CA2543169A1 - Controlled reluctance ac induction motor - Google Patents
Controlled reluctance ac induction motor Download PDFInfo
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- CA2543169A1 CA2543169A1 CA002543169A CA2543169A CA2543169A1 CA 2543169 A1 CA2543169 A1 CA 2543169A1 CA 002543169 A CA002543169 A CA 002543169A CA 2543169 A CA2543169 A CA 2543169A CA 2543169 A1 CA2543169 A1 CA 2543169A1
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Classifications
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K1/00—Details of the magnetic circuit
- H02K1/06—Details of the magnetic circuit characterised by the shape, form or construction
- H02K1/22—Rotating parts of the magnetic circuit
- H02K1/27—Rotor cores with permanent magnets
- H02K1/2706—Inner rotors
- H02K1/272—Inner rotors the magnetisation axis of the magnets being perpendicular to the rotor axis
- H02K1/274—Inner rotors the magnetisation axis of the magnets being perpendicular to the rotor axis the rotor consisting of two or more circumferentially positioned magnets
- H02K1/2753—Inner rotors the magnetisation axis of the magnets being perpendicular to the rotor axis the rotor consisting of two or more circumferentially positioned magnets the rotor consisting of magnets or groups of magnets arranged with alternating polarity
- H02K1/278—Surface mounted magnets; Inset magnets
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K19/00—Synchronous motors or generators
- H02K19/02—Synchronous motors
- H02K19/10—Synchronous motors for multi-phase current
- H02K19/103—Motors having windings on the stator and a variable reluctance soft-iron rotor without windings
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K1/00—Details of the magnetic circuit
- H02K1/06—Details of the magnetic circuit characterised by the shape, form or construction
- H02K1/22—Rotating parts of the magnetic circuit
- H02K1/223—Rotor cores with windings and permanent magnets
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Synchronous Machinery (AREA)
- Control Of Electric Motors In General (AREA)
Abstract
An electric motor operated by AC current, that includes a stator (11) and a rotor (14) supported for rotation about an axis relative to the stator. The stator is provided with field windings (12) angularly distributed about the rotor axis and capable of producing a magnetic field vector in the space of the rotor. Circuitry delivers AC current to the windings in a manner that produces an AC magnetic field vector that moves about the axis of the rotor.
The rotor has a construction, such as an axially extending conductive loop (17), that changes its reluctance in the AC magnetic field depending on its orientation to the AC magnetic field vector whereby the rotor is caused to rotate in synchronization with the movement of the AC magnetic field vector.
The rotor has a construction, such as an axially extending conductive loop (17), that changes its reluctance in the AC magnetic field depending on its orientation to the AC magnetic field vector whereby the rotor is caused to rotate in synchronization with the movement of the AC magnetic field vector.
Description
2 The invention relates generally to the field of 3 electric motors and specifically to an AC motor with 4 improved performance characteristics.
' PRIOR ART
6 Many types of electric motors are known to the 7 industry. Typically, these known motors have certain desirable characteristics such as high starting torque, 9 variable speed and/or high power density. Often, however, a motor with desirable characteristics for a 11 given application has certain disadvantages or 12 deficiencies. These undesirable characteristics often 13 include relatively high cost, electrical circuit 14 complexity, radio frequency or electromagnetic interference; energy inefficiency, limited reliability 16 and/or comparatively short service life.
1~ The invention provides an AC power operated 19 electric motor that exhibits desirable torque/speed characteristics when operated in an open loop condition 21 and is effectively speed and/or torque controlled with 22 relatively simple and economical electrical circuitry.
23 The motor has a stator with field windings that are 24 energized with alternating current and that, in one embodiment, are arranged to induce an AC current in a 26 conductive loop on a rotor or armature. In various 27 configurations of the motor, the field windings 2~ comprise at least two coils angularly displaced from 29 one another around the rotor axis. The positions of the windings in some configurations represent 31 physically or mechanically distinct phases.
1 The AC stator field is caused to move about the 2 axis of the rotor and, in the aforementioned 3 embodiment,~the induced AC field in the conductive loop 4 produces a torque on the rotor causing it to rotate in synchronization with the field rotation. The rotation 6 of the stator field is produced by switching or 7 appropriately modulating AC power to successive 8 angularly displaced field coils.
9 The motor can be arranged with 2, 4, 6 or even a greater number of even poles and with as many field 11 winding phases as suitable for a particular 12 application. Motor torque, and therefore power, is 13 multiplied in proportion to the number of poles 14 provided in the motor. The motor has open loop speed/torque characteristics approaching the desirable 16 ideal of constant horsepower. These characteristics 17 include high starting torque and high speed at low 18 load.
19 In another embodiment of the invention, the rotor comprises a cylindrical body formed of magnetic 21 material such as a stack of magnetic silicon steel 22 laminations having a diametral air gap running the 23 axial length of the laminations. The reluctance of the 24 air gap causes the rotor to synchronize its rotation with the rotation of the magnetic field produced by the 26 stator in a manner analogous to that described with the 27 first embodiment. The air gap rotor has the potential 28 of high operating efficiency since there are no 29 substantial I2R losses associated with currents induced in the rotor. In still another embodiment, the 31 diametral air gap in the rotor can be filled with an 32 electrically conductive non-magnetic plate or body to 33 increase the torque developed in the rotor.
1 Importantly, the motor lends itself to relatively 2 simple and energy efficient speed, control and/or torque 3 control. A standard speed control over a 10:1 ratio is 4 readily achieved. Rated torque can be achieved at zero speed with proper circuitry and therefore the speed 6 r-ange can be from zero to the maximum rated speed.
7 Some of the additional advantages of the motor include 8 low stall current, operation on simple square wave 9 power.without difficulty with harmonics, anal increased power and/or torque for a given physical size motor as 11 compared to conventional induction motors, fo.r example.
13 FIG. 1 is a schematic perspective view of a motor 14 illustrating principles of the invention;
FIG. 2 is a generalized graph illustrating the 16 relationship of torque versus rotor deflection angle I7 for motors onstructed in accordance with the c 18 invention; ' I9 FIG. 3 is a schematic perspective view of a motor constructed in accordance with the invention;
21 FIG. 4 is an electrical circuit diagram of a 22 controller or the motor of FIG. 3;
f 23 FIG. 5 is a generalized graph illustrating the 24 relationship of speed versus torque of a motor constructed in accordance with the invention;
26 FIG. 6A is a diagram of square wave power 27 available om an inverter illustrated in FIG. 7;
fr 28 FIG. 6B is a diagram of a modified square wave 29 power signal produced by the Circuit of FIG. 7; ' FIG. 7 is a circuit diagram for controlling the 31 speed of the motor of FIG. 3;
1 FIGS. 8A through SD are diagrammatic 2 representations of signals developed in the circuit of 3 FIG. 7;
4 FIG. 9 is a diagrammatic illustration of a system for controlling the speed of a motor constructed in 6 accordance with the invention;
7 FIG. 10 is a schematic illustration of a motor arranged for speed control by the control system of 9 FIG. 9;
FIG. 11 is an alternative circuit for driving the 11 motor of FIG.
3;
12 FIG. 12 is a schematic representation of a motor 13 of the invention having field windings arranged in 14 qu.adrature;
FIG. 13 is a circuit for driving the motor of FIG.
16 12;
17 FIG. 14 is a schematic perspective view of a four 18 pole three-phase motor constructed in accordance with 19 the invention;
FIG. 15 is a diagrammatic illustration of the 21 field vectors one of the windings of the motor of of 22 FIG. 14;
23 FIG. 16 is a diagrammatic representation of a 24 rotor for use the motor of the invention in in accordance with a second embodiment; and 26 FIG. l7 is a diagrammatic representation of a 27 rotor for use the motor of the invention in in 2~ accordance with a third embodiment.
Referring now to FIG. 1, a motor 10 has a stator 31 11 with a field winding 12 and a rotor or armature 14 32 supported~by suitable bearing structure for rotation 1 about an axis 16. The winding 12 is arranged in two 2 sections or portions 12a, 12b on diametrally opposite 3 sides of the rotor 14'. The rotor 14 has a conductive 4 loop 17 that has two diametrically opposite portions 18 5 near the periphery of the rotor that extend parallel to 6 the rotor axis 16 and two end portions 19. A main body 7 21 of the rotor 14 can be constructed of suitable 8 magnetic silicon steel laminations in a manner known in 9 the art. The two loop portions 18 that extend 10- longitudinally of the rotor lie in a common plane that 11 passes through the rotor axis 16. For purposes of this 12 disclosure, the plane of the conductive loop 17 is 13 taken as the plane of the conductor portions 18. The 14 conductive loop 17, which can be made of copper or aluminum, for example, is electrically continuous; the 16 end portions 19 shunt the longitudinal portions 18.
17 The stator 11 has its fief. windings 12a, 12b wound 18 about suitable magnetic material such as a stack of 19 magnetic silicon steel laminations 22a and b.
When the field coil or winding 12 is energized 21 with an AC voltage, a magnetic.field is created with a 22 vector that is parallel to an axis 23 extending between 23 the windings 12a, b. With the field coil 12 thus 24 energized with an AC voltage, when the rotor 14 is displaced from the. illustrated solid line position 26 through an angle ~r magnetic field conditions urge the 27 rotor 14 to return to the solid line position where the 28 plane of the conductive loop 17 is aligned with the 29 field axis~23. That is, the magnetic field conditions urge the rotor 14 to the position where the angle tar is 31 0.
32 FIG. 2 is a generalized diagram of the 33 relationship betweeiz. torque and angular displacement ~r .
1 The diagram shows that the torque tending to move the 2 rotor Z4 towards the position of alignment with the 3 axis 23 increases proportionately with the displacement 4 or angle fir. Torque reaches a maximum value at about S 70°; at displacements beyond this, the torque 6 diminishes . At ~r equal to 90°, i . a . when the plane of 7 the conductive loop 17 is transverse to the direction 8 of the field vector of the winding 12, the torque 9 reduces to 0. This ~r = 90° position can be called a hard neutral while the position at ~r equal to 0 can be 11 called a soft neutral.
12 When the plane of the conductive loop 17 is turned.
13 from alignment with the field vector of the stator 11, 14 i.e. tar not equal to 0, the AC magnetic field produced by the winding 12 induces an AC current in the 16 conductive loop 17. This rotor current produces its 17 own magnetic field which opposes the stator field. The 18 opposing field produced by the conductive loop 17 19 increases the reluctance of the flux path of the stator field. It can be shown that in an electromechanical 21 system, such as the motor 10 illustrated in FIG. 1, 22 physical laws,work to reduce the reluctance in the 23 system. Consequently, the motor 10 behaves as 24 discussed with the rotor 14 being urged to a position 2S where the plane of the conductive loop 17 is aligned 26 with the axes 23 and the reluctance of the motor system 27 being reduced.
28 The motor 10 of FIG. 1, as so far described, is 29 not practical as a general purpose rotating motor since it cannot sustain continuous rotation of the rotor. ' 31 However, the motor s characteristics, as described, are 32 helpful in understanding the operation of other motors, 1 constructed in accordance with the invention, such as 2 those described hereinbelow.
3 FIG. 3 diagrammatically shows a motor 26 that 4 applies the foregoing principles in a two pole rotor 14, like that described with reference to FIG. 1, but 6 with a three phase stator 28. (The "two pole"
7 designation pertains to the rotor or armature and 8 derives from north and south magnetic poles produced by 9 the conductive loop 17 when the loop is in an AC
magnetic field.) The stator 28 typically includes a 11 body formed by a stack of laminations of suitable 12 magnetic silicon steel with internal axially oriented 13 slots 30 distributed about the periphery of the rotor 14 14 as is generally conventional in motor construction.
A winding A has turns wrapped axially around the rotor.
16 The turns include longitudinal or axially oriented 17 portions disposed,in the lamination slots 30 on 18 diametrically opposite sides of the rotor 14 and end 19 portions circumferentially looped around the axial projection of the rotor in a manner known in the motor 21 art. The longitudinal portions of the turns of the.
22 winding A are~geometrically centered on a plane 23 represented at 31 that passes through the rotor axis 24 16. For clarity, only the winding A is illustrated. in FIG. 3 and it will be understood that the other 26 windings B and C are similar in construction. The 27 planes o~ the windings A, B and C are oriented at 120°
28 relative to one another with reference to the axis 14 29 of rotation of the rotor 14 and pass through this axis so that adjacent portions o~ the windings A, B and C
31 are centered at 60° intervals. The winding A, when 32 energized with AC power develops an AC magnetic ~ield 33 vector 32 in a plane 33 perpendicular to the plane 31 1 of the winding A. The other windings B, C, similarly, 2 produce AC magnetic field vectors perpendicular to 3 'their respective planes. The windings A, B and C are 4 thus in a physical or mechanical phase relationship to one another and are electrically isolated from one 6 another. By switching or modulating AC power 7 sequentially to the mechanically phased windings A, B
8 and C, the rotor 14 will be driven in rotation. As 9 explained hereinabove, the rotor 14 will tend to align itself with the field vector of an energized winding 11 (or as discussed later the resultant field vector of 12 simultaneously energized field windings). When the 13 plane of the rotor conductive loop 17 approaches the.
14 vector of the field from one energized winding, that winding is de-energized while the adjacent winding in 16 the direction of rotor rotation is energized. By 17 continuing this field switching process, the rotor 14 18 is caused to rotate continuously.
19 FIG. 4 illustrates an example of a circuit or controller 36 suitable for driving the two pole, three 21 winding phase motor 26 of FIG. 3. The motor windings 22 are represented as A, B and C in the circuit of FIG. 4.
23 In the circuit, commercial power, e.g. 60 Hz, 110 volt, 24 single phase power is connected to lines 37, 38. This power is converted to DC in a rectifier and voltage 26 doubler circuit comprising a pair of diodes 39, 41 and 27 capacitors 42, 43. Positive and negative voltages are 28 developed on respective lines or busses 46, 47.
29 Square wave AC power is supplied independently to each winding A, B or C from paired power mosfet 32 switches 51, 52 associated with each winding. One of 32 the mosfet switches 51 supplies positive voltage while 33 the other 52 supplies negative voltage. thereby 1 producing an AC power signal. The mosfet switches 51, 2 52 are driven by an associated integrated circuit 53 3 (such as an IR 2104). These drivers 53 are powered by 4 a suitable 12 volt DC source. Each driver 53 alternately operates the associated mosfets 51, 52 at a 6 frequency imposed by a frequency generator 54 (such as 7 an MCI 4046) signaling from its output (pin 4) to an 8 input (pin 2) of each driver 53. The frequency can be 9 any suitable frequency, preferably higher than commercial power of 60 or 50 Hz. A typical frequency 11 can be between 100 to 250 Hz but can be higher if 12 design parameters require such and appropriate 13 materials are used.
14 A shaft encoder 56 (FIG. 3) of any suitable type 1.5 and preferably a non-contact type monitors the angular 16 position of the rotor 27 and, therefore, the plane of 17 the conductive loop 17. In the illustrated example of 18 ~ FIG. 3, the shaft encoder 56 senses when a 60° arc on a 19 drum rotating with the rotor 14 associated with each winding A, B or C passes the reference point of a non-21 rotating part 59 of the encoder fixed relative to the 22 stator 28. The drum 57 of the encoder 5-6 is divided 23 into three channels, each channel corresponding to one 24 of the field windings A, B or C. The encoder 56 signals the driver 53 of a particular field winding A, 26 B or C when an angular sector on the drum 57 associated 27 with that particular winding is in proximity to the 28 non-rotating part 59 of the~encoder. The encoder 56 29 maintains the signal to the appropriate driver 53 for a time in which a field winding A,. B or C develops a 31 relatively large torque on the rotor. This period will 32 be, roughly when the plane of the conductive loop 17 is 33 between. 75 and 15° out of alignment with the magnetic I field vector of a particular winding (i.e. 75°_> ~r >_ 2 15°) .
3 The time period or, more properly, the angular 4~ duration of energization of a particular field A, B or 5 C can be set by the geometry of the codes on the drum 6 57 of the encoder 56. The drum 57 may be encoded with 7 arcs of detectable material that have a dwell of 60°.
8 This geometry allows each winding, where there are 9 three windings, to be energized twice for each 10 revolution of the rotor 14. While a driver 53 is 11' enabled (i.e. turned on) from a channel of the encoder 12 56, the driver cycles the associated mosfet switches 13 51, 52 on and off at the frequency produced by the 14 frequency generator 54. The mosfet switches 51, 52 thereby apply a square wave AC power signal, at the 16 frequency of the generator 54, to the associated field 17 winding A, B or C. With the circuit of FIG. 4 when one 18 of the windings A, B or C is energized the other two 19 windings are inactive.
The motor 26 of FIG. 3, driven by the open loop 21 circuit 36 of FIG. 4 has a desirable speed torque curve 22 schematically illustrated in FIG. 5. It will be seen 23 that the motor 26 approaches a constant horsepower 24 device. Additionally, the motor 26 is characterized by relatively high starting torque and is capable of 26 relatively high speed operation. A motor operating 27 with the principles of the motor 26 discussed in 28 connection with FIGS. 3 and 4 can be constructed with 29 more field windings or field phases. The windings, typically, can be evenly spaced around the stator and 31 suitable corresponding additional driver circuits and a 32 modified shaft encoder can be employed. Such a motor 1 has the advantage of less torque ripple than that of 2 the illustrated three phase motor 26.
3 ~ The speed of the motor 26 and like motors can be 4 controlled by either controlling the power delivered to .the motor or by controlling the position of the shaft 6 encoder signals relative to the stator. Each method 7 can have many variations. Controlling the power to the 8 motor may be implemented very simply, but such control 9 may not necessarily produce the best efficiency over a wide speed range. Controlling the relative positions 11 of the encoder signals may produce better efficiency, 12 but may be more complex in circuit implementation for 13 certain applications. In some applications, a 14 combination of both methods may be useful.
One way of controlling power for speed control is 16 to control the width of each i~ cycle of a voltage 17 square wave delivered to the motor. Full power of the 18 square wave is applied when each half cycle occupies 19 the total time of one half period as depicted in FIG.
6A. If the beginning of each half cycle is delayed by 21 some fraction of the half period, as depicted in FIG.
22 6B, then the total amount of power delivered to the 23 motor is reduced. The motor is not sensitive to 24 waveform (does not need sine waves) so that only the total energy per half cycle is significant. There are 26 many ways to implement this kind of control; a simple 27 version is shown in FIG. 7. This circuit is used in 28 conjunction with the circuit of FIG. 4. The frequency 29 generator 54 is redrawn here. As will be understood from the following discussion, the circuit of FIG. 7 is 31 interposed in the lines from the encoder 56 to the 32 drives,53 for the field windings A, B and C. The 33 frequency signal output of the frequency generator 54 I is 'fed into pin 2 of IC 12 which is a four stage binary 2 counter. Each stage divides the frequency by 2. At 3 pin 6 of IC 12 (the output of the 4th stage), the 4 frequency is 1/16 of the input at pin 2. The output frequency at pin 6 is fed into the driver stages 53 (at 6 pin 2) of each power mosfet switch 51, 52 (FIG. 4) that 7 delivers power to a particular stator winding phase or 8 coil A, B or C. In this arrangement, the freq-U.ency 9 generator 54 is typically set,to.a frequency that is 16 times greater than what is used in the original circuit 11 in FTG. 4.' The binary outputs from the other three 12 stages are connected to a summing resistor network 61 13 at the input of an operational amplifier~designated as I4 IC 13 at pin 2. The output signal at pin 1 of IC 13 will appear as a sawtooth waveform and will be related I6 to the square wave output on pin 6 of TC 12 as shown in 17 FIGS. 8A and 8B, respectively.
18 A speed command signal and a speed feedback signal 19 (e. g. derived from the shaft encoder) are summed algebraically at pin 9 of IC 13 and the difference 21 (speed error signal) is produced at pin 8 of IC 13. At 22 pin.rl4 of IC 13 the polarity inversion of the error is 23 signal. The error signal is then compared with the 24 sawtooth waveform by the comparator circuit composed of pins 6, 5 and 7 of IC 13. With reference to FIG. SC, 26 when the magnitude of the error signal is below the 27 sawtooth level, th e output of pin 7 is 0; when the 28 magnitude of the rror signal is above the sawtooth e 29 level, the output of pin 7 is positive (a logic 1").
This output signal modulates the encoder signals that 31 feed into the power mosfet drivers 53. In essence, the 32 signal controls the turn on of each driver 53 at its 33 pin 3. This is accomplished by dual input "and" gates l shown as IC 14 (MC 14081B). Signals from the encoder 2 56 feed into one gate input and the signal from pin 7 3 of IC 13 feeds into the second gate input. The output 4 of each gate IC 14 then feeds into the pin 3 of a respective driver 53. The result is a power signal 6 applied to the motor field windings A, B or C as shown 7 in FIG. 6D. As the speed error signal varies in 8 magnitude, the width of each half cycle will vary in 9 accordance. Where the power is supplied as a sine wave, such as from commercial power, a speed control 11 circuit can be arranged to eliminate the beginning of 12 each half cycle, typically in the manner an SCR is 13 regularly used in like. service.
14 The second method that can be used for speed control is to shift the encoder signals to different 16 phase or winding drivers in accordance to the magnitude 17 of the speed error signal. FIG. 9 illustrates 18 circuitry to accomplish this. The select signal is 19 derived from the speed control error signal.
A motor 62 schematically shown in FIG. 10 has 21 eight field windings (a - h) and, accordingly, eight 22 driver circuits (corresponding to elements 53, 51 and 23 52 in FIG. 4). The field windings a - h are like the 24 windings A, B and C in FIG. 3, If a shaft position.
encoder or sensor 63 has its signals directed to turn 26 on the field coils which produce the maximum torque, 27 then the motor speed will increase to the point where 28 the load torque is equal to the produced or developed 29 motor torque. To reduce the torque and lower the speed, it is necessary to direct the signals of the 31 position encoder 63 to different field coils. Speed 32 control can thus be obtained by switching the encoder, 33 signals to different coils, in response to the speed 1 control error signal. The plane of the armature 2 conductive loop 17 is shown in relationship to the 3 field coil position labeled a - h. If coil a is 4 energized, maximum torque is generated in the counter-s clockwise direction. A magnetic field vector 64 of 6 winding a is perpendicular to the plane of winding a.
7 If field coil b were energized, a lesser torque would 8 be created, and if field coil c were energized, an even 9 lesser torque would be developed. By shifting the encoder connection to energize different coils, the 1I torque is controlled. By using the speed error signal 12 to~determine the switching, the motor speed can be 13 regulated. The speed error signal magnitude is I4 compared to fixed signal voltage levels that are stepped by fixed increments. When the speed error 16 exceeds each fixed level, a new connection arrangement 17 is made.between the encoder and the field coils. For I8 example,~with eight field coils, suppose that at the 19 maximum level, encoder output A controls coil a and encoder B controls coil b, etc. Then, when the error 21 signal drops to the next level, a logic switching 22 action, takes place in a multiplex gate 63 (FTG. 9) to 23 connect encoder output A to coil b, and encoder output 24 B to coil c, encoder C to coil d, etc. Then, when the error signal drops to the next level down (third 26 level), the logic switching action connects encoder 27 output A to coil c, and encoder output B to coil d, 28 encoder output C to coil e, etc. Thus, the control 29 acts to shift the position of the encoder signals in - proportion to the magnitude of the error signal. This 31 action will then increase or decrease torque and, 32 accordingly, increase or decrease speed.
1 FTG. 11 shows an alternative controller or circuit 2 70, of simplified design, for operating the motor 26..
3 Single phase alternating current power such as 110 volt 4 60 Hz commercial power is supplied to the windings A, B
5 and C through corresponding triacs 71 or other 6 electrically controllable switches. A frequency 7 generator 73, (MCI 4046) produces a series of pulses 8 having a frequency~that is proportional to the voltage 9 set by a potentiometer 72. The pulses~are input to a 10 counter 74 such as a CMOS 4017. The three outputs of 11 the counter 74 are applied to sequentially fire the 12 , triacs 71 through a buffer 76 such as a CMOS 4049 13 inverting buffer that feeds the opto isolator trigger 14 to each triac. The counter 74 assures that the 15 windings or phases A, B and C are triggered 16 sequentially at a rate corresponding to the frequency 17 set by the voltage at the potentiometer 72. The motor I8 26, when operated by the circuit of FIG. 11, will run 19 at a speed synchronous with the rate that the field windings A, B and C are triggered. The circuit 70 with 21 the adjustable potentiometer 72 and variable frequency 22 of the generator 73 thus provides a simple method of 23 speed control for the motor 26.. As this circuit 70 of 24 FIG. 11 suggests, the motor 26 and others constructed like it in accordance with the invention can be 26 operated directly off a commercial single phase power 27 supply such as, for example, 120 volt 60Hz-power where 28 high speed operation is not required. Conversely, this 29 motor 26 and the circuit 70 can be supplied with a higher frequency power supply where it is desired to 31 operate the motor at higher speeds. Innumerable other 32 control systems and circuits are suitable for operating 33 a motor constructed in accordance with the invention as 1 will be apparent from an understanding of the present 2 disclosure. .
3 A flux vector drive is also contemplated for the 4 motor of the invention. Referring to FIG. 12, a simple field winding configuration for a two winding two pole 6 motor 80 is shown. Stator field or phase windings X, Y
7 are physically located in quadrature and labeled X and 8 Y to correspond with x and y axes. The windings X, Y
9 create magnetic flux vectors along the corresponding x and y axes. Currents flowing through both sets of 11 windings X and Y create a magnetic field flux vector 81 12 which is the vector sum of the individual magnetic flux 13 vectors created by the currents in the separate I4 windings X, Y. A vector angle O of the vector varies with respect to the X axis depending on respective 16 magnitudes of the currents in windings X, Y.
17 The magnitudes of the AC currents in the windings 18 X, Y are 19 IX=cos0 sin2nf~t; and IY=sin0 sin2nf~t;
21 where f~ is the frequency of the current supplied, such 22 as 60 Ha. The field flux vector 81 represents an 23 alternating magnetic field with the frequency f~. The 24 field flux vector 81 can be positioned at any angle O
by varying the currents in the field windings X, Y
26 according to the following relationship:
2~
_ r . e=sin . 1 ~ 'IX ~~Y
29 ~ . _. _.
The motor 80 has a rotor 14 like.that described in 31 connection with FIG. 1; the plane of the conductive 32 loop 17 is displaced from the'X axis by a rotor angle 1 ~. The rotor 14 rotates synchronously at the speed 2 that the field vector 81 is rotated. As discussed 3 below, the.field windings can be supplied with 4 modulated AC currents from power amplifiers operated by a signal processor to appropriately rotate the magnetic 6 field vector 81. -7 By creating and controlling a difference between 8 the field flux vector angle O and the rotor angle ~, 9 the torque output of the motor 80 can be controlled.
That is, the torque is controlled by controlling the 11 relative positions of the field flux vector and the 12 plane of the conductive loop 17 on the rotor 14. As 13 discussed previously with reference to FIG. 2, torque 14 is developed when the rotor or armature 14 is located where there is an angular deflection ~r between the 16 plane of the conductive loop 17 and the flux vector 17 between the winding portions 12a, b; this torque varies 18 with the magnitude of the angle fir. Similarly, in FIG.
19 12, the torque varies with the difference between the flux vector angle O and-the rotor angle ~. Note the 21 relationship ~r = O - ~ . -22 As previously discussed, the vector angle 0 is~
23 varied by varying the current amplitudes in the field 24 windings X, Y. Since the currents are AC, the field currents will be suppressed carrier amplitude modulated 26 sine waves that can be represented as:
27 IX=cos (c~Rt~~r) sin2nf~t ; and 28 IY=sin (c~Rt~~r) sin2nf~t ;
29 where c~R is the rotational speed of the rotor 14. The angular deflection ~r with respect to the field flux 31 vector is.determined by the respective field currents 32 Ix, IY and the angular velocity c~R, ~~r=s in-1 - ~-3 Referencing FIG. 2, the deflection angle 1[r is 4 varied to achieve the desired torque characteristics by varying the currents IX, IY. The rotor position ~ is 6 sensed, for example, by a transducer or electrical 7 parameters. Rotor position information is used to 8 control the flux vector position O to maintain the 9 desired deflection ~r and, therefore, the motor torque.
A flux vector control circuit 85 that applies the 'l1 foregoing principles and relationships of field 12 current, field vector and rotor angle for torque 13 control is shown in FTG. 13. The control 85 includes a 14 signal processor 86 with two outputs for generating the currents IX, Ix. The currents are fed through 16 respective power amplifiers 87 to the field windings X, 17 Y. Frequency F~ is set by a suitable frequency input.
18 A rotor position sensor 89, such as a numerical shaft 19 position sensor, provides rotor position information data to the signal processor 86. A torque command 21 input, corresponding to a deflection angle ~r is 22 provided to the signal processor to control torque.
23 The signal processor 86 in accordance with the 24 foregoing formulas generates the currents TX, IYas functions of the frequency F~, rotor position cp (which 26 indicates rotor speed wR), and torque command 27 deflection angle ~r to control the torque 28 characteristics of the motor 80. The speed of the 29 motor is controlled according to the rate c~ at which the carrier signal is modulated, which can be selected 31 by a speed input. The rotor position sensor can be 32 connected to provide speed or position feedback, 1 diagrammatically represented at 88, through a torque 2 control 84 to control the torque command angle setting 3 ~r .
4 A motor constructed in accordance with the invention can be made with four poles as schematically 6 shown in FIG. 14. The motor 90 can develop twice the 7 torque of a similarly sized two pole motor such as the 8 motor 26 in FIG. 3. The illustrated motor 90 has three 9 field winding phases designated Phase A, Phase B and Phase C. Each Phase A, B and C has f our coils 91,.92, 11 93, and 94. Each of these coils has a pair of spaced 12 axially extending portions 96 and a pair. of end turn 13 portions 97, one at each end of a stator typically of 14 suitable laminations represented by the circular line 98. The coils 91, 92, 93 and 94 are connected in 16 series with alternate coils wound in a clockwise 17 direction and intervening coils wound in counter-18 clockwise direction. Alternatively, the coils 91 - 94 19 Can be connected i:n parallel. For clarity, the coils 91 - 94 of only one phase (A) is shown, it being 21 understood that the other phases B and C are identical.
22 A rotor 99 of the motor 90 has four conductive wires or 23 rods 100 equally spaced around the circumference of the 24 rotor 99 and extending longitudinally of the rotor.
The conductors 100 are interconnected or shunted by end 26 wires or conductors 101 at each end of each conductor 27 100. The longitudinal conductors 100, like the 28 conductors 17 of the rotor 14 of FIG. 3, are parallel 29 with the axis of rotation of the rotor 99 on a shaft 95. The rotor 99 and stator 98 typically include 31 bodies formed of silicon steel laminations as 32 previously described. The windings of Phases A, B and 33 C can be energized by a circuit like that shown in 1 FIGS. 4 or 11.. Motors having a greater even number of 2 poles such as 6, 8 or more, can be constructed 3 similarly to the four pole motor of_FIG. 14 and such 4 motors will have a proportionately higher torque S capacity. .
6 As will be understood from the foregoing 7 disclosure, the motor of the invention can take various 8 forms and can be powered by innumerable electrical 9 circuit arrangements, both open and closed loop. .
10 Switches for the field windings can include triacs, 11 transistors, silicon controlled rectifiers (SCR's) and 12 magnetic amplifiers, for example. The rotor, rather 13 than having a conductive loop to present a variable 24 reluctance to the stator field, can be formed with a 1S diametrically disposed air gap (FIG. 16) or a 16 conductive plate (FIG. 17) in the plane otherwise 17 occupied by the conductive rotor loop.
28 In the embodiment of FIG. 16, a rotor is 19 diagrammatically illustrated at 120. The rotor 120 20 includes a stack of laminations 121 of magnetic silicon 21 steel. The laminations 121 can be "D" shaped elements 22 arranged on opposite sides of a diametral air gap 122.
' PRIOR ART
6 Many types of electric motors are known to the 7 industry. Typically, these known motors have certain desirable characteristics such as high starting torque, 9 variable speed and/or high power density. Often, however, a motor with desirable characteristics for a 11 given application has certain disadvantages or 12 deficiencies. These undesirable characteristics often 13 include relatively high cost, electrical circuit 14 complexity, radio frequency or electromagnetic interference; energy inefficiency, limited reliability 16 and/or comparatively short service life.
1~ The invention provides an AC power operated 19 electric motor that exhibits desirable torque/speed characteristics when operated in an open loop condition 21 and is effectively speed and/or torque controlled with 22 relatively simple and economical electrical circuitry.
23 The motor has a stator with field windings that are 24 energized with alternating current and that, in one embodiment, are arranged to induce an AC current in a 26 conductive loop on a rotor or armature. In various 27 configurations of the motor, the field windings 2~ comprise at least two coils angularly displaced from 29 one another around the rotor axis. The positions of the windings in some configurations represent 31 physically or mechanically distinct phases.
1 The AC stator field is caused to move about the 2 axis of the rotor and, in the aforementioned 3 embodiment,~the induced AC field in the conductive loop 4 produces a torque on the rotor causing it to rotate in synchronization with the field rotation. The rotation 6 of the stator field is produced by switching or 7 appropriately modulating AC power to successive 8 angularly displaced field coils.
9 The motor can be arranged with 2, 4, 6 or even a greater number of even poles and with as many field 11 winding phases as suitable for a particular 12 application. Motor torque, and therefore power, is 13 multiplied in proportion to the number of poles 14 provided in the motor. The motor has open loop speed/torque characteristics approaching the desirable 16 ideal of constant horsepower. These characteristics 17 include high starting torque and high speed at low 18 load.
19 In another embodiment of the invention, the rotor comprises a cylindrical body formed of magnetic 21 material such as a stack of magnetic silicon steel 22 laminations having a diametral air gap running the 23 axial length of the laminations. The reluctance of the 24 air gap causes the rotor to synchronize its rotation with the rotation of the magnetic field produced by the 26 stator in a manner analogous to that described with the 27 first embodiment. The air gap rotor has the potential 28 of high operating efficiency since there are no 29 substantial I2R losses associated with currents induced in the rotor. In still another embodiment, the 31 diametral air gap in the rotor can be filled with an 32 electrically conductive non-magnetic plate or body to 33 increase the torque developed in the rotor.
1 Importantly, the motor lends itself to relatively 2 simple and energy efficient speed, control and/or torque 3 control. A standard speed control over a 10:1 ratio is 4 readily achieved. Rated torque can be achieved at zero speed with proper circuitry and therefore the speed 6 r-ange can be from zero to the maximum rated speed.
7 Some of the additional advantages of the motor include 8 low stall current, operation on simple square wave 9 power.without difficulty with harmonics, anal increased power and/or torque for a given physical size motor as 11 compared to conventional induction motors, fo.r example.
13 FIG. 1 is a schematic perspective view of a motor 14 illustrating principles of the invention;
FIG. 2 is a generalized graph illustrating the 16 relationship of torque versus rotor deflection angle I7 for motors onstructed in accordance with the c 18 invention; ' I9 FIG. 3 is a schematic perspective view of a motor constructed in accordance with the invention;
21 FIG. 4 is an electrical circuit diagram of a 22 controller or the motor of FIG. 3;
f 23 FIG. 5 is a generalized graph illustrating the 24 relationship of speed versus torque of a motor constructed in accordance with the invention;
26 FIG. 6A is a diagram of square wave power 27 available om an inverter illustrated in FIG. 7;
fr 28 FIG. 6B is a diagram of a modified square wave 29 power signal produced by the Circuit of FIG. 7; ' FIG. 7 is a circuit diagram for controlling the 31 speed of the motor of FIG. 3;
1 FIGS. 8A through SD are diagrammatic 2 representations of signals developed in the circuit of 3 FIG. 7;
4 FIG. 9 is a diagrammatic illustration of a system for controlling the speed of a motor constructed in 6 accordance with the invention;
7 FIG. 10 is a schematic illustration of a motor arranged for speed control by the control system of 9 FIG. 9;
FIG. 11 is an alternative circuit for driving the 11 motor of FIG.
3;
12 FIG. 12 is a schematic representation of a motor 13 of the invention having field windings arranged in 14 qu.adrature;
FIG. 13 is a circuit for driving the motor of FIG.
16 12;
17 FIG. 14 is a schematic perspective view of a four 18 pole three-phase motor constructed in accordance with 19 the invention;
FIG. 15 is a diagrammatic illustration of the 21 field vectors one of the windings of the motor of of 22 FIG. 14;
23 FIG. 16 is a diagrammatic representation of a 24 rotor for use the motor of the invention in in accordance with a second embodiment; and 26 FIG. l7 is a diagrammatic representation of a 27 rotor for use the motor of the invention in in 2~ accordance with a third embodiment.
Referring now to FIG. 1, a motor 10 has a stator 31 11 with a field winding 12 and a rotor or armature 14 32 supported~by suitable bearing structure for rotation 1 about an axis 16. The winding 12 is arranged in two 2 sections or portions 12a, 12b on diametrally opposite 3 sides of the rotor 14'. The rotor 14 has a conductive 4 loop 17 that has two diametrically opposite portions 18 5 near the periphery of the rotor that extend parallel to 6 the rotor axis 16 and two end portions 19. A main body 7 21 of the rotor 14 can be constructed of suitable 8 magnetic silicon steel laminations in a manner known in 9 the art. The two loop portions 18 that extend 10- longitudinally of the rotor lie in a common plane that 11 passes through the rotor axis 16. For purposes of this 12 disclosure, the plane of the conductive loop 17 is 13 taken as the plane of the conductor portions 18. The 14 conductive loop 17, which can be made of copper or aluminum, for example, is electrically continuous; the 16 end portions 19 shunt the longitudinal portions 18.
17 The stator 11 has its fief. windings 12a, 12b wound 18 about suitable magnetic material such as a stack of 19 magnetic silicon steel laminations 22a and b.
When the field coil or winding 12 is energized 21 with an AC voltage, a magnetic.field is created with a 22 vector that is parallel to an axis 23 extending between 23 the windings 12a, b. With the field coil 12 thus 24 energized with an AC voltage, when the rotor 14 is displaced from the. illustrated solid line position 26 through an angle ~r magnetic field conditions urge the 27 rotor 14 to return to the solid line position where the 28 plane of the conductive loop 17 is aligned with the 29 field axis~23. That is, the magnetic field conditions urge the rotor 14 to the position where the angle tar is 31 0.
32 FIG. 2 is a generalized diagram of the 33 relationship betweeiz. torque and angular displacement ~r .
1 The diagram shows that the torque tending to move the 2 rotor Z4 towards the position of alignment with the 3 axis 23 increases proportionately with the displacement 4 or angle fir. Torque reaches a maximum value at about S 70°; at displacements beyond this, the torque 6 diminishes . At ~r equal to 90°, i . a . when the plane of 7 the conductive loop 17 is transverse to the direction 8 of the field vector of the winding 12, the torque 9 reduces to 0. This ~r = 90° position can be called a hard neutral while the position at ~r equal to 0 can be 11 called a soft neutral.
12 When the plane of the conductive loop 17 is turned.
13 from alignment with the field vector of the stator 11, 14 i.e. tar not equal to 0, the AC magnetic field produced by the winding 12 induces an AC current in the 16 conductive loop 17. This rotor current produces its 17 own magnetic field which opposes the stator field. The 18 opposing field produced by the conductive loop 17 19 increases the reluctance of the flux path of the stator field. It can be shown that in an electromechanical 21 system, such as the motor 10 illustrated in FIG. 1, 22 physical laws,work to reduce the reluctance in the 23 system. Consequently, the motor 10 behaves as 24 discussed with the rotor 14 being urged to a position 2S where the plane of the conductive loop 17 is aligned 26 with the axes 23 and the reluctance of the motor system 27 being reduced.
28 The motor 10 of FIG. 1, as so far described, is 29 not practical as a general purpose rotating motor since it cannot sustain continuous rotation of the rotor. ' 31 However, the motor s characteristics, as described, are 32 helpful in understanding the operation of other motors, 1 constructed in accordance with the invention, such as 2 those described hereinbelow.
3 FIG. 3 diagrammatically shows a motor 26 that 4 applies the foregoing principles in a two pole rotor 14, like that described with reference to FIG. 1, but 6 with a three phase stator 28. (The "two pole"
7 designation pertains to the rotor or armature and 8 derives from north and south magnetic poles produced by 9 the conductive loop 17 when the loop is in an AC
magnetic field.) The stator 28 typically includes a 11 body formed by a stack of laminations of suitable 12 magnetic silicon steel with internal axially oriented 13 slots 30 distributed about the periphery of the rotor 14 14 as is generally conventional in motor construction.
A winding A has turns wrapped axially around the rotor.
16 The turns include longitudinal or axially oriented 17 portions disposed,in the lamination slots 30 on 18 diametrically opposite sides of the rotor 14 and end 19 portions circumferentially looped around the axial projection of the rotor in a manner known in the motor 21 art. The longitudinal portions of the turns of the.
22 winding A are~geometrically centered on a plane 23 represented at 31 that passes through the rotor axis 24 16. For clarity, only the winding A is illustrated. in FIG. 3 and it will be understood that the other 26 windings B and C are similar in construction. The 27 planes o~ the windings A, B and C are oriented at 120°
28 relative to one another with reference to the axis 14 29 of rotation of the rotor 14 and pass through this axis so that adjacent portions o~ the windings A, B and C
31 are centered at 60° intervals. The winding A, when 32 energized with AC power develops an AC magnetic ~ield 33 vector 32 in a plane 33 perpendicular to the plane 31 1 of the winding A. The other windings B, C, similarly, 2 produce AC magnetic field vectors perpendicular to 3 'their respective planes. The windings A, B and C are 4 thus in a physical or mechanical phase relationship to one another and are electrically isolated from one 6 another. By switching or modulating AC power 7 sequentially to the mechanically phased windings A, B
8 and C, the rotor 14 will be driven in rotation. As 9 explained hereinabove, the rotor 14 will tend to align itself with the field vector of an energized winding 11 (or as discussed later the resultant field vector of 12 simultaneously energized field windings). When the 13 plane of the rotor conductive loop 17 approaches the.
14 vector of the field from one energized winding, that winding is de-energized while the adjacent winding in 16 the direction of rotor rotation is energized. By 17 continuing this field switching process, the rotor 14 18 is caused to rotate continuously.
19 FIG. 4 illustrates an example of a circuit or controller 36 suitable for driving the two pole, three 21 winding phase motor 26 of FIG. 3. The motor windings 22 are represented as A, B and C in the circuit of FIG. 4.
23 In the circuit, commercial power, e.g. 60 Hz, 110 volt, 24 single phase power is connected to lines 37, 38. This power is converted to DC in a rectifier and voltage 26 doubler circuit comprising a pair of diodes 39, 41 and 27 capacitors 42, 43. Positive and negative voltages are 28 developed on respective lines or busses 46, 47.
29 Square wave AC power is supplied independently to each winding A, B or C from paired power mosfet 32 switches 51, 52 associated with each winding. One of 32 the mosfet switches 51 supplies positive voltage while 33 the other 52 supplies negative voltage. thereby 1 producing an AC power signal. The mosfet switches 51, 2 52 are driven by an associated integrated circuit 53 3 (such as an IR 2104). These drivers 53 are powered by 4 a suitable 12 volt DC source. Each driver 53 alternately operates the associated mosfets 51, 52 at a 6 frequency imposed by a frequency generator 54 (such as 7 an MCI 4046) signaling from its output (pin 4) to an 8 input (pin 2) of each driver 53. The frequency can be 9 any suitable frequency, preferably higher than commercial power of 60 or 50 Hz. A typical frequency 11 can be between 100 to 250 Hz but can be higher if 12 design parameters require such and appropriate 13 materials are used.
14 A shaft encoder 56 (FIG. 3) of any suitable type 1.5 and preferably a non-contact type monitors the angular 16 position of the rotor 27 and, therefore, the plane of 17 the conductive loop 17. In the illustrated example of 18 ~ FIG. 3, the shaft encoder 56 senses when a 60° arc on a 19 drum rotating with the rotor 14 associated with each winding A, B or C passes the reference point of a non-21 rotating part 59 of the encoder fixed relative to the 22 stator 28. The drum 57 of the encoder 5-6 is divided 23 into three channels, each channel corresponding to one 24 of the field windings A, B or C. The encoder 56 signals the driver 53 of a particular field winding A, 26 B or C when an angular sector on the drum 57 associated 27 with that particular winding is in proximity to the 28 non-rotating part 59 of the~encoder. The encoder 56 29 maintains the signal to the appropriate driver 53 for a time in which a field winding A,. B or C develops a 31 relatively large torque on the rotor. This period will 32 be, roughly when the plane of the conductive loop 17 is 33 between. 75 and 15° out of alignment with the magnetic I field vector of a particular winding (i.e. 75°_> ~r >_ 2 15°) .
3 The time period or, more properly, the angular 4~ duration of energization of a particular field A, B or 5 C can be set by the geometry of the codes on the drum 6 57 of the encoder 56. The drum 57 may be encoded with 7 arcs of detectable material that have a dwell of 60°.
8 This geometry allows each winding, where there are 9 three windings, to be energized twice for each 10 revolution of the rotor 14. While a driver 53 is 11' enabled (i.e. turned on) from a channel of the encoder 12 56, the driver cycles the associated mosfet switches 13 51, 52 on and off at the frequency produced by the 14 frequency generator 54. The mosfet switches 51, 52 thereby apply a square wave AC power signal, at the 16 frequency of the generator 54, to the associated field 17 winding A, B or C. With the circuit of FIG. 4 when one 18 of the windings A, B or C is energized the other two 19 windings are inactive.
The motor 26 of FIG. 3, driven by the open loop 21 circuit 36 of FIG. 4 has a desirable speed torque curve 22 schematically illustrated in FIG. 5. It will be seen 23 that the motor 26 approaches a constant horsepower 24 device. Additionally, the motor 26 is characterized by relatively high starting torque and is capable of 26 relatively high speed operation. A motor operating 27 with the principles of the motor 26 discussed in 28 connection with FIGS. 3 and 4 can be constructed with 29 more field windings or field phases. The windings, typically, can be evenly spaced around the stator and 31 suitable corresponding additional driver circuits and a 32 modified shaft encoder can be employed. Such a motor 1 has the advantage of less torque ripple than that of 2 the illustrated three phase motor 26.
3 ~ The speed of the motor 26 and like motors can be 4 controlled by either controlling the power delivered to .the motor or by controlling the position of the shaft 6 encoder signals relative to the stator. Each method 7 can have many variations. Controlling the power to the 8 motor may be implemented very simply, but such control 9 may not necessarily produce the best efficiency over a wide speed range. Controlling the relative positions 11 of the encoder signals may produce better efficiency, 12 but may be more complex in circuit implementation for 13 certain applications. In some applications, a 14 combination of both methods may be useful.
One way of controlling power for speed control is 16 to control the width of each i~ cycle of a voltage 17 square wave delivered to the motor. Full power of the 18 square wave is applied when each half cycle occupies 19 the total time of one half period as depicted in FIG.
6A. If the beginning of each half cycle is delayed by 21 some fraction of the half period, as depicted in FIG.
22 6B, then the total amount of power delivered to the 23 motor is reduced. The motor is not sensitive to 24 waveform (does not need sine waves) so that only the total energy per half cycle is significant. There are 26 many ways to implement this kind of control; a simple 27 version is shown in FIG. 7. This circuit is used in 28 conjunction with the circuit of FIG. 4. The frequency 29 generator 54 is redrawn here. As will be understood from the following discussion, the circuit of FIG. 7 is 31 interposed in the lines from the encoder 56 to the 32 drives,53 for the field windings A, B and C. The 33 frequency signal output of the frequency generator 54 I is 'fed into pin 2 of IC 12 which is a four stage binary 2 counter. Each stage divides the frequency by 2. At 3 pin 6 of IC 12 (the output of the 4th stage), the 4 frequency is 1/16 of the input at pin 2. The output frequency at pin 6 is fed into the driver stages 53 (at 6 pin 2) of each power mosfet switch 51, 52 (FIG. 4) that 7 delivers power to a particular stator winding phase or 8 coil A, B or C. In this arrangement, the freq-U.ency 9 generator 54 is typically set,to.a frequency that is 16 times greater than what is used in the original circuit 11 in FTG. 4.' The binary outputs from the other three 12 stages are connected to a summing resistor network 61 13 at the input of an operational amplifier~designated as I4 IC 13 at pin 2. The output signal at pin 1 of IC 13 will appear as a sawtooth waveform and will be related I6 to the square wave output on pin 6 of TC 12 as shown in 17 FIGS. 8A and 8B, respectively.
18 A speed command signal and a speed feedback signal 19 (e. g. derived from the shaft encoder) are summed algebraically at pin 9 of IC 13 and the difference 21 (speed error signal) is produced at pin 8 of IC 13. At 22 pin.rl4 of IC 13 the polarity inversion of the error is 23 signal. The error signal is then compared with the 24 sawtooth waveform by the comparator circuit composed of pins 6, 5 and 7 of IC 13. With reference to FIG. SC, 26 when the magnitude of the error signal is below the 27 sawtooth level, th e output of pin 7 is 0; when the 28 magnitude of the rror signal is above the sawtooth e 29 level, the output of pin 7 is positive (a logic 1").
This output signal modulates the encoder signals that 31 feed into the power mosfet drivers 53. In essence, the 32 signal controls the turn on of each driver 53 at its 33 pin 3. This is accomplished by dual input "and" gates l shown as IC 14 (MC 14081B). Signals from the encoder 2 56 feed into one gate input and the signal from pin 7 3 of IC 13 feeds into the second gate input. The output 4 of each gate IC 14 then feeds into the pin 3 of a respective driver 53. The result is a power signal 6 applied to the motor field windings A, B or C as shown 7 in FIG. 6D. As the speed error signal varies in 8 magnitude, the width of each half cycle will vary in 9 accordance. Where the power is supplied as a sine wave, such as from commercial power, a speed control 11 circuit can be arranged to eliminate the beginning of 12 each half cycle, typically in the manner an SCR is 13 regularly used in like. service.
14 The second method that can be used for speed control is to shift the encoder signals to different 16 phase or winding drivers in accordance to the magnitude 17 of the speed error signal. FIG. 9 illustrates 18 circuitry to accomplish this. The select signal is 19 derived from the speed control error signal.
A motor 62 schematically shown in FIG. 10 has 21 eight field windings (a - h) and, accordingly, eight 22 driver circuits (corresponding to elements 53, 51 and 23 52 in FIG. 4). The field windings a - h are like the 24 windings A, B and C in FIG. 3, If a shaft position.
encoder or sensor 63 has its signals directed to turn 26 on the field coils which produce the maximum torque, 27 then the motor speed will increase to the point where 28 the load torque is equal to the produced or developed 29 motor torque. To reduce the torque and lower the speed, it is necessary to direct the signals of the 31 position encoder 63 to different field coils. Speed 32 control can thus be obtained by switching the encoder, 33 signals to different coils, in response to the speed 1 control error signal. The plane of the armature 2 conductive loop 17 is shown in relationship to the 3 field coil position labeled a - h. If coil a is 4 energized, maximum torque is generated in the counter-s clockwise direction. A magnetic field vector 64 of 6 winding a is perpendicular to the plane of winding a.
7 If field coil b were energized, a lesser torque would 8 be created, and if field coil c were energized, an even 9 lesser torque would be developed. By shifting the encoder connection to energize different coils, the 1I torque is controlled. By using the speed error signal 12 to~determine the switching, the motor speed can be 13 regulated. The speed error signal magnitude is I4 compared to fixed signal voltage levels that are stepped by fixed increments. When the speed error 16 exceeds each fixed level, a new connection arrangement 17 is made.between the encoder and the field coils. For I8 example,~with eight field coils, suppose that at the 19 maximum level, encoder output A controls coil a and encoder B controls coil b, etc. Then, when the error 21 signal drops to the next level, a logic switching 22 action, takes place in a multiplex gate 63 (FTG. 9) to 23 connect encoder output A to coil b, and encoder output 24 B to coil c, encoder C to coil d, etc. Then, when the error signal drops to the next level down (third 26 level), the logic switching action connects encoder 27 output A to coil c, and encoder output B to coil d, 28 encoder output C to coil e, etc. Thus, the control 29 acts to shift the position of the encoder signals in - proportion to the magnitude of the error signal. This 31 action will then increase or decrease torque and, 32 accordingly, increase or decrease speed.
1 FTG. 11 shows an alternative controller or circuit 2 70, of simplified design, for operating the motor 26..
3 Single phase alternating current power such as 110 volt 4 60 Hz commercial power is supplied to the windings A, B
5 and C through corresponding triacs 71 or other 6 electrically controllable switches. A frequency 7 generator 73, (MCI 4046) produces a series of pulses 8 having a frequency~that is proportional to the voltage 9 set by a potentiometer 72. The pulses~are input to a 10 counter 74 such as a CMOS 4017. The three outputs of 11 the counter 74 are applied to sequentially fire the 12 , triacs 71 through a buffer 76 such as a CMOS 4049 13 inverting buffer that feeds the opto isolator trigger 14 to each triac. The counter 74 assures that the 15 windings or phases A, B and C are triggered 16 sequentially at a rate corresponding to the frequency 17 set by the voltage at the potentiometer 72. The motor I8 26, when operated by the circuit of FIG. 11, will run 19 at a speed synchronous with the rate that the field windings A, B and C are triggered. The circuit 70 with 21 the adjustable potentiometer 72 and variable frequency 22 of the generator 73 thus provides a simple method of 23 speed control for the motor 26.. As this circuit 70 of 24 FIG. 11 suggests, the motor 26 and others constructed like it in accordance with the invention can be 26 operated directly off a commercial single phase power 27 supply such as, for example, 120 volt 60Hz-power where 28 high speed operation is not required. Conversely, this 29 motor 26 and the circuit 70 can be supplied with a higher frequency power supply where it is desired to 31 operate the motor at higher speeds. Innumerable other 32 control systems and circuits are suitable for operating 33 a motor constructed in accordance with the invention as 1 will be apparent from an understanding of the present 2 disclosure. .
3 A flux vector drive is also contemplated for the 4 motor of the invention. Referring to FIG. 12, a simple field winding configuration for a two winding two pole 6 motor 80 is shown. Stator field or phase windings X, Y
7 are physically located in quadrature and labeled X and 8 Y to correspond with x and y axes. The windings X, Y
9 create magnetic flux vectors along the corresponding x and y axes. Currents flowing through both sets of 11 windings X and Y create a magnetic field flux vector 81 12 which is the vector sum of the individual magnetic flux 13 vectors created by the currents in the separate I4 windings X, Y. A vector angle O of the vector varies with respect to the X axis depending on respective 16 magnitudes of the currents in windings X, Y.
17 The magnitudes of the AC currents in the windings 18 X, Y are 19 IX=cos0 sin2nf~t; and IY=sin0 sin2nf~t;
21 where f~ is the frequency of the current supplied, such 22 as 60 Ha. The field flux vector 81 represents an 23 alternating magnetic field with the frequency f~. The 24 field flux vector 81 can be positioned at any angle O
by varying the currents in the field windings X, Y
26 according to the following relationship:
2~
_ r . e=sin . 1 ~ 'IX ~~Y
29 ~ . _. _.
The motor 80 has a rotor 14 like.that described in 31 connection with FIG. 1; the plane of the conductive 32 loop 17 is displaced from the'X axis by a rotor angle 1 ~. The rotor 14 rotates synchronously at the speed 2 that the field vector 81 is rotated. As discussed 3 below, the.field windings can be supplied with 4 modulated AC currents from power amplifiers operated by a signal processor to appropriately rotate the magnetic 6 field vector 81. -7 By creating and controlling a difference between 8 the field flux vector angle O and the rotor angle ~, 9 the torque output of the motor 80 can be controlled.
That is, the torque is controlled by controlling the 11 relative positions of the field flux vector and the 12 plane of the conductive loop 17 on the rotor 14. As 13 discussed previously with reference to FIG. 2, torque 14 is developed when the rotor or armature 14 is located where there is an angular deflection ~r between the 16 plane of the conductive loop 17 and the flux vector 17 between the winding portions 12a, b; this torque varies 18 with the magnitude of the angle fir. Similarly, in FIG.
19 12, the torque varies with the difference between the flux vector angle O and-the rotor angle ~. Note the 21 relationship ~r = O - ~ . -22 As previously discussed, the vector angle 0 is~
23 varied by varying the current amplitudes in the field 24 windings X, Y. Since the currents are AC, the field currents will be suppressed carrier amplitude modulated 26 sine waves that can be represented as:
27 IX=cos (c~Rt~~r) sin2nf~t ; and 28 IY=sin (c~Rt~~r) sin2nf~t ;
29 where c~R is the rotational speed of the rotor 14. The angular deflection ~r with respect to the field flux 31 vector is.determined by the respective field currents 32 Ix, IY and the angular velocity c~R, ~~r=s in-1 - ~-3 Referencing FIG. 2, the deflection angle 1[r is 4 varied to achieve the desired torque characteristics by varying the currents IX, IY. The rotor position ~ is 6 sensed, for example, by a transducer or electrical 7 parameters. Rotor position information is used to 8 control the flux vector position O to maintain the 9 desired deflection ~r and, therefore, the motor torque.
A flux vector control circuit 85 that applies the 'l1 foregoing principles and relationships of field 12 current, field vector and rotor angle for torque 13 control is shown in FTG. 13. The control 85 includes a 14 signal processor 86 with two outputs for generating the currents IX, Ix. The currents are fed through 16 respective power amplifiers 87 to the field windings X, 17 Y. Frequency F~ is set by a suitable frequency input.
18 A rotor position sensor 89, such as a numerical shaft 19 position sensor, provides rotor position information data to the signal processor 86. A torque command 21 input, corresponding to a deflection angle ~r is 22 provided to the signal processor to control torque.
23 The signal processor 86 in accordance with the 24 foregoing formulas generates the currents TX, IYas functions of the frequency F~, rotor position cp (which 26 indicates rotor speed wR), and torque command 27 deflection angle ~r to control the torque 28 characteristics of the motor 80. The speed of the 29 motor is controlled according to the rate c~ at which the carrier signal is modulated, which can be selected 31 by a speed input. The rotor position sensor can be 32 connected to provide speed or position feedback, 1 diagrammatically represented at 88, through a torque 2 control 84 to control the torque command angle setting 3 ~r .
4 A motor constructed in accordance with the invention can be made with four poles as schematically 6 shown in FIG. 14. The motor 90 can develop twice the 7 torque of a similarly sized two pole motor such as the 8 motor 26 in FIG. 3. The illustrated motor 90 has three 9 field winding phases designated Phase A, Phase B and Phase C. Each Phase A, B and C has f our coils 91,.92, 11 93, and 94. Each of these coils has a pair of spaced 12 axially extending portions 96 and a pair. of end turn 13 portions 97, one at each end of a stator typically of 14 suitable laminations represented by the circular line 98. The coils 91, 92, 93 and 94 are connected in 16 series with alternate coils wound in a clockwise 17 direction and intervening coils wound in counter-18 clockwise direction. Alternatively, the coils 91 - 94 19 Can be connected i:n parallel. For clarity, the coils 91 - 94 of only one phase (A) is shown, it being 21 understood that the other phases B and C are identical.
22 A rotor 99 of the motor 90 has four conductive wires or 23 rods 100 equally spaced around the circumference of the 24 rotor 99 and extending longitudinally of the rotor.
The conductors 100 are interconnected or shunted by end 26 wires or conductors 101 at each end of each conductor 27 100. The longitudinal conductors 100, like the 28 conductors 17 of the rotor 14 of FIG. 3, are parallel 29 with the axis of rotation of the rotor 99 on a shaft 95. The rotor 99 and stator 98 typically include 31 bodies formed of silicon steel laminations as 32 previously described. The windings of Phases A, B and 33 C can be energized by a circuit like that shown in 1 FIGS. 4 or 11.. Motors having a greater even number of 2 poles such as 6, 8 or more, can be constructed 3 similarly to the four pole motor of_FIG. 14 and such 4 motors will have a proportionately higher torque S capacity. .
6 As will be understood from the foregoing 7 disclosure, the motor of the invention can take various 8 forms and can be powered by innumerable electrical 9 circuit arrangements, both open and closed loop. .
10 Switches for the field windings can include triacs, 11 transistors, silicon controlled rectifiers (SCR's) and 12 magnetic amplifiers, for example. The rotor, rather 13 than having a conductive loop to present a variable 24 reluctance to the stator field, can be formed with a 1S diametrically disposed air gap (FIG. 16) or a 16 conductive plate (FIG. 17) in the plane otherwise 17 occupied by the conductive rotor loop.
28 In the embodiment of FIG. 16, a rotor is 19 diagrammatically illustrated at 120. The rotor 120 20 includes a stack of laminations 121 of magnetic silicon 21 steel. The laminations 121 can be "D" shaped elements 22 arranged on opposite sides of a diametral air gap 122.
23 Non-magnetic end plates 123 with integral co-axial stub 24 shafts 124 are held in the illustrated assembled 2S configuration with tension rods 126 that are preferably 26 non-magnetic. Various other arrangements for 27 supporting the magnetic rotor halves or portions on~~the 28 shaft elements or their equivalent are envisioned.
29 This rotor with a suitable shaft encoder can be used in the general types of stators illustrated in FIGS. 3, 10 31 and 12. The reluctance of the air gap 122 enables the 32 rotor to follow the rotation of the field of the 33 stator. A motor employing the rotor 122 has the 1 potential of high efficiency since there is no 2 substantial I~R loss developed by induced currents in 3 the rotor.
4 FIG. 17 illustrates an embodiment of a rotor 130 similar to that of FIG. 16 (using identical reference 6 numerals for like parts) except that the air gap is 7 filled with an electrically conductive plate or body 8 131. As before, a suitable shaft encoder can be 9 employed. The motor can be used with the stators of FIGS. 3, 10 and 12. The rotor 130 has the potential of 11 producing a relatively high torque because of the high 12 magnetomotive .force that induced currents in the plate 13 131 can produce.
14 The rotor can be disposed around, rather than in, the stator. The conductive loop or loops on the rotor 16 can be skewed in a helical or like sense to reduce 17 torque ripple. The number of field windings and 18 related electronic switches, also, can be increased to 19 decrease torque ripple. Some of the turns of a particular winding can share the same stator lamination 21, slot or angular position as some of the winding turns 22 of an adj.,acent winding .
23 The motor can be supplied with a shaft encoder and 24 appropriate circuitry for operation as a stepping motor and is especially suitable for large size stepping 26 motors. A desired angular resolution for a stepping 27 motor application can be achieved by providing a 2,8' suitable number of field windings. As previously 29 discussed herein, the rotor will seek to align the plane of the conductive loop, or equivalent structure, 31 to the magnetic field vector. of a particular winding 32 that is energized. The motor is reversible simply by 1 reversing the sequence that the field. windings are 2 energized by the related circuitry.
3 A circuit powering the field windings. of the motor 4 can energize more than one field winding at a time to reduce torque ripple and/or the circuit can be arranged 6 to modulate power to the windings rather than simply 7 turning them on and off. Field windings on the stator can have various configurations besides those 9 illustrated in FIGS. 1, 3 and 14, it being important ~10, that the winding arrangement be capable of producing an 11 AC magnetic field in the space of the rotor that moves 12 around the axis of the rotor.
13 While the invention has been shown and described 14 with respect to particular embodiments thereof, this is for the purpose of illustration rather than limitation, 16 and other variations and modifications of the specific 17 embodiments herein shown and described will be apparent 18 to those skilled in the art all within the intended 19 spirit and scope of the invention. Accordingly, the patent is not to be limited in scope and effect to the -21 specific embodiments herein shown and described nor in 22 any other way that is inconsistent with the extent to 23 which the progress in the art has been advanced by the 24 invention.
29 This rotor with a suitable shaft encoder can be used in the general types of stators illustrated in FIGS. 3, 10 31 and 12. The reluctance of the air gap 122 enables the 32 rotor to follow the rotation of the field of the 33 stator. A motor employing the rotor 122 has the 1 potential of high efficiency since there is no 2 substantial I~R loss developed by induced currents in 3 the rotor.
4 FIG. 17 illustrates an embodiment of a rotor 130 similar to that of FIG. 16 (using identical reference 6 numerals for like parts) except that the air gap is 7 filled with an electrically conductive plate or body 8 131. As before, a suitable shaft encoder can be 9 employed. The motor can be used with the stators of FIGS. 3, 10 and 12. The rotor 130 has the potential of 11 producing a relatively high torque because of the high 12 magnetomotive .force that induced currents in the plate 13 131 can produce.
14 The rotor can be disposed around, rather than in, the stator. The conductive loop or loops on the rotor 16 can be skewed in a helical or like sense to reduce 17 torque ripple. The number of field windings and 18 related electronic switches, also, can be increased to 19 decrease torque ripple. Some of the turns of a particular winding can share the same stator lamination 21, slot or angular position as some of the winding turns 22 of an adj.,acent winding .
23 The motor can be supplied with a shaft encoder and 24 appropriate circuitry for operation as a stepping motor and is especially suitable for large size stepping 26 motors. A desired angular resolution for a stepping 27 motor application can be achieved by providing a 2,8' suitable number of field windings. As previously 29 discussed herein, the rotor will seek to align the plane of the conductive loop, or equivalent structure, 31 to the magnetic field vector. of a particular winding 32 that is energized. The motor is reversible simply by 1 reversing the sequence that the field. windings are 2 energized by the related circuitry.
3 A circuit powering the field windings. of the motor 4 can energize more than one field winding at a time to reduce torque ripple and/or the circuit can be arranged 6 to modulate power to the windings rather than simply 7 turning them on and off. Field windings on the stator can have various configurations besides those 9 illustrated in FIGS. 1, 3 and 14, it being important ~10, that the winding arrangement be capable of producing an 11 AC magnetic field in the space of the rotor that moves 12 around the axis of the rotor.
13 While the invention has been shown and described 14 with respect to particular embodiments thereof, this is for the purpose of illustration rather than limitation, 16 and other variations and modifications of the specific 17 embodiments herein shown and described will be apparent 18 to those skilled in the art all within the intended 19 spirit and scope of the invention. Accordingly, the patent is not to be limited in scope and effect to the -21 specific embodiments herein shown and described nor in 22 any other way that is inconsistent with the extent to 23 which the progress in the art has been advanced by the 24 invention.
Claims (17)
1. An AC electric motor comprising a stator and a rotor journalled for rotation about an axis relative to the stator, the rotor having an electrically continuous conductive loop, the loop having longitudinal portions spaced from and generally parallel to the axis and shunt portions extending between the ends of the longitudinal portions, the stator having at least two separate windings angularly displaced from one another about the axis of the rotor, an electrical circuit for selectively energizing. and de-energizing the field windings with separate AC currents to develop an AC
magnetic field vector that moves around the rotor axis, the field windings and conductive loop being arranged so that the AC magnetic field vector induces an AC
current in the conductive loop and the reluctance of the loop operates to develop torque on the rotor that tends to cause it to rotate in synchronization with the movement of the magnetic field vector.
magnetic field vector that moves around the rotor axis, the field windings and conductive loop being arranged so that the AC magnetic field vector induces an AC
current in the conductive loop and the reluctance of the loop operates to develop torque on the rotor that tends to cause it to rotate in synchronization with the movement of the magnetic field vector.
2. An electric motor as set forth in claim 1, wherein the field windings comprise 3 or more coils distributed about the rotor axis.
3. An AC motor as set forth in claim 2, including a circuit arranged to energize successive ones of said windings in a constant angular direction around said rotor axis while de-energizing angularly preceding ones of said windings.
4. An AC motor as set forth in claim 3, wherein said circuit provides an AC square wave for powering said windings.
5. An AC motor as set forth in claim 3, wherein said. circuit is arranged to provide an AC voltage waveform and to change the characteristics of said waveform to vary the speed or torque of the motor.
6. An AC motor as set forth in claim 1, wherein said field windings comprise first and second windings, said second winding being oriented to produce a magnetic field vector at right angles to the magnetic field vector of the first winding, said electric circuit being arranged to modulate the currents in said windings to produce a resultant magnetic field vector that is positioned about the axis of the rotor.
7. An AC motor as set forth in claim 1, wherein said circuit is arranged to control the position of the magnetic field vector in relation to the rotor to regulate speed or torque.
8. An AC motor as set forth in claim 1, wherein the rotor has a plurality of pairs of conductive loops and the windings are. arranged to produce magnetic field vectors that pass through the space of the rotor in chordal-like zones.
9. An electric motor comprising a stator and a rotor, field windings on the stator for producing an AC
magnetic field with a vector at successive angular positions around the axis of rotation of the motor when the windings are successively energized with single phase AC-power, the rotor having a construction by which it increases the reluctance in the magnetic field when it has an angular orientation out of alignment with the magnetic field vector compared to its reluctance when it is aligned with the magnetic field vector whereby the rotor seeks to rotate in synchronization with the magnetic field vector produced by the field windings.
magnetic field with a vector at successive angular positions around the axis of rotation of the motor when the windings are successively energized with single phase AC-power, the rotor having a construction by which it increases the reluctance in the magnetic field when it has an angular orientation out of alignment with the magnetic field vector compared to its reluctance when it is aligned with the magnetic field vector whereby the rotor seeks to rotate in synchronization with the magnetic field vector produced by the field windings.
10. An electric motor comprising a stator and a rotor, field windings on the stator for producing an AC
magnetic field with a vector at successive angular positions around the axis of rotation of the motor when the windings are successively energized with single phase AC power, the rotor having a construction by which it increases the reluctance in the magnetic field when it has an angular orientation out of alignment with the magnetic field vector compared to its reluctance when it is aligned with the magnetic field vector whereby the rotor seeks to rotate in synchronization with the magnetic field vector produced by the field windings, the rotor construction having a diametral high reluctance area and relatively low reluctance areas on opposite sides of said diametral area.
magnetic field with a vector at successive angular positions around the axis of rotation of the motor when the windings are successively energized with single phase AC power, the rotor having a construction by which it increases the reluctance in the magnetic field when it has an angular orientation out of alignment with the magnetic field vector compared to its reluctance when it is aligned with the magnetic field vector whereby the rotor seeks to rotate in synchronization with the magnetic field vector produced by the field windings, the rotor construction having a diametral high reluctance area and relatively low reluctance areas on opposite sides of said diametral area.
11. An electric motor as set forth in claim 10, wherein said high reluctance area includes an air gap.
12. An electric motor as set forth in claim 11, wherein said air gap extends uninterrupted across the diameter of the rotor.
13. An electric motor as set forth in claim 12, wherein a conductive non-magnetic body is disposed substantially throughout said air gap.
14. A controller circuit for an AC motor comprising a plurality of switches and/or amplifiers that generate separate power signals at respective outputs, each power signal having an AC frequency common with the other signals, the signals varying in amplitude in a cyclic manner corresponding to the speed of rotation of the rotor of the motor.
15. A method of operating an electric motor having a stator and a rotor which includes causing an AC
magnetic field vector to be displaced around the axis of the rotor by sequentially energizing field windings on the stator and providing the rotor with a construction that has a variable reluctance in the magnetic field whereby the rotor turns with the movement of the magnetic field vector because its reluctance in the magnetic field decreases when it is aligned in a particular orientation with the magnetic field vector.
magnetic field vector to be displaced around the axis of the rotor by sequentially energizing field windings on the stator and providing the rotor with a construction that has a variable reluctance in the magnetic field whereby the rotor turns with the movement of the magnetic field vector because its reluctance in the magnetic field decreases when it is aligned in a particular orientation with the magnetic field vector.
16. A method of converting electrical energy to mechanical.energy comprising the steps of assembling a rotor and stator in a manner enabling the rotor to rotate about an axis relative to the stator, providing field windings on the stator capable of producing an AC
magnetic field vector in the rotor, providing the rotor with a reluctance that varies with its angular orientation relative to the AC magnetic field vector produced by field windings, energizing the field windings with AC current in a manner that causes an AC
magnetic field vector to move around the axis of the rotor and thereby cause the rotor to rotate in synchronization with the movement of the AC magnetic field vector around the axis.
magnetic field vector in the rotor, providing the rotor with a reluctance that varies with its angular orientation relative to the AC magnetic field vector produced by field windings, energizing the field windings with AC current in a manner that causes an AC
magnetic field vector to move around the axis of the rotor and thereby cause the rotor to rotate in synchronization with the movement of the AC magnetic field vector around the axis.
17. A method as set forth in claim 16, wherein the rotor is constructed with at least one conductive loop that includes diametrically opposed axially extending portions adjacent the periphery of the rotor so that the AC magnetic field vector is able to induce an AC
current in the loop when a plane defined by said axially extending portions is at an angle relative to the AC magnetic field vector.
current in the loop when a plane defined by said axially extending portions is at an angle relative to the AC magnetic field vector.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| PCT/US2003/033565 WO2005050822A1 (en) | 2000-09-06 | 2003-10-22 | Controlled reluctance ac induction motor |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2543169A1 true CA2543169A1 (en) | 2005-06-02 |
Family
ID=35006360
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002543169A Abandoned CA2543169A1 (en) | 2003-10-22 | 2003-10-22 | Controlled reluctance ac induction motor |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP1678811A4 (en) |
| AU (1) | AU2003304678A1 (en) |
| CA (1) | CA2543169A1 (en) |
-
2003
- 2003-10-22 CA CA002543169A patent/CA2543169A1/en not_active Abandoned
- 2003-10-22 EP EP03819044A patent/EP1678811A4/en not_active Withdrawn
- 2003-10-22 AU AU2003304678A patent/AU2003304678A1/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| EP1678811A1 (en) | 2006-07-12 |
| AU2003304678A1 (en) | 2005-06-08 |
| EP1678811A4 (en) | 2009-10-21 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Discontinued |