WO1991002401A1 - A method and a device for sensorless control of a reluctance motor - Google Patents

A method and a device for sensorless control of a reluctance motor Download PDF

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Publication number
WO1991002401A1
WO1991002401A1 PCT/SE1990/000498 SE9000498W WO9102401A1 WO 1991002401 A1 WO1991002401 A1 WO 1991002401A1 SE 9000498 W SE9000498 W SE 9000498W WO 9102401 A1 WO9102401 A1 WO 9102401A1
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WIPO (PCT)
Prior art keywords
value
actual
flux
current
motor
Prior art date
Application number
PCT/SE1990/000498
Other languages
French (fr)
Inventor
Bengt Gunnar Hedlund
Original Assignee
Aktiebolaget Electrolux
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 Aktiebolaget Electrolux filed Critical Aktiebolaget Electrolux
Priority to AT90911814T priority Critical patent/ATE90487T1/en
Publication of WO1991002401A1 publication Critical patent/WO1991002401A1/en

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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
    • H02P6/00—Arrangements for controlling synchronous motors or other dynamo-electric motors using electronic commutation dependent on the rotor position; Electronic commutators therefor
    • H02P6/14—Electronic commutators
    • H02P6/16—Circuit arrangements for detecting position
    • H02P6/18—Circuit arrangements for detecting position without separate position detecting elements
    • 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
    • H02P25/00—Arrangements or methods for the control of AC motors characterised by the kind of AC motor or by structural details
    • H02P25/02—Arrangements or methods for the control of AC motors characterised by the kind of AC motor or by structural details characterised by the kind of motor
    • H02P25/08—Reluctance motors
    • H02P25/086—Commutation
    • H02P25/089—Sensorless control

Definitions

  • the present invention refers to a method and a device for sensor- less control of a reluctance motor in dependence on motor parameter values measured in the output stage of the motor.
  • a commutating signal is initiated for the actual phase of the reluctance motor.
  • a reluctance motor can be designed for single-phase or multi ⁇ phase operation and has a stator with excitation windings arranged polewise.
  • the stator comprises four poles while the rotor has two poles.
  • the four poles of the stator are arranged so as to form a cross and the rotor has a design locating its poles in diametrically opposite positions.
  • the stator poles are activated in pairs twice per revolution, whereby the pole pair, thus activated, generates a magnetic field forcing the rotor to take the position in which the magnetic resistance, or the reluc ⁇ tance, of the magnetic circuit has its minimum value.
  • a commutation is required of the current supply to the stator poles so that the stator pole pair to follow be activated at the same time as the ' stator pole pair presently supplied is cut- off.
  • this commutation is controlled by voltage or current pulses being synchronized with the position of the rotor.
  • one or several rotor position sensors are being used which generate control signals in dependence on the angular position of the rotor.
  • the sensors are optical or magnetic type sensors resulting in the need for an extra element to be disposed adjacent to the rotor.
  • the use of such rotor position sensors has been found to considerably complicate the manufacture and installation of the motor. Therefore, various types of sensorless commutation control have been suggested, in which some kind of measuring and/or calculation of the inductance of the motor has been used. Accordingly, it is known to make inductance calculations based upon: 1. the measurement of the frequency and/or the amplitude of an oscil ⁇ lator connected to the winding of the respective stator pole pair (US-A 4,520,302), or upon
  • the object of the present invention is to achieve, by relatively simple means, a method and a device for sensorless control of a reluctance motor, wherein the drawbacks of the known methods, referred to above, are remedied.
  • the object is achieved in accordance with the invention, contrary to the determination of the inductance taking place in the known devices, by determining of the actual mag- netic flux only, said flux being compared with a flux value which is a predetermined non-linear function of the current.
  • the present invention makes use of the fact that, for each angular position, the reluctance motor has a determined, non-linear relation between the magnetic flux and the current in the windings of the stator pole pair. It has been established that the flux is a monotonically increasing function of the current.
  • the actual magnetic flux ⁇ J can be calculated according to the formula ⁇ -/(u - -i ⁇ tf .
  • the actual value received is compared with a predetermined non-linear function of the current, being the motor flux as a function of current at a given angle of rotation. This angle is the angle at which a commutating signal is desired.
  • a commutating signal is initiated.
  • Fig. la shows a diagram of the basic relationship between the magnetic flux and the current in a reluctance motor
  • Fig. lb shows a diagram of the function ⁇ [i) for a commutation angle ⁇ ,
  • Fig. lc shows the calculated flux ⁇ of one phase during operation of the motor, the angle & being variable and the course of time indi ⁇ cated by arrows t
  • Fig. Id shows the superposed diagrams of Figures lb and lc, the point of intersection P " ⁇ between the graph Y ⁇ for the calculated flux in operation and the graph ⁇ (i) for tabulated values indicating the position where a commutation signal is desired
  • Fig. 2 shows a basic circuit diagram for current supply of the stator windings of the reluctance motor according to the present invention
  • Fig. 3 shows a block diagram for the control circuit of the current supply device according to Fig. 2.
  • DESCRIPTION OF THE PREFERRED EMBODIMENT In Fig. la a diagram is shown of the non-linear relationship prevailing in a reluctance motor between the magnetic flux ⁇ and the current i in one phase at different angles of rotation of the rotor in said motor.
  • the magnetic flux is a onoto- nically increasing function of the current for each angular position.
  • the mutual inductance between the poles is negligible. Then, flux and current in one phase can be studied disregarding the remaining phases.
  • stator poles are interconnected in pairs and the poles of the rotor are disposed in diametrically opposite positions.
  • the stator poles are activated in pairs twice per revolution. Each phase is activated during an angular interval in which a positive torque is emitted.
  • a rotor position sensor is used to control the turn-on and turn-off of the phases.
  • the rotor position sensor emits a commutation signal used by the control device to supply drive pulses to the motor.
  • the drive signals are synchronized with the commutation signal of the sensor, however, not necessarily identical to said signal.
  • a commutation signal a signal is meant to which the commutation is referred and not a signal giving a direct commutation.
  • the commutation signal is not created by a rotor position sensor but instead by a comparison, Fig. Id, between the actual value of the magnetic flux y ,Fig. lc, and a given function ⁇ ( j of the instan ⁇ taneous current, Fig. lb.
  • Fig. 2 shows a basic circuit diagram of the current supply of the stator windings in a two-phase reluctance motor.
  • Each winding terminal H10, Hll, H12, H13 has been allotted a power stage 1, 2, 3 and 4, respectively. Because the stator windings operate in pairs, the power stages cooperate too.
  • the power stages 1 and 2 refer to the phase with the terminals H10, Hll while the power stages 3 and 4 refer to the phase having the terminals H12, H13.
  • the power stages 1-4 are supplied with voltage from the power supply U of the motor.
  • Each power stage 1-4 comprises a drive stage, having two transistors Tl, T2, and a trigger transistor T3.
  • the output of the drive stage Tl, T2 is connected to the respective one of the winding terminals H10 - H13, while the input of said stage is cont- rolled by the trigger transistor T3, the base of which is intended to be supplied with commutation signals applied to the respective input terminal P15 - P18, connected to the base of said trigger transistor T3.
  • the instan- taneous values of voltage and current in the power stages are sampled. Accordingly, sampling of voltage takes place via a voltage divider Rl, R2 connected across the voltage source U, the sampled voltage u being tapped at the terminal P7. The sampled current is tapped at the ter ⁇ minal P8 in the form of a voltage value R . i, where R is the added resistance of the actual pole winding and the actual power stage.
  • the sampled values, tapped at the terminals P7, P8, are fed to the input terminals, having the same reference numerals, of a control circuit, the block diagram of which is shown in Fig. 3.
  • the control circuit comprises a microprocessor 5, to which is connected a memory 6 and an analog/digital converter 7.
  • a memory 6 predetermined values ⁇ / of the magnetic flux as a function.of the current are stored in tabulated form for different angular positions of the rotor poles in which a commutation signal is ' to be emitted.
  • the micro- processor 5 has a control output P15 - P18 for each power stage 1, 2, 3, 4, the control inputs of which have been given the same reference numerals as in Fig. 2.
  • the power stages 1, 2 and 3, 4 of the stator pole pair are activated alternately.
  • R is the resistance in the winding plus the power stage, and ⁇ - the time interval for which ⁇ /"is calculated.
  • control can be performed in many different ways.
  • the way chosen does not influence on the generation of the commutation signal in accordance with the present invention.
  • the device according to the invention by simple means, a method is created for sensorless control of reluctance motors.
  • the principal assembly of a 4/2-pole motor has been used, however, not restricting the invention to this specific motor type.
  • the embodiment chosen must not be considered as restricted to a control technique making use of transistors,_ even if, at present, this technique is the most advantageous one.

Abstract

In a method for sensorless control of a reluctance motor the actual magnetic flux is compared with tabulated values of the non-linear function between the magnetic flux and the current for the angular position at which a commutation signal (via P15 - P18) is to be emitted to the power stages (1 - 4) for the stator pole windings (H10 - H13) of the motor. The actual value of the magnetic flux is calculated for each sample interval, based on the sampled values of voltage (u via P7) and current (i via P8) according to the relation Δγ=(u-R.i)Δt, where R is the resistance of the actual pole winding and the actual power stage. The instantaneous flux value Δγ received is added to the value of the magnetic flux previously received. The added value constitutes the actual value, referred to above, which is to be compared with tabulated values.

Description

A method and a device for sensorless control of a reluctance motor BACKGROUND OF THE INVENTION
1. Field of the invention
The present invention refers to a method and a device for sensor- less control of a reluctance motor in dependence on motor parameter values measured in the output stage of the motor. By processing in a microprocessor of said values, at predetermined values a commutating signal is initiated for the actual phase of the reluctance motor.
2. Description of the prior art
A reluctance motor can be designed for single-phase or multi¬ phase operation and has a stator with excitation windings arranged polewise. In a common type reluctance motor the stator comprises four poles while the rotor has two poles. The four poles of the stator are arranged so as to form a cross and the rotor has a design locating its poles in diametrically opposite positions. In this 4/2-ρole motor the stator poles are activated in pairs twice per revolution, whereby the pole pair, thus activated, generates a magnetic field forcing the rotor to take the position in which the magnetic resistance, or the reluc¬ tance, of the magnetic circuit has its minimum value. For the continued operation of the rotor a commutation is required of the current supply to the stator poles so that the stator pole pair to follow be activated at the same time as the' stator pole pair presently supplied is cut- off.
Normally, this commutation is controlled by voltage or current pulses being synchronized with the position of the rotor. In order to achieve this, usually, one or several rotor position sensors are being used which generate control signals in dependence on the angular position of the rotor. The sensors are optical or magnetic type sensors resulting in the need for an extra element to be disposed adjacent to the rotor. In practice, the use of such rotor position sensors has been found to considerably complicate the manufacture and installation of the motor. Therefore, various types of sensorless commutation control have been suggested, in which some kind of measuring and/or calculation of the inductance of the motor has been used. Accordingly, it is known to make inductance calculations based upon: 1. the measurement of the frequency and/or the amplitude of an oscil¬ lator connected to the winding of the respective stator pole pair (US-A 4,520,302), or upon
2. the measurement of the derivative of the current in the winding during a voltage pulse applied (SE-B-8604308-0) , or upon
3. the calculation of the magnetic flux by dividing the applied voltage by the current measured (SE-B-8604307-2) .
In principle, in all of the solutions presented a measurement of the inductance, or the differential inductance, of a phase takes place and the value thus measured is then compared with a limit value for the commutation. The known solutions operate in a bad way or doesn't operate at all when the reluctance motor is operated at high speed or at high load. In the latter case the motor is saturated, i.e. the inductance changes due to the fact that the current changes. Various variants of current compensation have been tested with varying success. However, such current compensation causes the construction of the circuit to become more complicated. SUMMARY OF THE INVENTION
Accordingly, the object of the present invention is to achieve, by relatively simple means, a method and a device for sensorless control of a reluctance motor, wherein the drawbacks of the known methods, referred to above, are remedied. The object is achieved in accordance with the invention, contrary to the determination of the inductance taking place in the known devices, by determining of the actual mag- netic flux only, said flux being compared with a flux value which is a predetermined non-linear function of the current.
The present invention makes use of the fact that, for each angular position, the reluctance motor has a determined, non-linear relation between the magnetic flux and the current in the windings of the stator pole pair. It has been established that the flux is a monotonically increasing function of the current. By sampling of the voltage and current of the output stages for the motor windings, for each sample interval, the actual magnetic flux ΛJ can be calculated according to the formula ^ -/(u - -i^ tf . The actual value received is compared with a predetermined non-linear function of the current, being the motor flux as a function of current at a given angle of rotation. This angle is the angle at which a commutating signal is desired. When the actual value of the flux ψ^ equals or crosses the value determined by the predetermined function of the current fij , a commutating signal is initiated.
BRIEF DESCRIPTION OF THE DRAWINGS
The method for sensorless control of a reluctance motor according to the invention will be described more in detail below in connection with a preferred embodiment of a device by which the method can be performed, said device being disclosed in the drawings enclosed here¬ with, in which:
Fig. la shows a diagram of the basic relationship between the magnetic flux and the current in a reluctance motor, Fig. lb shows a diagram of the function ^ [i) for a commutation angle Θ ,
Fig. lc shows the calculated flux ^ of one phase during operation of the motor, the angle & being variable and the course of time indi¬ cated by arrows t, Fig. Id shows the superposed diagrams of Figures lb and lc, the point of intersection P "^ between the graph Y^ for the calculated flux in operation and the graph ^(i) for tabulated values indicating the position where a commutation signal is desired,
Fig. 2 shows a basic circuit diagram for current supply of the stator windings of the reluctance motor according to the present invention, and
Fig. 3 shows a block diagram for the control circuit of the current supply device according to Fig. 2. DESCRIPTION OF THE PREFERRED EMBODIMENT In Fig. la a diagram is shown of the non-linear relationship prevailing in a reluctance motor between the magnetic flux ^ and the current i in one phase at different angles of rotation of the rotor in said motor. As appears from the diagram, the magnetic flux is a onoto- nically increasing function of the current for each angular position. For a reluctance motor having doubly-salient poles, normally, the mutual inductance between the poles is negligible. Then, flux and current in one phase can be studied disregarding the remaining phases.
The invention will be described below, however not limited to it, in connection with a reluctance motor having salient poles and compri- sing a four-pole stator and a two-pole rotor. The windings of the stator poles are interconnected in pairs and the poles of the rotor are disposed in diametrically opposite positions. In a 4/2-pole reluctance motor, thus referred to, the stator poles are activated in pairs twice per revolution. Each phase is activated during an angular interval in which a positive torque is emitted. Normally, a rotor position sensor is used to control the turn-on and turn-off of the phases. The rotor position sensor emits a commutation signal used by the control device to supply drive pulses to the motor. The drive signals are synchronized with the commutation signal of the sensor, however, not necessarily identical to said signal. In this connection, by a commutation signal a signal is meant to which the commutation is referred and not a signal giving a direct commutation. In accordance with the present invention the commutation signal is not created by a rotor position sensor but instead by a comparison, Fig. Id, between the actual value of the magnetic flux y ,Fig. lc, and a given function ^( j of the instan¬ taneous current, Fig. lb.
Fig. 2 shows a basic circuit diagram of the current supply of the stator windings in a two-phase reluctance motor. Each winding terminal H10, Hll, H12, H13 has been allotted a power stage 1, 2, 3 and 4, respectively. Because the stator windings operate in pairs, the power stages cooperate too. The power stages 1 and 2 refer to the phase with the terminals H10, Hll while the power stages 3 and 4 refer to the phase having the terminals H12, H13. The power stages 1-4 are supplied with voltage from the power supply U of the motor. Each power stage 1-4 comprises a drive stage, having two transistors Tl, T2, and a trigger transistor T3. The output of the drive stage Tl, T2 is connected to the respective one of the winding terminals H10 - H13, while the input of said stage is cont- rolled by the trigger transistor T3, the base of which is intended to be supplied with commutation signals applied to the respective input terminal P15 - P18, connected to the base of said trigger transistor T3.
In the preferred embodiment of the present invention the instan- taneous values of voltage and current in the power stages are sampled. Accordingly, sampling of voltage takes place via a voltage divider Rl, R2 connected across the voltage source U, the sampled voltage u being tapped at the terminal P7. The sampled current is tapped at the ter¬ minal P8 in the form of a voltage value R . i, where R is the added resistance of the actual pole winding and the actual power stage.
The sampled values, tapped at the terminals P7, P8, are fed to the input terminals, having the same reference numerals, of a control circuit, the block diagram of which is shown in Fig. 3. The control circuit comprises a microprocessor 5, to which is connected a memory 6 and an analog/digital converter 7. In the memory 6 predetermined values </ of the magnetic flux as a function.of the current are stored in tabulated form for different angular positions of the rotor poles in which a commutation signal is' to be emitted. The micro- processor 5 has a control output P15 - P18 for each power stage 1, 2, 3, 4, the control inputs of which have been given the same reference numerals as in Fig. 2.
As indicated above, in the example of the two-phase motor type, in operation of the reluctance motor the power stages 1, 2 and 3, 4 of the stator pole pair are activated alternately. For each drive pulse the microprocessor periodically samples the voltage U (terminal P7) and the current i (terminal P8), the values of which are being inputted in the microprocessor 5. From these values the function Δ * "- (<£ - β - c) <7zf is created, where u = U when both power stages are conducting, u = 0 when only one of the power stages is conducting, u = -U when none of the power stages is conducting,
R is the resistance in the winding plus the power stage, and Δ - the time interval for which Δ /"is calculated.
By adding of Δ « " to the previous flux value, the actual valued, of the magnetic flux is achieved. At the beginning of each drive pulse = 0. The actual flux value V^ is compared with the tabulated value ( )in the memory 6. If, then, the value V^, equals or has crossed the value β), commutation signals are being initiated by the microproces¬ sor 5. This commutation signal is thus received at a determined angular position for each pulse. This signal is then used by the microprocessor as if it was a signal from an external rotor position sensor. Except for the fact that the generation of the commutation signal takes place without the use of any sensor the control device operates in the same way as a device using a sensor. As known from the literature, see for example T.J.E Miller: "Switched Reluctance Motor Drives", Ventura, California 1988, the control can be performed in many different ways. The way chosen does not influence on the generation of the commutation signal in accordance with the present invention.
Hence, by the device according to the invention, by simple means, a method is created for sensorless control of reluctance motors. As indicated above, for the purpose of illustration only, the principal assembly of a 4/2-pole motor has been used, however, not restricting the invention to this specific motor type. In addition, the embodiment chosen must not be considered as restricted to a control technique making use of transistors,_ even if, at present, this technique is the most advantageous one.

Claims

C l a i s
1. A method for sensorless control of . a reluctance motor in depen¬ dence on measured parameter values taken from the power stages (1 - 4) of the reluctance motor, said values by being processed in a micro¬ processor (5) and at predetermined values initiating a commutation signal for the actual pole windings (H10 - H13) .in the motor, c h a r a c t e r i z e d in that the relationship between the mag¬ netic flux and the current in the respective pole winding (H10 - H13) is predetermined for each angular position (Fig. 1) taken by the rotor poles of the motor, the actual value of the magnetic flux{γ )being determined, which value is compared with a predetermined non-linear function C'f'ti}) °f tne current in order to initiate the commutation signal when the actual value equals or crosses the value of said non- linear function.
2. A method according to claim 1, c h a r a c t e r i z e d in that the determination of the value of the magnetic flux is performed by sampling of the instantaneous voltage (u) and current (i), respective¬ ly, said values of voltage and current being fed to the microprocessor (5) for the calculation of the change of flux according to the rela¬ tion Δ ^ - ( - Z < ϊ) , where R is the resistance of the actual pole winding and the actual power stage, said change of flux being added to the value of
Figure imgf000009_0001
previously received, the added value constituting the actual value of the flux.
3. A device for sensorless control of a reluctance motor, comprising a power stage (1 - 4) for each pole winding (H10 -H13) of the stator of the motor, said power stage being connected to the power supply (U) of the motor and being activated in dependence of a commutation signal (via P15 - P18) received from a control circuit (Fig. 3) including a microprocessor (5), c h a r a c t e r i z e d in that a memory (6), connected to the microprocessor (5), is provided for storing of a predetermined non-linear function (y /of current for the magnetic flux in the respective pole winding (H10 - H13) for the angular position in which a commutation signal is desired, the control circuit (Fig. 3) comprising means for determining of the actual value of the magnetic ±l~ι~-f \to be compared with the corresponding non-linear function ( (t/)- stored in the memory (6), in order to initiate a commutation signal when the actual value equals or crosses the value of the function.
4. A device according to claim 3, c h a r a c t e r i z e d in that the means for determining of the actual value of the magnetic flux
Figure imgf000010_0001
comprises sampling means ,for sampling of the instantaneous values of voltage (u) and current (i), respectively, of the actual power stage (1 - 4), said sampled values, via an analog/digital converter (7), being fed to the microprocessor (5) for calculating of the change of flux(^ -ή according to the relation Δ ' - (£> - &'i-) ϊt } where R is the resistance of the actual pole winding and the actual power stage, an addition taking place in the microprocessor of the value received of the change of flux and the value of flux previously received ( 7^ ) _ the added value constituting the actual value of the flux.
5. A device according to claim 3 or claim 4, c h a r a c t e ¬ r i z e d in that each power stage (1 -4) comprises a transistor (T3) controlled by the commutation signal.
6. A device according to claim 4, c h a r a c t e r i z e d in that the sampling of the supply voltage (U) for the motor takes place via a voltage divider (Rl, R2) and that the sampling of the current through the pole windings (H10 - H13) takes place via a current measuring resistor (R3).
PCT/SE1990/000498 1989-07-28 1990-07-20 A method and a device for sensorless control of a reluctance motor WO1991002401A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT90911814T ATE90487T1 (en) 1989-07-28 1990-07-20 METHOD AND DEVICE FOR SENSORLESS CONTROL OF A RELUCTANCE MOTOR.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE8902619A SE464213B (en) 1989-07-28 1989-07-28 PROCEDURE AND DEVICE FOR SENSOR-FREE CONTROL OF AN ELECTRIC ENGINE
SE8902619-9 1989-07-28

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US5467025A (en) * 1992-06-03 1995-11-14 Switched Reluctance Drives Limited Sensorless rotor position measurement in electric machines
EP0573198A1 (en) * 1992-06-03 1993-12-08 Switched Reluctance Drives Ltd Sensorless rotor position measurement in electric machines
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GB2284513B (en) * 1992-08-21 1997-03-05 British Tech Group Method of and apparatus for determining a rotor displacement parameter
US6005364A (en) * 1992-08-21 1999-12-21 Btg International Limited Rotor position measurement
US5793179A (en) * 1995-12-19 1998-08-11 Switched Reluctance Drives Limited Sensorless rotor position monitoring in reluctance machines
US6586903B2 (en) 1999-12-15 2003-07-01 Switched Reluctance Drives Ltd. Rotor position monitoring of a reluctance drive
US6614256B2 (en) 2000-03-15 2003-09-02 Valeo Electronique Processes and devices for monitoring the rotation of DC electric motors
EP1134884A1 (en) * 2000-03-15 2001-09-19 Valeo Electronique Method and device for following the rotation of DC electric motor
FR2806551A1 (en) * 2000-03-15 2001-09-21 Valeo Electronique METHODS AND DEVICES FOR MONITORING THE ROTATION OF DIRECT CURRENT ELECTRIC MOTORS
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EP1471629A2 (en) * 2003-04-24 2004-10-27 Switched Reluctance Drives Limited Rotor position determination in a switched reluctance machine
US6979974B2 (en) 2003-04-24 2005-12-27 Switched Reluctance Drives Limited Rotor position determination in a switched reluctance machine
EP1471629A3 (en) * 2003-04-24 2006-05-03 Switched Reluctance Drives Limited Rotor position determination in a switched reluctance machine
US6989668B2 (en) 2003-06-04 2006-01-24 Switched Reluctance Drives Limited Rotor position detection of a switched reluctance drive
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EP1655831A1 (en) 2004-11-03 2006-05-10 Switched Reluctance Drives Limited Operation of an electrical machine
US7176650B2 (en) 2004-11-03 2007-02-13 Switched Reluctance Drives Limited Operation of an electrical machine
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SE464213B (en) 1991-03-18
DK0437575T3 (en) 1993-11-08
DE69001891T2 (en) 1994-01-20
EP0437575B1 (en) 1993-06-09
EP0437575A1 (en) 1991-07-24
AU6064090A (en) 1991-03-11
SE8902619D0 (en) 1989-07-28
CA2037042A1 (en) 1991-01-29
SE8902619L (en) 1991-01-29
ES2042305T3 (en) 1993-12-01
US5173650A (en) 1992-12-22
CA2037042C (en) 1996-03-12
ATE90487T1 (en) 1993-06-15
DE69001891D1 (en) 1993-07-15
JPH04500899A (en) 1992-02-13

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