MXPA96001042A - Improvement of torsional force in reluctant machines - Google Patents

Abstract

The present invention relates to a switched reluctance drive system comprising: a two-phase switched reluctance motor having a stator with stator poles, a rotor and phase windings housed in relation to the stator for energizing the poles stator, switch means connected to each of the phase windings, position indicator means to produce signals indicative of the position of the rotor in relation to the sensor, and control means that respond to an input demand and said signals from the position indicator means for actuating the switch means for controlling the current in the phase windings, characterized in that the control means are also operable to drive the switch means of both phases simultaneously when the rotor is in a position in which the energization of both phases will contribute to the production of torsional force in the same direction of acue with the demand of enter

Description

IMPROVES DB TROPICAL FPE IN RELUCTANCE MACHINES Inventor: Norman Neilson Fulton, of English nationality, residing at 3 Birkdale Walk, Leeds LS17 7SX, England.

Owner: SWITCHED RELUCTANCE ORIVES LIMITED, of English nationality, domiciled in Springfield House, Hyde Terrace, Leeds, LS2 9LN, England.

Background of the Invention This invention relates to reluctance machines and more particularly to switched reluctance motors. In particular, the present invention relates to a method and apparatus for increasing the torsional force of start and stroke of a two phase switched reluctance motor.

In general, a reluctance machine is an electric motor in which the torsional force is produced by the tendency of its moving part to move to a position where the reluctance of a magnetic circuit is minimized, for example, the inductance of the exciting winding It is maximized.

In a type of reluctance motor the energization of the phase windings occurs at a controlled frequency. These motors are generally referred to as synchronized reluctance motors. In a second type of reluctance motor, the circuits are provided to detect the angular position of the rotor and energize the phase windings as a function of the rotor position. This second type of reluctance motor is generally referred to as a switched reluctance motor.

Figure 1 illustrates an exemplary switched reluctance motor having a stator 10 including six stator poles 11-16. Placed inside the hole formed inside the stator and the stator poles pointing inwards 11-16 is a rotor 18 which is mounted on the bearings and is free to rotate. The rotor 18 has a number of outwardly extending projections 19 which form the poles of the rotor.

A coiled winding of wire 17 is associated with each stator pole. In the illustrated motor, the coils of the opposite stator poles are coupled together to form three phases: Phase A (coils of poles 11 and 14); Phase B (coils of poles 12 and 15); and Phase C (coils of poles 13 and 16). In the example illustrated in Figure 1, when Phase A is activated, electric current will flow through its coils so that the stator pole 11 becomes, say, an electro-magnet pointing inward of a polarity. positive and the stator pole 14 becomes an electromagnet of negative polarity. These electromagnets will produce a force of attraction between the energized stator poles and the rotor poles which will produce a torsion.

By energizing commuted from one phase to another, the desired torsional phase can be maintained regardless of the angular position of the rotor. By switching the energization of the phase windings to develop positive torsional force, the rotor can be operated as a motor; by energizing the phase windings to develop a force torsional delay the motor can be operated as a brake and generator.

Figure 2 generally illustrates torsional force profiles for the three phases of the engine illustrated in Figure 1 on three hundred and sixty degrees of rotor rotation. The profiles of torsional force have been simplified by clarity of explanation. The torsional force profile 20 generally illustrates the torsional force profile of Phase A of the motor illustrated in Figure 1 which will result if a constant current is passed through the winding coils positioned around the stator poles 11 and 14 as a function of the angular position of the rotor. As indicated in Figure 2, there is an initial rotor position 21 when the rotor poles are completely misaligned with the stator poles 11 and 14. In this position, the energization of the phase winding for Phase A does not produce torsional force . When the rotor is moved from this initial position, a positive torsional force is exerted on the rotor. As indicated by line 20 in Figure 2, as the position of the rotor approaches the stator pole, the torsional force produced by the energized winding around the stator pole increases. The torsional force will continue to increase until just after the rotor and stator poles begin to overlap and then decrease. When the rotor and stator poles are completely aligned, for example in position 22, the torsional force will fall to zero. By continuing to change the As the rotor position with respect to the stator pole, the negative torsional force will occur until the rotor is again completely misaligned with the stator pole, for example, at point 23, where the torsional force produced becomes again zero. As indicated in figure 2, the torsional force profile corresponding to the rotation of the rotor from 180 to 360 degrees is identical to the profile of torsional force 0-180 but offset 180 degrees.

Because the rotor and stator poles are regularly positioned around the rotor and the stator in the example of Figure 1, the torsional force profiles for the other two phases are the same as those for Phase A, but are move by 60 degrees. In figure 2, the torsional force profile for Phase B will be represented by line 24 and the torsional force profile for Phase C is illustrated by line 25. In general, for a reluctance machine with rotor poles and Stator arranged in a symmetrical form, the torsional force profiles of all the phases will be the same but displaced 360 / ^ * p) where Nr is the number of rotor poles and p is the number of phases.

In many motor applications it is desirable to be able to energize the motor so that it produces a relatively high torsional force. Such desired constant torsional force is illustrated by line TD in Figure 2.

Referring again to Figure 2, it may be noted that, for any given rotor position there is always a phase that can be energized to give positive torsional force near the desired torsional force TD. For example, if the rotor is in a position 26, Phase A can be energized to provide a torsional force near the desired torsional force TD. If the rotor is in a position 27, Phase B can be energized to give a torsional force near TD; and if the rotor is in a position 28, Phase C can be energized to produce a torsional force close to the torsional force TD.

In addition to having the ability to provide a relatively high torsional force TD, regardless of the position of the rotor, the reluctance motor of Figure 1 is also capable of providing a relatively constant continuous torsional force, by always energizing the winding that produces the torsional force closest to the desired torsional force TD. In general, for any reluctance motor having three or more phases, it is always possible to energize a winding and produce a torsional force at or near the desired constant TD torsional force.

Typical two-phase reluctance motors, unlike the motor illustrated in FIG. 1, are not capable of producing relatively high desired TD torsional force in all possible rotor positions. This is because, for two-phase motors, the regions of positive torsional force for the different phases do not overlap significantly. This is generally illustrated in Figures 3 and 4.

Figure 3 generally illustrates a typical two-phase reluctance motor. The two-phase motor includes a stator 30 having four stator poles 31-3, around which the coils 17 are positioned. The opposing coils are connected to form two phase windings: Phase A, comprising the coil of the poles 32 and 34, and Phase B comprising the coils around the poles 31 and 33. The motor also includes a rotor 35 having two rotor poles In the motor illustrated in Figure 3, the rotor 35 is constructed so that a "stepped air separation" 36 is provided at each rotor pole. As will be recognized by those skilled in the art, the introduction of stepped air separation 36"stretches" the positive region of the torsional force profile for each rotor phase. This makes the torsional force profile of each phase of the asymmetric motor in the sense that the region of positive torsional force extends over a larger angle than the region of the negative torsional force. This asymmetric torsional force profile provides a slight overlap between the positive torsional force regions of the two-phases and ensures that, for any position of the rotor, the general positive torsional force is possible. The use of separations Staggered air allows the start of a two-phase motor in any rotor position. The use of stepped air separation rotors for two-phase reluctance motors is generally known in the art and is discussed, for example, in the work of El-Khazendar & Stephenson, Proceedings of the ICEM Munich (1986).

Fig. 4 generally illustrates the torsional force profile for the two-phase motor of Fig. 3 over one hundred and eighty degrees of rotation when a constant current flows through the motor windings. Line 41 generally illustrates the torsional force profile for Phase A and the line 42 generally illustrates the torsional force profile for Phase B. As illustrated, the use of the stepped air separation rotor stretches the torsional force profiles of the two-phases so that there are regions of overlap, near the points 43 and 43 ', where the torsional force produced from both phases is positive. Points 43 and 43 'represent the points where the two torsional force profiles intersect.

In known two-phase switched reluctance motors, a rotor pointer transducer (RPT) with a unique position sensor, such as the Hall effect device, an optical device or a capacitively or magnetically based device, was used to control the energization of the windings. A unique sensor device is used because the Two phase windings are each energized by one half of the electric cycle. Therefore, when the output of the single sensor is a level (eg, a logical one), the first phase winding is energized. When the output of the single sensor changes to the opposite logic level (eg, logic zero) the first phase winding is de-energized and the second phase winding is energized. Under this approach, the energization of the two-phase windings is mutually exclusive and the lifetime of the single logical sensor one is virtually equal to the duration time of the logic zero output of the sensor. Typically, the points at which one phase winding is de-energized and the other energized is the point at which the torsional force profiles of the two-phases intersect (for example, points 43 and 43 'in FIG. 4). ).

Figures 5 and 6 illustrate a typical motor position transducer of the type used with two-phase switched reluctance motors. In the typical configuration, an axis 50 is coupled to the rotor 35 of a two-phase switched reluctance motor. Coupled to the axis 50, so that it rotates are the axis, there is a fin 51 having two different regions: regions of mark 52 and regions of space 53. A sensor element 54 is placed in a sufficiently close to the axis to perceive whether it is near a region of mark or space of the fin. In known two-phase switched reluctance motors, each region of fin and fin spacing is substantially the same, with each being generally defined by an angular extent of approximately (180 / N,) degrees, where Nr is the number of rotor poles.

In operation, the sensing element 54 produces a first signal of a logical value (eg, a high voltage or a logical "1") when a fin marking region is located near the sensing element 54 and produces a second signal of a different logic level (for example, a low voltage or logical "0") when a region of fin space is located near the sensor. As will be understood by those skilled in the art, when a fin 51 is used having a digit, two equal marking / space regions, on each 180 degree rotation of the rotor the sensing device 54 will produce a logical signal "1" about half the rotation and a logical signal "0" on the other half of the rotation. This is generally illustrated in Figure 6A where the output of the sensing device 54 is shown as being a logical "1" as the rotor rotates from the position defined as 0 degrees to the position defined as 90 degrees, and a "0" logical when the rotor rotates from the 90 degree position to the 180 degree position. Since the construction of the fin is symmetrical, the signal is repeated over the rotation period from 180 degrees to 360 degrees.

In two-phase switched reluctance motors, since each phase winding is mutually energized exclusive of the other, the output of the single sensor device 54 can be used to control motor energization. For example, during the interval when the output of the sensor 54 is logic "1", a phase winding, for example, Phase A is normally energized and Phase B is de-energized. During the interval over which the output of the sensing device 54 is the logical "0" the other phase winding, the Phase B in this example, and the Phase A is de-energized. This is generally illustrated in Figures 6B and 6E. As will be recognized by those skilled in the art, the electronics required to convert the output of the sensor device 54 to a switched signal for the phase windings are correct and can be constructed at a low cost.

There are a number of fin types 51 and sensor devices 54 that are used in the switched reluctance motors. For example, the flap 51 may comprise a disk with light blocking and light transmissive elements defining the marking and space regions, and a sensor device 54 may comprise a sensor with a light source and a light detector in where the marking regions of flap 51 interrupt the light beam from the source to the detestor. For light blocking / light transmitting flaps it is sometimes desirable to slightly adjust the angular extent of the marking regions to compensate for the finite width of the light beam so that the sensor 54 produces high logical and low logic signals of equal durations. As another example, the fin 51 it may include the branding regions of ferromagnetic material and the sensing device 54 may comprise a Hall effect device which produces a first logical signal when the sensor is in the presence of the ferromagnetic signal and a second logical signal in another way. By the type of seneor device illustrated in Fig. 5, it is known to adjust the angular extent of the marking region to compensate for the effect of proximity of the flow in the air adjacent to the ferromagnetic fin. The adjustment is made so that the sensor 54 produces high logical and low logic signals of equal duration.

For typical two-phase motors, such as the motor of FIG. 3, there is a rotor position, near points 43 and 43 'in FIG. 4, where the torque that the motor is capable of producing is relatively low . In many two-phase engines, the torsional force at this low point may be 30% or less of the maximum torsional force that the engine can produce. This point of low torsional force can cause problems in the sense that it can be difficult to start the engine if the rotor is put to rest in a position near the positions represented by points 43 and 43 '. Additionally when the engine is running, the low torsional force point results in significant positions in the torsional force output of the engine. These variations in torsional force output, referred to as torsional force crimps, are generally undesirable.

A known method for increasing the torsional force at the start of the motor and decreasing the amount of torsional force ripple is to profile the magnitude of the current applied to the phase windings so that the current flowing through the phase winding (and therefore the torsional force produced) is greater at points 43 and 43 'than would otherwise be the case. This approach is undesirable because it not only requires a relatively complex control circuit that decentrates the low cost, the simple design advantages that make the two-phase reluctance engines desirable, but also requires considerable reconditioning of the force converter. to handle the increased current.

The present invention provides a method and apparatus for increasing the torsional starting force of two-phase re-phasing motors and for decreasing torsional force crimps in two-phase machines without profiling the current in the phase windings and without increasing the current rating of the switches in the power sonder.

The present invention is defined in the accompanying independent clauses. Preferred features are passionate in the dependent clauses.

The present invention is generally directed to a method for operating a two phase switched reluctance motor for producing softer and increased torsional force, wherein the motor includes a rotor, a first phase winding and a second phase winding, by energizing both phase windings simultaneously during part of the rotational period of the rotor.

In one embodiment of the present invention, a control system for controlling two-phase reluctance motors is provided to produce torsional force in a desired direction. The control system includes a first rotor position transducer which produces a signal of a first level whenever the energization of the first phase winding produces torsional force in the desired direction, a second rotor position transducer which produces a signal of the first level whenever the energization of the second phase winding produces torsional force in the desired direction. The control system also includes a first switching device electrically coupled to the first rotor position transducer for energizing the first phase winding provided that the signal produced by the first rotor position transducer is of the first level and a second switching device electrically coupled to the second rotor position transducer to energize the second phase winding provided that the signal produced by the second rotor position transducer is of the first level.

Still a further embodiment of the present invention includes a switched reluctance motor system comprising a two-phase switched reluctance motor including a stator, a first phase winding, a second phase winding and a rotor. Associated with the motor are the first and second rotor position transducer sensors to produce signals that respectively control the energization of the first and second phase windings.

Yet another embodiment of the present invention provides a rotor position transducer assembly for a two-phase switched reluctance motor including a rotor, an axis coupled to the rotor, a first phase winding and a second phase winding wherein the rotor and the phase windings are arranged to produce the torsional force in a desired direction. The rotor position transducer assembly of this embodiment includes a first sensor device for producing signals for controlling the energization of the first phase winding; a second sensor device for producing signals for controlling the energization of the second phase winding, and a fin coupled to the axis where the fin includes marking regions and space regions.

Brief Description of the Drawings Other aspects and advantages of the present invention will be apparent from reading the following detailed description of the exemplary embodiments and with reference to the drawings in which: Figure 1 illustrates a typical three-phase reluctance motor having six stator poles and two rotor poles; Figure 2 generally illustrates the torsional force profile for the three-phase reluctance motor of Figure 1; Figure 3 illustrates a two-phase commutated reversing motor having four stator poles and a two-pole stepped air separation rotor; Figure 4 generally illustrates the torsional force profile for the two-phase reluctance motor of Figure 3; Fig. 5 generally illustrates a motor position transducer of the type used in the known switched reluctance motors; Figures 6A-6C generally illustrate the output of the sensing device of the motor position transducer of the FIG. 5 and the signals are muted for the phase windings of the two-phase reluctance motor of FIG. 3.

Figure 7 generally illustrates a two phase switched reluctance system constructed in accordance with the present invention.

Figure 8 schematically illustrates a controller that can be used in the present invention; Figure 9A generally illustrates the torsional force profile of a two phase switched reluctance motor that can be used in the present invention; Fig. 9B generally illustrates the switching and torsional force signals available for a switched reluctance motor system constructed in accordance with the present invention; Figure 10 illustrates in more detail the construction and positioning of the motor position transducer of the present invention; Figures 11A-11D generally illustrate the generation of switched signals in response to the angular position of the rotor according to the present invention.

Detailed description of the invention Similar reference characters indicate similar parts through the various views of the drawings.

In the present invention, the switching arrangement is provided to energize the phase windings of a two-phase switched reluctance motor so that the torsional starting force of the motor is increased and the torsional force ripple is decreased. In the present invention, a motor position transducer with two perception heads was used to control the energization of the phase windings wherein each motor position transducer sensor head independently controls the energization and de-energization of one of the windings of phase. Furthermore, in the present invention, each of the two motor position transducer sensor heads is configured so that the phase winding which corresponds to the motor position transducer is ignited near the point where its energization will produce a force positive torsional and will turn off when its torsional force falls near zero. In this switching scheme, there are periods during full rotor rotation in which both phase windings are energized at the same time. During these periods the torsional force produced by the energization of the two windings is additive, resulting in a force production torsional greater than what would be available if only the single-phase winding had been energized.

Figure 7 generally illustrates a two-phase switched-over relustansia engine system constructed in accordance with the present invention. The system generally includes a switched reluctance motor 70, including stator 71 and rotor 72 and a motor position transducer comprising a specially configured fin 74 coupled to the motor shaft and two sensing devices 75 and 76. The outputs of the sensor devices 75 and 76 are provided to an electronic controller 77 which controls the energization of the phase windings of the motor 70.

The rotor 72 of the engine 70 in Figure 7 is a two-pole stepped air separation rotor similar to that illustrated in Figure 3. The present invention is not limited to the use of staggered air separation rotors, but is applied All two-phase reluctance engines in the suas phase can produce positive torsional force for more than one half of the angular rotation of the rotor. The invention is applicable to staggered, graduated or other forms of rotor.

The construction of the motor for use in the present invention can be exsept by the motor position transducer, follow the conventional switched reluctance motor construction methods. For example, the stator can be constructed of a number of stator laminations stacked having stator poles around which the motor windings are wound. The rotor may be constructed from a number of stacked rotor laminations fixed to an axis. The construction of reluctansia motors with two phases is generally understood and is not established in detail here.

In contrast to two-phase motor systems, such as that illustrated in FIG. 5, the two-phase motor system of the present invention uses a motor position transducer, two sensor devices 75 and 76 are sublevels. influenced by the same flap 74. In the present invention, each of the two sensing devices is associated with a different winding phase and each sensor device is configured and positioned to produce a first logical level signal (eg logic high) when the energization of its associated phase winding will result in a positive torsional force, and a second logical level signal (for example, low wind) at all other times.

The electron sonder 77 is also coupled to the switch devices (not shown in Figure 7) which are coupled between the phase windings of the motor and a DC voltage source.

Figure 8 illustrates schematically a simplified diagram of the controller 77 that can be used in the present invention. As illustrated in Fig. 8, a DC + V voltage source is provided across the bus lines DC 80 and 81. Coupled through the busbar lines DC 80 and 81 are the phase windings of the motor 70 schematically represented as inductances 82 (representing Phase A) and 83 (representing Phase B). The switch devices 84a and 85a couple the phase windings to the positive line and the switch devices 84b and 85b couple the phase windings to the ground or negative line 81 of the DC busbar. The switch devices can be elevators, force transistors, force MOSFETs, IGBTs, MOS controlled transistors (MCTs) or the like. The return diodes 86a and 87a are coupled to the phase winding and the positive line 80 of the busbar DC to provide a current path when the switch devices 84 and / or 85 are turned off and there is a current still in the winding of phase asosiado. Similarly, the diodes 86b and 87b are the phase winding to the lower DC bus bar line.

As illustrated in FIG. 8, the controller 77 receives the output signals from the sensor devices 75 and 76 and generates the switch signals to control the switch devices. In the simplified scheme of the 8, the electronic controller comprises the signal conditioning circuits 88 and 89 which receive, clean and amplify the output signals from the sensor devices 75 and 76 respectively, to provide the switch signals for the switch devices. In the alternate modes the conditioning circuits 88 and 89 can be eliminated and the outputs of the sensing devices 75 and 76 can be used directly to control the switch devices. In the example scheme of Fig. 8 the switch devices are such that a high logic output of the sensing devices will produce a switch signal which will teach the appropriate switch devices and energize the phase winding associated with these devices. For example, if the output of the sensor device 75 is high logic, the controller 77 will produce a signal that turns on the switch devices 84a and 84b, thereby providing an electrical path between the positive bus line or bus 80 and the bus line 80. ground bus ibus 81 through the phase winding 82. When the switch devices 84a and 84b are turned on, current will flow through the phase winding 82 until the switch devices 84a and 84b are turned off, in whose moment the current in the phase winding 82 will decay through the path provided by the diodes 86a and 86b.

As those skilled in the art will recognize, the simplified controller 77 illustrated in FIG. 8 is only an example of a controller that can be used in accordance with the present invention. The present invention is applicable to a large number of controllers and is not intended to be limited to the example controller of FIG. 8. For example, a more complicated controller can be used to probe the current in the phase windings by cutting the voltage applied to the windings through the controlled interruption of the switch devices.

As discussed above, the present invention relates to the control of a two-phase switched reluctance motor so that the initial torsional pitch is increased and the torque of the torsional force is decreased. The manner in which these advantages are obtained in the present invention is generally explained with reference to Figures 9A and 9B.

Figure 9A illustrates in solid lines the torsional force profile for the two-phase motor of Figure 7 on 360 degrees of rotation of the rotor. Some of the details have been exaggerated to help the explanation. The line marked 90 represents the profile of torsional force that will result if a constant sorrent is aplied to the winding of phase A and the line marked 91 illustrates the same information for phase B. As illustrated, there is a point 93 where the force torsional The positive result produced by the energization of any of the phases A or of the phase B alone is relatively low. The inventor of the present invention has realized that by energizing the windings according to the present invention it is possible to greatly increase the starting torsional force of a two-phase motor if it must stop at a position corresponding to position 93 and to diminish the curl of the torsional force. In particular, if the windings are energized independently of one another, it is possible to effectively bend the minimum torsional force and minimize the curl of the torsional force. For example, if each phase winding is energized close to the moment it starts to produce positive torsional force and is deenergized as soon as it begins to produce negative torsional force, there will be rotor positions with respect to which both phase windings are energized. During these intervals, the torsional force produced by the two windings will be additive, resulting in increased torsional force production of the motor.

Figure 9B illustrates in a dotted line the profile of torsional force that will result if the phase winding for phase A is energized at point 94 (cersa of the point where phase A begins to produce positive torsional force) and is de-energized in point 96 (near the point where phase A begins to produce negative torsional force) and phase winding for phase B is energized at the corresponding point 95 and it is de-energized at point 98. Cone indicates the dotted line, during the interval when both phases are energized, the torsional force is additive and the torsional force produced will increase significantly, resulting in a much greater starting torsional force at point 93 and a torsional force loop much smaller. It should be noted that the specific enrogization and deenergization positions illustrated in Figure 9B are not critical to the present invention. Whenever there are time intervals during which both phase windings are energized and produce positive force, it is possible to increase the starting torisional force of the motor and reduce the torsional force ripple.

In order to implement the interruption arrangement of the present invention, a motorized position transducer is specially configured and placed with two sensing devices can be used to control the energization of the phase windings. Sensor devices are necessary because a single sensor device is used to independently control the energization of each phase winding. A motor position transducer specially configured is necessary because the time duration of the high logic signal of each sensor device is required to be different from the duration time of its logic low signal. This is different from the known motor position transducers for two-phase motors. In the present invention, the Specially configured motor position transducer is used because, with stepped separation motors, the proportion of the duration of the positive torsional force region d the motor torsion force curve to the region of negative torsion force is greater than one. In the present invention, the motor position transducer is configured and arranged so that a sensor device produces a first logic level signal (eg logical 1) over the portion of the electrical cycle during which energization of the phase winding with the The device will produce a positive torsional force on the rotor and a second logic level signal (eg sero logical) during the portion of the electrical cycle during which the energization of the phase winding associated with the device will produce negative torsional force on the rotor.

The lower portion of Figure 9B generally illustrates the desired outputs of the motor position transducer that may be used in the present invention, even when the absolute values of the angles used are exemplary. A first digital signal motor A position transducer represents a desired output for the sensor device associated with the phase A winding. As illustrated in FIG. 9B the output of this sensor device is highly logical on the portion of the rotation cistern. of the rotor during which such positive torsional force is produced by the rotor when phase A is energized and low logic at all other times. Similarly, the output of the engine position transducer B is high logic when the torsion force produced by energizing phase B is positive and low logic at all other times. Notably, between points 95 and 96 (the point corresponding to the energization of the phase B winding and the de-energization of the phase A winding) the output of both sensor devices is skipped since the energization of each phase will produce positive torsional force. In a similar manner both windings will be energized between points 97 and 98, 99 and 100, 101 and 102 and 94.

As discussed above, in the present invention the outputs of the motorized position transducer sensing devices are appended to the electronic sonder 77 the sual uses the motor position transducer outputs as well as switching signals to supply current to the appropriate windings . In the example given above, the electronic controller 77 must supply current to the winding phase A as long as the output of the air position transducer A is high and supply current to the winding B when the RPTb output is high. The construction of the resistive controllers supplying current to the phase windings in a reluctance motor in response to the motor position transducer signals is known in the art and is not discussed in detail because the particular sonorousness of the electronic controller do not it is essential for the present invention as long as the current is applied according to the motor position transducer signals as described above.

As FIG. 9B illustrates the ratio of the rotor rotation cycle rate during which the output of the given motor position transducer is high logic to the proportion over the portion of the rotor rotation cycle during which it is low. it is not a unit as is typical with known motor position transducers. Therefore, the specially configured motor position transducers must be used.

Figure 10 illustrates in more detail the RPT configuration of the present invention the signal is generally illustrated in Figure 7. Figure 10 generally illustrates the shape of the flap 74 and the positioning of the sensing devices 75 and 76.

In the embodiment of Figure 10, the sensor devices 75 and 76 are of the type that includes a light source and a light detector. Thus, the tab 74 illustrated in FIG. 10 shows the light transmitting proportions 110 and 111 (the "space" portions of the fin and the light inhibiting portions 112 and 113 (the "marking" portions of the fin). Unlike the fins used with reluctance engines With two known phase switches, the wing 74 constructed in accordance with the present invention has the marking and space regions that are not equal.

The operation of the engine position transducer using interruption fins or mute and light detectors is well understood. Generally, a beam of light is supplied to the sual from a light source to a detector. When the beam of light hits the detector, the detector produces a digital signal at a first logical level (for example, logical "0"). When the beam of light is interrupted, for example, by the passage of a fin between the source of the beam and the detector, the beam does not strike the detector and the detector produces a digital output at a second logical level (for example, " 1"Logic). In the present example, the time interval when the detector produces a logical "1" signal is referred to as the "mark" period and the time interval over which the detector produced a logical "0" signal is referred to as the period Of space".

Referring again to Figure 10, it can be noted that the angular extent of the mark portions 112 and 113 of the flap 74 will vary significantly from the angular extent of the flap space portions 110 and 111. In this embodiment of the present invention, the wing 74 should be constructed so that the fin marking portions. correspond directly to the regions of positive torsional force of the torsional force profile. For example, referring to Figure 9B it can be noted that the region of positive torsional force for phase A extends over the region defined by the rotation of the engine from the position of 0 degrees to the position of 120 degrees and over the defined region by the rotation of the engine from the position of 180 degrees to the position of 300 degrees. Thus, the flap 74 has a first mark region 112 with an angular extension from a position of 0 degrees to a position of 120 degrees and a second mark region 113 with an angular extension from the position of 180 degrees to the position of 300 degrees.

The construction of the rotor blade 74 in FIG. 10 is exemplary only. As those skilled in the art will recognize, the present invention is applicable to other two phase motors having different torsional force profiles are different regions of positive torsional force and two phase motors with different pole numbers. In general, however, the marking regions of the fin must correspond to the regions of positive torsional force of a given phase of the engine. In practice, the positive torsional force produced by the region for a given engine can be calculated experimentally or preferably determined empirically by examining the engine. Each phase winding can be energized and the rotor can be rotated from the Possession that corresponds to 0 mechanical degrees to 360 mechanical degrees while the resulting torsional force is measured through the use of torsional force measurement tunnels sonosidas.

As mentioned above, once the regions that produce positive torsional force of the phase windings are known, the construssion of the appropriate fin is quite simple thereafter. The region that produces positive torsional force for a given phase was determined and the rotor marking regions are then designed to correspond to the regions of positive torsional force. After the fin marking and spacing regions have been determined, the engine position transducer fin can be constructed using conical cutting and fabrication techniques.

As those skilled in the art will recognize and as discussed generally above, in order to generate the appropriate motor position transducer signals it is sometimes necessary to slightly increase the desired mark region to compensate for the fact that the beam of light that is being interrupted by the fin has a finite width. In the extinction in which the beamwidth compensation is required, it should be added on the fin after the mark / spas regions have been determined in accordance with the present invention. When such modifications have been made, the extension The angular region of the fin marking region will generally, but not exactly, correspond to the region that produces positive torsional force of the phase windings. A similar modification may be required for other types of sensing devices. In all cases, however, the object is to produce motor position transducer signals whose mark / space ratios correspond to the proportions of the angular periods of the positive and negative torsional forces.

The placement of the two sensor devices 75 and 76 in the present invention takes advantage of the hesho that the placement of the rotor poles around the rotor is symmetrical and that each rotor pole is off-centered from the next adjacent rotor pole by 180. mechanical grades. When using a rotor having two symmetrical rotor poles, the two sensor devices 75 and 76 must be positioned so that the angle formed by the two sensor devices 75 and 76 extends 90 mechanical degrees. This is illustrated in Figure 10 where the angle expanded by the sensor devices 75 and 76 is 90 mechanical degrees.

When the motor position transducer fin is suitably constructed and the sensing devices are placed in accordance with the present invention, the appropriate switching signals will be generated.

This is illustrated in Figures 11A-11B. As indicated in FIG. 11A, during the interval over which the rotor rotates from an angular position represented by O to the angular position represented by 30 degrees, the output of the perception detector 75 and the RPTA and the output of the perception detector 76 and the RPTB are both logical "1", resulting in the energization of the A and B phase windings. By continuing to rotate the rotor from 30 degrees to 90 degrees the fin marking region will continue to block the light from the perceptual detector. 75, resulting in a stronger "1" RPTA signal over this range, and the continued energization of the phase A winding. In this period there is nothing to block the light to the perception detector 76 and the output RPTB signal is a "Logical 0" This is illustrated in Figure 11B.

Figure 11C illustrates the rotor rotation from 90 degrees to 120 degrees. During this period of rotation, the outputs of both RPT sensors are high and both phase windings are energized.

Figure 11D illustrates the outputs for rotor rotation from 120 degrees to 180 degrees. During this interval, the RPTA output is a logical "0" and the RPTB output is a logical "1". Because the rotor is symmetrical, the RPT output for the region defined by 180 ° to 360"is a duplicate of the region defined by 0o to 180". As explained above, the RPT outputs are applied to the electronic controller to control the switching of the phase windings.

The invention uses the overlapping angular region in which the torsional force in the desired direction is available from both phases of a two-phase reluctance machine. To achieve this in at least a part of the region in which the torsional force is available, both phases are energized simultaneously. Even though this is described above in relation to the complete region in which the torsional force of both phases is available, the skilled person will appreciate that a proportion of the region can be used for simultaneous energization instead of this.

The invention is also applicable to reluctance generators in which the input torsional force applied is translated to output voltage. By means of the simultaneous interconnection of the windings, according to the invention a smoother output voltage can be produced.

The skilled person will also be aware that the reluctance machines can be arranged with the rotor embracing an internal stator. The invention is equally applicable to this sonetrussidn also. Similarly, the invention can be used in relation to the linear reluctance motors in which the moving member moves to through a stator path sequentially energized. The movable member in a linear reluctance motor is often referred to as the rotor. The term "rotor" is intended to encompass such member mdvilee in linear reluctance motorways.

Although the invention has been described in connection with the illustrative modes discussed above, those skilled in the art will recognize that there may be many variations without departing from the present invention. For example, the examples discussed utilized a d motor position transducer making use of a light sensor and a fin including regions of light blocking and light transmission. As those skilled in the art will be aware that the regions of light reflection and non-reflection of light can be used or other types of RPT, including RPT using a Hall or layer effect, magnetic or inductive base devices and RPT is where the Branded and spaced regions may be used without departing from the scope of the present invention. In addition, the marsa and space regions in the examples given above were provided for illustrative purposes only. It should be understood that different regions of space and marsa can be used without departing from the present invention.

The description mentioned above of several modalities is done by way of example and not for purposes of limitation. In particular, the invention is applicable to switched reluctance machines having stator and rotor pole numbers different from those illustrated above. The present invention is intended to be limited only by the scope of the following clauses.

Claims (12)

CLAIMS Having described the invention, it is considered as a novelty, and therefore the content of the following clauses is claimed as property:

1. A switched reluctance drive system comprising: a two phase phased rejection motor having a stator with stator poles, a rotor and phase d windings arranged in relation to the stator for the energization of the stator poles; Switch means with states are each of the phase windings; position indicator means for producing signals indicative of the position of the rotor relative to the stator; Y control means responsive to an input demand and said signals from the position indicator means for driving the switch means for controlling the current in the phase windings; sarasterized because the sontrol means are also operable to operate the switch means of both phases simultaneously when the rotor is in a position in which the energization of both phases will contribute to the production of torsional force in the same direction as according to the input demand. .

2. A system as claimed in clause 1, characterized in that the position indicator means comprise the first position sensing means arranged to produce on and off signals for the switch means according to the torsional force producing regions. of the position of the rotor in relation to the stator in the desired direction for one of the phases, and second means of position perception arranged to produce on and off signals according to the torsional force producing regions of the rotor poicide in relation to the stator in said desired direction for the other of the phases.

3. A system as claimed in clause 2, characterized in that a sensor output influencing member is arranged to rotate with the rotor, the first and second position sensing means being arranged in relation to said member to be influenced by the same.

4. A system as claimed in clause 3, characterized in that the member is a fin defining the first and second sensor output influence regions, so that the sensor means produces a binary output corresponding to the signals of switching on and off of the switch means when rotating the rotor.

5. A system as claimed in clauses 2, 3 or 4, characterized in that the control means include means of signal signaling to assimilate the output of the first position pursuit means and second signal conditioning means for conditioning the output of the second position tracking means, the outputs of the conditioning means being operatively controlled in a respectable manner to drive the switch means of the two phases.

6. A system as claimed in any of the preceding clauses, characterized in that the rotor is an aerated air separation rotor, having at least one outer pole face radially defining two arcuate surfaces relatively and radially closer to and more spaced apart from each other. the faces of the stator poles.

7. A system as claimed in any of the preceding clauses in which the control means and rotor position tracking means are arranged to run the switched reluctance machine as a motor.

8. A system as claimed in any of clauses 1 to 6, characterized in that the control means and the rotor position sensing means are arranged to run the switched reluctance machine as a generator.

9. A method for controlling the output of a two-phase switched reluctance machine having a rotor, a stator and at least one phase winding for each phase, comprising: perceive the position of the rotor in relation to the stator; to activate the switch means according to the position of the rotor in relay to the stator to activate the phase windings in sequence to produce an output; Y furthermore, the augmenting switch means are the position of the rotor in relation to the stator to energize the phase windings simultaneously while the rotor is in a position in which the energization of both phases contributes to the output torsional phase in a desired direction.

10. A method as claimed in clause 9, characterized in that it includes perceiving the position of the rotor in relation to the poles associated with the at least one winding of a phase and separately perceiving the position of the rotor in relation to the poles of stator associated with the at least one winding of the other phase.

11. A position transducer for a two phase switched reluctance machine, having a stator with stator poles, a rotor and phase windings arranged in relation to the stator for the energization of the eetator poles, the transducer somprende: first means for positioning sensors to produce inductive signals of the rotor output in relation to the stator in which a desired direction of torsional force production is available from one of the phases; second position indicator means for producing position signals indicative of the position of the rotor relative to the stator in which the desired direction of the TSrsional force production is available from the other of the phases; the first and second position indicator means being arranged to produce signals indicative of rotor positions in which the desired direction of torsional force production is available from both phases simultaneously.

12. Such a transducer is claimed in clause 11, characterized in that the first and second position indicator means share a member that can be mounted to rotate with the rotor of the machine, each of the position indicator means having a sensor. operable to produce the position signals under the influence of the member. In testimony of which I sign the present in Mexico, D.F., on March 19, 1996. SWITCHED RELUCTANCE DRIVES LIMITED po was o. SUMMARY A method and apparatus for increasing the starting torsional force of a two-phase switched reluctance motor is described. The method involves the use of a specially constructed rotor position transducer with two sensing devices, each associated with a two phase motor faece winding. The signals from the rotor position transducer are provided to a motor controller that activates each winding whenever the winding of the winding will produce torsional force in the desired direction.