EP0414662A1 - Procede et dispositif d'entrainement d'un moteur asynchrone, la vitesse etant reglee par un onduleur commande - Google Patents

Procede et dispositif d'entrainement d'un moteur asynchrone, la vitesse etant reglee par un onduleur commande

Info

Publication number
EP0414662A1
EP0414662A1 EP87902819A EP87902819A EP0414662A1 EP 0414662 A1 EP0414662 A1 EP 0414662A1 EP 87902819 A EP87902819 A EP 87902819A EP 87902819 A EP87902819 A EP 87902819A EP 0414662 A1 EP0414662 A1 EP 0414662A1
Authority
EP
European Patent Office
Prior art keywords
motor
desired value
value
frequency
inverter
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.)
Withdrawn
Application number
EP87902819A
Other languages
German (de)
English (en)
Inventor
Bo Ake Elfner
Per Lindvall
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
DIGIMOTO OF SWEDEN AB
Original Assignee
DIGIMOTO OF SWEDEN AB
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by DIGIMOTO OF SWEDEN AB filed Critical DIGIMOTO OF SWEDEN AB
Publication of EP0414662A1 publication Critical patent/EP0414662A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P27/00—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage
    • H02P27/04—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage
    • H02P27/06—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage using dc to ac converters or inverters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/18—Arrangements for adjusting, eliminating or compensating reactive power in networks
    • H02J3/1892—Arrangements for adjusting, eliminating or compensating reactive power in networks the arrangements being an integral part of the load, e.g. a motor, or of its control circuit
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P23/00—Arrangements or methods for the control of AC motors characterised by a control method other than vector control
    • H02P23/26—Power factor control [PFC]

Definitions

  • the present invention relates a method and a device for driving an asynchronous motor with speed control by means of a controlled inverter.
  • the asynchronous motor Today, the most frequently used electric motor in machines and processes is the asynchronous motor, largely because it is a standard product which is produced in long series and therefore has a low price and also because it is simple and robust. However, one disadvantage of the asynchronous motor is that speed control is difficult.
  • a much improved speed control of asynchronous motors is achieved by controlling the motor speed by means of a motor voltage of variable frequency.
  • a frequency converter is usually employed which consists of a rectifier supplied by the mains voltage, followed by a frequency-controlled inverter.
  • Speed control by varying the frequency of the motor voltage requires that the supply voltage is changed at the same time, if the torque is to remain unchanged. Adaptation to the load on the motor, which usually varies with varying speed, may then also be ef- fected.
  • the voltage change has been achieved by some form of preprogramming, i.e. such that each motor voltage frequency is associated with a predeter ⁇ mined value of the voltage applied to the motor. It will be appreciated that such preprogramming enables the motor to operate at maximum efficiency over the entire speed range only on condition that the depen ⁇ dency of the load on the speed is not changed, and that the preprogramming has been correctly adapted to the dependency on the speed. If, however, the depen ⁇ dency of the load on the speed is changed in time, which is normal in many applications, maximum effi ⁇ ciency will not be achieved because the preprogrammed supply voltage is incorrect.
  • this object is achieved in that the desired value of the phase difference between the motor voltage and the motor current is determined as a function of the fre ⁇ quency of the voltage supplied by the inverter, and that the amplitude of the voltage supplied by the inverter is controlled to make the actual value of said phase difference equal to the desired value at the frequency at issue.
  • the device is characterised by a detector for determining the actual value of the phase difference between the motor voltage and the motor current, a comparator for determining the difference between said actual value and a desired value of said phase difference, said desired value being a function of the frequency of the voltage supplied by the inverter, and a control unit actuated by the diffe ⁇ rence between said actual value and said desired value, for controlling the amplitude of the alternating voltage supplied by the inverter toward equality between said actual value and said desired value at the frequency at issue.
  • the invention utilises the fact that, upon correct magnetisation of the motor, i.e. at the ideal power factor or phase shift between the motor voltage and the motor current and, thus, the correct magnetisation current, the output torque is proportional to the product of the peak value of the magnetisation current and the cosine of the phase angle between the voltage applied and the current supplied to the motor. Further ⁇ more, use is made of the fact that the optimal phase angle as a function of the motor speed can be deter ⁇ mined in advance on the basis of the maximum motor phase angle at normal speed, i.e. when the frequency of the mains voltage is 50 or 60 Hz.
  • the determination of the desired value made in the method according to the invention is repeated at suitable intervals in order to maintain a correct actual value independently of changes in the frequency and the motor load.
  • the desired value function is determined on the basis of the desired value given for each individual motor at nominal frequency.
  • the desired value function is preferably stored permanent- ly, and the desired value at issue is produced from the stored desired value function. Equivalent to the utilisation of the phase difference is the utilisation of a function thereof, such as the power factor, which is the cosine of the phase difference.
  • the device according to the invention preferably comprises a memory for permanently storing the desired value function as determined on the basis of the de- sired value given for each individual motor at nominal frequency, said memory being addressable by means of the frequency of the voltage supplied by the inverter.
  • the invention thus makes it possible to achieve correct magnetisation of the motor independently of the motor speed and load.
  • the torque supplied can then also be readily calculated and, furthermore, may be utilised for control purposes.
  • the device according to the in ⁇ vention may preferably be provided with a calculating unit which gives the motor torque as a function of the said actual value and the amplitude of the motor current. Furthermore, the device then preferably has a second control unit to change the frequency of the voltage supplied by the inverter in response to the motor torque. Moreover, the device may be provided with an indicator to show the motor torque.
  • Fig. 1 is a diagram showing the motor torque as a function of the speed.
  • Fig. 2 is a block diagram illu ⁇ strating an embodiment of the device according to the invention.
  • Fig. 3 illustrates the relationship between the power factor and the motor speed.
  • Fig. 4 is a block diagram illustrating a possibility of expanding the device shown in Fig. 2.
  • Fig. 1 shows the torque of an asynchronous motor as a function of the speed at two different supply voltage frequencies and for different motor currents.
  • Curves A and B are examples of the speed dependency of a load.
  • the motor has an operating point corresponding to the intersection between curves II and A, and if the motor load is decreased to the load according to curve B, the motor torque must be reduced in accordance with the curve IV.
  • Every asynchronous motor has an individual power factor (cos ⁇ ) which is indicated by the manufacturer for the nominal frequency f , i.e. usually 50 or 60 Hz.
  • this power factor value is known, it is possible to determine the desired value of the power factor or the phase difference between motor voltage and motor current for each frequency f within the entire frequency range from direct current up to maximum motor speed.
  • the appearance of this desired value function as regards cos ⁇ will appear from Fig. 3.
  • the appearance of the desired value function is pro- prised more particularly by means of the frequency dependency of the basic equivalent diagram of the asynchronous motor at nominal load, and the given power factor at nominal frequency and the said nominal load. It will thus be of the type e -k «f wherein k is given by the individual power factor at f .
  • the present invention utilises the fact that the desired value of the power factor or, generally, the desired value of the phase difference between motor voltage and motor current can be determined for each frequency or speed.
  • the device comprises a rectifier 1 connect ⁇ ed to the A.C. mains and supplying direct voltage to a controlled inverter 2 which in turn drives an asynchronous motor 3.
  • the voltage supplied by the inverter 2 is determined by means of a voltage con ⁇ trol unit 4 which supplies the requisite control pulses to the inverter 2 in response to two input parameters, viz. a desired value f, of the motor voltage frequen- cy and a value U of the motor voltage.
  • the desired value f can be set manually or automatically in response to a parameter in the process or machine in which the motor 3 is operating.
  • a voltage detector 5 is connected to the output of the unit 4 to produce at its output a signal whose phase corresponds to the phase of the voltage applied to the motor.
  • the voltage detector 5 may be connected to the lines between the inverter 2 and the motor 3.
  • a current detector 6 is connected to one of the lines between the inverter 2 and the motor 3 to produce a second A.C. voltage signal whose phase corresponds to the phase of the motor current.
  • the outputs from the detectors 5 and 6 are connected to two inputs to a phase detector 7 which is adapted to supply at its output a signal
  • ⁇ ?__ + representing the actual value of the phase dif- ference between motor voltage and motor current.
  • This signal is supplied to an input to a comparator 8 whose other input is supplied with the desired value of the said phase difference.
  • This desired value is ob ⁇ tained from a memory unit 9 in which the desired value function is permanently stored. The desired value at issue is obtained at the output of the memory unit
  • This signal ⁇ is supplied to a calculating unit
  • the device according to the invention will control the amplitude of the voltage supplied by the inverter in such a manner that the actual value of the phase difference between motor voltage and motor current is made equal to the desired value of said phase difference at the frequency at issue. In this manner, there is obtained automatical ⁇ ly the correct magnitisation current in the motor, independently of the speed and load.
  • the device according to the invention will thus automatically adjust the amplitude of the A.C. voltage from the inverter 2 until the output signal of the comparator 8 is zero.
  • the block diagram in Fig. 4 illustrates a possibi- lity of expanding the control in the device according to Fig. 2.
  • a calculating unit 11 is adapted to cal ⁇ culate the motor output torque T which, at maximum power factor, is proportional to the peak value I ⁇ f the motor current, obtained for example from the current detector 6 in Fig. 2, and the power factor.
  • the output signal T of the unit 11 can be utilised for display in an indicator 12 and can also be supplied to a second comparator 13 for comparison with a refe ⁇ rence value T - of the torque.
  • the voltage control unit 4 can be supplied, by means of a correcting unit
  • Fig. 4 also shows the units 4, 8 and 10.
  • the reference value T - of the motor torque may represent, for example, a maximum value of this torque. If the maximum value is exceeded, the correct- ing unit 14 may produce, for example, a torque reduc ⁇ tion by reducing the frequency f in relation
  • the correcting unit 14 may be desig 3 ned to control fcorr. in such a manner that ⁇ T is made equal to zero, which means that the motor is driven at constant torque.

Abstract

Dans un procédé d'entraînement d'un moteur asynchrone où la vitesse est réglée par un onduleur commandé, la valeur recherchée du déphasage entre la tension et le courant du moteur est déterminée en fonction de la fréquence de la tension fournie par l'onduleur. L'amplitude de la tension fournie par l'onduleur est réglée de manière à rendre la valeur réelle dudit déphasage égale à la valeur recherchée pour la fréquence en question. La fonction de la valeur recherchée est déterminée sur la base de la valeur recherchée indiquée pour le moteur individuel à une fréquence nominale et à l'aide du diagramme correspondant du moteur. Un dispositif de mise en oeuvre du procédé comporte un détecteur (7) pour déterminer la valeur réelle du déphasage entre la tension et le courant du moteur, un comparateur (8) pour déterminer la différence entre ladite valeur réelle et une valeur recherchée dudit déphasage, cette valeur recherchée étant fonction de la fréquence de la tension fournie par l'onduleur, et un bloc de commande (10) activé par la différence entre ladite valeur réelle et la valeur recherchée, afin de régler l'amplitude de la tension de courant alternatif fourni par l'onduleur tendant à obtenir une égalité entre ladite valeur réelle et la valeur recherchée à la fréquence dont il est question.
EP87902819A 1986-04-14 1987-04-10 Procede et dispositif d'entrainement d'un moteur asynchrone, la vitesse etant reglee par un onduleur commande Withdrawn EP0414662A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE8601667A SE452934B (sv) 1986-04-14 1986-04-14 Sett och anordning for att driva en via en vexelriktare varvtalsreglerad asynkronmotor
SE8601667 1986-04-14

Publications (1)

Publication Number Publication Date
EP0414662A1 true EP0414662A1 (fr) 1991-03-06

Family

ID=20364167

Family Applications (1)

Application Number Title Priority Date Filing Date
EP87902819A Withdrawn EP0414662A1 (fr) 1986-04-14 1987-04-10 Procede et dispositif d'entrainement d'un moteur asynchrone, la vitesse etant reglee par un onduleur commande

Country Status (5)

Country Link
EP (1) EP0414662A1 (fr)
JP (1) JPH01502952A (fr)
FI (1) FI884699A (fr)
SE (1) SE452934B (fr)
WO (1) WO1987006403A1 (fr)

Families Citing this family (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5010287A (en) * 1988-02-24 1991-04-23 Matsushita Electric Works, Ltd. Induction motor control system
US4833389A (en) * 1988-09-26 1989-05-23 Westinghouse Electric Corp. Current source inverter control system for load commutated induction motor drive
JPH05227795A (ja) * 1992-02-10 1993-09-03 Alex Denshi Kogyo Kk 誘導電動機制御装置および制御方法
FR2700080B1 (fr) * 1992-12-30 1995-01-27 Unite Hermetique Sa Alimentation optimale d'un moteur électrique.
JPH07194183A (ja) * 1993-12-24 1995-07-28 Alex Sogo Kenkyusho:Kk 誘導電動機用電力制御装置
US6636011B2 (en) * 2001-06-13 2003-10-21 Emerson Electric Co. Induction motor control system
BRPI0400456B1 (pt) * 2004-01-05 2016-12-06 Weg S A conversor estático de frequência com função automática para otimização do fluxo magnético e minimização das perdas de motores elétricos de indução
FI121491B (fi) * 2004-11-11 2010-11-30 Vacon Oyj Taajuusmuuttajan ylijännitesuojaus
WO2012037983A1 (fr) * 2010-09-24 2012-03-29 Lenze Drives Gmbh Procédé de régulation optimisée en termes de pertes (dans le cuivre) pour un moteur asynchrone au moyen d'un convertisseur
RU2543970C1 (ru) * 2013-10-15 2015-03-10 Открытое акционерное общество "Научно-исследовательский институт электромеханики" (ОАО "НИИЭМ") Устройство для управления цифровым частотно-регулируемым электроприводом
JP2016001939A (ja) * 2014-06-11 2016-01-07 シャープ株式会社 インバータ制御装置

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4249120A (en) * 1979-07-26 1981-02-03 Mcgraw-Edison Co. Variable speed induction motor control system
US4420718A (en) * 1980-12-05 1983-12-13 Hitachi, Ltd. Control system for induction motor using inverter for AC power supply
US4469997A (en) * 1981-05-11 1984-09-04 Imec Corporation Self generative PWM voltage source inverter induction motor drive
WO1984002404A1 (fr) * 1982-12-11 1984-06-21 Fairford Electronics Ltd Procede et appareil de reglage automatique de la demande du signal d'entree d'un retard de phase dans un controleur de facteur de puissance d'un moteur a induction

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO8706403A1 *

Also Published As

Publication number Publication date
SE8601667D0 (sv) 1986-04-14
FI884699A0 (fi) 1988-10-12
SE452934B (sv) 1987-12-21
SE8601667L (sv) 1987-10-15
WO1987006403A1 (fr) 1987-10-22
JPH01502952A (ja) 1989-10-05
FI884699A (fi) 1988-10-12

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