ES2629685T3 - Uniform gear control procedure of a reluctance motor and connection current limiting device - Google Patents

Abstract

Procedure for controlling a reluctance motor with a rotor (1) and a stator, in which the rotor (1) has a plurality of rotor segments (2) and the stator has a number of coils (3) dependent on it , as specifically six coils (3) in the case of four rotor segments (2), and with a control device that applies a voltage to a coil (3) of a respective phase (PH1 to PH3) of the stator, characterized because at a time when a first coil (3) is already excited, specifically when moving a rotor segment (2) with respect to the coil (3), the next second coil (3) is already additionally excited in the direction of rotation (r) of the rotor (1).

Description

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DESCRIPTION

Uniform gear control procedure of a reluctance motor and connection current limiting device.

The invention concerns a method for controlling a reluctance motor according to the features of the preamble of claim 1.

In commuted reluctance motors, which are generally known, the uniform running of the rotor and the starting of the rotor depend on its position with respect to the stator field. Thus, according to the position of the rotor with respect to the stator field, the torque, especially at low revs, can be so small that the rotor remains stationary. Likewise, it has been proven that in a position of a rotor segment between two stator coils, the number of revolutions is raised due to the high torque that acts in this position.

From document FR 2161602 A stepper motor is known in which a step-by-step movement of the rotor is carried out by means of a phase connection and disconnection. Uniform rotor travel is not provided.

Starting from the cited state of the art, the invention deals with the problem of indicating a control procedure of a reluctance motor that makes a uniform rotor run possible, even at low revs.

This problem is solved with the object of claim 1, wherein it is stated that at a time when a first coil is already excited, specifically during the movement of a rotor segment with respect to the coil, it is already further excited the second next coil in the direction of rotation of the rotor. This means that in an area where a rotor segment reaches an overlapping proximity with respect to the next immediate stator coil, in which situation one has to fear a stop or at least a reduction in the number of revolutions due to the torque very small that acts here, the next immediate phase for torque compensation is connected, whereby the rotor segment rotates uniformly and with running stability ahead of the first coil. Advantageously, the connection of the next immediate phase is carried out in a rotation position of the rotor segment which, considered in the direction of rotation of the rotor segment, is located at a point before the superposition position of the rotor is reached. rotor and coil segment.

It is also necessary that at a time when the first coil is not yet excited, the second second coil is already further excited in the direction of rotation of the rotor. In this way, a torque hole can also be bridged, thereby counteracting a rotor stop situation even at low revs. In addition, the rotor start is also guaranteed. By connecting the next immediate coil or the next immediate phase, phase overlap is achieved. An improvement in the starting behavior and the driving behavior of the rotor at low rpm is also achieved because the current in the second coil is additionally excited to the first coil is increased. Therefore, in addition to the excitation of the next immediate coil, a current amplification is also performed, whereby a homogenization of the torque image is achieved. It is preferred in this regard that the current is increased for a predetermined period of time.

The desired running stability of the rotor can also be improved by increasing the current intensity of this coil with a movement of the rotor segment with respect to a coil, this increase in current being more preferably made before the additional excitation of the second next coil. The connection of the next second phase and the increase of the current of the first coil are made according to the position of the rotor with respect to the stator field. In order to detect this position of the rotor, this rotor can be connected in a rotational manner with an emitting disk that has a distinctly defined association with the position of the rotor, whereby the position of the rotor can be determined by means of suitable measures, such as sensors. Thus, for example, on the emitter disk, emitter formations associated with a rotor segment that can be detected by a stationary sensor can also be defined.

In the process according to the invention, the smoothing of the torque is achieved by using a simple rotor location sensor by means of a rotor-dependent current supply to each individual phase. The corresponding stator phase is fed with a correspondingly encoded signal from the emitting disk with a calculated nominal current value. Since the motor has a high torque in this area, this current value has to be relatively low to avoid an increase in the number of revolutions. When the rotor pole is closer to the stator pole, it is then guaranteed by a corresponding configuration of the emitter disk that, when this area of smaller torque is reached, a corresponding signal is generated. At this point the current through the coil is increased by a corresponding factor that compensates for the weakening of the torque. Since the current in the next immediate stator coil must first be established, the motor has a very small torque at the moment of commutation.

Therefore, during the switching, the preceding coil is not immediately disconnected; it increases so

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corresponding the nominal value of the current. The still existing decreasing torque of the old phase is added to the increasing torque of the new phase.

The torque remains almost constant in the sum. The first coil is disconnected before the negative torque zone is reached. The current profile achieved is made possible, for example, by a transmitter disk that offers 24 pulses for each revolution.

An embodiment is preferred in which more pulses are captured, such as preferably 360 pulses for each revolution, thereby further improving the desired homogenization of the pair image. It also makes possible an ideal current curve that is adapted to the evolution of the pair.

In a refinement of the procedure, it is provided that a connection current produced when the reluctance motor is connected is limited in its magnitude. Without additional measures, the connection current reaches extremely high values that are clearly above the nominal values. As a consequence of this, a current limiting measure is necessary. This is solved, for example, by limiting it by means of resistors connected in series.

These resistors are part of an intermediate circuit through which a continuous voltage is available to power the reluctance motor. When the reluctance motor is connected, an electrolytic capacitor of the intermediate circuit is charged through resistors that are bridged after the motor starts. The resistors are bridged during the usual operation of the reluctance motor.

As a consequence of this procedure, the peak current is limited to a completely uncritical value, such as, for example, a fifth of the nominal current. The bridging of the necessary resistors during motor operation is done by means of a switch. The latter can be a semiconductor or a relay.

The limitation of the starting current assumes that a certain delay must be present until the reluctance motor starts. In this case, the capacitor is charged at a nominal voltage, such as, for example, in the case of operation with a 230 volt network in alternating current, at a nominal voltage of 325 volts in direct current.

When the engine has started, the resistors are bridged by means of the switch. A unipolar relay is preferably used here. Preferably, resistors connected in series are arranged in front of the capacitor. Likewise, thermal cut-off resistors that interrupt the current in case of excessive heating can be used in this regard.

The limitation of the connection current can also be combined with a monitoring of the intermediate circuit voltage, in which case simple resistances can be used instead of the usual thermal shear resistances. If the resistances have not been bridged, a critical state is reached only when a certain current circulates that can exceed the permissible loss power of the resistances. This critical current then also corresponds to a certain voltage in the intermediate circuit, that is to say that a certain lower voltage is adjusted. In regulated current motors, a current can be imparted to detect the state of the bypass switch.

The voltage in the intermediate circuit can be measured before the power supply. The voltage surge during the power supply then gives direct information about whether resistance bridging is active. If this is not active, a correspondingly high voltage brown will then be adjusted in the resistors. This then leads to a voltage break in the intermediate circuit that can be detected reliably. During the operation of the motor and in case of failure of the bypass switch, the intermediate circuit voltage will also break depending on the motor load.

In this case, it is necessary to disconnect the motor when it falls below a certain voltage. A minimum voltage rating is then carried out taking into account the motor current.

The moment of bridging of the resistors can be determined in different ways. First, pure time control is possible without surveillance. Only a fixed time is expected until the relay or switch is maneuvered. The time can be set with the help of the resistance time constant and the electrolytic capacitor. The observation of the intermediate circuit voltage after connection is more informative. The observation of the evolution of the curve allows to accurately recognize a manifestation about the correct functioning. Likewise, the resistances can be bridged as soon as the intermediate circuit voltage is not strong enough or it has exceeded a certain value.

The choice of voltage variation as a criterion allows operation at different input voltages without variations being necessary. As a whole, certain plausibility controls can be made by means of a microcontroller by means of which the operation of the connection current limitation can be tested.

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Next, the invention will be explained in more detail using the attached drawing, which represents only one embodiment. They show:

Figure 1, in schematic representation in perspective, a rotor of a reluctance motor with a united emitting disk integral with rotation in rotation with the rotor and with stationary sensors to capture the position of the rotor;

Figure 2, a schematic view of the rotor and the stator coils, with an arrangement of the sensors represented in dashed and dotted lines, relative to a first rotor position;

Figure 3, a consecutive representation to Figure 2;

Figure 4, a consecutive representation to Figure 3;

Figure 5, another consecutive representation;

Figure 6, a diagram to illustrate the magnitude of the torque as a function of the angle of rotation of a rotor segment; Y

Figure 7, a development diagram concerning the signals of the two sensors cooperating with the rotor emitting disk as a function of rotor rotation.

A rotor 1 with four rotor segments 2 angularly arranged around a rotor axis x and intended to be associated in a reluctance motor M of four / six is represented and described first with reference to FIG.

The tetrapolar rotor 1 can be associated with a stator not shown in detail with six coils 3 angularly arranged around the axis of rotation x of the rotor 1 (see Figure 2).

In the rotor 1, a hollow cylindrical emitting disk 4 arranged coaxially to the x-axis of the rotor is fixed in rotation. Two pairs of emitting projections 5 associated with a rotor segment 2 have been carved on the cylinder wall of this emitting disk 4, each emitting projection 5 forming a pair 6, referred to the axis of rotation x, an angle at 15 ° . The opposite edges of contiguous emitting projections 5 of a pair 6 also form an angle p of 15 °.

The association of the emitting projections 5 with the rotor segments 2 is unique. Thus, an emitting projection 5 of a pair 6 is always positioned in the center of the associated rotor segment 2. The other emitting projection 5 of the pair 6 is arranged, according to the direction of rotation of the rotor 1, in front of or behind the rotor segment. 2 with an angular offset relative to the first emitting projection 5.

To capture the situation of the rotor, sensors 8 are provided that form sensor barriers 7 and are arranged in a stationary position such that, in the course of the rotation of the rotor, the emitting projections 5 of the emitting disk 4 run through these sensor barriers 7.

The sensors 8 or the sensor barriers 7 are also positioned so that they form, with reference to the axis of rotation x, an angle of approximately 45 °.

By means of the above-described arrangement of the sensors 8 and the configuration of the emitter disk 4, a unique recognition of the location of the rotor segments 2 as a function of the coils 3 can be achieved, and this for 24 pulses for each revolution. A corresponding development scheme is shown in Figure 7, which is limited to phases PH1 and PH3, with the rotor angles being registered under 6. S1 shows the sensor signals of a first sensor barrier when passing the emitting projections 5 and S2 shows the signals of the second sensor barrier, each time depending on the angle of the rotor. It can be seen that a detection scheme has been achieved that provides four different results E. The value of the results is digital, with which result values between 0 and 3 can be achieved.

If the result corresponds to the value 1, 2 or 3, the situation of the rotor is uniquely recognized in this example of configuration of the emitting disk 4. On the contrary, if an E value of 0 is obtained, the momentary situation of the rotor is then decided after capturing the next value that must be obtained.

The digital result values are used to activate phases PH1 to PH3.

With the aid of figures 2 to 5, referring to a rotor segment 2, the obtaining of the rotor situation and the activation of the coils 3 or of the phases PH3 and PH1 are explained below.

In Figure 2, the rotor segment 2 forms an angle 6 of -37.5 ° with the next coil 3 or the next phase PH3. In this position, an emitting projection 5 travels through the area of the sensor barrier 7 designated with S2. In contrast, the other sensor barrier 7 designated with S1 does not emit any signals in this position. As can be seen in the development scheme of Figure 7, a result value E = 2 is derived from this. This result value causes

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The power supply to the PH3 phase is to the coil 3, towards which the rotor segment 2 moves.

The current diagram I refers to the total current absorption of the motor M, but each coil being individually supplied with current. The increase of the total current represented in the angular position -37.5 ° results from the activation of the PH2 phase located in front of the PH3 phase in the direction of rotation of the rotor 1 and activated.

In a following position of the rotor according to Figure 3, in which an angle 6 of -22.5 ° is formed, no signals are emitted by the sensor barrier S2 or by the sensor barrier S1, which results in a result value E = 0. Depending on the result value E = 2 previously obtained, with this result value E = 0, a current increase of the PH3 phase previously connected is caused. Preferably, a doubling of the current intensity is performed in this case (see the diaphragm of Figure 7).

In the course of the additional rotation of the rotor in the direction of the arrow r the rotor 1 reaches a position in which both the first sensor barrier Si and the second sensor barrier S2 emit signals when passing through the emitting projections 5. This is it performs at an angular range of rotation in which the rotor segment 2 forms with the coil 3 on both sides of a neutral position an angle 6 of 7.5 °. With the beginning of this interval at 6 = -7.5 ° according to figure 4, when the result value E = 3 is acquired, a connection of the PHi phase arranged behind the already connected phase PH3 in the direction of rotation r of rotor 1, whereby phase overlap is achieved. In this way, a significant decrease of the torque is bridged in the overlapping zone of the rotor segment 2 and the associated coil 3 of the PH3 phase, which guarantees a uniform rotor run 1 free of pulls even at low revs. .

As can be seen in the current diagram of Figure 7, in this rotation interval the total current absorption triples.

The overlapping of phases achieved is temporarily limited in such a way that even before reaching the 0 ° position phase PH3 is disconnected and, therefore, the total current absorption is reset again to the single value, since the current supply is disconnected to the PH3 phase and only the simple power supply to the PH1 phase is presented below. The time control is preferably monitored by means of a microcontroller. Actually only the next coil or phase in the direction of rotation r (here phase PH1). "

After exceeding the 0 ° position between the rotor segment 2 and the associated stator coil 3, the emitting projections 5 leave the sensor barriers S2 and S1 at an angle 6 of 7.5 °. Depending on the result value E = 3 previously obtained, a first current increase of the PH1 phase is induced when the now existing result value E = 0 is captured. Next, the same development scheme as described is carried out, but now referred to the PH1 phase and the PH2 phase arranged behind it.

The diagram in Figure 6 shows the torque curves as a function of the rotation angle 6 when a first phase PH3 is excited and a subsequent additional situation of the phase PH1 occurs. It can be seen that the torque curves rise first with a lot of slope and descend to a flat orientation after exceeding a maximum, the pair not reaching a quantum value close to 0 at any angular interval due to phase overlap, but, on the contrary , an approximate homogenization of the pair is achieved by adding pairs.

As a consequence of the procedure described above according to the invention, the danger of an uneven running of the rotor 1 and, in addition, of even a stopping situation thereof. Also, by overlapping phases and regulating current dependent on the rotor situation, an over-rise in the number of revolutions of the rotor 1 is counteracted.

Claims (10)

5 10 fifteen twenty 25 1. Procedure for controlling a reluctance motor with a rotor (1) and a stator, in which the rotor (1) has a plurality of rotor segments (2) and the stator has a number of coils (3) dependent on the same, as specifically six coils (3) in the case of four rotor segments (2), and with a control device that applies a voltage to a coil (3) of a respective phase (PH1 to PH3) of the stator , characterized in that at a time when a first coil (3) is already excited, specifically when moving a rotor segment (2) with respect to the coil (3), the next second coil (3) is already additionally excited in the direction of rotation (r) of the rotor (1). 2. Method according to claim 1, characterized by an increase in current in a second coil (3) additionally excited to the first coil (3). 3. Method according to claim 2, characterized in that the current is increased during a predetermined period of time. Method according to any one of claims 1 to 3, characterized in that a connection current produced when connecting the reluctance motor (M) is limited in its magnitude. 5. Method according to claim 4, characterized in that the limitation is effected by means of resistors (11). Method according to claim 5, characterized in that a capacitor is charged through the above resistors (11) and the resistors (11) are bridged after starting the reluctance motor (M). 7. Method according to claim 6, characterized in that the capacitor is an electrolytic capacitor (10). Method according to any one of claims 6 or 7, characterized in that the bridging is carried out by means of a switch (13). 9. Method according to claim 8, characterized in that the switch (13) is a semiconductor or a relay (14). 10. Method according to any of claims 6 to 9, characterized in that the bridging is performed only when the capacitor is charged.