characteristics of
signal SD, and hence this effective value U1 and/or this
frequency fl, depend for example on the position of one or
more switches provided on a control-board of the
generating set 1. For instance, in a case where voltage V1
is a monophase voltage, it is possible to provide a two-
position switch on the control-board and so arrange
control circuit 4 that the effective value U1 and the
frequency fl of voltage V1 will respectively be 220V and
50 Hz or llOV and 60 Hz depending on whether the switch is
in one or other of its positions.
212~7~6
Moreover, the fact that the effective value U1 of the
a.c. voltage V1 produced by the generating set 1 is
independent of the effective value U2 of the a.c. voltage
V2 produced by generator 5 avoids having to regulate
voltage V2.
As a result the generating set 1 has the additional
advantage of comprising no device that is similar to the
device that serves to adjust, in known generating sets,
the strength of the current flowing through the excitation
windings of the generator's rotor.
Furthermore, the rotor of generator 5 of the
generating set 1 need not necessarily include such
excitation windings, as these can be replaced to advantage
by permanent magnets. This constitutes another advantage
of the generating set 1 in relation to known generating
sets, for it is known that a generator having a rotor
fitted with permanent magnets is generally less bulky and
less expensive than a generator having a rotor fitted with
excitation windings.
From the above it will be apparent that whatever the
rotational speed R of motor 3, the latter supplies most of
the time a mechanical power which is a defined fraction of
its maximum power at that speed. It is therefore possible
to so dimension motor 3 that its efficiency is maximal or
at least nearly so and that the amount of polluting gas it
discharges is minimal or at least nearly so, when it
supplies this defined fraction of its maximal power.
Such optimization of the efficiency and of the amount
of polluting gases being discharged is not possible with
the motors of known generating sets, since these motors
must rotate at constant rotational speed while supplying a
variable mechanical power and since they therefore hardly
ever operate under optimal conditions of efficiency and
polluting gas discharge.
In the embodiment diagrammatically illustrated in
Figure 5, the generating set according to the present
.: ,.
' ~ ': ~:
--- 212~766
21
invention, referenced 21, comprises a motor which is
similar to the motor 3 of the generating set 1 in Figure 1
and which bears the same reference. The motor 3 of the
generating set 21 comprises like the motor 3 of the
generating set 1, a carburettor having a butterfly-valve
whose position depends on the value of a signal, also
referenced SM, that is produced by a control circuit 24.
Control circuit 24 will not be described in detail as
it can be made in various ways and without difficulty by a
man of the art who knows the operation of the generating
set 21.
In particular, and as with control circuit 4 of
Figure 1, control circuit 24 may for example be
constructed by combining a microcomputer with suitable
interface circuits and by programming this microcomputer
to perform the requisite functions.
Motor 3 is mechanically coupled to the rotor, not
shown, of a generator 25 whose stator includes, in this
example, three windings 25a, 25b and 25c that are
electrically insulated from one another.
The generating set 21 further comprises three groups
of elements each including a first converter 6, a source
7, a monitoring circuit 8, a second converter 9 and a
measurement circuit 10, these numerical references being
completed with a letter a, b or c depending on the group
to which each element belongs.
Each of these elements 6a to lOa, 6b to lOb and 6c to
lOc is similar to the element bearing the same numerical
reference in Figure 1 and, in each group, the elements are
connected to one another like the corresponding elements
in Figure 1. These elements and their connections will
therefore not again be described here.
Suffice it to say that the inputs of converters 6a to
6c are respectively connected to the windings 25a to 25c
of generator 25. Similarly, converters 9a to 9c are so
arranged in this example that the a.c. voltages Vla, Vlb
-- 2124766
22
and Vlc they produce are monophase. It should however be
noted that this feature is not mandatory and that, in
other embodiments, converters 9a, 9b and 9c may be so
arranged that one or several of voltages Vla, Vlb and Vlc
are polyphase, e.g. three-phase, voltages.
By analogy with the Figure 1 case, the control
signals of converters 6a to 6c and 9a to 9c, produced by
control circuit 24, and the signals supplied to control
circuit 24 by monitoring circuits 8a to 8c and by
measurement circuits lOa to lOc are also referenced SC,
SD, SQ and SP respectively, these references being
completed by the same letter a, b or c as the numerical
reference of the element concerned.
The generating set 21 further comprises output
terminals Sla, S2a, Slb, S2b, Slc and S2c, which are each
connected to an output of one of converters 9a to 9c via
measurement circuits lOa to lOc. The a.c. voltages
produced by converters 9a to 9c, respectively referenced
Vla, Vlb and vlc, thus appear across terminals Sla and
S2a, Slb and S2b, and Slc and S2c, respectively.
The generating set 21 also comprises a circuit for
measuring the rotational speed of generator 25 which is
similar to circuit 11 in Figure 1 and similarly referenced
as the latter circuit. Measurement circuit 11 is connected
to the winding 25a of generator 25 and supplies to control
circuit 24 a signal, also referenced SR, which is
representative of the frequency of voltage V2a produced by
winding 25a in response to the rotation of the rotor of
generator 25, and hence representative of the rotational
speed of motor 3.
The operation of the generating set 21 will not be
described in detail as it is very similar to that of
generating set 1.
It should however be noted that the generating set 21
may be used to supply electrical energy to one or more
consuming devices, as will be explained later, and that in
~ 2124766
23
this latter case, the consuming devices may absorb
electrical powers that differ from one another.
Control circuit 24 is therefore so arranged that
motor 3, whatever may be the total electrical power being
consumed by the consuming devicets), will rotate most of
the time at the speed for which the mechanical power it
supplies, which is equal to the above total electrical
power, is equal to a defined fraction, e.g. 80%, of its
maximum mechanical power at that speed.
To ensure such adjustment, control circuit 24
permanently sums up signals SPa, SPb and SPc, compares
this sum with the value of signal SR and determines in
dependence on this comparison the value of signals SM,
SCa, SCb and SCc in a manner similar to that described
earlier in connection with the operation of the generating
set 1.
The effective values and the frequencies of the three
voltages Vla, Vlb and Vlc are obviously independent of the
electrical power absorbed by the consuming device(s)
supplied by the generating set 21 for the same above-
mentioned reasons as in the case of voltage Vl produced by
the generating set 1.
These three voltages Vla, Vlb and Vlc may of course
have identical effective values and frequencies in which
case the three signals SDa, SDb and SDc may also be
identical.
But, and this is an additional advantage of the
generating set 21, control circuit 24 may be so arranged
that the characteristics of signals SDa, SDb and SDc are
such that the effective value and/or the frequency of one
of the three voltages Vla, Vlb and Vlc differ from the
effective value and/or the frequency of the other two
voltages, or even that the effective values and/or the
frequency of all three voltages differ from one another.
Control circuit 24 may also be so arranged that the
characteristics of signals SDa, SDb and SDc, and hence the
~::
r~` 2 1 2 ~ 7 6 ~
24
effective value and/or the frequency of each of voltages
Vla, Vlb and Vlc depend, separately for each of these
signals, on the position of one or more switches disposed
on a control-board of the generating set 21. Thus, for
example, the control-board may be provided with three two-
position switches and control circuit 24 may be so
arranged that each one of voltages Vla, Vlb and Vlc has an
effective value of 220V and a frequency of 50 Hz or an
effective value of llOV and a frequency of 60 Hz according
to the position of one of these switches. ~
These properties of the generating set 21 enable it ~ -
to be used to supply three separate consuming devices.
Such a case is shown in Figure 6 wherein the generating
set 21 is merely represented by its output terminals Sla,
S2a, Slb, S2b, Slc and S2c and wherein the three consuming
devices are referenced 31, 32 and 33.
As mentioned earlier, the generating set 21 can
readily supply these three consuming devices 31, 32 and 33
even if the latter require supply voltages having ~ -
effective values and/or frequencies different from one
another.
The maximum electrical power that can be supplied by
each of the groups of elements 6a to lOa, 6b to lOb and 6c
to lOc of the generating set 21 is obviously limited by
the constitution of these elements.
But the above-mentioned properties of the generating
set 21 enable the latter to be used to supply a consuming
device that operates under monophase voltage and which
absorbs more electrical power than the maximum electrical
power that can be supplied by each of these groups of
elements. ~ -
Figure 7 illustrates such a case wherein the
generating set 21, which again is merely represented by
its output terminals Sla, S2a, Slb, S2b, Slc and S2c, is
used to supply a consuming device, referenced 34, that
absorbs more electrical power than the maximum electrical
:. ~,:
: . - . . . . .. ~ , ,
-~ 2124766 ~ ~
power that each group of elements 6a to 10a and 6b to 10b
can supply, but less than or equal to the sum of these
maximum powers.
In this case, the terminals Sla and Slb of the
generating set 21 are connected, together, to one of the
supply terminals of the consuming device 34, and the
terminals S2a and S2b of the generating set 21 are
connected, together, to the other supply terminal of the
consuming device 34. The electrical power consumed by the
latter is thus supplied by the two groups of elements 6a
to 10a and 6b to 10b operating in parallel.
In such a case, the control circuit 24 of the
generating set 21 must of course be so arranged that the
signals SDa and SDb that are applied to the converters 9a
and 9b are identical for the two voltages Vla and Vlb to
have the same effective value and the same frequency and
to be moreover in phase with one another.
Still in such a case, a second consuming device,
referenced 35, may also be supplied by the generating set
21. Obviously, it would then be possible for the voltage
Vlc produced by the latter across its terminals Slc and
S2c, to which is connected the consuming device 35, to
have an effective value and/or a frequency that are
different from those of voltages Vla and Vlb.
In a similar manner, not shown, the generating set 21
may be used to supply a consuming device that operates
under monophase voltage and which absorbs greater
electrical power than that which is absorbed by consuming
device 34 in the preceding example, but less than or equal
to the sum of the maximum powers that can be supplied
respectively by the groups of elements 6a to 10a, 6b to
10b and 6c to 10c.
In such a case, the terminals Sla, Slb and Slc of the
generating set 21 arP connected, together, to one of the
supply terminals of the consuming device, and the
terminals S2a, S2b and S2c of the generating set 21 are
.
... : : ~ ~ : ; ::
2124766 ::
26
connected, together, to the other terminal of the
consuming device.
The electrical power absorbed by the latter is then
supplied by the three groups of elements 6a to lOa, 6b to
lOb and 6c to lOc operating in parallel.
Further, the control circuit 24 of generating set 21
must of course be arranged, in this case, for the signals
SDa, SDb and SDc being applied to converters 9a, 9b and 9c
to be identical for the three voltages Vla, vlb and Vlc to
have the same effective value and the same frequency and
to be in phase with one another.
The above-mentioned properties of the generating set
21 also enable the latter to be used to supply a consuming
device operating under three-phase star voltage.
Such a case is illustrated in Figure 8 wherein the
generating set 21 is again merely represented by its
output terminals Sla, S2a, Slb, S2b, Slc and S2c and
wherein the consuming device it supplies is referenced 36.
In this case, the neutral terminal N of consuming
device 36 is connected to the three terminals Sla, Slb and
Slc of the generating set 21, and the other three
terminals R, S and T of consuming device 36 are
respectively connected to the terminals S2a, S2b and S2c
of the generating set 21. Moreover, the control circuit
2~ of the latter is arranged for the signals SDa, SDb and
SDc being applied to converters 9a, 9b and 9c to be such
that voltages Vla, Vlb and Vlc have the same effective
value and the same frequency, but with each of these three
voltages being out of phase by 120 in relation to the
other two.
Still in this case, the electrical power that is
absorbed by consuming device 36 is of course supplied by
the three groups of elements 6a to lOa, 6b to lOb and 6c
to lOc operating in parallel. The electrical power that
is absorbed by consuming device 36 can therefore be at
most equal to the sum of the maximum electrical powers
- : ,. : : . . : - . : . : - . ~ -.
-` 212~76fi
that the groups of elements 6a to lOa, 6b to lOb and 6c
to lOc can respectively supply.
In the examples described above and illustrated by
Figures 6 to 8, the various connections that are needed
for the generating set 21 to supply one or more consuming
devices in one or other of the described manners are made
outside the generating set 21.
These connections may also be made inside the
generating set 21.
Whenever the generating set 21 is intended to supply
a definite number of consuming devices in a manner that is
also definite, these connections may be fixed. But these
connections may also be made with a multiposition switch
disposed on the control-board of the generating set 21 and
so connected to the output terminals of the latter and to
the outputs of converters 9a, 9b and 9c that, in each of
these positions, it establishes the necessary connections
for one of the above-described uses of the generating set
21. The switch may also be connected to the control
circuit 24 and the latter may be adapted to produce
signals SDa, SDb and SDc with the requisite
characteristics in each position of the switch.
In the embodiment diagrammatically represented in
Figure 9, the generating set according to the invention,
referenced 41, serves to supply a consuming device 2 and -
comprises a motor 3, a control circuit 4, a generator 5
and measurement circuits 10 and 11. These various
elements are similar to the elements bearing the same
references in Figure 1 and will therefore not be described
again. ;
The a.c. voltage V2 produced by generator 5 when its
rotor is driven by motor 3 is applied to the input of a
converter 6' having three output terminals 6'a, 6~b and
6'c.
Converter 6' is arranged to produce across its
terminals 6'a and 6'b a d.c. voltage V3 similar to voltage
- - , - :
,............ . .- - - , ... .:
--- 2~24766
28 ~
': ' .
~. .~ , .
v3 produced by the converter 6 of the generating set 1.
Converter 6' is moreover arranged to produce across
its terminals 6~a and 6~c a second d.c. voltage,
referenced V3', having the same value U3 as voltage v3 but
of opposite sign, meaning that if terminal 6'b is for
instance positive in relation to terminal 6~a, terminal
6~c is negative in relation to this same terminal 6'a.
Further, as with the converter 6 of the generating set 1, -~
converter 6' is arranged for the value U3 of voltages V3
and V3' to be substantially constant whatever may be the -
effective value of voltage V2, and arranged to adjust the ~ -
electrical power it supplies to the elements connected
thereto in dependence on the value of an adjustment
signal, also referenced SC.
Converter 6' will not be described in greater detail as it
is also a circuit that is well known to specialists.
The generating set 41 also comprises a rechargeable
source of electrical energy, referenced 7', having three
output terminals 7'a, 7'b and 7'c respectively connected
to terminals 6'a, 6'b and 6'c of converter 6. Source 7'
is arranged to produce across its terminals 7~a and 7'b a
first voltage having substantially the same value U3 and
the same polarity as voltage V3, and to produce across
this selfsame terminal 7'a and its terminal 7'c a second
voltage having the same value U3 and the same polarity as
voltage V3'.
Such a source 7' may for example be constituted by a
battery of conventional accumulators having two extreme
terminals respectively constituting terminals 7'b and 7'c
and an intermediate terminal constituting terminal 7'a.
The generating set 41 further comprises a monitoring
circuit, also referenced 8, which is connected to source
7' to supply a signal, also termed SQ, and that is
representative of the amount of electrical energy
contained in source 7'. This monitoring circuit is
., ~ .
:.
-- 2~24766
29
identical to the circuit 8 of the generating set 1 and
will therefore not again be described.
The output terminals 6~a, 6'b and 6~c of converter 6~
are respectively connected to the inputs 9'a, 9'b and 9'c
of a second converter 9' arranged to produce the output
a.c. voltage of the generating set 31, also referenced V1,
in response to the d.c. voltages V3 and v3~.
Like the converter 9 of the generating set 1,
converter 9~ is a circuit of the same kind as the circuits
commonly known as inverters and will therefore not be
described here either. Suffice it to say that converter
9~, like the converter 9 of the generating set 1, includes
electronic elements such as transistors and thyristors.
Further, the electronic elements of converter 9~ are
controlled by signals of the same kind as the signals for
controlling the electronic elements of converter 9 and are
collectively identified by the same reference SD as these
latter elements.
It should however be noted that because converter 9
receives two voltages V3 and V3~ of opposite sign, it can
comprise half as many electronic elements as converter 9.
This is a clear advantage of the generating set 41 over
the generating set l since such electronic elements, which
have to stand high voltages and large currents, are
expensive elements.
The operation of the generating set 41 will not be
described as it is identical to that of the generating set
1 in Figure 1.
Obviously converters 6a to 6c, sources 7a to 7c and
converters 9a to 9c of a generating set such as the
generating set 21 of Figure 5 may also respectively be
similar to converter 6~, source 7~ and converter 9~ just
described, with the same advantage.
As already indicated, the rechargeable source of
electrical energy 7 of the generating group 1 may consist
- 2~24766
.
~.
of a battery of conventional, e.g. lead or cadmium-nickel,
accumulators. - -
It is however known that the peak value of the a.c. -
voltage supplied by a converter such as converter 9 is at
most equal to the value of the d.c. voltage applied to ~ -
this converter.
Thus, for example, if the voltage Vl produced by
generating set 1 must have an effective value of 220V, the
value U3 of the d.c. voltage V3 must be at least equal
to ~r2 . 220 volts, i.e. about 312V.
To supply such a voltage, a battery of conventional,
e.g. lead, accumulators must number at least 142 elements
since each of them delivers a voltage of about 2.2 volts.
Such a battery of accumulators is therefore expensive and - -
cumbersome.
Figure 10 illustrates an example of a device that may
be used to advantage to realize the source 7 of the
generating set 1 as it is very much cheaper and
considerably less cumbersome than a battery of
conventional accumulators.
The source of electrical energy that is ~ `
diagrammatically shown in Figure 10 by way of non-limiting
example and which is also referenced 7, comprises a
battery of accumulators 71 that delivers across its
positive terminal 71a and its negative terminal 71b a d.c.
voltage V5 having a value U5 distinctly less than the
value U3 of voltage V3. The value U5 of voltage V5 may
for example be 12V or 24V.
Source 7 also comprises a voltage amplifier 72 whose
input terminals 72a and 72b are respectively connected to
terminals 71a and 71b of the battery of accumulators 71.
Voltage amplifier 72 also comprises a pair of output
terminals 72c and 72d which are connected to the terminals
7.la and 7.lb of source 7, these being the terminals that
are collectively referenced 7.1 in Figure 1. -
. . :: : : - ... i . . . .
3 l
Voltage amplifier 72 will not be described in detail
as it is a circuit that is well known to specialists.
Suffice it to say that it is arranged to produce across
its terminals 72c and 72d, from voltage V5, a d.c. voltage
having a value at least substantially equal to the value
of voltage V3 when terminals 72c and 72d are connected to
no other element. This d.c. voltage, which is that
referenced V4 in Figure 1, is of course strictly equal to
voltage V3 when terminals 72c and 72d are connected to the
output terminals of converter 6 via the terminals 7.la and
7.lb of source 7.
The arrows extending from terminals 7.la and 7.lb of
Figure 10 symbolize the connections of source 7 with
converters 6 and 9 of Figure 1.
Source 7 of Figure 10 further comprises a battery
charger 73 whose inputs 73a and 73b are respectively
connected to the outputs 72c and 72d of voltage amplifier
72 and whose outputs 73c and 73d are respectively
connected to the terminals 71a and 71b of the accumulator
battery 71.
Battery charger 73 will not be described in detail
either as it is a well-known device. Suffice it to say
that battery charger 73 is arranged such as to be capable
of supplying to accumulator battery 71 the current needed
for its recharging, at a voltage obviously equal to
voltage V5. For a reason that will be made clear later,
battery charger 73 is further arranged to supply the
current needed for recharging accumulator battery 71 or to
interrupt this current according to whether a signal Ss it
receives on a control input 73e is in a first or second
state.
As explained hereabove, source 7 supplies to
consuming device 2 the electrical power that the latter no
longer receives when converter 6 is blocked, totally or
partially, i.e. after any increase in the electrical power
.: - ~: -
'. :. ~
- 212~7~6 ~
32
: . '
-: : -~.
Pe and until the rotational speed R of motor 7 has reached
its new value.
It has also been explained that, once the rotational
speed R of motor 3 has reached this new value, source 7 is
recharged until the signal SQ representative of the amount
of electrical energy it contains reaches its maximum value
SQ1.
When source 7 is constituted as shown in Figure 10,
control circuit 4 is arranged to supply to battery charger
73 the above-mentioned signal Ss and to give to signal SB
its first state when source 7 must be recharged, i.e. in
the circumstances just described, and its second state for
the remainder of the time.
It will readily be seen that when the electrical
power Pe absorbed by consuming device 2 increases and that
when converter 6 is totally or partially blocked as
described above, the difference between this electrical
power Pe and that which is still being supplied by
converter 6 is supplied by the battery of accumulators 71
at a voltage V5 and transmitted to converter 9 at a
voltage V3 by voltage amplifier 72.
Signal SB is then in its second state so that charger
73 supplies no current to the accumulator battery 71.
When the rotational speed R of motor 3 reaches its
new value and converter 6 again starts to supply all of
the electrical power produced by generator 5, control
circuit 4 gives to signal SB its first state whereby
charger 73 starts recharging the accumulator battery 71,
the electrical power that is needed for this recharging
operation being of course supplied in mechanical form by
motor 3 which then supplies its full mechanical power as
described earlier.
When the signal SQ that is produced by monitoring
circuit 8, not shown in Figure 10, reaches its maximum
value SQ1 thereby indicating that accumulator battery 71
is fully recharged, control circuit 4 returns signal SB to
-- 212476~
33
its second state, thereby interrupting the recharging
operation of battery 71, and at the same time gives to
signal SM its value SM2 as has been described earlier.
As regards source 7, the above-described process
repeats itself of course after each increase in the
electrical power Pe absorbed by consuming device 2.
It will be apparent that a rechargeable source of
electrical energy like that of Figure 10 uses an
accumulator battery having only a reduced number of
elements to produce the relatively high voltage V3 needed
for the generating set 1 to work. As a result such a
source is clearly less bulky and cheaper than an
equivalent device consisting solely of a battery of
accumulators that produces voltage V3 directly, even after
taking into account the bulk and cost of voltage amplifier
72 and charger 73.
A rechargeable source of electrical energy like that
of Figure 10 may obviously be used in all of the
embodiments of the generating set according to the present
invention, particularly to constitute each of the sources
7a, 7b and 7c of the generating set 21 in Figure 5.
The generating set according to the present invention
may be modified in many ways within the framework of the
latter.
For instance, motor 3, which as will be recalled
consists in the described examples of a petrol engine fed
by a carburettor, may be replaced by any kind of internal
combustion engine, provided of course that the mechanical
power supplied by the motor may be adjusted in dependence
on the value of a signal similar to signal SM described
hereinabove. Such a motor may for instance also be a
petrol engine but one fed by an injection system, or a
Diesel engine or a gas turbine, etc.
Motor 3 may also be constituted, still by way of
example, by a steam or water turbine.
- 21247~6
34
Among the modifications that may be made to the
generating set according to the invention, one may still
mention that which consists in replacing the measurement
circuit ll by a device comprising a disc concentrically
fixed to the shaft connecting motor 3 to generator 5 or
25, a photo-electrical or magnetic sensor producing
pulses in response to teeth or holes regularly arranged at
the periphery of the disc and travelling past the sensor,
and an electronic circuit supplying the signal SR in
response to these pulses.
Similarly, a generating set such as that described
with reference to Figure l may be modified by replacing
generator 5 by a generator of a type, that is also well-
known, such that voltage V2 is a d.c. voltage and not an
a.c. voltage as before. In such a case, converter 6 must
obviously be arranged to produce the constant d.c. voltage
v3 whatever value voltage v2 may have. Further, the
measurement circuit ll producing the signal SR
representative of the rotational speed R of motor 3 must
be adapted accordingly, e.g. by making it in the manner
just set forth, i.e. with a disc fixed to the shaft
connecting motor 3 to generator 5, a sensor and a suitable
electronic circuit.
A generating set such as the one described with
reference to Figure 9 may clearly be modified in the same
way.
A generating set like that described with reference
to Figure l may also be modified by adding thereto one or
more converters similar to converter 9, and by connecting
the inputs of the additional converter(s) to the outputs
of converter 6 and source 7, the control circuit 4 of this
generating set being of course adapted to supply the
control signals, similar to signal SD, needed for the
operation of the additional converters. A generating set
thus modified may therefore supply one or more consuming
- 212~766
devices, like the generating set 21 in Figure 5, while
being simpler than the latter.
It is also possible to make each of the rechargeable
sources of electrical energy 7 (Figure 1), 7a to 7c
(Figure 5) or 7' (Figure 9) in the form of a set of
capacitors, e.g. electrolytic capacitors.
But it is well known that, unlike an accumulator, a
capacitor only releases the energy it contains if the
voltage across its terminals can drop.
Consequently, when sources 7, 7a to 7c or 7~ consist
of capacitors, the respective converters 6 (Figure 1), 6a
to 6c (Figure 5) or 6' (Figure 9) must be so adapted that
the voltages V3, V3a to V3c or V3' they supply decrease
while they are blocked after an increase in the electrical
power Pe.
