[0001] The present invention relates to a control method and control apparatus for a displacement-type
fluid machine to control the number of revolutions of a drive motor by means of an
inverter or the like in operating a displacement-type fluid machine such as a Roots-type
blower or a vane pump.
[0002] A displacement-type fluid machine for handling fluid such as a displacement-type
pump is, for example, employed for lowering or decreasing pressure on an intake side
of a displacement-type pump, increasing the pressure on a discharge side of the pump,
or transporting liquid across the pump. A displacement-type pump is normally used
together with a sealable container such as a tank, and processing values such as pressure
and liquid level within the tank, etc., are detected and controlled so as to be within
a predetermined range, by actuating or stopping the displacement pump. When an inverter
or the like is employed to adjust the number of revolutions of the motor, the frequency
is gradually increased or decreased to avoid abrupt acceleration or deceleration upon
driving or stopping, or the number of revolutions is selected according to fluctuations
in process values.
[0003] In a so-called ON/OFF control method, a displacement-type pump is actuated when an
allowable limit of a process value is detected and the pump is stopped when a predetermined
process value is detected. In this control method, however, the pump may be actuated
too frequently depending on the operating conditions, resulting in damage to the motor
and related equipment and a decrease in the working life of the equipment. In order
to restrain the actuation frequency to within allowable times, a sealable container
such as a tank must have sufficient capacity, which leads to increased facility costs.
Further, since abrupt changes in process values are unavoidable in the ON/OFF control
method, great fluctuations in the pressure or liquid level on the intake side or discharge
side of the pump are caused, preventing stable operation of the system. Moreover,
since the aforementioned control method greatly relies on detectors for detecting
a pressure and liquid level, a proper operation of the apparatus is often prevented
by the malfunctioning of these detectors.
[0004] Further attention is drawn to the US patent US 4,511,312 which discloses a method
and apparatus for driving an impeller in a turbo-type liquid pump operating at relatively
low power and relatively high delivery head by means of an a.c. motor. The motor is
driven by a static inverter which operates at an operating frequency of 100-1000 Hz.
This enables high specific speed impellers to be used, and therewith provides a considerable
increase in the efficiency and capacity of the pump at unchanged motor sizes.
[0005] The present invention has been made in the light of the aforementioned problems,
and the object thereof is to provide a method and an apparatus for controlling a displacement-type
fluid machine which enables to keep the process values within an allowable limit without
effecting repeated actuation and stopping of the pump.
[0006] In order to accomplish the object of the invention stated above, according to a first
aspect of the invention, in a method for controlling a displacement-type fluid machine
which handles fluid including gas and/or liquid for increasing or decreasing pressure
of the fluid or transporting the fluids, the method comprises: provision of an alternating
current motor for driving the displacement-type fluid machine; and provision of a
frequency converter which is capable of conducting frequency conversion up to a range
higher than the power source frequency to adjust the number of revolutions of the
aforementioned motor; wherein the number of revolutions is adjusted so that an input
current to the motor is kept constant, regardless of any change in operating pressure
of the displacement-type fluid machine.
[0007] According to a second aspect of the invention, in a method for controlling a displacement-type
fluid machine according to the first aspect, an input current value to the motor is
detected either within the frequency converter or at the primary or secondary side
thereof, a current setting device is provided to set a constant current value according
to the motor rating, and wherein input frequency to the motor is adjusted so that
the input current value to the motor is maintained constant, based on an output signal
from a comparator/adjuster device which compares the input current value with the
set current value.
[0008] According to a third aspect of the invention, in a method for controlling a displacement-type
fluid machine according to the first or second aspect, an upper limit is provided
for the input frequency to the motor, whereby the number of revolutions of the motor
and displacement-type fluid machine is maintained at a predetermined value or lower.
[0009] According to a fourth aspect of the invention, in a method for controlling a displacement-type
fluid machine according to any of the first aspect to the third aspect, the motor
and displacement-type fluid machine are stopped when the input frequency to the motor
reaches a predetermined minimum value, and the reduction in pressure difference or
liquid level difference between the upstream side and downstream side of the displacement-type
fluid machine is measured, and the motor and displacement-type fluid machine are actuated
when the reduction reaches a predetermined value.
[0010] According to a fifth aspect of the invention, in an apparatus for controlling a displacement-type
fluid machine which handles fluid including gas and/or liquid for increasing or decreasing
pressure of the fluid or transporting the fluids, the aforementioned apparatus comprises:
an alternating current motor for driving the displacement-type fluid machine; a frequency
converter which is capable of conducting frequency conversion up to a range higher
than the power source frequency to adjust the number of revolutions of said motor;
and control means for adjusting the number of revolutions of the motor so that input
current to the motor is constant, regardless of any change in operating pressure of
the displacement-type fluid machine.
[0011] According to a sixth aspect of the invention, in an apparatus for controlling a displacement-type
fluid machine according to the fifth aspect, further comprises: means for detecting
the input current value to the motor either within said frequency converter or at
the primary or secondary side thereof, a current setting device for setting a constant
current value according to the motor rating; and a comparator/adjuster device which
compares the input current value with the constant current value set at the current
setting device; wherein the control means adjusts input frequency to the motor so
that the input current value to the motor is maintained constant based on the output
signal of the comparator/adjuster device.
[0012] According to a seventh aspect of the invention, in an apparatus for controlling a
displacement-type fluid machine according to the fifth or sixth aspect, means for
providing an upper limit for the input frequency to the motor is provided, thereby
maintaining the number of revolutions of the motor and displacement-type fluid machine
at a predetermined value or lower.
[0013] According to eighth aspect of the invention, in an apparatus for controlling a displacement-type
fluid machine according to a fifth to seventh aspect, further comprises: means for
stopping the motor and displacement-type fluid machine when the input frequency to
the motor reaches a predetermined minimum value, and means for measuring the reduction
in pressure difference or liquid level difference between the upstream side and downstream
side of the displacement-type fluid machine, and actuating the motor and displacement-type
fluid machine when said reduction reaches a predetermined value.
[0014] The aforementioned displacement-type fluid machine may comprises two-lobe or three-lobe
Roots-type vacuum pump or compressor, gear pump, rotary vane-type pump or compressor,
water sealing vacuum pump or compressor, reciprocating liquid pump or compressor,
or reciprocating vacuum pump.
[0015] With the arrangement according to the invention, since the number of revolutions
is adjusted so that the input current to the drive motor of the displacement-type
pump is kept constant regardless of any change in operating pressure of the displacement-type
pump, when the operating difference pressure or operating pressure of the displacement-type
pump decreases and the required motive power decrease, the number of revolutions is
increased, and thus the intake flow rate increases proportionally. On the other hand,
when the operating pressure of the displacement-type pump increase and the required
motive power increases, the number of revolutions is decreased so as to maintain the
input current to the motor at a constant level, and thus the intake flow rate decreases
proportionally.
[0016] In general, the maximum operating pressure and flow rate of the displacement-type
pump driven by an alternating current motor is achieved at the rated number of revolutions
at the power source frequency. However, the operation stated above can be realized
by means of a frequency converter which is capable of conducting frequency conversion
up to a range higher than the power source frequency, to enable the motor speed to
be increased when the operating pressure is decreased.
[0017] By selecting the capacity of the displacement-type pump around the average value
with time for the fluctuating demand, the displacement-type pump is not actuated and
stopped repeatedly, but is rather continuously driven in such a way that the number
of revolutions is increased or decreased according to fluctuation on demand, resulting
in a simple control mechanism and lower costs.
[0018] An apparatus including a displacement-type pump is actuated either manually or automatically
upon detection of a value lower than the predetermined operating pressure difference
or liquid level difference across the displacement-type pump. However, since the pressure
or liquid level exerts little load on the displacement-type pump upon actuation, the
number of revolutions of the motor and the flow rate are increased rapidly in the
early operating stage, thereby providing a predetermined pressure and liquid level
in a short time.
[0019] When the input current value to the motor is detected either within the frequency
converter or at the primary or secondary side thereof, and a comparator/adjuster device
compares the input current value with a constant current value set at the current
setting device, it is possible to maintain an input current value to the motor at
the constant value based on the motor rating.
[0020] When an upper limit is provided for the input frequency signal, it is possible to
prevent an excessive increase in the number of revolutions.
[0021] And when a lower limit is provided for the aforementioned input frequency signal,
it is possible to prevent an excessive load by detecting this lower limit and stopping
the drive motor.
[0022] The above and other objects, features and advantages of the present invention will
become more apparent from the following description when taken in conjunction with
the accompanying drawings in which preferred embodiments of the present invention
are shown by way of illustrative examples.
[0023] Fig. 1 is a block diagram illustrating the control apparatus of the displacement-type
vaccum pump of the first embodiment of the present invention.
[0024] Fig. 2 is a graph illustrating the performance of the displacement-type vaccum pump
according to the control method of the first embodiment of the present invention.
[0025] Fig. 3 is a block diagram illustrating the control apparatus of the displacement-type
liquid pump of the second embodiment of the present invention.
[0026] Fig. 4 is a graph illustrating the performance of the displacement-type liquid pump
according to the control method of the second embodiment of the present invention.
[0027] Fig. 5 is a block diagram illustrating the control apparatus of the displacement-type
compressor of the third embodiment of the present invention.
[0028] Fig. 6 is a graph illustrating the performance of the displacement-type compressor
according to the control method of the third embodiment of the present invention.
[0029] Fig. 1 illustrates a first embodiment of the present invention applied to a vacuum
blower for a vacuum-type sewage collection system. This system is provided with a
vacuum tank 1 at a vacuum pumping station, and effects continuous collection of sewage
via connected piping 2 by maintaining the tank under a vacuum state.
[0030] An alternating current motor 4 which drives the vacuum pump 3 is supplied with electrical
power from an inverter (frequency converter) 5. A current detector 6 is provided at
the primary side of the inverter 5, and the detected current is input to a comparator/adjuster
device 7. On the other hand, a signal from a current setting device 8 which sets the
current value according to the rating of the motor 4 is compared with the detected
current value in the comparator/adjuster device 7, from which a frequency increase/decrease
signal based on the deviation of the above comparison is input to the frequency setting
portion of the inverter 5, thereby increasing or decreasing the number of revolutions
of the motor 4, i.e., the vacuum pump 3. The reference numeral 9 denotes a frequency
detector for measuring the secondary side frequency of the inverter 5, which can be
used for setting the upper limit of frequency.
[0031] Fig. 2 is a diagram describing the change in performance of the vacuum pump 3 shown
in Fig. 1 in the event that the input current to the motor 4 is controlled so as to
be a constant value. This figure illustrates the theoretical performance of a displacement-type
vaccum pump when it is operated at different numbers of revolutions. Namely, when
the theoretical flow rate Q at each constat number of revolutions of the motor is
represented by the ordinate in the upper half of Fig. 2, and the degree of vacuum
P is represented by the abscissa, the flow rate of the displacement-type pump is proportional
to the number of revolutions, and the flow rate at each of the number of revolutions
is constant value as represented by horizontal lines Q 100%N, 120%N, ... On the other
hand, the required motive power changes according to the degree of vacuum P. The required
motive power is represented as being 100% when the rated flow under the rated number
of revolutions is taken to be 100% and the rated degree of vacuum is taken to be P
0 at which the required motive power reaches a maximum. When the operation of the vacuum
pump is taken to be adiabatic compression, the required theoretical motive power at
each of the number of revolutions regarding the degree of vacuum P is represented
by a group of curves; L 100%N, 120%N ... The points of intersection a1, a2, a3 ...
between these curves and the horizontal line L100% representing constant motive power
indicate degrees of vacuum which provide a constant value of 100% theoretical motive
power at each of the number of revolutions. The flow rate corresponding to these degrees
of vacuum at each number of revolutions can be obtained from the points of intersection
b1, b2, b3 ... between these degrees of vacuum and the horizontal lines of the flow
Q100%, 120% ... corresponding to each number of revolutions. Thus, by controlling
the number of revolutions of the motor so that the primary current to the motor or
the input motive power to the motor is made constant under a constant power source
voltage, the pump exhibits flow rate to vacuum degree properties as indicated by the
curved line Q-P
(L const) in the figure.
[0032] Although in Fig. 2, the adiabatic efficiency of the vacuum pump and the mechanical
efficiency are taken as being constant, and further, the efficiency of the motor and
inverter are also taken as being constant, the fluctuations of these efficiencies
in practical apparatus are relatively small even when the number of revolutions or
degree of vacuum fluctuates, so that the relation between the degree of vacuum P and
flow rate Q under a constant input motive power indicates a tendency shown by the
curve of Q-P (L const). As can be clearly seen from Fig. 2, when the degree of vacuum
P drops, i.e., when the intake absolute pressure increases, the motor power source
frequency, i.e., the number of revolutions increases so that the input current is
kept at constant value and the intake flow rate is remarkably increased. For example,
in Fig. 2, when the degree of vacuum reaches P
1, the number of revolutions increases to 160% of the rated revolution number and the
flow rate is increased accordingly.
[0033] Conventionally, with vacuum sewage collection systems, etc., the vacuum pump is operated
at a constant speed, and when the degree of vacuum drops to an intermediate degree
of vacuum such as P
1, the pump is actuated, and when the degree of vacuum reaches the maximum P
0, the pump is stopped, thereby repeating this actuation and stopping. The vacuum tank
pressure is normally operated at a value between the maximum degree of vacuum P
0, and an intermediate degree of vacuum P
1. In this invention, by setting the vacuum pump capacity to a predetermined air capacity
which is most frequently used, and by controlling the number of a revolutions so that
the required motive power is kept at constant value, the vacuum pump is not needed
to be turned on and turned off during this process, but can be continuously operated
at a number of revolutions corresponding to the degree of vacuum. Further, a conventional
vacuum tank having a great capacity to avoid the frequent actuation of the vacuum
pump is not needed.
[0034] Since the degree of vacuum of the vacuum tank is low when starting up the facilities,
the vacuum pump operates at a high speed, thereby obtaining the predetermined degree
of vacuum in a short time. Subsequently, continuous operation is maintained while
the number of revolutions is automatically adjusted according to demand. The vacuum
pump may be arranged in such a way that the minimum value of the number of revolutions,
i.e. minimum frequency, is detected by the frequency detector 9, then the pump is
shut down when the facilities are inoperative, such as at night. The pump is actuated
by detecting the intermediate degree of vacuum P
1 upon start-up of the facilities.
[0035] In order to prevent an excessive increase in speed of the vacuum pump when the degree
of vacuum in the vacuum tank is low, by detecting the frequency at the secondary side
of the inverter 5, and by setting an upper limit in the frequency detector 9, the
vacuum pump can be operated at all times at a number of revolutions which is within
an allowable limit.
[0036] With frequency converters employing general-use inverters, the ratio between a secondary
voltage and secondary frequency is constant, but at frequencies higher than the power
source frequency, the secondary voltage is limited by the power source voltage and
consequently is the same value. Therefore, by controlling the primary current to be
constant, the motor current becomes approximately constant around the rated value,
thereby avoiding problems such as an increase in the temperature of the motor and
excessive load, etc.
[0037] As a second embodiment, Fig. 3 illustrates an apparatus which pressurizes fluid and
accumulates the pressurized fluid in a pressure tank 12 by means of a displacement-type
liquid pump 11, for applying the pressurized fluid to various processing. Automatic
ON/OFF operation of the pressure-oil pump 11 is generally conducted to maintain the
pressure or liquid level in the pressure tank within a predetermined range.
[0038] Fig. 4 illustrates a theoretical performance of the displacement-type liquid pump
when it is controlled in the apparatus shown in Fig. 3. At rated-speed operation,
the flow rate Q is constant against the operating pressure P and is represented by
a horizontal line Q (100%N). The required motive power L
p at rated speed operation increases proportionally to the pressure P and is represented
by a straight line L
p 100%N.
[0039] By controlling the number of revolutions so that the input current to the displacement-type
pump driving motor is kept at a constant level according to the present invention,
the relation between the flow rate and operating pressure becomes such as that represented
by the curve Q-P (L
p const). Consequently, the number of revolutions is increased with a drop in operating
pressure, and the flow rate is remarkably increased. An upper limit Nmax is set for
the number of revolutions.
[0040] Upon starting up the apparatus, the displacement-type pump 11 is actuated after having
detected pressure of P
1 or lower. Since the flow rate after actuation of the pump is great, the pressure
or liquid level of the predetermined level can be attained in a short period. Further,
by appropriately selecting the capacity of the displacement-type pump, the pump is
operated continuously between pressures P
1 and P
0 so that the frequency of actuation can be reduced. Thus, a pressure tank having a
great capacity, which was needed to cope with the frequent activation of the pump
in the conventional ON/OFF operation under the fixed motor speed, becomes unnecessary.
The displacement-type pump is stopped upon detection of lower limit value Nmin of
the number of revolutions, i.e., minimum frequency. This Nmin is set so that the secondary
side current of the frequency converter 5, i.e., motor current, does not exceed the
allowable value.
[0041] As a third embodiment, Fig. 5 illustrates an apparatus which pressurizes gas and
accumulates pressure in a pressure tank 14 by means of a displacement-type compressor
13, for applying the pressurized gas to various processing. Fig. 6 illustrates a theoretical
performance of an adiabatic compression of the displacement-type compressor with a
rated compression ratio of P
2/P
1=2.5. When the apparatus is operated at the set speed or rated speed, the intake flow
rate Q
1 is constant regarding the operating compression ratio P
2/P
1, and is represented by a horizontal line Q
1 100%N. On the other hand, the required motion power Lad increases with the compression
ratio P
2/P
1, and is represented by a curve Lad 100%N.
[0042] By controlling the number of revolutions so that an input current to the motor driving
the displacement-type compressor is kept constant according to the present invention,
the relation between the intake flow rate and the compression ratio is represented
by a curve Q
1 (Lad const), so that the intake flow rate is remarkably increased with a decrease
of the compression ratio. An upper limit Nmax of the number of revolutions is set
in the frequency detector 9, which detects the frequency of the secondary side of
the frequency converter apparatus, and limits the speed of the motor.
[0043] By appropriately selecting the capacity of the displacement-type compressor, taking
into consideration the operation under variable speed, the compressor can be operated
in continuous basis between (P
2/P
1)
0 ∼ (P
2/P
1)
1 during operation of the apparatus. When the minimum number of revolutions Nmin is
detected from the input frequency to the motor, the motor is stopped, thereby preventing
an excessive load on the motor.
As described above, according to the present invention, by controlling the number
of revolutions of a displacement-type fluid machine so that the input electrical power
to the drive motor of the machine is made constant, it is possible to continuously
operate the unit in an automatic manner according to the operating pressure or liquid
level, and to exhibit the utmost capability as a unit including a drive motor. Also,
while relatively large-scale pressure or decompression containers were needed in the
conventional ON/OFF operation to restrain the actuation frequency of the machine within
a allowable limit, with the present invention such large-scale containers are unnecessary
or can be made quite small. Further, when starting up the apparatus, the number of
revolutions is increased to the upper limit of mobile power, so that the pressure,
vacuum level, liquid level, compression ratio, etc. created by the displacement-type
fluid machine can be increased to a usable level in a short period. Moreover, continuous
operation is made possible according to demand while avoiding excessive activation
and stopping, by selecting the rated capacity of the displacement-type pump to be
compatible to the demand.
1. A method for controlling a displacement-type fluid machine (3) which handles fluid
including gas and/or liquid for increasing or decreasing pressure of fluid or transporting
fluid, said method comprising: provision of an alternating current motor (4) for driving
the displacement-type fluid machine (3); and provision of a frequency converter (5)
which is capable of conducting frequency conversion up to a range higher than the
power source frequency to adjust the number of revolutions of said motor (4);
wherein the number of revolutions is adjusted so that an input current to the motor
(4) is kept constant, regardless of any change in operating pressure of said displacement
type fluid machine,
wherein said motor (4) and displacement-type fluid machine (3) are stopped when the
input frequency to said motor (4) reaches a predetermined minimum value, and the reduction
in pressure difference or liquid level difference between the upstream side and downstream
side of the displacement-type fluid machine (3) is measured, and the motor (4) and
displacement-type fluid machine (3) are actuated when said reduction reaches a predetermined
value.
2. A method for controlling a displacement-type fluid machine (3) according to Claim
1, wherein the input current value to said motor (4) is detected either within said
frequency converter (5) or at the primary or secondary side thereof, a current setting
device (8) is provided so as to set a constant current value according to the motor
rating, and wherein input frequency to said motor (4) is adjusted so as to maintain
the input value to said motor (4) constant, based on the output of a comparator/adjuster
device (7) which compares said input current value and set current value.
3. A method for controlling a displacement-type fluid machine (3) according to Claim
I or 2, wherein an upper limit is provided for said input frequency to said motor
(4), thereby maintaining the number of revolutions of said motor (4) and displacement-type
fluid machine (3) to a predetermined value or lower.
4. An apparatus for controlling a displacement-type fluid machine (3) which handles fluid
including gas and/or liquid for increasing or decreasing pressure of the fluid or
transporting the fluid, said apparatus comprising: an alternating current motor (4)
for driving the displacement type fluid machine; a frequency converter (5) which is
capable of conducting frequency conversion up to a range which is higher than the
power source frequency to adjust the number of revolutions of said motor (4); and
control means (7,8) for adjusting the number of revolutions so that input current
to said motor (4) is constant, regardless of change in operating pressure of said
displacement-type fluid machine (3) and further comprising means for stopping said
motor (4) and displacement-type fluid machine (3) when the input frequency to said
motor (4) reaches a predetermined minimum value, and means for measuring the reduction
in pressure difference or liquid level difference between the upstream side and downstream
side of said displacement-type fluid machine (3), and actuating said motor (4) and
displacement-type fluid machine (3) when said reduction reaches a predetermined value.
5. An apparatus for controlling a displacement-type fluid machine (3) according to Claim
4, further comprising:
means (6) for detecting the input current value to said motor (4) either within said
frequency converter (5) or at the primary or secondary side thereof, a current setting
device (8) for setting a constant current value according to the motor rating; and
a comparator/adjuster (7) device which compares said input current value with the
constant current value set at said current setting device; wherein said control means
(7,8) adjusts an input frequency to said motor (4) so that the input value to said
motor (4) is maintained constant based on the output signal of said comparator/adjuster
device.
6. An apparatus for controlling a displacement-type fluid machine (3) according to Claim
4 or 5, wherein means for providing an upper limit for input frequency to said motor
(4) is provided, thereby maintaining the number of revolutions of said motor (4) and
displacement-type fluid machine (3) to a predetermined value or lower.
7. An apparatus for controlling a displacement-type fluid machine (3) according to any
of claims 4 to 6, wherein said displacement-type fluid machine (3) comprises a two-lobe
or three-lobe Roots-type vacuum pump or a compressor, a gear pump, a rotary vane-type
pump or compressor, a water-ring vacuum pump or compressor, a reciprocating liquid
pump or compressor, or reciprocating vacuum pump.
1. Verfahren zur Steuerung einer Strömungsmittelmaschine vom Verdrängungstyp (3), die
Strömungsmittel einschließlich von Gas und/oder Flüssigkeit handhabt, und zwar zur
Erhöhung oder Erniedrigung des Drucks des Strömungsmittels oder für den Transport
des Strömungsmittels, wobei das Verfahren Folgendes aufweist: Vorsehen eines Wechselstrommotors
(4) für den Antireb der Verdrängungstyp-Strömungsmittelmaschine (3); und Vorsehen
eines Frequenzwandlers (5), der eine Frequenzwandlung bis zu einem Bereich höher als
die Frequenz der Leistungsquelle zum Einstellen einer Umdrehungszahl des Motors (4)
durchführen kann;
wobei die Umdrehungszahl bzw. Drehzahl derart eingestellt wird, dass ein Eingangsstrom
des Motors (4) konstant gehalten wird, und zwar ohne Rücksicht auf irgend eine Änderung
des Betriebsdrucks der Verdrängungstyp-Strömungsmittelmaschine,
wobei der Motor (4) und die Verdrängungstyp-Strömungsmittelmaschine (3) angehalten
werden, wenn die Eingabefrequenz in den Motor (4) einen vorbestimmten Minimalwert
erreicht, und wobei die Reduktion des Druckunterschiedes oder des Flüssigkeitspegelunterschieds
zwischen der Stromaufwärts- und der Stromabwärtsseite der Verdrängungstyp-Strömungsmittelmaschine
(3) gemessen wird und der Motor (4) und die Verdrängungstyp-Strömungsmittelmaschine
(3) betätigt wird, wenn die Reduktion einen vorbestimmten Wert erreicht.
2. Verfahren zur Steuerung einer Strömungsmittelmaschine vom Verdrängungstyp (3) nach
Anspruch 1, wobei der Eingabestromwert des Motors (4) entweder im Frequenzwandler
(5) oder an einer Primär- oder einer Sekundärseite desselben detektiert wird, wobei
eine Stromeinstellvorrichtung (8) vorgesehen ist, so dass ein konstanter Stromwert
gemäß der Motorleistung eingestellt wird, und wobei die Eingabefrequenz in den Motor
(4) eingestellt wird, so dass der Eingabewert in den Motor (4) konstant gehalten wird,
und zwar basierend auf den Ausgang einer Vergleicher/Einsteller-Vorrichtung (7), die
den Eingabestromwert und den Einstellstromwert vergleicht.
3. Verfahren zur Steuerung einer Strömungsmittelmaschine vom Verdrängungstyp (3) gemäß
Anspruch 1 oder 2, wobei eine obere Grenze vorgesehen ist für die Eingabefrequenz
in den Motor (4), wodurch die Drehzahl des Motors (4) und der Verdrängungstyp-Strömungsmittelmaschine
(3) auf einem vorbestimmten Wert oder weniger gehalten wird.
4. Vorrichtung zur Steuerung einer Strömungsmittelmaschine vom Verdrängungstyp (3), die
ein Strömungsmittel einschließlich Gas und/oder Flüssigkeit handhabt für eine Erhöhung
oder Erniedrigung des Drucks des Strömungsmittels oder für den Transport des Strömungsmittels,
wobei die Vorrichtung Folgendes aufweist: Einen Wechselstrommotor (4) für den Antrieb
des Verdrängunstyp-Strömungsmittelmaschine; einen Frequenzwandler (5), der eine Frequenzwandlung
bis zu einem Bereich durchführen kann, der höher ist als die Leistungsquellenfrequenz
zum Einstellen der Drehzahl bzw. Anzahl der Umdrehungen des Motors (4); und Steuermittel
(7, 8) für das Einstellen der Drehzahl, so dass der Eingabestrom in den Motor (4)
konstant ist, und zwar ohne Betracht des Betriebsdrucks der Verdrängungstyp-Strömungsmittelmaschine
(3), und die ferner Mittel für das Anhalten des Motors (4) und der Verdrängungstyp-Strömungsmittelmaschine
(3) aufweist, wenn die Eingabefrequenz in den Motor (4) einen vorbestimmten Minimalwert
erreicht, und Mittel für das Messen der Reduktion des Druckunterschiedes oder des
Flüssigkeitspegelunterschieds zwischen der Stromaufwärts- und der Stromabwärtsseite
der Verdrängungstyp-Strömungsmittelmaschine (3) und zum Betätigen des Motors (4) und
der Verdrängungstyp-Strömungsmittelmaschine (3), wenn die Reduktion einen vorbestimmten
Wert erreicht.
5. Vorrichtung zur Steuerung einer Strömungsmittelmaschine vom Verdrängungstyp (3) nach
Anspruch 4, die weiter Folgendes aufweist:
Mittel (6) für das Detektieren des Eingabestromwertes in den Motor (4) entweder
innerhalb des Frequenzwandlers (5) oder an einer Primär- oder Sekundärseite davon,
eine Stromeinstellvorrichtung (8) für das Einstellen eines konstanten Stromwertes
gemäß der Motorleistung und eine Vergleicher/Einsteller (7) -Vorrichtung, die den
Eingabestromwert mit dem konstanten Stromwert vergleicht, der durch die Stromeinstellvorrichtung
eingestellt wird; wobei die Steuermittel (7, 8) die Eingabefrequenz in den Motor (4)
derart steuert, dass der Eingabewert in den Motor (4) konstant gehalten wird basierend
auf dem Ausgangssignal der Vergleicher/Einsteller-Vorrichtung.
6. Vorrichtung zur Steuerung einer Strömungsmittelmaschine vom Verdrängungstyp (3) nach
Anspruch 4 oder 5, wobei Mittel zum Vorsehen einer oberen Grenze für die Eingabefrequenz
in den Motor (4) vorgesehen sind, um dadurch die Drehzahl des Motors (4) und der Verdrängungstyp-Strömungsmittelmaschine
(3) auf einem vorbestimmten Wert oder geringer zu halten.
7. Vorrichtung zur Steuerung einer Strömungsmittelmaschine vom Verdrängungstyp (3) gemäß
einem der Ansprüche 4 bis 6, wobei die Verdrängungstyp-Strömungsmittelmaschine (3)
eine Roots-Typ- bzw. eine Wälzkolbenvakuumpumpe oder Kompressor mit zwei oder drei
Wälzkolben, eine Zahnradpumpe, eine Pumpe oder einen Kompressor vom Drehschaufeltyp,
eine Wasserring-Vakuumpumpe oder Kompressor, eine sich hin und her bewegende bzw.
eine Kolbenflüssigkeitspumpe oder Kompressor oder eine Kolbenvakuumpumpe aufweist.
1. Procédé pour commander une machine fluidique (3) de type volumétrique, qui traite
un fluide y compris un gaz et/ou un liquide, pour accroître ou réduire la pression
du fluide ou transporter le fluide, ledit procédé comprenant :
l'utilisation d'un moteur à courant alternatif (4) pour entraîner la machine fluidique
de type volumétrique (3); et l'utilisation d'un convertisseur de fréquence (5), qui
est à même de réaliser une conversion de fréquence jusque dans une gamme supérieure
à la fréquence de la source d'alimentation pour régler le nombre de tours dudit moteur
(4);
selon lequel le nombre de tours est réglé de telle sorte qu'un courant d'entrée envoyé
au moteur (4) est maintenu constant, indépendamment d'une quelconque variation de
la pression de fonctionnement de ladite machine fluidique de type volumétrique, et
selon lequel ledit moteur (4) et la machine fluidique de type volumétrique (3) sont
arrêtés lorsque la fréquence d'entrée envoyée audit moteur (4) atteint une valeur
minimale prédéterminée, et la réduction de la différence de pression ou la différence
de niveau de liquide entre le côté amont et le côté aval de la machine fluidique de
type volumétrique (3) est mesurée, et le moteur (4) et la machine fluidique de type
volumétrique (3) sont actionnés lorsque ladite réduction atteint une valeur prédéterminée.
2. Procédé pour commander une machine fluidique de type volumétrique (3) selon la revendication
1, selon lequel la valeur du courant d'entrée envoyé audit moteur (4) est détectée
soit à l'intérieur dudit convertisseur de fréquence (5), soit sur le côté primaire
ou le côté secondaire de ce dernier, un dispositif (8) de réglage du courant est prévu
de manière à régler une valeur de courant constant conformément à la puissance nominale
du moteur, et selon lequel la fréquence d'entrée envoyée audit moteur (4) est réglée
de manière à maintenir constante la valeur du courant d'entrée envoyée audit moteur
(4), sur la base du signal de sortie d'un comparateur/dispositif d'ajustement (7),
qui compare ladite valeur du courant d'entrée et ladite valeur de courant réglé.
3. Procédé pour commander une machine fluidique de type volumétrique (3) selon la revendication
1 ou 2, selon lequel une limite supérieure est prévue pour ladite fréquence d'entrée
envoyée audit moteur (4), ce qui maintient la vitesse de rotation dudit moteur (4)
et de la machine fluidique de type volumétrique (3) égale ou inférieure à une valeur
prédéterminée.
4. Dispositif pour commander une machine fluidique de type volumétrique (3), qui traite
un fluide y compris un gaz et/ou un liquide pour augmenter ou réduire la pression
du fluide ou transporter le fluide, ledit dispositif comprenant : un moteur à courant
alternatif (4) pour entraîner la machine fluidique de type volumétrique; un convertisseur
de fréquence (5) qui peut exécuter une conversion de fréquence jusque dans une gamme
qui est supérieure à la fréquence de la source d'alimentation pour régler le nombre
de tours dudit moteur (4); et des moyens de commande (7,8) pour ajuster le nombre
de tours de telle sorte que le courant d'entrée envoyé audit moteur (4) est constant
indépendamment de la variation de la pression de fonctionnement de ladite machine
fluidique de type volumétrique (3), et comprenant en outre des moyens pour arrêter
ledit moteur (4) et ladite machine fluidique de type volumétrique (3) lorsque la fréquence
d'entrée envoyée audit moteur (4) atteint une valeur minimale prédéterminée, et des
moyens pour mesurer la réduction de la différence de pression ou de la différence
du niveau de liquide entre le côté amont et le côté aval de ladite machine fluidique
de type volumétrique (3), et actionner ledit moteur (4) et ladite machine fluidique
de type volumétrique (3) lorsque ladite réduction atteint une valeur prédéterminée.
5. Dispositif pour commander une machine fluidique de type volumétrique (3) selon la
revendication 4, comprenant en outre :
des moyens (6) pour détecter la valeur du courant d'entrée envoyé audit moteur (4)
soit dans ledit convertisseur de fréquence (5), soit au niveau du côté primaire ou
du côté secondaire de ce convertisseur, un dispositif (8) de réglage du courant servant
à régler une valeur constante du courant en fonction de la puissance nominale du moteur;
et un comparateur/dispositif d'ajustement (7) qui compare ladite valeur du courant
d'entrée à la valeur de courant constante réglée dans ledit dispositif de réglage
du courant; et dans lequel lesdits moyens de commande (7,8) ajustent une fréquence
d'entrée envoyée audit moteur (4) de telle sorte que la valeur d'entrée envoyée audit
moteur (4) est maintenue constante sur la base du signal de sortie dudit comparateur/dispositif
d'ajustement.
6. Dispositif pour commander une machine fluidique de type volumétrique (3) selon la
revendication 4 ou 5, dans lequel les moyens pour délivrer une limite supérieure pour
la fréquence d'entrée envoyée audit moteur (4) sont prévus, maintenant ainsi le nombre
de tours dudit moteur (4) et de la machine fluidique de type volumétrique (3) à une
valeur prédéterminée ou inférieure.
7. Dispositif pour commander une machine fluidique de type volumétrique (3) selon l'une
quelconque des revendications 4 à 6, dans lequel ladite machine fluidique de type
volumétrique (3) comprend une pompe à vide du type Roots à deux lobes ou à trois lobes
ou un compresseur, une pompe à engrenages, une pompe ou un compresseur du type à ailettes
rotatives, une pompe à vide ou un compresseur à anneau d'eau, une pompe ou un compresseur
à liquide à déplacement alternatif ou une pompe à vide à déplacement alternatif.