EP0584713B1 - Method of controlling an electric motor driving a centrifugal pump - Google Patents
Method of controlling an electric motor driving a centrifugal pump Download PDFInfo
- Publication number
- EP0584713B1 EP0584713B1 EP93113211A EP93113211A EP0584713B1 EP 0584713 B1 EP0584713 B1 EP 0584713B1 EP 93113211 A EP93113211 A EP 93113211A EP 93113211 A EP93113211 A EP 93113211A EP 0584713 B1 EP0584713 B1 EP 0584713B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- motor
- control device
- power
- pump
- signal
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
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Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04D—NON-POSITIVE-DISPLACEMENT PUMPS
- F04D15/00—Control, e.g. regulation, of pumps, pumping installations or systems
- F04D15/0066—Control, e.g. regulation, of pumps, pumping installations or systems by changing the speed, e.g. of the driving engine
Definitions
- the present invention relates to a method according to the preamble of claim 1 for controlling an electric motor driving a centrifugal pump.
- the diameter ratio D 1 /D 2 is the ratio between the impeller diameters at the fluid inlet to and the fluid outlet from the centrifugal pump.
- such a motor-pump combination is controlled with a view to producing a constant pressure by measuring the output pressure and increasing the rotational speed of the motor, when the pressure decreases, and decreasing the rotational speed of the motor, when the pressure rises.
- the pressure is measured by means of a differential pressure sensor, producing one signal when the pressure is too low and another signal when the pressure is too high, and no signal when the pressure is correct. Then, these signals are used for regulating the rotational speed of the motor, thus achieving a substantially constant delivery pressure from the pump.
- the primary disadvantage with this arrangement is that the differential pressure sensor has a certain hysteresis, so that the regulating function does not occur continously, but in steps, causing a certain variation in the delivery pressure of the pump.
- EP-A-0 226 858 discloses a method according to the preamble of claim 1 in which the measurement comprises the measuring of at least two parameters, namely speed of rotation and current consumption.
- DE-A-38 24 057 discloses a method by which several measuring values are taken from the electricl power supply to the motor for generating a parameter which corresponds to the characteristic line for pressure versus flow. The generation of this parameter necessitates that the measuring values comprise the current, the effective power and a certain frequency corresponding to the slip of the motor. There is no mention of a possibility of using the current alone directly for controlling the motor via the power control device, without complex computation and frequency analysis.
- the present invention is based on the realization that in a pump-motor combination with a diameter ratio D 1 /D 2 less than 1/2, and in which the delivery pressure of the pump is maintained constant, there exists a unique correlation between the current drawn by the motor and the rotational speed of the motor.
- the motor is a three-phase asynchronous motor, the rotational speed of which is controlled by means of a frequency converter.
- the asynchronous motor is replaced by a synchronous motor, which like the asynchronous motor may be constructed with a so-called wet-running rotor, and in which the rotor can be in the form of a permanent-magnet rotor, the characteristic properties of the synchronous motor produce a substantially improved regulating characteristic with the above-mentioned regulating based on the current drawn, and the efficiency is also improved.
- a frequency converter is used for the regulating function, the usual known starting problems for synchronous motors are easily solved by always letting the frequency converter start with a low frequency, i.e. a kind of "gentle start".
- the motor can e.g. be a shunt motor for alternating or direct current, and the controlling of the rotational speed can be achieved by controlling a shunt-winding resistance.
- Fig. 1 shows a motor 2, connected to a supply mains marked RST through a frequency converter 1.
- the motor 2 drives a centrifugal pump 3, the output pressure of which is monitored by means of a differential pressure sensor 4, in a known manner controlling a servo-motor 5, with which the frequency of the frequency converter 1 is controlled.
- the differential pressure sensor 4 produces a signal to the servo-motor 5 to increase the frequency of the frequency converter 1, while when the pressure is too high, the differential pressure sensor produces a signal to the servo-motor to decrease the frequency of the frequency converter.
- the differential pressure sensor 4 has a certain hysteresis, so that the frequency of the frequency converter 1 is held constant within a certain pressure interval about the desired pressure.
- figure 2 shows a frequency converter 1, a motor 2 and a centrifugal pump 3, but in this case, the frequency of the frequency converter 1 is controlled by means of a control device 7, receiving an electrical measuring signal either I or I', being proportional to the current I drawn by the frequency converter 1 and the current I' drawn by the motor 2 respectively. Based on this signal, the control device 7 produces a frequency-control signal f, that is a function of the measuring signal I.
- the control device 7 When the current I or the current I' rises, corresponding to an increase in the fluid flow Q through the centrifugal pump 3, the control device 7 will adjust the frequency f of the frequency converter 1 upwardly, so that the increase in the rotational speed of the motor 2 will compensate for the decrease in pressure H, when the fluid flow through the pump 3 increases. With a decreasing current I, the control device 7 will adjust the frequency f for the frequency converter 1 downwardly, so that the decrease in the fluid flow Q corresponding to the decrease in the current I, and the consequent increase in the pressure H, will be compensated by a reduction of the rotational speed of the motor.
- the method according to the invention may be used in connection with other types of motors 2 with associated power controllers 1, as it is sufficient to have a basic principle, according to which there will be produced an electrical measuring signal I, that is proportional to the current drawn by either the motor or the power-control device, and that this measuring signal I is processed so as to produce a control signal f for the power-control device 1 in such a manner, that the control signal f ensures a substantially constant output pressure from the pump.
- a dimensioning criterium could be that the pressure at the first consumer be maintained substantially constant.
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Control Of Non-Positive-Displacement Pumps (AREA)
- Control Of Motors That Do Not Use Commutators (AREA)
Abstract
Description
- The present invention relates to a method according to the preamble of claim 1 for controlling an electric motor driving a centrifugal pump.
- The diameter ratio D1/D2 is the ratio between the impeller diameters at the fluid inlet to and the fluid outlet from the centrifugal pump.
- Conventionally, such a motor-pump combination is controlled with a view to producing a constant pressure by measuring the output pressure and increasing the rotational speed of the motor, when the pressure decreases, and decreasing the rotational speed of the motor, when the pressure rises. Normally, the pressure is measured by means of a differential pressure sensor, producing one signal when the pressure is too low and another signal when the pressure is too high, and no signal when the pressure is correct. Then, these signals are used for regulating the rotational speed of the motor, thus achieving a substantially constant delivery pressure from the pump. The primary disadvantage with this arrangement is that the differential pressure sensor has a certain hysteresis, so that the regulating function does not occur continously, but in steps, causing a certain variation in the delivery pressure of the pump.
- EP-A-0 226 858 discloses a method according to the preamble of claim 1 in which the measurement comprises the measuring of at least two parameters, namely speed of rotation and current consumption.
- DE-A-38 24 057 discloses a method by which several measuring values are taken from the electricl power supply to the motor for generating a parameter which corresponds to the characteristic line for pressure versus flow. The generation of this parameter necessitates that the measuring values comprise the current, the effective power and a certain frequency corresponding to the slip of the motor. There is no mention of a possibility of using the current alone directly for controlling the motor via the power control device, without complex computation and frequency analysis.
- On the basis of this prior art it is the aim of the present invention to provide a method according to the preamble of claim 1 which is substantially simplified compared to the above known methods. This is achieved by the features according to the characterizing clause of claim 1. The current measurement is relatively easy to perform and there is no need to introduce sensors in the pump construction to be able to measure the speed of rotation and accordingly, the method can be performed on a standard motor-pump construction without complex modification thereof.
- The present invention is based on the realization that in a pump-motor combination with a diameter ratio D1/D2 less than 1/2, and in which the delivery pressure of the pump is maintained constant, there exists a unique correlation between the current drawn by the motor and the rotational speed of the motor. Normally, the motor is a three-phase asynchronous motor, the rotational speed of which is controlled by means of a frequency converter.
- If the asynchronous motor is replaced by a synchronous motor, which like the asynchronous motor may be constructed with a so-called wet-running rotor, and in which the rotor can be in the form of a permanent-magnet rotor, the characteristic properties of the synchronous motor produce a substantially improved regulating characteristic with the above-mentioned regulating based on the current drawn, and the efficiency is also improved. If a frequency converter is used for the regulating function, the usual known starting problems for synchronous motors are easily solved by always letting the frequency converter start with a low frequency, i.e. a kind of "gentle start".
- Alternatively, the motor can e.g. be a shunt motor for alternating or direct current, and the controlling of the rotational speed can be achieved by controlling a shunt-winding resistance.
- In the following detailed portion of the present description, the invention will be explained in more detail with reference to the exemplary embodiments shown in the drawing, in which
- fig. 1 shows a motor-pump arrangement being controlled in a known manner by a frequency converter, and
- fig. 2 shows a motor-pump arrangement being controlled by means of the method according to the present invention.
- Fig. 1 shows a
motor 2, connected to a supply mains marked RST through a frequency converter 1. Themotor 2 drives acentrifugal pump 3, the output pressure of which is monitored by means of a differential pressure sensor 4, in a known manner controlling a servo-motor 5, with which the frequency of the frequency converter 1 is controlled. When the pressure is too low, the differential pressure sensor 4 produces a signal to the servo-motor 5 to increase the frequency of the frequency converter 1, while when the pressure is too high, the differential pressure sensor produces a signal to the servo-motor to decrease the frequency of the frequency converter. The differential pressure sensor 4 has a certain hysteresis, so that the frequency of the frequency converter 1 is held constant within a certain pressure interval about the desired pressure. - Correspondingly, figure 2 shows a frequency converter 1, a
motor 2 and acentrifugal pump 3, but in this case, the frequency of the frequency converter 1 is controlled by means of acontrol device 7, receiving an electrical measuring signal either I or I', being proportional to the current I drawn by the frequency converter 1 and the current I' drawn by themotor 2 respectively. Based on this signal, thecontrol device 7 produces a frequency-control signal f, that is a function of the measuring signal I. In connection with this configuration, the transfer function for thecontrol device 7 is preferablymotor 2 and thecentrifugal pump 3. - When the current I or the current I' rises, corresponding to an increase in the fluid flow Q through the
centrifugal pump 3, thecontrol device 7 will adjust the frequency f of the frequency converter 1 upwardly, so that the increase in the rotational speed of themotor 2 will compensate for the decrease in pressure H, when the fluid flow through thepump 3 increases. With a decreasing current I, thecontrol device 7 will adjust the frequency f for the frequency converter 1 downwardly, so that the decrease in the fluid flow Q corresponding to the decrease in the current I, and the consequent increase in the pressure H, will be compensated by a reduction of the rotational speed of the motor. - It is conceivable that the method according to the invention may be used in connection with other types of
motors 2 with associated power controllers 1, as it is sufficient to have a basic principle, according to which there will be produced an electrical measuring signal I, that is proportional to the current drawn by either the motor or the power-control device, and that this measuring signal I is processed so as to produce a control signal f for the power-control device 1 in such a manner, that the control signal f ensures a substantially constant output pressure from the pump. - The desired transfer function
control device 7 can be achieved by means of a self-balancing bridge circuit, in which an unbalance in the bridge causes a change in the control signal f until balance is achieved, and in which one branch of the bridge circuit comprises a first element that is proportional to the control signal f, and a second element that is proportional to I (-K I) or I (-kI), so that balance is achieved for f-K I = f0, i.e. f = f0 + K I, or f-kI = R0, i.e. f = R0 + kI. - In those cases, in which the pump is connected to a pipe system or the like having a certain flow resistance, it may be an advantage that the delivery pressure of the pump increases with increasing fluid flow, thus compensating to some extent for the flow resistance in the pipe system. Thus, a dimensioning criterium could be that the pressure at the first consumer be maintained substantially constant.
Claims (9)
- Method of controlling an electric motor (2) driving a centrifugal pump (3) having a varying fluid flow-through (Q), said motor (2) being connected to a supply mains (R,S,T) through a power-control device (1), by which method, for causing the delivery pressure (H) of the pump (3) to be substantially constant over a large interval of variation for the fluid flow-through (Q), a measurement is made on the electrical supply system for the motor and based on the known characteristics of the motor (2) and the pump (3), the measurement is processed so as to produce a control signal (f), used as an input signal to the power-control device (1), characterized in that the centrifugal pump (3) has a diameter ratio D1/D2 less than approximately 1/2, and that the measurement only comprises the measurement of one parameter (I) being proportional to the current drawn by the motor (2) or by the power-control device (1).
- Method according to claim 1, characterized in that the power-control device (1) is a frequency converter and the motor (2) is a three-phase synchronous motor.
- Method according to claim 1, characterized in that the power-control device (1) is a frequency converter and the motor (2) is a three-phase asynchronous motor.
- Method according to claim 2 or 3, characterized in that the control signal (f) is a frequency-adjustment signal and that f = F(I).
- Method according to claim 1, characterized in that the motor (2) is a shunt motor for alternating or direct current, and that the power-control device (1) operates by controlling a shunt-winding resistance.
- Method according to claim 6, characterized in that the control signal (f) is an adjustment signal for the shunt-winding resistance, and that f = F(I) .
- Method according to claim 2, characterized in that F(I) = R0 + k · I .
- Method according to any one of the preceding claims, characterized in that the control signal (f) is produced by means of a self-balancing bridge circuit, in which an unbalance causes a change of the control signal (f) until balance is achieved, and in which a bridge-circuit branch comprises a first element being proportional to the control signal (f) and a second element being proportional to the current (I) or the square root of the current (
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DK1041/92 | 1992-08-21 | ||
DK104192A DK104192D0 (en) | 1992-08-21 | 1992-08-21 | PROCEDURE FOR CONTROLING AN ELECTRIC ENGINE DRIVING A CENTRIFUGAL PUMP |
DK001293A DK1293A (en) | 1992-08-21 | 1993-01-06 | Method of controlling an electric motor operating a centrifugal pump |
DK12/93 | 1993-01-06 |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0584713A1 EP0584713A1 (en) | 1994-03-02 |
EP0584713B1 true EP0584713B1 (en) | 1997-07-16 |
Family
ID=26063115
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP93113211A Expired - Lifetime EP0584713B1 (en) | 1992-08-21 | 1993-08-18 | Method of controlling an electric motor driving a centrifugal pump |
Country Status (4)
Country | Link |
---|---|
EP (1) | EP0584713B1 (en) |
AT (1) | ATE155552T1 (en) |
DE (1) | DE69312183T2 (en) |
DK (1) | DK1293A (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN101871447A (en) * | 2009-04-21 | 2010-10-27 | Itt制造企业公司 | Pump controller |
Families Citing this family (12)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5673732A (en) * | 1995-07-11 | 1997-10-07 | Fe Petro Inc. | Variable speed pump-motor assembly for fuel dispensing system |
GB2309746B (en) * | 1996-02-05 | 1999-08-18 | Nuaire Ltd | Fan controller |
DE19630384A1 (en) * | 1996-07-29 | 1998-04-23 | Becker Kg Gebr | Process for controlling or regulating an aggregate and frequency converter |
US5883489A (en) * | 1996-09-27 | 1999-03-16 | General Electric Company | High speed deep well pump for residential use |
JP3922760B2 (en) * | 1997-04-25 | 2007-05-30 | 株式会社荏原製作所 | Fluid machinery |
DE19931961A1 (en) * | 1999-07-12 | 2001-02-01 | Danfoss As | Method for controlling a delivery quantity of a pump |
FI115322B (en) | 2003-09-19 | 2005-04-15 | Vacon Oyj | Energy measurement with frequency converter |
JP2007162700A (en) * | 2007-01-31 | 2007-06-28 | Ebara Corp | Pump device |
US8425200B2 (en) | 2009-04-21 | 2013-04-23 | Xylem IP Holdings LLC. | Pump controller |
DE102011010218B4 (en) | 2011-02-03 | 2019-09-12 | Robert Bosch Gmbh | A method of regulating the pressure of a fluid delivered by a variable speed pump |
WO2013068016A1 (en) | 2011-11-08 | 2013-05-16 | Wärtsilä Svanehøj A/S | Correcting speed of pumps |
US11034253B2 (en) * | 2017-04-24 | 2021-06-15 | Chargepoint, Inc. | Liquid cooled charging cable for charging electric vehicles |
Family Cites Families (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE2946049A1 (en) * | 1979-11-15 | 1981-05-27 | Hoechst Ag, 6000 Frankfurt | Circulation pump flow-rate regulation system - measures pump loading and rotation to obtain actual flow-rate |
DE3542370C2 (en) * | 1985-11-30 | 2003-06-05 | Wilo Gmbh | Procedure for regulating the head of a pump |
DE3824057A1 (en) * | 1988-07-15 | 1990-01-25 | Loewe Pumpenfabrik Gmbh | Method for regulating the operation of pumps |
-
1993
- 1993-01-06 DK DK001293A patent/DK1293A/en not_active Application Discontinuation
- 1993-08-18 EP EP93113211A patent/EP0584713B1/en not_active Expired - Lifetime
- 1993-08-18 AT AT93113211T patent/ATE155552T1/en not_active IP Right Cessation
- 1993-08-18 DE DE69312183T patent/DE69312183T2/en not_active Expired - Fee Related
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN101871447A (en) * | 2009-04-21 | 2010-10-27 | Itt制造企业公司 | Pump controller |
CN101871447B (en) * | 2009-04-21 | 2015-12-16 | 埃克斯雷姆Ip控股有限责任公司 | Pump controller |
Also Published As
Publication number | Publication date |
---|---|
DE69312183T2 (en) | 1998-01-08 |
DK1293D0 (en) | 1993-01-06 |
EP0584713A1 (en) | 1994-03-02 |
DE69312183D1 (en) | 1997-08-21 |
DK1293A (en) | 1994-02-22 |
ATE155552T1 (en) | 1997-08-15 |
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