METHOD FOR DETERMINING A STATOR CURRENT VECTOR FOR STARTING A SYNCHRONOUS MACHINE OF A DRIVE OF A PASSENGER TRANSPORTATION APPARATUS

Abstract

A method for determining a stator current vector for starting a synchronous machine of a drive of a passenger transportation apparatus having a rotor and a stator with a stator winding may involve imposing different stator current vectors with different stator current vector directions on the stator winding over the course of a plurality of current application operations, determining from the different stator current vectors a minimum stator current vector with a minimum stator current vector direction at which a minimum driving torque acting on the rotor is generated in the synchronous machine, determining a starting stator current vector with a starting stator current vector direction from the minimum stator current vector, and imposing the starting stator current vector on the stator winding for starting the synchronous machine.

Claims

1.-15. (canceled)

16. A method for determining a stator current vector for starting a synchronous machine of a drive of a passenger transportation apparatus that includes a rotor and a stator with a stator winding, the method comprising: imposing different stator current vectors with different stator current vector directions on the stator winding over a course of a plurality of current application operations; determining from the different stator current vectors a minimum stator current vector with a minimum stator current vector direction at which a minimum driving torque acting on the rotor is generated in the synchronous machine; determining from the minimum stator current vector a starting stator current vector with a starting stator current vector direction; and imposing the starting stator current vector on the stator winding for starting the synchronous machine.

17. The method of claim 16 comprising at least one of: determining from the different stator current vectors a zero stator current vector as the minimum stator current vector at which no driving torque acting on the rotor is generated in the synchronous machine; or determining from the minimum stator current vector a maximum stator current vector as the starting stator current vector at which a maximum driving torque acting on the rotor is generated in the synchronous machine.

18. The method of claim 16 comprising determining each of the different stator current vectors of the plurality of current application operations based on a predefined criterion.

19. The method of claim 18 wherein for determining each subsequent stator current vector direction of a subsequent stator current vector in a subsequent of the plurality of current application operations, a preceding stator current vector direction of a preceding stator current vector in a preceding of the plurality of current application operations is used as the predefined criterion.

20. The method of claim 19 wherein each subsequent stator current vector direction is determined by adding or subtracting an angular value to/from each preceding stator current vector direction.

21. The method of claim 20 wherein the angular value that is added or subtracted is halved for each subsequent stator current vector direction.

22. The method of claim 20 wherein whether the angular value is added or subtracted to/from each preceding stator current vector direction depends on a direction of a driving torque acting on the rotor that is generated by each preceding stator current vector.

23. The method of claim 16 wherein after the minimum stator current vector is determined, the method further comprises performing a check as to whether the minimum driving torque acting on the rotor is generated upon imposing the minimum stator current vector on the synchronous machine.

24. The method of claim 23 wherein the check comprises: imposing multiple stator current vectors of different amplitudes in the minimum stator current vector direction on the stator winding in multiple further current application operations; and determining whether the minimum driving torque acting on the rotor is generated in each of the multiple further current application operations.

25. The method of claim 16 further comprising imposing prior to each subsequent stator current vector an inverse stator current vector with an inverse stator current vector direction on the stator winding, wherein the inverse stator current vector direction is 180° relative to the subsequent stator current vector direction of each subsequent stator current vector.

26. The method of claim 16 wherein during the plurality of current application operations each of the different stator current vectors is imposed on the stator winding for a time interval that does not exceed 100 ms.

27. The method of claim 16 wherein during the plurality of current application operations each of the different stator current vectors is imposed on the stator winding for a time interval that does not exceed 25 ms.

28. The method of claim 16 comprising considering only a direction of a driving torque or a direction of a movement generated by each preceding stator current vector as input for each subsequent stator current vector and each subsequent stator current vector direction.

29. The method of claim 16 further comprising pausing for a time interval of at least 25 ms between each of the plurality of current application operations.

30. The method of claim 16 further comprising determining a commutation offset based on the starting stator current vector.

31. A drive for a passenger transportation apparatus with a synchronous machine, the drive comprising: a rotor; a stator with a stator winding; and a control unit configured to impose different stator current vectors with different stator current vector directions on the stator winding over a course of a plurality of current application operations, determine from the different stator current vectors a minimum stator current vector with a minimum stator current vector direction at which a minimum driving torque acting on the rotor is generated in the synchronous machine, determine from the minimum stator current vector a starting stator current vector with a starting stator current vector direction, and impose the starting stator current vector on the stator winding for starting the synchronous machine.

32. A passenger transportation apparatus configured as an escalator, a travellator, or an elevator system with a cabin that travels in an elevator shaft, the passenger transportation apparatus comprising a drive that comprises: a rotor; a stator with a stator winding; and a control unit configured to impose different stator current vectors with different stator current vector directions on the stator winding over a course of a plurality of current application operations, determine from the different stator current vectors a minimum stator current vector with a minimum stator current vector direction at which a minimum driving torque acting on the rotor is generated in the synchronous machine, determine from the minimum stator current vector a starting stator current vector with a starting stator current vector direction, and impose the starting stator current vector on the stator winding for starting the synchronous machine.

Description

DESCRIPTION OF FIGURES

[0054] FIG. 1 shows a schematic representation of a preferred configuration of a passenger transportation apparatus according to the invention, with a preferred configuration of a drive according to the invention.

[0055] FIG. 2 shows a schematic representation of stator current vector diagrams, which can be determined in the course of a preferred embodiment of a method according to the invention.

[0056] FIG. 3 shows a schematic representation of an alternative preferred configuration of a passenger transportation apparatus according to the invention, with a preferred configuration of a drive according to the invention.

[0057] FIG. 4 shows a schematic representation of a further alternative preferred configuration of a passenger transportation apparatus according to the invention, with a preferred configuration of a drive according to the invention.

[0058] FIG. 1 shows a schematic representation of a preferred configuration of a passenger transportation apparatus according to the invention, denoted by the number 100. In this example, the passenger transportation apparatus is configured as an elevator system 100.

[0059] The elevator system 100 comprises a cabin 102 which is arranged to move in an elevator shaft 101. The cabin 102 is suspended on a suspension rope 103, and is connected to a counterweight 106 via a pulley 104 and a deflection pulley 105.

[0060] The elevator system 100 comprises a preferred configuration of a drive 110 according to the invention which, in the present example, is configured as a pulley drive. The pulley drive 110 comprises the pulley 104 and a synchronous machine 111 configured as a rotary motor. The synchronous machine 111 is connected to the pulley 104 via a shaft 112, and can drive the latter. The pulley drive 110 further comprises a control unit 113, which actuates the synchronous machine 111, and is identified by the reference number 114.

[0061] The synchronous machine 111 is configured, for example, as a three-phase synchronous machine. A stator 121 or primary part of the synchronous machine 111 comprises a stator winding having, for example, three phase windings. A rotor 122 or secondary part of the synchronous machine 111 comprises, for example, an excitation winding or a permanent magnet arrangement. The phase windings of the stator 121 are connected to a power converter circuit 123. This power converter circuit 123 comprises appropriate switching elements such as, for example, MOSFETs (metal oxide semiconductor field-effect transistors) (in FIG. 1, for exemplary purposes only, a single MOSFET is represented). The individual switching elements of the power converter circuit 123 are actuated by the control unit 113.

[0062] In order to drive the pulley 104, the synchronous machine 111 is energized. A rotary stator current vector is thus imposed on the stator winding of the synchronous machine 111. In order to operate the synchronous machine 111 at optimum efficiency and to generate the maximum possible driving torque for application to the rotor, an in-phase stator current vector must be imposed on the stator winding. A maximum stator current vector is thus imposed on the stator winding, at which a maximum driving torque acting on the rotor is generated in the synchronous machine 111. The maximum stator current vector customarily leads the magnetic flux of the rotor by an angle of 90°.

[0063] Specifically upon the starting or start-up of the synchronous machine 111, this maximum stator current vector is unknown. For the starting of the synchronous machine 111, an appropriate starting stator current vector must firstly be determined.

[0064] To this end, the control unit 113 is designed to execute a preferred embodiment of a method according to the invention. In this preferred embodiment, in the course of a plurality of current application operations, different stator current vectors with different stator current vector directions are consecutively imposed on the stator winding. From these different stator current vectors, a minimum stator current vector is firstly determined, at which no driving torque acting on the rotor is generated. From this minimum stator current vector, the maximum stator current vector is determined as the starting stator current vector.

[0065] This preferred embodiment is described hereinafter with reference to FIG. 2. FIG. 2 shows a schematic representation of stator current vector diagrams or space vector diagrams in a fixed-stator αβ-coordinate system, which can be determined in the course of the preferred embodiment. Each of the eight stator current vector diagrams in FIGS. 2a to 2h is respectively characteristic of one of the plurality of current application operations which are executed in the course of this preferred embodiment of the method according to the invention.

[0066] Stator current vectors or current indices are represented in a stator current vector diagram as vectors or indices. Stator current vectors are characteristic of the energization of the stator winding of the synchronous machine 111. All the stator current vectors intersect at the origin of the αβ-coordinate system and terminate at the circumference of a circle, the center of which coincides with the origin. A stator current vector direction of a stator current vector is described by a relative angle to a reference axis.

[0067] In the stator current vector diagrams in FIGS. 2a to 2h, this circle is represented in each case. The circles are subdivided into two semi-circles by a first reference axis. In FIGS. 2a to 2h, this first reference axis is identified by the symbol “F.sub.min”. A first semi-circle is identified by the symbol “+”, and a second semi-circle by the symbol “−”.

[0068] This first reference axis gives an exemplary minimum direction for the starting rotor position. Stator current vectors which are oriented in this minimum direction, or parallel to the first reference axis, are designated as minimum stator current vectors with a minimum stator current vector direction in which, respectively, no driving torque is generated at the initial rotor position in the synchronous machine 111.

[0069] In the synchronous machine 111, upon the imposition of stator current vectors which are oriented in the first semi-circle, in the present example, a movement or a driving torque in the positive direction of movement is generated respectively. Conversely, upon the imposition of stator current vectors which are oriented in the second semi-circle, in this exemplary representation, a movement or a driving torque in the negative direction of movement is generated respectively in the synchronous machine 111.

[0070] A second reference axis gives an exemplary maximum direction for the initial rotor position. In the present example, this second reference axis is oriented perpendicularly to the first reference axis. In FIGS. 2a to 2h, this second reference axis is identified by the symbol “F.sub.max”. Stator current vectors which are oriented in this maximum direction, or parallel to the second reference axis, are designated as maximum stator current vectors which, in the synchronous machine 111, generate the maximum driving torque at the initial rotor position.

[0071] This preferred embodiment of the method according to the invention, in the course of which a plurality of current application operations are executed with different stator current vectors, is described hereinafter.

[0072] FIG. 2b describes a first of the plurality of current application operations with a first stator current vector U.sub.1, having a first stator current vector direction. This first stator current vector U.sub.1 is oriented, for example, in the direction of a corresponding commutation offset, which has been assumed upon the stopping of the synchronous machine 111.

[0073] Before this first current application operation is executed, an inverse current application operation is firstly executed in accordance with FIG. 2a, with an inverse stator current vector direction to the first stator current vector direction. This inverse stator current vector direction is offset from the first stator current vector direction by an angle of 180°.

[0074] An inverse stator current vector, designated in FIG. 2a as U.sub.1*, is imposed on the stator winding. Thereafter, in accordance with FIG. 2b, the first of the plurality of current application operations is executed. As can be seen in FIG. 1, the first stator current vector U.sub.1 and the inverse stator current vector U.sub.1* are oriented in parallel, but in opposing directions.

[0075] Thereafter, in FIG. 2c, a second of the plurality of current application operations is executed with a stator current vector U.sub.2, having a second stator current vector direction. Before the second stator vector U.sub.2 with the second stator current vector direction is imposed on the stator winding, a further inverse current application operation can be executed, in the course of which an inverse stator current vector U.sub.2* having a stator current vector direction which is offset from the second stator current vector direction by an angle of 180° is imposed on the stator winding.

[0076] A respective next stator current vector direction of a next of the plurality of current application operations is determined in each case, wherein a different angular value is added to a present stator current vector direction of the present of the plurality of current application operations, or is subtracted therefrom. This different angular value is halved in each case for each of the next of the plurality of current application operations.

[0077] The second stator current vector direction is thus determined, wherein a first angular value is added to the first stator current vector direction, or is subtracted therefrom. In the present example, this first angular value is 90°.

[0078] Whether the respective angular value is added or subtracted is dependent upon a direction of movement of a present movement generated in the synchronous machine 111 for the initial rotor position. As can be seen from the first stator current vector U.sub.1 in FIG. 2b, the first of the current application operations in the synchronous machine 111 generates a movement in the positive direction of movement. In the event of such a positive direction of movement, the respective angular value is subtracted.

[0079] The second stator current vector direction is determined accordingly, wherein the first angular value of 90° is subtracted from the first stator current vector direction.

[0080] As can be seen from the second stator current vector U.sub.2 in FIG. 2c, the second of the plurality of current application operations in the synchronous machine 111 also generates a movement in the positive direction of movement. A third stator current vector direction is determined accordingly, wherein a second angular value of 45° is subtracted from the second stator current vector direction.

[0081] According to FIG. 2d, a third of the plurality of current application operations is executed with a third stator current vector U.sub.3, having this third stator current vector direction. Prior to this third current application operation, an inverse current application operation is executed with an inverse stator current vector U.sub.3*. The third of the plurality of current application operations generates a movement in the negative direction of movement, for the initial rotor position in the synchronous machine 111. A fourth stator current vector direction is determined accordingly, wherein a third angular value of 22.5° is added to the third stator current vector direction.

[0082] According to FIG. 2e, a fourth of the plurality of current application operations is executed with a fourth stator current vector U.sub.4, having this fourth stator current vector direction. Prior to this fourth current application operation, an (optional) inverse current application operation is executed with an inverse stator current vector U.sub.4*. The fourth of the plurality of current application operations again generates a movement in the positive direction of movement, for the initial rotor position. From the fourth stator current vector direction, a fourth angular value of 11.25° is therefore subtracted, in order to determine a fifth stator current vector direction.

[0083] In this fifth stator current vector direction, according to FIG. 2f, an inverse current application operation with an inverse stator current vector U.sub.5* is firstly executed, and thereafter a fifth of the plurality of current application operations with a fifth stator current vector U.sub.5. This fifth of the plurality of current application operations generates a movement in the negative direction of movement, for the initial rotor position. A fifth angular value of 5.625° is added to the fifth stator current vector direction, in order to determine a sixth stator current vector direction.

[0084] A sixth of the plurality of current application operations is executed, in accordance with FIG. 2g, with this sixth stator current vector direction and with a corresponding sixth stator current vector U.sub.6. Beforehand, an (optional) inverse current application operation is executed with an inverse stator current vector U.sub.6*.

[0085] This sixth stator current vector U.sub.6 is oriented in parallel with the first reference axis and, upon the imposition thereof on the synchronous machine for the initial rotor position, generates no driving torque or no movement. This sixth stator current vector U.sub.6 represents the desired minimum stator current vector. The sixth stator current vector direction represents the desired minimum stator current vector direction.

[0086] In order to determine the maximum stator current vector U.sub.max for the initial rotor position from this minimum stator current vector U.sub.6 and this minimum stator current vector direction, in accordance with FIG. 2h, an angular value of 90° is added to or subtracted from the minimum stator current vector direction. Whether this angular value of 90° is to be added or subtracted is specifically dependent upon a desired direction of movement upon the start-up of the synchronous machine 111. For the starting of the synchronous machine 111, this maximum stator current vector U.sub.max is imposed on the stator winding as the starting stator current vector.

[0087] Moreover, from this maximum stator current vector U.sub.max, a commutation offset is determined for the subsequent routine operation of the synchronous machine 111. This commutation offset establishes a relationship between the actual rotor position and a measuring signal from a rotor position sensor, and is required for the correct alternating energization of the phase winding of the stator 121.

[0088] Each of the current application operations and the inverse current application operations according to FIGS. 2a to 2g is executed for a predetermined time interval of 50 ms in each case, and a pause is applied between each of the current application operations according to FIGS. 2a to 2g, also for a predetermined time interval of 50 ms in each case. Moreover, each of these current application operations according to FIGS. 2a to 2g is executed with the same amplitude.

[0089] If, in the course of the first current application operation with the first stator current vector U.sub.1 and/or in the course of the corresponding inverse current application operation with the inverse stator current vector U.sub.1*, no movement is detected, the current application operation is repeated with a higher amplitude, until such time as a movement is established. If the amplitude is increased in this case to a definable amplitude threshold value, without the detection of any movement, the first direction is established as the minimum stator current vector direction.

[0090] Specifically, moreover, further to the respective final current application operation by means of which the minimum stator current vector direction has been established, a plurality of further current application operations can be executed. In the course of this plurality of further current application operations, different stator current vectors having the minimum stator current vector direction established, and of different respective amplitudes, are imposed respectively on the stator winding. In each case, a check is executed here as to whether no driving torque acting on the rotor is generated in the synchronous machine respectively, and whether the minimum stator current vector direction established is actually the desired minimum stator current vector direction.

[0091] FIG. 3 shows an elevator system 100, having a linear motor drive system actuated according to the invention as a synchronous machine. The synchronous machine here comprises a stator 121 of longitudinal configuration, which essentially extends over the full height of the elevator shaft 101. The stator 121 generates a magnetic field which travels along the elevator shaft. A rotor 122 is securely fitted to the elevator cage 102, and is actuated by the traveling magnetic field. By means of an acceleration sensor 124 which is rigidly connected to the rotor, the smallest movements of the elevator cage and/or of the rotor 122 can be detected. Otherwise, the design and function substantially correspond to the configuration represented in FIGS. 1 and 2.

[0092] FIG. 4 shows a travelator 100 having a linear motor drive system actuated according to the invention as a synchronous machine. The synchronous machine comprises here a stator 121 of longitudinal configuration, which essentially extends over the full length of the travelator. The stator 121 generates a magnetic field which travels along the length of travel. A rotor 122 is securely fitted to a pallet 125, and is actuated by the traveling magnetic field. By means of an acceleration sensor 124, which is rigidly connected to the rotor, the smallest movements of the pallet 125 and/or of the rotor 122 can be determined.

[0093] Alternatively, positional sensors installed in the travelator can also be used to detect movements of the pallet. Otherwise, the design and function substantially correspond to the configurations represented in FIGS. 1 to 3.

LIST OF REFERENCE SYMBOLS

[0094] 100 Passenger transportation apparatus (elevator system, travelator)
101 Elevator shaft

102 Cabin

[0095] 103 Suspension rope

104 Pulley

[0096] 105 Deflection pulley

106 Counterweight

[0097] 110 Drive, pulley drive
111 Synchronous motor, rotary motor, linear motor

112 Shaft

[0098] 113 Control unit
114 Synchronous motor actuation system
121 Stator, primary part
122 Rotor, secondary part
123 Power converter circuit
124 Acceleration sensor

125 Pallet

[0099] α Coordinate axis
β Coordinate axis
F.sub.min first reference axis
F.sub.max second reference axis
U.sub.1 first stator current vector
U.sub.2 second stator current vector
U.sub.3 third stator current vector
U.sub.4 fourth stator current vector
U.sub.5 fifth stator current vector
U.sub.6 sixth stator current vector, minimum stator current vector
U.sub.1* inverse stator current vector
U.sub.2* inverse stator current vector
U.sub.3* inverse stator current vector
U.sub.4* inverse stator current vector
U.sub.5* inverse stator current vector
U.sub.6* inverse stator current vector
U.sub.max maximum stator current vector