EP0045675B1 - Control circuit and speed control of the rotation of a rotor, especially the one of a rotatable-anode x-ray tube - Google Patents

Control circuit and speed control of the rotation of a rotor, especially the one of a rotatable-anode x-ray tube Download PDF

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Publication number
EP0045675B1
EP0045675B1 EP19810401155 EP81401155A EP0045675B1 EP 0045675 B1 EP0045675 B1 EP 0045675B1 EP 19810401155 EP19810401155 EP 19810401155 EP 81401155 A EP81401155 A EP 81401155A EP 0045675 B1 EP0045675 B1 EP 0045675B1
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Prior art keywords
voltage
circuit
terminals
fraction
phase
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EP19810401155
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German (de)
French (fr)
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EP0045675A1 (en
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Raoul Setbon
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Thales SA
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Thomson CSF SA
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05G—X-RAY TECHNIQUE
    • H05G1/00—X-ray apparatus involving X-ray tubes; Circuits therefor
    • H05G1/08—Electrical details
    • H05G1/66—Circuit arrangements for X-ray tubes with target movable relatively to the anode

Definitions

  • the invention relates to a circuit for controlling and regulating the speed of rotation of a drive rotor, in particular that of a rotating anode of an X-ray tube, intended to maintain a substantially constant speed and to allow, for example, the application of the very high voltage between the anode and the cathode of this tube, as soon as the speed of rotation has reached a preset reference value.
  • relays are often used which are sensitive to a threshold value of a current whose windings are inserted in series with the stator windings constituting respectively the main and auxiliary phases which generate orthogonal magnetic fields and which are supplied respectively by currents out of phase with each other by means of a capacitor in series with the winding of the auxiliary phase, for example, in order to generate a rotating magnetic field.
  • a voltage-sensitive relay which goes into the working position when the alternating voltage across the capacitor exceeds a predetermined threshold is connected in parallel with the phase-shifting capacitor supplying the auxiliary phase.
  • the contacts of three relays are inserted in series in an authorization circuit for energizing the X-ray tube. The disadvantage of this arrangement is that it gives no indication of the actual speed of rotation.
  • This increase in the voltage at the terminals of the winding of the auxiliary phase of the stator with that of the speed of rotation of the rotor is mainly due according to the aforementioned publication, to the increase in the apparent impedance of this winding which is caused by the variable reaction with the speed of the currents induced in the rotor on the stator.
  • the apparent impedance of the winding then has an increasing inductive component which is of opposite sign to that of the capacitive reactance of the phase shift capacitor, which leads to an increase in the current in the auxiliary phase.
  • the relay has a first threshold voltage for which it goes into the working position and a second threshold voltage lower than the first for which it returns to the rest position and which respectively correspond to two speeds of rotation of the low anode away from nominal speed.
  • the relay contact When in the working position, the relay contact authorizes energizing of the X-ray tube. This has the drawback of allowing the tube to be energized, when the voltage across the auxiliary phase winding exceeds a threshold which can also come from an increase in the voltage of the supply network, even with the rotor stopped, for example, because of a main phase cut. It will therefore be necessary to stabilize the stator supply voltage.
  • the circuit which is the subject of the invention not only makes it possible to alleviate the above drawbacks and to authorize the application of very high voltage only when a predetermined speed of rotation, close to its set value is reached and to inhibit this application or to stop it when this speed has not yet been reached or has fallen below this set speed, but also the regulation of this speed by putting in series with the supply of the two phases d '' a continuously variable ballast between two resistance values.
  • a circuit for controlling and regulating the speed of rotation of a rotor in particular that for driving a rotating anode of an X-ray tube of the type in which this rotor, disposed inside a glass envelope, is driven using a rotating magnetic field generated by means of a stator located outside the envelope and comprising at least two pairs of windings, the first of which constitutes the main phase and the second the auxiliary phase and whose respective axes of symmetry, normal to the axis of rotation of the rotor, are angularly offset relative to each other, these two phases being joined together by one of their terminals to constitute a common power supply terminal coupled to one of the terminals of a single-phase alternating voltage source, the other terminal of the main phase being connected directly and the other terminal of the auxiliary phase being connected by means of a capacitor phase shift, at the other terminal of the so single-phase urce, which circuit includes first comparison means providing a first signal which indicates that the voltage across the main phase has reached or exceeded a fixed and pre
  • FIG. 1 a schematic section of the rotor which carries the rotating anode of the X-ray tube and which is arranged inside the glass envelope 2, shown in dotted lines.
  • the stator 3 comprises two pairs of windings 4 and 5 wound on a magnetic circuit (not shown), intended to generate two alternating and orthogonal magnetic fields, passing through the rotor 1 composed, for example, of a hollow outer cylinder of conductive material , such as copper, and possibly an inner cylinder also made of ferromagnetic material, such as soft iron or an alloy with low remanence, fitted one on the other and supported by two bearings or bearings.
  • the first terminal 6 of the first pair of windings 4 which are connected in series and arranged on either side of the casing 2, which constitute the main phase, is connected to a first output terminal 11 of a source of single-phase alternating voltage 10, such as a cycloconverter (possibly static) or multiplier (doubler or tripler) of conventional frequency, whose inputs 12 are supplied by the single- or three-phase distribution network (50 or 60 Hz) and which provides a higher frequency alternating voltage (150 or 180 Hz, for example) than the network, making it possible to reach a rotation speed of between 8,000 and 10,000 rpm.
  • a source of single-phase alternating voltage 10 such as a cycloconverter (possibly static) or multiplier (doubler or tripler) of conventional frequency
  • the first terminal 7 of the second pair of windings 5, also connected in series and constituting the auxiliary phase, is joined to the first output terminal 11 of the source 10 by means of a phase-shifting element 8, constituted here by a capacitor 8, to produce a phase shift between the output 11 and the terminal 7.
  • the second respective terminals of the main 4 and auxiliary 5 phases of the stator 3 are connected together to form a common terminal 9 which is joined, by means of a variable ballast circuit 20, to the other output terminal 13 of the single-phase source 10.
  • This common terminal 9 constitutes for the control and regulation circuit of this figure the reference potential point (or isolated ground).
  • the ballast circuit 20 is a dipole comprising between its terminals 21 and 22 a first ballast resistor 23 (of a few hundred ohms, for example) and, in parallel with this first resistor 23, a bridge composed of four diodes 24, 25, 26 and 27.
  • the common point of the anode of the first diode 24 with the cathode of the second 25 constitutes the first terminal 21 of the ballast dipole 20 and that of the cathode of the third diode 26 with the anode of the fourth 27, its second terminal 21.
  • a power transistor 30 which constitutes a variable resistance element, low in the saturated state and very high in the blocked state, and which varies continuously between these two states.
  • the resistance of the collector-emitter path of transistor 30 constitutes the variable element of the ballast circuit 20 which is in parallel with the first resistance 23 of fixed value.
  • the power transistor 30, of high-voltage type (such as type BU 208 of SESCOSEM having a collector-emitter breakdown voltage V cEx of approximately 1,500 V), has its collector joined to its base by means of a second polarization resistor 31 (of a few kiloohms, for example) which forms with the phototransistor 32 of a first photocoupler 33 a voltage divider providing variable polarization to the transistor 30, when the light-emitting diode 34 whose photoemissive surface is optically coupled on the photosensitive surface of the phototransistor 32, is traversed a current in the direct direction.
  • the control of the ballast resistor 20 between terminals 21 and 22 will be described later.
  • the alternating voltage present between the terminal 6 of the main phase 4 and the common terminal 9 is rectified using a fifth diode 40 which feeds through a third 41 and a fourth resistor 42 in series, which serve to filter and to reduce the level of the rectified, a ⁇ -shaped filter cell composed of a second capacitor 43, a fifth resistor 44 and a third electrochemical capacitor 45.
  • One 46 of the armatures of the second capacitor 43 connected to the junction of the fourth 42 and the fifth 44 resistor is also connected to one of the terminals of a sixth resistor 47, the other terminal of which is connected to the cathode of a Zener diode 48 and to the positive armature of a fourth capacitor 49, for example, electrochemical.
  • the other armature of the second capacitor 43, the respective negative armatures of the third 45 and of the fourth capacitor 49 and the anode of the Zener diode 48 are connected to the common terminal 9.
  • the junction 50 of the cathode of the Zener diode 48 with the resistor 47 and the capacitor 49 provides a stabilized (and filtered) direct voltage, positive with respect to the reference potential of the terminal 9 (of 24 volts, for example) which makes it possible, on the one hand, to supply the five amplifiers operational equipping the circuit and, on the other hand, to develop a fixed reference voltage used for comparison.
  • a first resistive voltage divider composed of a seventh 51 and an eighth resistor 52 in series, is connected to the terminals of the Zener diode 48, their common point 53 joined to the non-inverting input of a first integrated operational amplifier 54 by means of a ninth resistor 55, supplies it with a reference voltage which this amplifier, used as a voltage comparator, compares to a predetermined fraction of the rectified and filtered voltage across the terminals of the third capacitor 45, the level is proportional to the peak value of the alternating voltage supplying the main phase 4.
  • This fraction is supplied by means of a second resistive voltage divider connected in parallel with the third capacitor 45 and comprising a tenth 56 and an eleventh 57 resistor in series whose common point 58 is united, by means of a twelfth resistor 59 (of the same value as the ninth 55), at the inverting input of the first amplifier 54.
  • the fate ie 60 of the first amplifier 54 therefore supplies a positive voltage substantially equal to its supply voltage (high logic state), when the reference voltage applied to its non-inverting input is greater than the fraction of the rectified main phase voltage, applied at its inverting input.
  • the output 60 provides a zero voltage (low state) relative to the reference potential of terminal 9 .
  • the alternating voltage present between the terminal 7 of the auxiliary phase 5 and the common terminal 9 is also rectified by means of a sixth diode 70 whose cathode is connected through a thirteenth 71 and a fourteenth 72 resistance to one of the armatures of a fifth capacitor 73, the other armature of which is connected to the common terminal 9.
  • the common point of the resistor 72 and of the capacitor 73 is also connected to one of the terminals of a fifteenth resistor 74, the l 'other terminal is connected to the positive armature of a sixth capacitor 75, for example, electrochemical whose negative armature is connected to the common terminal 9.
  • the elements 73 to 75 form a filter cell in ⁇ similar to that which is formed by elements 43 to 45.
  • the sixth capacitor 75 is connected in parallel with a third resistive voltage divider of adjustable division factor, which for this purpose is composed of a sixteenth resistor 76, a potentiometer 77 and a seventeenth resistor 78 connected in series.
  • the cursor 79 of the potentiometer 77 thus provides an adjustable fraction of a direct voltage proportional to the peak amplitude of the alternating voltage applied between the terminals 7 and 9 of the auxiliary phase 5.
  • a second operational amplifier 80 is used as a second comparator, the non-inverting input of which is connected, via an eighteenth resistor 81, to the cursor 79 of the potentiometer 77 and the inverting input of which is connected to the junction, one 58 of the second divider 56-57 providing a DC voltage proportional to the peak amplitude of the AC voltage across the main phase 4, via a nineteenth resistor 82.
  • the second operational amplifier 80 makes it possible to compare the peak amplitudes of the two main phases 4 and auxiliary 5.
  • the output 83 of the second comparator 80 is in its high state (where it provides a positive voltage substantially equal to its supply voltage), when the adjustable fraction of the voltage of the auxiliary phase rectified and filtered, taken from the cursor 79 of potentiometer 77, is greater than the fixed fraction of the voltage of the main phase rectified and filtered, on the common point 58 of the second divider 56-57. If the voltage at the terminals of the main phase 4 exceeds that at the terminals of the auxiliary phase 5, the output 83 of the second comparator 80 provides a zero voltage (relative to terminal 9), that is to say a logic state low.
  • the combination comprising the second voltage divider 56, 57 fixed, the third voltage divider 76, 77, 78 adjustable and the second comparator 80 constitutes a means for determining the ratio of the voltages at the respective terminals of the auxiliary 5 and main 4 phases which corresponds at the set speed. More precisely, when there are equality of the fractions of voltages applied to the respective inputs of the second comparator 80, the ratio of the voltage of the auxiliary phase 5 to the voltage of the main phase 4 is equal to the quotient of the division factors of the second and the first divider. This quotient being adjustable using the potentiometer 77, it makes it possible to signal by a change of state (switching) at the output 83 of the second comparator 80 when this voltage ratio has reached its chosen reference value.
  • the output 83 of the second comparator 80 is connected to the anode of a light-emitting diode 35 of a second photocoupler 36, the cathode of which is connected to the anode of a seventh diode 85 and which ensures the isolation between circuits.
  • the cathode of the seventh diode 85 is brought together by means of a twenty-first resistor 86 at the output 60 of the first comparator 54. This gives the light-emitting diode 35 of the second photocoupler 36 only being supplied with current when the output 83 of the second comparator 80 is in its high state and when, at the same time, the output 60 of the first comparator 54 is in the low state.
  • the light-emitting diode 35 only conducts when the peak amplitude of the voltage of the main phase V 4 exceeds a determined value, proportional to the continuous reference voltage V 53 and when the speed of rotation of the rotor 2 is sufficient to that the fraction adjustable as a function of the desired target speed, of the peak amplitude of the voltage of the auxiliary phase V5 exceeds the predetermined and constant fraction of the peak amplitude of the voltage of the main phase V 4 .
  • the light-emitting diode 35 of the second photocoupler 36 illuminates, when it is supplied with direct current, the photosensitive surface of a phototransistor of the NPN type 37, for example, the emitter of which is connected to the ground 38 of the radiological generator (not shown ), for example, and whose collector is connected, via the winding 39 of a relay or a contactor with electromagnetic control, to the positive pole 87 of a DC supply voltage source (+ V DC ).
  • the phototransistor 37 becomes saturated and the movable contacts 61, 62, 63 coupled together pass from their rest position to their working position.
  • the first movable contact 61 connects together two fixed contacts 64 and 65 which are inserted in the authorization circuit for energizing the X-ray tube, located in the X-ray generator, for example.
  • the speed regulation circuit includes a third operational amplifier 90, the non-inverting input of which is connected, via a twenty-second resistor 91, to the cursor 79 of the potentiometer 77 supplying the DC voltage V 79 of which the level represents the above adjustable voltage of the amplitude of the voltage across the auxiliary phase V 6 . It further comprises a fourth operational amplifier 92, the non-inverting input of which is brought together, via a twenty-third resistor 93, at the common point 58 of the second divider 56-57, which supplies the DC voltage V 58 whose level represents the constant fraction of the amplitude of the voltage across the main phase V 4 .
  • the outputs of amplifiers 90 and 92 are respectively connected by means of a twenty-fourth 94 and a twenty-fifth 95 feedback resistance, to their inverting inputs which are. joined together using a twenty-sixth resistor 96.
  • the stages comprising the amplifiers 90 and 92 constitute amplification stages without reverse polarity, with high input impedance. Their outputs supply respectively, via a twenty-seventh 97 and a twenty-eighth 98 resistor, the non-inverting and inverting inputs of a fifth operational amplifier 99.
  • the output 100 of the fifth operational amplifier 99 is joined to its inverting input by a threshold feedback circuit comprising a twenty-ninth resistor 101, an eighth 102, a ninth 103 and a tenth 104 diode in series.
  • a threshold feedback circuit comprising a twenty-ninth resistor 101, an eighth 102, a ninth 103 and a tenth 104 diode in series.
  • the output 100 of the amplifier 99 is joined, moreover, to the common terminal 9 via, on the one hand, a thirtieth resistor 105 and, on the other hand, by an eleventh diode 106 and a thirty and a first resistor 107 in series with the light-emitting diode 34 of the first photocoupler 33.
  • the light-emitting diode 34 of the first photocoupler 33 in series with the eleventh diode 106 have a predetermined conduction threshold which must be reached as soon as the set fraction V 79 of the rectified auxiliary phase voltage has exceeded the fixed fraction V 58 of the voltage main phase rectified.
  • the three diodes 102 to 104 in series with the feedback resistance 101 provide the amplifier 99 with a gain close to its open loop value until its output voltage has reached this conduction threshold. Thereafter its gain is determined by the feedback resistors 101 and input 98 so that the variation of the current in the light-emitting diode 34 is gradual.
  • the output 100 provides a zero voltage (since it is not supplied by a negative voltage with respect to terminal 9).
  • the light-emitting diode 34 of the first photocoupler 33 remains off and the phototransistor 32 remains blocked, so that the high-voltage power transistor 30 becomes saturated during almost all of the alternations of the alternating voltage supplying the windings 4, 5 by the common terminal 9.
  • This saturation occurs shortly after each zero crossing of the alternating voltage due to the conduction thresholds of the transistor 30 and the diodes 24 to 27 of the bridge, two of which are each conductor in series, through intermediary of the collector-emitter path of the transistor 30 which is only polarized through the resistor 31.
  • the residual voltage drop between the terminals 21 and 22 of the ballast circuit 20 is then low (approximately 7 volts) compared to the voltage (of approximately 1000 V peak) supplied by the cycloconverter 10. This allows the starting (starting) of the motor with high currents and voltages, that is to say at full power which is also nt applied during the acceleration phase.
  • the output 100 of the fifth amplifier 99 provides a positive voltage which causes a current through the diode light emitting 34 having the effect of making the phototransistor 32 conductive so that it reduces the bias voltage of the base-emitter junction of the power transistor 30.
  • the resistance of the collector-emitter path of this transistor 30 then increases with the increasing illumination of the phototransistor 32.
  • This increase in the resistance of the collector-emitter path of the power transistor 30 has the effect of reducing the voltage across the main and auxiliary phases by the voltage drop between the terminals 21 and 22 of the ballast circuit 20, so that the currents flowing through them are reduced to their values just necessary to maintain the desired speed of rotation.
  • the rectified and filtered voltages undergo a significant reduction.
  • the fixed contacts of the relay connected by its movable contacts 62 and 63 are respectively connected so as to short-circuit the third 41 and the thirteenth 71 resistance of the respective rectifier circuits of the voltages of the main and auxiliary phases.
  • the ballast circuit 20 can be inserted in the circuit of the primary bearings of a three-phase transformer equipping the cycloconverter 10 which is then a static tripler, whose cold terminals (not connected to the network phases) are then each connected to the junction of the cathode of a diode and the anode of another diode in series, the other electrodes of which are connected respectively to terminals 21 and 22 of the ballast circuit 20 which then appears as a variable resistor in series with the three primary windings.
  • This resistance has the effect of influencing the voltage appearing at the terminals of the series combination of the three secondary windings, which constitute the output terminals 11 and 13 of the cycloconverter 10 which is then of the type with saturable core.
  • NO logic inverter
  • capacitors 14, 15 and 16 of high capacity for example, of the electrochemical type, between the outputs 53, 58 and 79 respectively of the first (51, 52), second ( 56, 57) and third (76, 77, 78) voltage dividers in order to perfect the filtering of the fractions of DC voltages, respectively applied to the inputs of the operational amplifiers 54 and 80.

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Description

L'invention concerne un circuit de contrôle et de régulation de la vitesse de rotation d'un rotor d'entraînement, notamment celui d'une anode tournante de tube radiogène, destiné à maintenir une vitesse sensiblement constante et à autoriser, par exemple, l'application de la très haute tension entre l'anode et la cathode de ce tube, dès que la vitesse de rotation a atteint une valeur de consigne préréglée.The invention relates to a circuit for controlling and regulating the speed of rotation of a drive rotor, in particular that of a rotating anode of an X-ray tube, intended to maintain a substantially constant speed and to allow, for example, the application of the very high voltage between the anode and the cathode of this tube, as soon as the speed of rotation has reached a preset reference value.

Dans des dispositifs connus de ce genre, on utilise souvent des relais sensibles à une valeur de seuil d'un courant dont on insère les bobinages en série avec les enroulements du stator constituant respectivement les phases principale et auxiliaire qui engendrent des champs magnétiques orthogonaux et qui sont alimentés respectivement par des courants déphasés l'un par rapport à l'autre au moyen d'un condensateur en série avec l'enroulement de la phase auxiliaire, par exemple, afin d'engendrer un champ magnétique tournant. En outre, on branche en parallèle avec le condensateur de déphasage alimentant la phase auxiliaire, un relais sensible à la tension qui se met en position de travail lorsque la tension alternative aux bornes du condensateur dépasse un seuil prédéterminé. Les contacts de trois relais y sont insérés en série dans un circuit d'autorisation de la mise sous tension du tube radiogène. L'inconvénient de cette disposition est de ne donner aucune indication de la vitesse de rotation réelle.In known devices of this kind, relays are often used which are sensitive to a threshold value of a current whose windings are inserted in series with the stator windings constituting respectively the main and auxiliary phases which generate orthogonal magnetic fields and which are supplied respectively by currents out of phase with each other by means of a capacitor in series with the winding of the auxiliary phase, for example, in order to generate a rotating magnetic field. In addition, a voltage-sensitive relay which goes into the working position when the alternating voltage across the capacitor exceeds a predetermined threshold is connected in parallel with the phase-shifting capacitor supplying the auxiliary phase. The contacts of three relays are inserted in series in an authorization circuit for energizing the X-ray tube. The disadvantage of this arrangement is that it gives no indication of the actual speed of rotation.

Dans la publication US-A-2185826 (voir préambule de la revendication 1), il a été proposé d'inhiber l'application de toute la très haute tension aux électrodes du tube radiogène, lorsque la vitesse de rotation du rotor est notablement inférieure à sa valeur normale, au moyen d'un dispositif interrupteur commandé genre relais actionné à l'aide d'un bobinage qui réagit aux variations de la tension aux bornes de l'enroulement de la phase auxiliaire. Cette tension alternative, si elle lui est appliquée par l'intermédiaire d'un condensateur, augmente avec la vitesse de rotation. Cette augmentation de la tension aux bornes de l'enroulement de la phase auxiliaire du stator avec celle de la vitesse de rotation du rotor, est principalement due selon la publication précitée, à l'augmentation de l'impédance apparente de cet enroulement qui est provoquée par la réaction variable avec la vitesse des courants induits dans le rotor sur le stator. L'impédance apparente de l'enroulement présente alors une composante inductive croissante qui est de signe opposé à celui de la réactance capacitive du condensateur de déphasage, ce qui entraîne une augmentation du courant dans la phase auxiliaire. Le relais présente une première tension de seuil pour laquelle il se met en position de travail et une seconde tension de seuil inférieure à la première pour laquelle il se remet en position de repos et qui correspondent respectivement à deux vitesses de rotation de l'anode peu éloignées de la vitesse nominale. Lorsqu'il est en position de travail, le contact du relais autorise la mise sous tension du tube radiogène. Ceci présente l'inconvénient d'autoriser la mise sous tension du tube, lorsque la tension aux bornes de l'enroulement de la phase auxiliaire dépasse un seuil qui peut également provenir de l'augmentation de la tension du réseau d'alimentation, même avec le rotor arrêté, par exemple, à cause d'une coupure de phase principale. Il faudra donc stabiliser la tension d'alimentation du stator.In publication US-A-2185826 (see preamble to claim 1), it has been proposed to inhibit the application of all very high voltage to the electrodes of the X-ray tube, when the speed of rotation of the rotor is significantly less than its normal value, by means of a relay-type controlled switching device actuated by means of a winding which reacts to variations in the voltage across the winding of the auxiliary phase. This alternating voltage, if applied to it via a capacitor, increases with the speed of rotation. This increase in the voltage at the terminals of the winding of the auxiliary phase of the stator with that of the speed of rotation of the rotor, is mainly due according to the aforementioned publication, to the increase in the apparent impedance of this winding which is caused by the variable reaction with the speed of the currents induced in the rotor on the stator. The apparent impedance of the winding then has an increasing inductive component which is of opposite sign to that of the capacitive reactance of the phase shift capacitor, which leads to an increase in the current in the auxiliary phase. The relay has a first threshold voltage for which it goes into the working position and a second threshold voltage lower than the first for which it returns to the rest position and which respectively correspond to two speeds of rotation of the low anode away from nominal speed. When in the working position, the relay contact authorizes energizing of the X-ray tube. This has the drawback of allowing the tube to be energized, when the voltage across the auxiliary phase winding exceeds a threshold which can also come from an increase in the voltage of the supply network, even with the rotor stopped, for example, because of a main phase cut. It will therefore be necessary to stabilize the stator supply voltage.

Dans le brevet américain n° 3,518,434, une régulation de la vitesse de rotation de l'anode est décrite qui met en jeu la mesure des courants traversant les phases principale et auxiliaire du moteur alternatif. Les valeurs obtenues sont comparées périodiquement à une rampe de tension qui permet d'élaborer un signal de commande de la tension d'alimentation du moteur. Mais les corrections d'un tel circuit sont assez imprécises, les courants dans les enroulements du stator variant assez peu et en sens contraire avec la vitesse du rotor. De plus, il ne tient pas compte des fluctuations de la tension d'alimentation du stator.In US Patent No. 3,518,434, a regulation of the speed of rotation of the anode is described which involves the measurement of the currents flowing through the main and auxiliary phases of the alternating motor. The values obtained are periodically compared with a voltage ramp which makes it possible to develop a signal for controlling the supply voltage of the motor. However, the corrections of such a circuit are quite imprecise, the currents in the stator windings varying little and in the opposite direction with the speed of the rotor. In addition, it does not take into account fluctuations in the supply voltage of the stator.

Le circuit, objet de l'invention, permet non seulement de pallier les inconvénients ci-dessus et de n'autoriser l'application de la très haute tension que lorsqu'une vitesse de rotation prédéterminée, proche de sa valeur de consigne est atteinte et d'inhiber cette application ou de l'arrêter lorsque cette vitesse n'a pas encore été atteinte ou est devenue inférieure à cette vitesse de consigne, mais également la régulation de cette vitesse par la mise en série avec l'alimentation des deux phases d'un ballast variable de façon continue entre deux valeurs de résistance.The circuit which is the subject of the invention not only makes it possible to alleviate the above drawbacks and to authorize the application of very high voltage only when a predetermined speed of rotation, close to its set value is reached and to inhibit this application or to stop it when this speed has not yet been reached or has fallen below this set speed, but also the regulation of this speed by putting in series with the supply of the two phases d '' a continuously variable ballast between two resistance values.

Suivant l'invention, un circuit de contrôle et de régulation de la vitesse de rotation d'un rotor, notamment celui d'entraînement d'une anode tournante de tube radiogène du type dans lequel ce rotor, disposé à l'intérieur d'une enveloppe de verre, est entraîné à l'aide d'un champ magnétique tournant engendré au moyen d'un stator situé à l'extérieur de l'enveloppe et comprenant au moins deux paires d'enroulements dont la première constitue la phase principale et la seconde la phase auxiliaire et dont les axes de symétrie respectifs, normaux à l'axe de rotation du rotor, sont angulairement décalés l'un par rapport à l'autre, ces deux phases étant réunies ensemble par l'une de leurs bornes pour constituer une borne d'alimentation commune couplée à l'une des bornes d'une source de tension alternative monophasée, l'autre borne de la phase principale étant reliée directement et l'autre borne de la phase auxiliaire étant réunie au moyen d'un condensateur de déphasage, à l'autre borne de la source monophasée, lequel circuit comporte des premiers moyens de comparaison fournissant un premier signal qui indique que la tension aux bornes de la phase principale a atteint ou dépassé un niveau de référence fixe et prédéterminé et des seconds moyens de comparaison des tensions de la phase principale et de la phase auxiliaire à une valeur réglable, est caractérisé en ce que les seconds moyens de comparaison fournissent un second signal qui indique que le rapport des tensions prélevées respectivement aux bornes des phases auxiliaire et principale a atteint ou dépassé une valeur réglable correspondant à une vitesse de consigne choisie et en ce qu'il comporte des moyens de combinaison du premier et du second signal fournissant, lors de la présence simultanée de ces derniers, un troisième signal indiquant que les deux conditions susmentionnées sont remplies, notamment pour autoriser l'application de la très haute tension aux électrodes du tube radiogène.According to the invention, a circuit for controlling and regulating the speed of rotation of a rotor, in particular that for driving a rotating anode of an X-ray tube of the type in which this rotor, disposed inside a glass envelope, is driven using a rotating magnetic field generated by means of a stator located outside the envelope and comprising at least two pairs of windings, the first of which constitutes the main phase and the second the auxiliary phase and whose respective axes of symmetry, normal to the axis of rotation of the rotor, are angularly offset relative to each other, these two phases being joined together by one of their terminals to constitute a common power supply terminal coupled to one of the terminals of a single-phase alternating voltage source, the other terminal of the main phase being connected directly and the other terminal of the auxiliary phase being connected by means of a capacitor phase shift, at the other terminal of the so single-phase urce, which circuit includes first comparison means providing a first signal which indicates that the voltage across the main phase has reached or exceeded a fixed and predetermined reference level and second means for comparing the voltages of the main phase and the auxiliary phase with an adjustable value, is characterized in that the second means comparators provide a second signal which indicates that the ratio of the voltages drawn respectively at the terminals of the auxiliary and main phases has reached or exceeded an adjustable value corresponding to a chosen reference speed and in that it comprises means for combining the first and of the second signal providing, during the simultaneous presence of the latter, a third signal indicating that the two aforementioned conditions are met, in particular to authorize the application of very high voltage to the electrodes of the X-ray tube.

On remarquera que suivant l'invention, c'est le rapport des tensions respectives de la phase auxiliaire et de la phase principale qui permet d'évaluer la vitesse de rotation et ce rapport est défini ici par les facteurs de division respectifs de deux diviseurs potentiométriques dont l'un est réglable pour définir une vitesse de consigne.It will be noted that according to the invention, it is the ratio of the respective voltages of the auxiliary phase and of the main phase which makes it possible to evaluate the speed of rotation and this ratio is defined here by the respective division factors of two potentiometric dividers one of which is adjustable to define a set speed.

L'invention sera mieux comprise et d'autres de ses caractéristiques et avantages apparaîtront à l'aide de la description ci-après et du dessin annexé s'y rapportant, donnés à titre d'exemple, dont la figure unique est un schéma de principe, partiellement synoptique, d'un mode de réalisation avantageux du circuit de l'invention.The invention will be better understood and other of its characteristics and advantages will appear with the aid of the description below and of the appended drawing relating thereto, given by way of example, the single figure of which is a diagram of principle, partially synoptic, of an advantageous embodiment of the circuit of the invention.

Sur la figure annexée, on a représenté en 1 une coupe schématique du rotor qui porte l'anode tournante du tube radiogène et qui est disposé à l'intérieur de l'enveloppe de verre 2, représentée en pointillé. Le stator 3 comprend deux paires d'enroulements 4 et 5 bobinés sur un circuit magnétique (non représenté), destinés à engendrer deux champs magnétiques alternatifs et orthogonaux, traversant le rotor 1 composé, par exemple, d'un cylindre extérieur creux en matériau conducteur, tel que le cuivre, et, éventuellement d'un cylindre intérieur également creux en matériau ferromagnétique, tel que le fer doux ou un alliage à faible rémanence, emmanchés l'un sur l'autre et supportés à l'aide de deux paliers ou roulements.In the appended figure, there is shown in 1 a schematic section of the rotor which carries the rotating anode of the X-ray tube and which is arranged inside the glass envelope 2, shown in dotted lines. The stator 3 comprises two pairs of windings 4 and 5 wound on a magnetic circuit (not shown), intended to generate two alternating and orthogonal magnetic fields, passing through the rotor 1 composed, for example, of a hollow outer cylinder of conductive material , such as copper, and possibly an inner cylinder also made of ferromagnetic material, such as soft iron or an alloy with low remanence, fitted one on the other and supported by two bearings or bearings.

La première borne 6 de la première paire d'enroulements 4 qui sont connectés en série et disposés de part et d'autre de l'enveloppe 2, qui constituent la phase principale, est reliée à une première borne de sortie 11 d'une source de tension alternative monophasée 10, telle qu'un cycloconvertisseur (éventuellement statique) ou multiplicateur (doubleur ou tripleur) de fréquence classique, dont les entrées 12 sont alimentées par le réseau de distribution mono- ou triphasé (50 ou 60 Hz) et qui fournit une tension alternative de fréquence plus élevée (150 ou 180 Hz, par exemple) que le réseau, permettant d'atteindre une vitesse de rotation comprise entre 8 000 et 10 000 tours/minute.The first terminal 6 of the first pair of windings 4 which are connected in series and arranged on either side of the casing 2, which constitute the main phase, is connected to a first output terminal 11 of a source of single-phase alternating voltage 10, such as a cycloconverter (possibly static) or multiplier (doubler or tripler) of conventional frequency, whose inputs 12 are supplied by the single- or three-phase distribution network (50 or 60 Hz) and which provides a higher frequency alternating voltage (150 or 180 Hz, for example) than the network, making it possible to reach a rotation speed of between 8,000 and 10,000 rpm.

La première borne 7 de la seconde paire d'enroulements 5, également connectés en série et constituant la phase auxiliaire, est réunie à la première borne de sortie 11 de la source 10 par l'intermédiaire d'un élément déphaseur 8, constitué ici par un condensateur 8, pour produire un déphasage entre la sortie 11 et la borne 7.The first terminal 7 of the second pair of windings 5, also connected in series and constituting the auxiliary phase, is joined to the first output terminal 11 of the source 10 by means of a phase-shifting element 8, constituted here by a capacitor 8, to produce a phase shift between the output 11 and the terminal 7.

Les secondes bornes respectives des phases principale 4 et auxiliaire 5 du stator 3 sont reliées ensemble pour former une borne commune 9 qui est réunie, par l'intermédiaire d'un circuit de ballast variable 20, à l'autre borne de sortie 13 de la source monophasée 10. Cette borne commune 9 constitue pour le circuit de contrôle et de régulation de cette figure le point de potentiel de référence (ou masse isolée).The second respective terminals of the main 4 and auxiliary 5 phases of the stator 3 are connected together to form a common terminal 9 which is joined, by means of a variable ballast circuit 20, to the other output terminal 13 of the single-phase source 10. This common terminal 9 constitutes for the control and regulation circuit of this figure the reference potential point (or isolated ground).

Le circuit de ballast 20 est un dipôle comportant entre ses bornes 21 et 22 une première résistance de ballast 23 (de quelques centaines d'ohms, par exemple) et, en parallèle avec cette première résistance 23, un pont composé de quatre diodes 24, 25, 26 et 27. Le point commun de l'anode de la première diode 24 avec la cathode de la seconde 25 constitue la première borne 21 du dipôle de ballast 20 et celui de la cathode de la troisième diode 26 avec l'anode de la quatrième 27, sa seconde borne 21. A travers l'autre diagonale du pont, c'est-à-dire entre la jonction 28 des cathodes des diodes 24 et 27 et celle 29 des anodes des diodes 25 et 26, est connecté le trajet collecteur-émetteur d'un transistor de puissance 30 qui constitue un élément à résistance variable, faible à l'état saturé et très élevée à l'état bloqué, et.qui varie de manière continue entre ces deux états. La résistance du trajet collecteur-émetteur du transistor 30 constitue l'élément variable du circuit de ballast 20 qui est en parallèle avec la première résistance 23 de valeur fixe.The ballast circuit 20 is a dipole comprising between its terminals 21 and 22 a first ballast resistor 23 (of a few hundred ohms, for example) and, in parallel with this first resistor 23, a bridge composed of four diodes 24, 25, 26 and 27. The common point of the anode of the first diode 24 with the cathode of the second 25 constitutes the first terminal 21 of the ballast dipole 20 and that of the cathode of the third diode 26 with the anode of the fourth 27, its second terminal 21. Across the other diagonal of the bridge, that is to say between the junction 28 of the cathodes of diodes 24 and 27 and that 29 of the anodes of diodes 25 and 26, is connected the collector-emitter path of a power transistor 30 which constitutes a variable resistance element, low in the saturated state and very high in the blocked state, and which varies continuously between these two states. The resistance of the collector-emitter path of transistor 30 constitutes the variable element of the ballast circuit 20 which is in parallel with the first resistance 23 of fixed value.

Le transistor de puissance 30, de type à haute tension (tel que le type BU 208 de SESCOSEM ayant une tension de claquage collecteur-émetteur VcEx de 1 500 V environ), a son collecteur réuni à sa base par l'intermédiaire d'une seconde résistance de polarisation 31 (de quelques kiloohms, par exemple) qui forme avec le phototransistor 32 d'un premier photocoupleur 33 un diviseur de tension fournissant une polarisation variable au transistor 30, lorsque la diode électroluminescente 34 dont la surface photoémissive est optiquement couplée à la surface photosensible du phototransistor 32, est parcourue d'un courant dans le sens direct. La commande de la résistance de ballast 20 entre les bornes 21 et 22 sera décrite plus loin.The power transistor 30, of high-voltage type (such as type BU 208 of SESCOSEM having a collector-emitter breakdown voltage V cEx of approximately 1,500 V), has its collector joined to its base by means of a second polarization resistor 31 (of a few kiloohms, for example) which forms with the phototransistor 32 of a first photocoupler 33 a voltage divider providing variable polarization to the transistor 30, when the light-emitting diode 34 whose photoemissive surface is optically coupled on the photosensitive surface of the phototransistor 32, is traversed a current in the direct direction. The control of the ballast resistor 20 between terminals 21 and 22 will be described later.

La tension alternative présente entre la borne 6 de la phase principale 4 et la borne commune 9 est redressée à l'aide d'une cinquième diode 40 qui alimente à travers une troisième 41 et une quatrième 42 résistance en série, qui servent à filtrer et à réduire le niveau de la redressée, une cellule de filtrage en forme de π composée d'un second condensateur 43, d'une cinquième résistance 44 et d'un troisième condensateur 45 électrochimique. L'une 46 des armatures du second condensateur 43 reliée à la jonction de la quatrième 42 et de la cinquième 44 résistance est également relié à l'une des bornes d'une sixième résistance 47 dont l'autre borne est reliée à la cathode d'une diode Zener 48 et à l'armature positive d'un quatrième condensateur 49, par exemple, électrochimique. L'autre armature du second condensateur 43, les armatures négatives respectives du troisième 45 et du quatrième condensateur 49 et l'anode de la diode Zener 48 sont reliées à la borne commune 9. La jonction 50 de la cathode de la diode Zener 48 avec la résistance 47 et le condensateur 49 fournit une tension continue stabilisée (et filtrée), positive par rapport au potentiel de référence de la borne 9 (de 24 volts, par exemple) qui permet, d'une part, d'alimenter les cinq amplificateurs opérationnels équipant le circuit et, d'autre part, d'élaborer une tension de référence fixe servant à la comparaison.The alternating voltage present between the terminal 6 of the main phase 4 and the common terminal 9 is rectified using a fifth diode 40 which feeds through a third 41 and a fourth resistor 42 in series, which serve to filter and to reduce the level of the rectified, a π-shaped filter cell composed of a second capacitor 43, a fifth resistor 44 and a third electrochemical capacitor 45. One 46 of the armatures of the second capacitor 43 connected to the junction of the fourth 42 and the fifth 44 resistor is also connected to one of the terminals of a sixth resistor 47, the other terminal of which is connected to the cathode of a Zener diode 48 and to the positive armature of a fourth capacitor 49, for example, electrochemical. The other armature of the second capacitor 43, the respective negative armatures of the third 45 and of the fourth capacitor 49 and the anode of the Zener diode 48 are connected to the common terminal 9. The junction 50 of the cathode of the Zener diode 48 with the resistor 47 and the capacitor 49 provides a stabilized (and filtered) direct voltage, positive with respect to the reference potential of the terminal 9 (of 24 volts, for example) which makes it possible, on the one hand, to supply the five amplifiers operational equipping the circuit and, on the other hand, to develop a fixed reference voltage used for comparison.

A cette fin, un premier diviseur de tension résistif composé d'une septième 51 et d'une huitième résistance 52 en série, est connecté aux bornes de la diode Zener 48, leur point commun 53 réuni à l'entrée non inverseuse d'un premier amplificateur opérationnel intégré 54 au moyen d'une neuvième résistance 55, lui fournit une tension de référence que cet amplificateur, utilisé comme comparateur de tension, compare à une fraction prédéterminée de la tension redressée et filtrée aux bornes du troisième condensateur 45, dont le niveau est proportionnel à la valeur crête de la tension alternative alimentant la phase principale 4. Cette fraction est fournie au moyen d'un second diviseur de tension résistif connecté en parallèle avec le troisième condensateur 45 et comprenant une dixième 56 et une onzième 57 résistance en série dont le point commun 58 est réuni, au moyen d'une douzième résistance 59 (de même valeur que la neuvième 55), à l'entrée inverseuse du premier amplificateur 54. La sortie 60 du premier amplificateur 54 fournit donc une tension positive sensiblement égale à sa tension d'alimentation (état logique haut), lorsque la tension de référence appliquée à son entrée non inverseuse est supérieure à la fraction de la tension de phase principale redressée, appliquée à son entrée inverseuse. Dans le cas contraire, c'est-à-dire lorsque la fraction de la tension de phase principale redressée dépasse la tension de référence fixe, la sortie 60 fournit une tension nulle (état bas) par rapport au potentiel de référence de la borne 9.To this end, a first resistive voltage divider composed of a seventh 51 and an eighth resistor 52 in series, is connected to the terminals of the Zener diode 48, their common point 53 joined to the non-inverting input of a first integrated operational amplifier 54 by means of a ninth resistor 55, supplies it with a reference voltage which this amplifier, used as a voltage comparator, compares to a predetermined fraction of the rectified and filtered voltage across the terminals of the third capacitor 45, the level is proportional to the peak value of the alternating voltage supplying the main phase 4. This fraction is supplied by means of a second resistive voltage divider connected in parallel with the third capacitor 45 and comprising a tenth 56 and an eleventh 57 resistor in series whose common point 58 is united, by means of a twelfth resistor 59 (of the same value as the ninth 55), at the inverting input of the first amplifier 54. The fate ie 60 of the first amplifier 54 therefore supplies a positive voltage substantially equal to its supply voltage (high logic state), when the reference voltage applied to its non-inverting input is greater than the fraction of the rectified main phase voltage, applied at its inverting input. In the opposite case, that is to say when the fraction of the rectified main phase voltage exceeds the fixed reference voltage, the output 60 provides a zero voltage (low state) relative to the reference potential of terminal 9 .

La tension alternative présente entre la borne 7 de la phase auxiliaire 5 et la borne commune 9 est également redressée au moyen d'une sixième diode 70 dont la cathode est reliée à travers une treizième 71 et une quatorzième 72 résistance à l'une des armatures d'un cinquième condensateur 73 dont l'autre armature est reliée à la borne commune 9. Le point commun de la résistance 72 et du condensateur 73 est relié, en outre, à l'une des bornes d'une quinzième résistance 74 dont l'autre borne est reliée à l'armature positive d'un sixième condensateur 75, par exemple, électrochimique dont l'armature négative est reliée à la borne commune 9. Les éléments 73 à 75 forment une cellule de filtrage en π semblable à celle qui est formée par les éléments 43 à 45.The alternating voltage present between the terminal 7 of the auxiliary phase 5 and the common terminal 9 is also rectified by means of a sixth diode 70 whose cathode is connected through a thirteenth 71 and a fourteenth 72 resistance to one of the armatures of a fifth capacitor 73, the other armature of which is connected to the common terminal 9. The common point of the resistor 72 and of the capacitor 73 is also connected to one of the terminals of a fifteenth resistor 74, the l 'other terminal is connected to the positive armature of a sixth capacitor 75, for example, electrochemical whose negative armature is connected to the common terminal 9. The elements 73 to 75 form a filter cell in π similar to that which is formed by elements 43 to 45.

Le sixième condensateur 75 est connecté en parallèle avec un troisième diviseur de tension résistif de facteur de division réglable, qui à cette fin est composé d'une seizième résistance 76, d'un potentiomètre 77 et d'une dix-septième résistance 78 connectés en série. Le curseur 79 du potentiomètre 77 fournit ainsi une fraction réglable d'une tension continue proportionnelle à l'amplitude crête de la tension alternative appliquée entre les bornes 7 et 9 de la phase auxiliaire 5.The sixth capacitor 75 is connected in parallel with a third resistive voltage divider of adjustable division factor, which for this purpose is composed of a sixteenth resistor 76, a potentiometer 77 and a seventeenth resistor 78 connected in series. The cursor 79 of the potentiometer 77 thus provides an adjustable fraction of a direct voltage proportional to the peak amplitude of the alternating voltage applied between the terminals 7 and 9 of the auxiliary phase 5.

Un second amplificateur opérationnel 80 est utilisé en tant que second comparateur, dont l'entrée non inverseuse est réunie, par l'intermédiaire d'une dix-huitième résistance 81, au curseur 79 du potentiomètre 77 et dont l'entrée inverseuse est reliée à la jonct,on 58 du second diviseur 56-57 fournissant une tension continue proportionnelle à l'amplitude crête de la tension alternative aux bornes de la phase principale 4, par l'intermédiaire d'une dix-neuvième résistance 82.A second operational amplifier 80 is used as a second comparator, the non-inverting input of which is connected, via an eighteenth resistor 81, to the cursor 79 of the potentiometer 77 and the inverting input of which is connected to the junction, one 58 of the second divider 56-57 providing a DC voltage proportional to the peak amplitude of the AC voltage across the main phase 4, via a nineteenth resistor 82.

Le second amplificateur opérationnel 80 dont la sortie 83 est réunie à son entrée non inverseuse au moyen d'une vingtième résistance 84 de réaction positive permettant d'accélérer le basculement entre ses deux états, permet de comparer les amplitudes crête des deux phases principale 4 et auxiliaire 5. La sortie 83 du second comparateur 80 est dans son état haut (où il fournit une tension positive sensiblement égale à sa tension d'alimentation), lorsque la fraction réglable de la tension de la phase auxiliaire redressée et filtrée, prélevée sur le curseur 79 du potentiomètre 77, est supérieure à la fraction fixe de la tension de la phase principale redressée et filtrée, sur le point commun 58 du second diviseur 56-57. Si la tension aux bornes de la phase principale 4 dépasse celle aux bornes de la phase auxiliaire 5, la sortie 83 du second comparateur 80 fournit une tension nulle (par rapport à la borne 9), c'est-à-dire un état logique bas.The second operational amplifier 80, the output 83 of which is joined to its non-inverting input by means of a twentieth resistor 84 of positive reaction making it possible to accelerate the switching between its two states, makes it possible to compare the peak amplitudes of the two main phases 4 and auxiliary 5. The output 83 of the second comparator 80 is in its high state (where it provides a positive voltage substantially equal to its supply voltage), when the adjustable fraction of the voltage of the auxiliary phase rectified and filtered, taken from the cursor 79 of potentiometer 77, is greater than the fixed fraction of the voltage of the main phase rectified and filtered, on the common point 58 of the second divider 56-57. If the voltage at the terminals of the main phase 4 exceeds that at the terminals of the auxiliary phase 5, the output 83 of the second comparator 80 provides a zero voltage (relative to terminal 9), that is to say a logic state low.

En effet, au cours du démarrage et de l'accélération du rotor 2, la réactance inductive apparente X5 = wL5 de la phase auxiliaire 5 (où w = 2πf et f est la fréquence de la tension alternative fournie par le cycloconvertisseur 10) augmente, de sorte que la réactance Xs = wLs - 1/wC8 résultant de sa combinaison en série avec celle du condensateur-déphaseur 8 dont la réactance capacitive 1/ωC8 est supérieure à la valeur initiale de wLs, diminue. Cette diminution de la réactance Xs entraîne une augmentation du courant 15 dans la phase auxiliaire 5 dont l'effet est cumulatif avec l'augmentation de la réactance apparente Xs, de sorte que l'amplitude de la tension V5 de la phase auxiliaire 5 égale à X5 - Is = ωL5· 15, augmente également, c'est-à-dire l'on obtient une augmentation de la tension de la phase auxiliaire 5, tandis que la tension de la phase principale 4 correspondant à la tension entre les bornes 11 et 13 de la source 10, reste sensiblement constante, pendant les phases de lancement et d'accélération.Indeed, during the start-up and acceleration of the rotor 2, the apparent inductive reactance X 5 = wL 5 of the auxiliary phase 5 (where w = 2πf and f is the frequency of the alternating voltage supplied by the cycloconverter 10) increases, so that the reactance X s = wL s - 1 / wC 8 resulting from its combination in series with that of the capacitor-phase shifter 8 whose capacitive reactance 1 / ωC 8 is greater than the initial value of wL s , decreases. This decrease in the reactance X s results in an increase in the current 1 5 in the auxiliary phase 5 whose effect is cumulative with the increase in the apparent reactance X s , so that the amplitude of the voltage V5 of the auxiliary phase 5 equal to X 5 - I s = ωL 5 · 1 5 , also increases, i.e. an increase in the voltage of the auxiliary phase 5 is obtained, while the voltage of the main phase 4 corresponds at the voltage between terminals 11 and 13 of the source 10, remains substantially constant, during the phases of launch and acceleration.

La combinaison comprenant le deuxième diviseur de tension 56, 57 fixe, le troisième diviseur de tension 76, 77, 78 réglable et le second comparateur 80 constitue un moyen pour déterminer le rapport des tensions aux bornes respectives des phases auxiliaire 5 et principale 4 qui correspond à la vitesse de consigne. Plus précisément, lorsqu'il y a égalité des fractions de tensions appliquées aux entrées respectives du second comparateur 80, le rapport de la tension de la phase auxiliaire 5 à la tension de la phase principale 4 est égale au quotient des facteurs de division du second et du premier diviseur. Ce quotient étant réglable à l'aide du potentiomètre 77, il permet de signaler par un changement d'état (basculement) à la sortie 83 du second comparateur 80 quand ce rapport de tensions a atteint sa valeur de consigne choisie. L'expérience a montré que c'est surtout ce rapport de tensions et non pas uniquement la tension de la phase auxiliaire utilisée dans la publication US-A-2185826 précitée et qui varie également en fonction de la tension entre les bornes 11 et 13 de sortie de la source fournissant la tension alternative monophasée 10, qui indique de façon fiable qu'une vitesse de consigne préalablement choisie a été atteinte. Ceci est encore plus vrai si l'on modifie notablement la tension d'alimentation des deux phases lors d'une régulation de la vitesse à l'aide d'un circuit de ballast variable 20, comme dans le circuit de la figure annexée, qui sera décrit ultérieurement.The combination comprising the second voltage divider 56, 57 fixed, the third voltage divider 76, 77, 78 adjustable and the second comparator 80 constitutes a means for determining the ratio of the voltages at the respective terminals of the auxiliary 5 and main 4 phases which corresponds at the set speed. More precisely, when there are equality of the fractions of voltages applied to the respective inputs of the second comparator 80, the ratio of the voltage of the auxiliary phase 5 to the voltage of the main phase 4 is equal to the quotient of the division factors of the second and the first divider. This quotient being adjustable using the potentiometer 77, it makes it possible to signal by a change of state (switching) at the output 83 of the second comparator 80 when this voltage ratio has reached its chosen reference value. Experience has shown that it is above all this voltage ratio and not only the voltage of the auxiliary phase used in the aforementioned publication US-A-2185826, which also varies according to the voltage between terminals 11 and 13 of output of the source supplying the single-phase alternating voltage 10, which reliably indicates that a previously chosen reference speed has been reached. This is even more true if the supply voltage of the two phases is notably modified during speed regulation using a variable ballast circuit 20, as in the circuit of the appended figure, which will be described later.

En résumé, c'est le rapport des facteurs de division des deux diviseurs de tension qui permettent de déterminer le rapport des tensions des deux phases qui correspond à la vitesse de consigne. Lorsque cette vitesse de consigne est atteinte, l'égalité des tensions réglable (V79) et fixe (V53) fait basculer le second comparateur 80 de son état bas à son état haut.In summary, it is the ratio of the division factors of the two voltage dividers which makes it possible to determine the ratio of the voltages of the two phases which corresponds to the set speed. When this set speed is reached, the adjustable (V 79 ) and fixed (V53) voltage equality causes the second comparator 80 to switch from its low state to its high state.

L'autorisation de l'application de la très haute tension aux électrodes du tube radiogène ne devant être donnée que lorsque, simultanément, la tension aux bornes 6, 9 de la phase principale 4 dépasse un niveau correspondant à la tension de référence V53 et le rapport des tensions susmentionné, correspondant à la vitesse de consigne, est atteint ou dépassé, il faut donc combiner les états de sortie respectifs du premier 54 et du second comparateur 80 pour en déterminer la coïncidence.Authorization for the application of very high voltage to the electrodes of the X-ray tube should only be given when, simultaneously, the voltage at terminals 6, 9 of the main phase 4 exceeds a level corresponding to the reference voltage V 53 and the aforementioned voltage ratio, corresponding to the set speed, is reached or exceeded, it is therefore necessary to combine the respective output states of the first 54 and of the second comparator 80 to determine their coincidence.

A cette fin, la sortie 83 du second comparateur 80 est reliée à l'anode d'une diode électroluminescente 35 d'un second photocoupleur 36, dont la cathode est reliée à l'anode d'une septième diode 85 et qui assure l'isolement entre les circuits. La cathode de la septième diode 85 est réunie au moyen d'une vingt et unième résistance 86 à la sortie 60 du premier comparateur 54. On obtient ainsi que la diode électroluminescente 35 du second photocoupleur 36 n'est alimentée en courant que lorsque la sortie 83 du second comparateur 80 est dans son état haut et lorsque, en même temps, la sortie 60 du premier comparateur 54 est dans l'état bas.To this end, the output 83 of the second comparator 80 is connected to the anode of a light-emitting diode 35 of a second photocoupler 36, the cathode of which is connected to the anode of a seventh diode 85 and which ensures the isolation between circuits. The cathode of the seventh diode 85 is brought together by means of a twenty-first resistor 86 at the output 60 of the first comparator 54. This gives the light-emitting diode 35 of the second photocoupler 36 only being supplied with current when the output 83 of the second comparator 80 is in its high state and when, at the same time, the output 60 of the first comparator 54 is in the low state.

Ceci signifie que la diode électroluminescente 35 ne conduit que lorsque l'amplitude crête de la tension de la phase principale V4 dépasse une valeur déterminée, proportionnelle à la tension de référence continue V53 et lorsque la vitesse de rotation du rotor 2 est suffisante pour que la fraction réglable en fonction de la vitesse de consigne désirée, de l'amplitude crête de la tension de la phase auxiliaire V5 dépasse la fraction prédéterminée et constante de l'amplitude crête de la tension de la phase principale V4.This means that the light-emitting diode 35 only conducts when the peak amplitude of the voltage of the main phase V 4 exceeds a determined value, proportional to the continuous reference voltage V 53 and when the speed of rotation of the rotor 2 is sufficient to that the fraction adjustable as a function of the desired target speed, of the peak amplitude of the voltage of the auxiliary phase V5 exceeds the predetermined and constant fraction of the peak amplitude of the voltage of the main phase V 4 .

La diode électroluminescente 35 du second photocoupleur 36 éclaire, lorsqu'elle est alimentée en courant continu, la surface photosensible d'un phototransistor du type NPN 37, par exemple, dont l'émetteur est relié à la masse 38 du générateur radiologique (non représenté), par exemple, et dont le collecteur est réuni, par l'intermédiaire du bobinage 39 d'un relais ou d'un contacteur à commande électromagnétique, au pôle positif 87 d'une source de tension continue d'alimentation (+ Vcc). Lorsque la diode électroluminescente 35 conduit, le phototransistor 37 devient saturé et les contacts mobiles 61, 62, 63 couplés ensemble passent de leur position de repos à leur position de travail. Le premier contact mobile 61 relie ensemble deux contacts fixes 64 et 65 qui sont insérés dans le circuit d'autorisation de la mise sous tension du tube radiogène, situé dans le générateur radiologique, par exemple.The light-emitting diode 35 of the second photocoupler 36 illuminates, when it is supplied with direct current, the photosensitive surface of a phototransistor of the NPN type 37, for example, the emitter of which is connected to the ground 38 of the radiological generator (not shown ), for example, and whose collector is connected, via the winding 39 of a relay or a contactor with electromagnetic control, to the positive pole 87 of a DC supply voltage source (+ V DC ). When the light-emitting diode 35 conducts, the phototransistor 37 becomes saturated and the movable contacts 61, 62, 63 coupled together pass from their rest position to their working position. The first movable contact 61 connects together two fixed contacts 64 and 65 which are inserted in the authorization circuit for energizing the X-ray tube, located in the X-ray generator, for example.

Le circuit de régulation de la vitesse de rotation comporte un troisième amplificateur opérationnel 90 dont l'entrée non inverseuse est réunie, par l'intermédiaire d'une vingt-deuxième résistance 91, au curseur 79 du potentiomètre 77 fournissant la tension continue V79 dont le niveau représente la tension réglable précitée de l'amplitude de la tension aux bornes de la phase auxiliaire V6. Il comporte, en outre, un quatrième amplificateur opérationnel 92 dont l'entrée non inverseuse est réunie, par l'intermédiaire d'une vingt-troisième résistance 93, au point commun 58 du second diviseur 56-57, qui fournit la tension continue V58 dont le niveau représente la fraction constante de l'amplitude de la tension aux bornes de la phase principale V4.The speed regulation circuit includes a third operational amplifier 90, the non-inverting input of which is connected, via a twenty-second resistor 91, to the cursor 79 of the potentiometer 77 supplying the DC voltage V 79 of which the level represents the above adjustable voltage of the amplitude of the voltage across the auxiliary phase V 6 . It further comprises a fourth operational amplifier 92, the non-inverting input of which is brought together, via a twenty-third resistor 93, at the common point 58 of the second divider 56-57, which supplies the DC voltage V 58 whose level represents the constant fraction of the amplitude of the voltage across the main phase V 4 .

Les sorties des amplificateurs 90 et 92 sont respectivement réunies au moyen d'une vingt- quatrième 94 et d'une vingt-cinquième 95 résistance de contre-réaction, à leurs entrées inver- seuses qui sont. réunies ensemble à l'aide d'une vingt-sixième résistance 96. Les étages comprenant les amplificateurs 90 et 92 constituent des étages d'amplification sans inversion de polarité, à impédance d'entrée élevée. Leurs sorties alimentent respectivement, par l'intermédiaire d'une vingt-septième 97 et une vingt-huitième 98 résistance, les entrées non inverseuse et inverseuse d'un cinquième amplificateur opérationnel 99. La sortie 100 du cinquième amplificateur opérationnel 99 est réunie à son entrée inverseuse par un circuit de contre-réaction à seuil comportant une vingt-neuvième résistance 101, une huitième 102, une neuvième 103 et une dizième 104 diode en série. Cette disposition permet de réduire notablement le gain de l'amplificateur 99 dès qu'une tension de seuil déterminée par le seuil de conduction des éléments 102-104, lesquels compensent le seuil de conduction de la diode électroluminescente 34, est dépassée.The outputs of amplifiers 90 and 92 are respectively connected by means of a twenty-fourth 94 and a twenty-fifth 95 feedback resistance, to their inverting inputs which are. joined together using a twenty-sixth resistor 96. The stages comprising the amplifiers 90 and 92 constitute amplification stages without reverse polarity, with high input impedance. Their outputs supply respectively, via a twenty-seventh 97 and a twenty-eighth 98 resistor, the non-inverting and inverting inputs of a fifth operational amplifier 99. The output 100 of the fifth operational amplifier 99 is joined to its inverting input by a threshold feedback circuit comprising a twenty-ninth resistor 101, an eighth 102, a ninth 103 and a tenth 104 diode in series. This arrangement makes it possible to significantly reduce the gain of the amplifier 99 as soon as a threshold voltage determined by the conduction threshold of the elements 102-104, which compensate for the conduction threshold of the light-emitting diode 34, is exceeded.

La sortie 100 de l'amplificateur 99 est réunie, en outre, à la borne commune 9 par l'intermédiaire, d'une part, d'une trentième résistance 105 et, d'autre part, par une onzième diode 106 et une trente et unième résistance 107 en série avec la diode électroluminescente 34 du premier photocoupleur 33.The output 100 of the amplifier 99 is joined, moreover, to the common terminal 9 via, on the one hand, a thirtieth resistor 105 and, on the other hand, by an eleventh diode 106 and a thirty and a first resistor 107 in series with the light-emitting diode 34 of the first photocoupler 33.

La diode électroluminescente 34 du premier photocoupleur 33 en série avec la onzième diode 106 présentent un seuil de conduction prédéterminé qui doit être atteint dès que la fraction de consigne V79 de la tension de phase auxiliaire redressée a dépassé la fraction fixe V58 de la tension de phase principale redressée. Les trois diodes 102 à 104 en série avec la résistance de contre-réaction 101 assurent à l'amplificateur 99 un gain proche de sa valeur à boucle ouverte jusqu'à ce que sa tension de sortie ait atteint ce seuil de conduction. Par la suite son gain est déterminé par les résistances de contre-réaction 101 et d'entrée 98 pour que la variation du courant dans la diode électroluminescente 34 soit graduelle.The light-emitting diode 34 of the first photocoupler 33 in series with the eleventh diode 106 have a predetermined conduction threshold which must be reached as soon as the set fraction V 79 of the rectified auxiliary phase voltage has exceeded the fixed fraction V 58 of the voltage main phase rectified. The three diodes 102 to 104 in series with the feedback resistance 101 provide the amplifier 99 with a gain close to its open loop value until its output voltage has reached this conduction threshold. Thereafter its gain is determined by the feedback resistors 101 and input 98 so that the variation of the current in the light-emitting diode 34 is gradual.

Pendant que la fraction fixe V58 de la tension de phase principale V4 est supérieure à la fraction de consigne préréglée V79 de la tension de phase auxiliaire V5, la sortie 100 fournit une tension nulle (puisqu'elle n'est pas alimentée par une tension négative par rapport à la borne 9). La diode électroluminescente 34 du premier photocoupleur 33 reste éteinte et le phototransistor 32 reste bloqué, de sorte que le transistor de puissance haute-tension 30 devient saturé au cours de la quasi-totalité de chacune des alternances de la tension alternative alimentant les enroulements 4, 5 par la borne commune 9. Cette saturation se produit peu après chaque passage par zéro de la tension alternative du fait des seuils de conduction du transistor 30 et des diodes 24 à 27 du pont, dont deux sont chaque fois conducteurs en série, par l'intermédiaire du trajet collecteur-émetteur du transistor 30 qui n'est polarisé qu'à travers la résistance 31. La chute de tension résiduelle entre les bornes 21 et 22 du circuit de ballast 20 est alors faible (7 volts environ) par rapport à la tension (de 1 000 V crête environ) fournie par le cycloconvertisseur 10. Ceci permet le démarrage (lancement) du moteur avec des courants et tensions élevées, c'est-à-dire à pleine puissance qui est également appliquée pendant la phase d'accélération.While the fixed fraction V58 of the main phase voltage V 4 is greater than the preset reference fraction V 79 of the auxiliary phase voltage V5, the output 100 provides a zero voltage (since it is not supplied by a negative voltage with respect to terminal 9). The light-emitting diode 34 of the first photocoupler 33 remains off and the phototransistor 32 remains blocked, so that the high-voltage power transistor 30 becomes saturated during almost all of the alternations of the alternating voltage supplying the windings 4, 5 by the common terminal 9. This saturation occurs shortly after each zero crossing of the alternating voltage due to the conduction thresholds of the transistor 30 and the diodes 24 to 27 of the bridge, two of which are each conductor in series, through intermediary of the collector-emitter path of the transistor 30 which is only polarized through the resistor 31. The residual voltage drop between the terminals 21 and 22 of the ballast circuit 20 is then low (approximately 7 volts) compared to the voltage (of approximately 1000 V peak) supplied by the cycloconverter 10. This allows the starting (starting) of the motor with high currents and voltages, that is to say at full power which is also nt applied during the acceleration phase.

Lorsque la vitesse de rotation réelle du rotor 2 a dépassé de peu la vitesse de consigne pour laquelle la tension V79 est égale à la tension Vsa, la sortie 100 du cinquième amplificateur 99 fournit une tension positive qui provoque un courant à travers la diode électroluminescente 34 ayant pour effet de rendre le phototransistor 32 conducteur de sorte que celui-ci réduise la tension de polarisation de la jonction base-émetteur du transistor de puissance 30. La résistance du trajet collecteur-émetteur de ce transistor 30 augmente alors avec l'éclairement croissant du phototransistor 32. Cette augmentation de la résistance du trajet collecteur-émetteur du transistor de puissance 30 a pour effet de diminuer la tension aux bornes des phases principale et auxiliaire par la chute de tension entre les bornes 21 et 22 du circuit de ballast 20, pour que les courants qui les parcourent soient réduits à leurs valeurs juste nécessaires au maintien de la vitesse de rotation désirée.When the actual rotation speed of the rotor 2 has slightly exceeded the set speed for which the voltage V 79 is equal to the voltage V sa , the output 100 of the fifth amplifier 99 provides a positive voltage which causes a current through the diode light emitting 34 having the effect of making the phototransistor 32 conductive so that it reduces the bias voltage of the base-emitter junction of the power transistor 30. The resistance of the collector-emitter path of this transistor 30 then increases with the increasing illumination of the phototransistor 32. This increase in the resistance of the collector-emitter path of the power transistor 30 has the effect of reducing the voltage across the main and auxiliary phases by the voltage drop between the terminals 21 and 22 of the ballast circuit 20, so that the currents flowing through them are reduced to their values just necessary to maintain the desired speed of rotation.

Il est à noter ici que du fait de l'augmentation de la résistance du trajet collecteur-émetteur du transistor de puissance 30, les tensions redressées et filtrées subissent une réduction notable. Afin d'éviter que cette baisse de tension ne change les conditions de fonctionnement du circuit de contrôle et de régulation, les contacts fixes du relais reliés par ses contacts mobiles 62 et 63 sont respectivement connectés de manière à court-circuiter la troisième 41 et la treizième 71 résistance des circuits redresseurs respectifs des tensions des phases principale et auxiliaire.It should be noted here that due to the increase in the resistance of the collector-emitter path of the power transistor 30, the rectified and filtered voltages undergo a significant reduction. In order to prevent this drop in voltage from changing the operating conditions of the control and regulation circuit, the fixed contacts of the relay connected by its movable contacts 62 and 63 are respectively connected so as to short-circuit the third 41 and the thirteenth 71 resistance of the respective rectifier circuits of the voltages of the main and auxiliary phases.

L'invention n'est pas limitée au mode de réalisation décrit précédemment et illustré par la figure annexée, mais s'étend à des variantes équivalentes de celui-ci. Par exemple, le circuit de ballast 20 peut être inséré dans le circuit des roulements primaires d'un transformateur triphasé équipant le cycloconvertisseur 10 qui est alors un tripleur statique, dont les bornes froides (non reliées aux phases du réseau) sont alors reliées chacune à la jonction de la cathode d'une diode et de l'anode d'une autre diode en série, dont les autres électrodes sont reliées respectivement aux bornes 21 et 22 du circuit de ballast 20 qui apparaît alors comme une résistance variable en série avec les trois enroulements primaires. Cette résistance a pour effet d'influer sur la tension apparaissant aux bornes de la combinaison série des trois enroulements secondaires, qui constituent les bornes de sortie 11 et 13 du cycloconvertisseur 10 qui est alors du type à noyau saturable.The invention is not limited to the embodiment described above and illustrated by the appended figure, but extends to equivalent variants thereof. For example, the ballast circuit 20 can be inserted in the circuit of the primary bearings of a three-phase transformer equipping the cycloconverter 10 which is then a static tripler, whose cold terminals (not connected to the network phases) are then each connected to the junction of the cathode of a diode and the anode of another diode in series, the other electrodes of which are connected respectively to terminals 21 and 22 of the ballast circuit 20 which then appears as a variable resistor in series with the three primary windings. This resistance has the effect of influencing the voltage appearing at the terminals of the series combination of the three secondary windings, which constitute the output terminals 11 and 13 of the cycloconverter 10 which is then of the type with saturable core.

On peut également envisager de combiner les états de sortie du premier 54 et du second comparateur 80 au moyen d'une porte logique du type ET ou NON-ET dont l'une des entrées serait précédée d'un inverseur logique (NON) qui pourrait être remplacé par l'inversion des connections des entrées de l'un des comparateurs 54 ou 80. La sortie de cette porte pouvant alors alimenter le bobinage 39 du relais.One can also consider combining the output states of the first 54 and the second comparator 80 by means of a logic gate of the AND or NAND type, one of the inputs of which would be preceded by a logic inverter (NO) which could be replaced by reversing the connections of the inputs of one of the comparators 54 or 80. The output of this door can then supply the winding 39 of the relay.

Le circuit objet de l'invention présente, par rapport à l'état de la technique, notamment les avantages suivants :

  • - d'ajuster automatiquement le temps de lancement à pleine puissance aux caractéristiques de l'ensemble composé du stator, du rotor et de la charge (anode), variables dans le temps et d'un tube ou moteur à l'autre ;
  • - d'autoriser la mise sous tension des électrodes du tube radiogène uniquement lorsque la vitesse du rotor est proche de sa valeur de consigne ; et
  • - de ne fournir aux enroulements du stator que le courant nécessaire au maintien de la vitesse rotation choisie.
The circuit object of the invention has, compared to the state of the art, in particular the following advantages:
  • - to automatically adjust the launch time at full power to the characteristics of the assembly consisting of the stator, the rotor and the load (anode), variable over time and from one tube or motor to another;
  • - authorize the energization of the electro of the X-ray tube only when the speed of the rotor is close to its set value; and
  • - only supply the stator windings with the current necessary to maintain the chosen rotation speed.

On remarquera ici qu'il peut s'avérer avantageux de connecter des condensateurs 14, 15 et 16 de capacité élevée, par exemple, du type électrochimique, entre les sorties 53, 58 et 79 respectives des premier (51, 52), second (56, 57) et troisième (76, 77, 78) diviseurs de tension afin de parfaire le filtrage des fractions de tensions continues, respectivement appliquées aux entrées des amplificateurs opérationnels 54 et 80.It will be noted here that it may prove advantageous to connect capacitors 14, 15 and 16 of high capacity, for example, of the electrochemical type, between the outputs 53, 58 and 79 respectively of the first (51, 52), second ( 56, 57) and third (76, 77, 78) voltage dividers in order to perfect the filtering of the fractions of DC voltages, respectively applied to the inputs of the operational amplifiers 54 and 80.

Claims (11)

1. Circuit for control and regulation of the speed of rotation of a rotor (1), in particular for the drive of a rotating anode in an.X-ray tube of the type in which said rotor (1) disposed in the interior of a glass envelope (2) is driven with the aid of a rotating magnetic field produced by means of a stator (3) situated on the outside of the envelope (2) and comprising at least two pairs of windings (4, 5), of which the first constitutes the main phase (4) and the second the auxiliary phase (5) and of which the respective axes of symmetry perpendicular to the axis of rotation of the rotor are angularly offset with respect to each other, said two phases (4, 5) being connected together by one of their terminals to form a common supply terminal (9) coupled to one of the terminals (13) of a monophase alternating voltage source (10), the other terminal (6) of the main phase (4) being connected directly and the other terminal (7) of the auxiliary phase (5) being connected by way of a phase shift capacitor (8) to the other terminal (11) of the monophase source (10), the circuit comprising first comparison means (54) for comparing the voltage of the main phase (4) with a fixed and predetermined reference level, which furnish a first signal when the main phase voltage exceeds the reference voltage, and second comparison means (80) for comparing the voltages of the main phase (4) and the auxiliary phase (5) with an adjustable value, characterized in that the second comparison means (80) supply a second signal which indicates that the ratio of the voltages taken respectively from the terminals (6-9, 7-9) of the auxiliary phase (5) and of the main phase (4) has reached or exceeded an adjustable value corresponding to a chosen desired speed, and that it comprises combination means for combining the first and the second signal furnishing on the simultaneous presence of said signals a third signal indicating that the two aforementioned conditions are fulfilled, in particular to permit the application of the very high voltage to the electrodes of the X-ray tube.
2. Circuit according to claim 1, characterized in that it comprises a first rectifier (4) and a filter (41-45) in cascade furnishing a first DC voltage proportional to the peak amplitude of the AC voltage at the terminals (6, 9) of the main phase (4) ; a first fixed potentiometer circuit (56, 57) furnishing a first predetermined fraction (Vss) of the first DC voltage ; a reference DC voltage source (47-52) ; a first voltage comparator (54) constituting the first comparison means supplied respectively by the first fraction (V58) and the constant reference voltage (V53) in order to furnish at its output (60) the first signal in the form of a first predetermined logic state when the former reaches or exceeds the latter.
3. Circuit according to claim 2, characterized in that it comprises in addition a second rectifier (70) and filter (71-75) in cascade furnishing a second DC voltage proportional to the peak amplitude of the AC voltage at the terminals (7, 9) of the auxiliary phase (5) ; a second adjustable potentiometer circuit (76, 77, 78) furnishing a second adjustable fraction (V79) of the second DC voltage and forming part of the first fixed circuit (56, 57) of the second comparison means which further comprise a second voltage comparator (80) comparing the second adjustable fraction (V79) with the first predetermined fraction (V58), the equality of which represents a predetermined and ajustable ratio of the voltages at the terminals of the auxiliary phase (5) and of the main phase (4) corresponding to a chosen desired speed, the output (83) of the second comparator (80) furnishing the second signal in the form of a second predetermined logic state when the second fraction reaches or exceeds the first.
4. Circuit according to claim 3, characterized in that the combination means comprise a circuit combining the respective output states of the two comparators and furnishing the third enable signal in response to the simultaneous presence of the first and second signal at its inputs.
5. Circuit according to claim 4, characterized in that the circuit combining the output states of the two comparators (54, 80) comprises a photocoupler (36) of which the light-emitting diode (35) is inserted between the respective outputs (83, 60) thereof and connected so as to conduct a sufficient current so that the radiation thus generated saturates the phototransistor (37) of said photocoupler (36) only when one (60) of the outputs furnishes a low logic state indicating that the first fraction (V58) exceeds the reference voltage (V53) and when the other output (83) furnishes a high logic state indicating that the ratio corresponding to the desired speed has been reached or exceeded, the saturation of the phototransistor (37) enabling a continuity to be established in the control circuit for the application of the voltage to the tube, the photocoupler (36) ensuring an insulation between the circuits.
6. Circuit according to any one of claims 3 to 5, characterized in that it comprises an operational amplifier (99) whose differential inputs are fed respectively with the first (V58) and the second (V79) fraction and a ballast circuit (20) in the form of a dipole whose terminals (21, 22) are inserted into the supply circuit of the two phases (4, 5) between their common terminal (9) and one (13) of the terminals of the monophase source (10), said ballast circuit (20) constituting a resistance variable in continuous manner between a minimum value which it has during the starting and acceleration of the rotor (2) until the second fraction (V79) has slightly exceeded the first (Vss) and a maximum value determined with the aid of a first fixed resistor (23) connected between its terminals (21, 22).
7. Circuit according to claim 6, characterized in that the ballast circuit (20) comprises a rectifier bridge composed of four diodes (24-27) of which the input diagonal (21, 22) constitutes the terminals of the dipole and which comprises in addition a power transistor (30) connected via its collector-emitter path between the terminals (28, 29) of its output diagonal and the base of which is connected to its collector via a polarization resistor (31) which in the absence of the signal from the operational amplifier (99) causes the saturation of the transistor (30) after each of the zero passages of the voltage furnished by the monophase source (10) so that its collector-emitter path shunts the first resistor (23).
8. Circuit according to claim 7, characterized in that a variable resistance element (32) whose resistance is controlled so as to diminish with the increase in the difference between the second (V79) and the first fraction (V58) is connected between the base and the emitter of the transistor (30) in order to reduce the polarization of the transistor (30) and as a result to increase the resistance of its collector-emitter path as a function of said difference when the latter is positive.
9. Circuit according to claim 8, characterized in that the variable resistor element is constituted by a phototransistor (32) of another photocoupler (33) whose collector-emitter path is connected between the base and the emitter of the power transistor (30), the light-emitting diode (34) of said other photocoupler (33) being inserted between the output (100) of the differential amplifier (99) and the common terminal (9) so as to be traversed by a current which varies with the difference between the second (V79) and the first (Vsa) fraction as soon as it has become positive.
10. Circuit according to claims 6 to 9, characterized in that the output (100) of the operational amplifier (99) is connected to its inverting input via a threshold feedback circuit (101, 102, 103, 104) which comprises a feedback resistor (101) permitting an appreciable reduction of its gain as soon as a threshold voltage is exceeded which is determined by elements (102-104) having a conduction threshold, connected in series with said resistor (101) and compensating the conduction threshold, in particular of the light-emitting diode (34) of the other photocoupler (33).
11. X-ray generator comprising a X-ray tube having a rotating anode, characterized in that it comprises a circuit for control and regulation of the speed of rotation of the anode according to one of the preceding claims.
EP19810401155 1980-07-25 1981-07-21 Control circuit and speed control of the rotation of a rotor, especially the one of a rotatable-anode x-ray tube Expired EP0045675B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8016491 1980-07-25
FR8016491A FR2487540A1 (en) 1980-07-25 1980-07-25 CIRCUIT FOR MONITORING AND REGULATING THE ROTATION SPEED OF A ROTOR AND IN PARTICULAR THAT OF A ROTATING ANODE OF A RADIOGENIC TUBE

Publications (2)

Publication Number Publication Date
EP0045675A1 EP0045675A1 (en) 1982-02-10
EP0045675B1 true EP0045675B1 (en) 1984-05-02

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP19810401155 Expired EP0045675B1 (en) 1980-07-25 1981-07-21 Control circuit and speed control of the rotation of a rotor, especially the one of a rotatable-anode x-ray tube

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EP (1) EP0045675B1 (en)
DE (1) DE3163389D1 (en)
FR (1) FR2487540A1 (en)

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2185826A (en) * 1938-06-07 1940-01-02 Gen Electric X Ray Corp Rotatable anode x-ray tube
US3094618A (en) * 1961-05-23 1963-06-18 Picker X Ray Corp X-ray tube protection mechanism
FR1372570A (en) * 1963-08-02 1964-09-18 Picker X Ray Corp Waite Mfg Improvements to x-ray machines
US3518434A (en) * 1968-03-13 1970-06-30 Picker Corp X-ray tube rotatable anode control circuit with means to sense and control anode motor current
US3564254A (en) * 1968-07-17 1971-02-16 Westinghouse Electric Corp Spin motor controller for a rotating anode motor of an x-ray generator tube
DE2356459C2 (en) * 1973-11-12 1983-08-25 Siemens AG, 1000 Berlin und 8000 München X-ray diagnostic apparatus for fluoroscopy and exposure with a rotating anode X-ray tube and a power controller for the transition from transmission to exposure
DE2815893A1 (en) * 1978-04-12 1979-10-18 Siemens Ag X-RAY DIAGNOSTIC GENERATOR WITH AN INVERTER FEEDING THE HIGH VOLTAGE TRANSFORMER

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Publication number Publication date
EP0045675A1 (en) 1982-02-10
FR2487540B1 (en) 1983-08-05
FR2487540A1 (en) 1982-01-29
DE3163389D1 (en) 1984-06-07

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