FR2509101A1 - ELECTRICAL DRIVE WITH ASYNCHRONOUS MOTOR - Google Patents

Abstract

The electrical drive with an asynchronous motor contains a series circuit comprising an in-phase current sensor (1) of the stator of the short-circuit asynchronous motor, a coordinate converter (2), a phase-sensitive rectifier unit (3), and a controllable power source (4) which is connected to the stator windings of the asynchronous motor (5). The other output of the in-phase current sensor (1) is connected to the control input (7) of a frequency generator (8) for the rotor currents, whose output is connected to the input (9) of a reference signal former (10). The other input of the latter is connected to the output of the reference frequency adjuster (12) and its outputs are connected to the reference signal inputs (13, 14, 15) of the unit (3). The electrical drive also contains a rotor rotation frequency multiplier (18), whose inputs (19, 20) are connected to the outputs of the rotation angle sensor (6) of the rotor and of a reference frequency adjuster (12), and whose output is connected to the input (21) of the reference signal former (10). At the same time, the outputs of a sinusoidal signal generator (17) are connected to the inputs (22, 23) of the coordinate converter (2).

Description

ELECTRIC DRIVE WITH ASYNCHRONOUS MOTOR
The present invention relates to an electric motor drive asynchronous squirrel cage.

 Asynchronous motor electric drives are used in particular to communicate a movement to the processing members of high-precision machine tools with numerical control. They can be used for fast and accurate displacement of any load in an asynchronous motor rotor rotation speed gamma range.

 Asynchronous motor drives exiz tants are either insufficiently fast or unable to provide a fairly consistent torque over time, which is far from meeting the specifications in terms of precision and speed of movement of the processing devices of the machine tools. numerical control.

There is an electric drive with asynchronous motor (see "Devices and elements of automatic control and adjustment systems", vol.
VV Solodovnikov, Technicheskaya kibernetika "," Actuators and servomechanisms ", Editions" Machinostrojenie ", Mos cou, 1976, pp.266-271) comprising an angular position sensor of the rotor of the -asynchronous motor which has its stator windings electrically connected through an adjustable current source at the outputs of a phase-sensitive rectifying block, the control inputs of which are electrically connected to the reactive and active stator current connection members, the remainder of its inputs being connected to the outputs of a polyphase voltage source.

 The output signals of the current and reactive current feedback components of the stator are supplied by the excitation circuit of the angular position sensor of the asynchronous motor rotor to the control inputs of the phase-sensitive rectification unit. The excitation circuit of the angular position sensor of the rotor has an appreciable time constant, which is the cause of a speed of operation of the electric drive and a low precision of displacement of the processing members of the electrodes. machine tools with metal at dynamic speeds.

 There is an asynchronous electric motor drive with a stator asynchronous squirrel cage motor asynchronous current setter, a coordinate converter, a phase-sensitive rectifier and an adjustable current source connected to the power supply. stator windings of the asynchronous motor; the other output of the stator active current setpoint is connected to the control input of a frequency converter of the rotor currents, the output of which is connected to the input of a reference signal formatter which has its other input connected to a reference frequency generator (see the RFP patent application

 No. P 3036760.3).

 the signal of the stator active current reference element arrives at the amplitude input of the coordinate converter which receives at its reference inputs the output signals of the angular position sensor of the rotor.

the coordinate converter supplies to the phase-sensitive rectification unit a variable signal with the flow rate of the stator active current setpoint.

 the output signals of the phase-sensitive rectification unit, which are proportional to the signal of the stator active current setpoint, are converted into stator currents of the asynchronous motor by means of the adjustable current source. A torque is thus obtained on the asynchronous motor shaft, the value of which is a function of the amplitude of the signal supplied by the stator active current reference element.

 In this electrical drive, the torque on the shaft depends on the rotational speed of the rotor of the asynchronous motor. This is because the overall transfer coefficient of the circuit taken by the active current setpoint signal and composed of the coordinate converter, the phase-sensitive rectification block and the adjustable current source depends on the rotational speed of the rotor. In this case, said dependence of the overall transfer coefficient is determined by that of the transfer coefficient of the coordinate converter with respect to the speed of rotation of the rotor of the asynchronous motor. The reason is that the amplitude of the signals at the The output of the coordinate converter is subject to that of the signals that it receives on its reference inputs of the angular position sensor of the rotor, variable with the speed of rotation of the rotor of the asynchronous motor.

 The dependence of the provided torque with respect to the rotational speed of the electric drive shaft is particularly troublesome for electrical drives with a wide range of speed control since it degrades the accuracy and speed. moving the machine tool processing members to dynamic regimes.

 The object of the invention is therefore to provide an asynchronous motor electric drive which, by virtue of the independence of the transfer coefficient of the signal routing circuit of the stator active current setpoint member with respect to the speed of rotation of the stator. rotor of the asynchronous motor, to improve the consistency of the torque on the shaft of electrical power in a wide range of rotational speeds, and therefore to increase, the accuracy and speed of control of the speed and movement of processing members of the machine tools controlled by said electrical drive.

 According to the invention, asynchronous motor electric drive comprises, in series, an active current setpoint component of the stator of the squirrel cage asynchronous motor, a coordinate converter, a phase-sensitive rectifying block, and a source. adjustable current connected to the stator windings of the asynchronous motor, another output of the stator active current reference element being connected to the control input of a frequency converter of the rotor currents having its output connected to the input a reference signal formatter having its other input connected to a reference frequency generator and its outputs connected to the reference inputs of said phase sensitive rectification unit, the latter being in turn in electrical connection with a sensor of angular position of the rotor and with a sinusoidal signal former connected to the output of the reference frequency generator, carac characterized in that it further comprises a rotation frequency multiplier of the rotor which has its inputs connected to the outputs of the angular position sensor of the rotor and of the reference frequency generator, and its output connected to the input of the rotor. reference signal formatter, the outputs of the sine-wave signal former being connected to the reference inputs of the coordinate converter.

 It is advantageous to include in the rotor frequency multiplier, in series, a rotor angle of rotation increment, and an adjustable frequency divider whose input is connected to the output of the frequency generator. reference.

 This makes it possible to have, even with widely variable working speeds, a quasi-continuous signal representative of the speed of rotation of the rotor and thereby to reduce to a low level the fluctuations of the torque on the shaft of the rotor. where a greater regularity and a better precision of the displacement of the processing organs of the machine-tools with metals.

It is also advantageous that, when using a stator reactive current setpoint and an asynchronous motor temperature sensor in electrical connection with the frequency converter of the rotor currents, the latter comprises a modulator. pulses and a summing circuit having its output connected to the reference input of the pulse modulator in duration, the control input thereof forming the control input of the frequency converter of the rotor currents being connected to the output of the active current setpoint member of the stator, the input of the summing circuit constituting the second control input of the frequency converter of the rotor currents being connected to the output of the reactive current setpoint member of the stator also connected to the input of adjustment of the rustic characteristic slope of the temperature sensor whose output is connected to the second input of the circuit som an emitter forming the thermal correction input of the frequency converter of the rotor currents, and the input of the pulse modulator in duration being; in this case, connected to the output of the reference frequency generator
This allows, whatever the range of speeds and temperatures of the motor, to produce with a good precision the required frequency of the rotor currents and consequently, the torque on the shaft and to obtain, consequently, the maximum of accuracy in the movement of metalworking machinery.

 In the asynchronous electric motor drive according to the invention, the transfer coefficient of the signal routing circuit of the stator active current setpoint element is subtracted from the action of the roaming speed of the shaft. connecting the output of the angular position sensor of the asynchronous motor rotor with a frequency multiplier of rotation of the rotor at the input of a reference signal formatter whose output signals do not react, when they come on them. reference inputs of the phase-aware rectification block, only on the frequency of the output signals of the latter.

 On the other hand, the elimination of the dependence of the transfer coefficient of the signal routing circuit of the stator active current setpoint member with respect to the speed of rotation of the shaft is also made possible by the connection of the reference inputs of the coordinate converter to the outputs of the sinusoidal signal former, the amplitude of which is constant with the speed of rotation of the shaft.

 This results in stator currents or torques on the variable electrical drive shaft in strict accordance with the stator active current setpoint.

 In the electrical direction, according to the invention, the servocontrol of the frequency of the rotor currents to the ratio of the signals of the active and reactive current regulator members of the stator, whatever the temperature of the asynchronous motor, comes from, on the one hand, of the specific embodiment of the frequency converter of the rotor currents which comprises a modulator of pulses in duration and a summing circuit whose output is connected to the reference input of said modulator and, on the other hand, of the connection of the inputs of the summing circuit and from the modulator to the outputs of the temperature sensor and the reference frequency formatter.

 The servocontrolling of the frequency of the rotor currents to the ratio of the signals supplied by the active and reactive current setpoints of the stator associated with the possibility of maintaining the stator currents exactly at the required level gives the electrical drive an excellent coherence over time. the torque provided.

 The electric drive according to the invention has a precise and progressive adjustment of the circular frequency of rotation of the rotor by the use of a series assembly of a rotor angle of rotation angle converter and a adjustable frequency divider which has its input connected to the output of the reference frequency generator.

 the meeting of a precise and continuous adjustment circular frequency of rotation of the rotor and the maintenance at an exact level of the stator currents and the frequency of the rotor currents is at the origin of a better coherence of the torque on the retaining shaft electric over time.

The invention will be better understood and other objects, details and advantages thereof will appear better in the light of the following explanatory description of various embodiments given solely as non-limiting examples, with references to drawings in which:
FIG. 1 represents the block diagram of the asynchronous motor electrical entanglement according to the invention;
Fig. 2 represents the diagram of the frequency founder of the rotor currents according to the invention;
Figs. 3a to 3d represent the timing diagrams of the electrical signals at the inputs and outputs of the frequency converter of the rotor currents according to the invention.

 the asynchronous electric drive comprises, in series, an active current setpoint member of the stator 1 (FIG. 1), a coordinate converter 2, a rectifying block sensitive to phase 3 and an adjustable current source 4 connected to the stator windings of FIG. an asynchronous motor 5 with a squirrel cage. the rotor of the angular position sensor 6 of the rotor of the asynchronous motor 5 is integral with the rotor of the latter. the other output of the stator active current setpoint member 1 is connected to the control input 7 of a frequency converter 8 of the rotor currents whose output is connected to the input 9 of a signal generator reference signals 10. the input 71 of the formatter 10 is connected to the output of a reference frequency generator 12, its outputs being connected to the inputs 13, 14 and 15 of the sensitive rectification block phase 3. the input 16 of a sinusoidal signal trainer 17 is connected to the output of the reference frequency generator 12.

 The electrical drive also comprises a rotation frequency multiplier of the rotor 18 which has its inputs 19 and 20 connected to the outputs respectively of the angular position sensor 6 of the rotor of the asynchronous motor and of the reference frequency generator 12 and its output connected to the input 21 of the reference signal formatter 10. The outputs of the sine-wave signal formatter 17 are connected to the reference inputs of the coordinate converter 2. the phase of the output signals of the frequency multiplier of the rotor 18 is subject to that of the signals supplied by the reference frequency generator 12.

 In order to be able to keep the power on the asynchronous motor shaft 5 constant and to take account of the temperature variation, the electrical drive is provided with a reactive current setpoint member of the stator 22 and a temperature sensor 23 of the motor, both connected to the trainer 8.

 The frequency converter 8 of the rotor currents comprises a duration pulse modulator 24 and a summing circuit 25 whose output is connected to the reference input 26 of said pulse duration modulator 24.

 The control input of the modulator 24 which constitutes the control input 7 of the frequency converter of the rotor currents 8 is connected to the output of the active current setpoint member of the stator 1. One of the inputs of the summing circuit 25 represents the second control input 27 of the formatter 8 and is connected to the output of the reactive current setpoint member of the stator 22.

 The input 28 for adjusting the characteristic slope of the temperature sensor 23 is connected to the output of the reactive current setpoint member of the stator 22; the output of the sensor 23 is connected to the second input of the summing circuit 25 constituting the thermal correction input 29 of the frequency converter of the rotor currents 8. The input of the pulse modulator in duration 24 forming the synchronization input 30 the frequency converter of the rotor currents 8 is connected to the output of the reference frequency generator 12.

 In the electrical drive, the rotation frequency multiplier of the rotor 18 comprises in series a trainer 31 of increments of rotation angle of the rotor and an adjustable frequency divider 32, one of whose inputs serves as input 20 to the rotor. rotor frequency multiplier 18, connected to the output of the reference frequency generator 12.

 In the particular embodiment considered of the electrical drive according to the invention the coordinate converter 2 contains a summing circuit 33 which has its inputs connected to the outputs of the multipliers 34 and 35. the first inputs of the multipliers 34 and 35 constitute the inputs of amplitude 36 and 37 respectively of the coordinate converter 2, the second inputs forming the reference inputs of the latter. The output of the summing circuit 33 forms the output of the coordinate converter 2 connected to the amplitude inputs 39 and 40 of the phase 3 rectifying block.

In the particular embodiment in question of the invention the block 3 comprises three rectifiers sensitive to the phase 41, 42 and 43. the angular position sensor of the rotor of the asynchronous motor 6 represents a full-code angular rotation sensor . The primary sensor is supposed to be a syncro-trigonometer operating as a phase shifter. the rest of the elements of the electric drive are made classically.

 the duration pulse modulator 24 (FIG. 2) comprises in series a comparator 44 with a hysteretic response, a clock latch 45, a multiplier 46 of value of the signal by the sign of the function and a filter RC whose output is connected at the input 47 of the comparator 44. the other input of the comparator 44 forms the control input 7 of the frequency converter 8 of the rotor currents.

the second input of the clock-flip-flop 45 constitutes the synchronization input 30 of the formatter 8, its output forming the output of the latter. the second input of the multiplier 46 is connected to the output of the summing circuit 25
It should be noted that the duration pulse modulator 24 represents a voltage pulse generator with adjustable width.

 To better understand the behavior of the electrical entanglement, figs. 3a to 3d represent the timing diagrams of the signals at the input 7 and at the output of the pulse modulator in duration 24, where on the abscissa the time and the ordinate have been taken to the voltage. the timing diagrams apply to the operation of the modulator 24 in the event of a signal U1 of the active current setpoint member of the stator 1 which is variable in time and of constant amplitude signals of the reactive current setpoint member of the stator 22 and temperature sensor 23.

 FIG. 3a represents the timing diagram of the voltage U1 at the input 7 of the frequency converter of the rotor currents 8, that is to say at the input of the comparator 44 whose hysteresis cycle is 2U; FIG. 3b represents the timing diagram of the voltage Uc on the capacitor C, that is to say on the second input of the comparator 44; fig. 3c represents the chronograxroene of the pulse voltage U7 at the output of the frequency converter of the rotor currents 8, that is to say at the output of the clock latch 45 and at the input of the multiplier 46; FIG. 3d represents the timing diagram of the pulse voltage U8 at the output of the multiplier 46.

 the operation of asynchronous motor electric traction according to the invention consists in what follows.

 It should be noted that the designations "active current" and "reactive current" of the stator are arbitrary.

In the practical electrical drive, the signal U1 (FIG. 3a) in the form of a DC voltage at the output of the reference device 1 (FIG. 1) produces a stator current component oriented orthogonal to the flow axis. total effective rotor of the asynchronous motor 5, the signal U2 in the form of a DC voltage at the output of the reference member 22 showing a stator current component oriented along the axis of the total effective flux of the rotor. This orientation is obtained automatically by the appropriate choice of the scales of the signals U1 and U2 and the frequency o31 of the rotor currents supplied by the trainer 8. Let us examine the behavior of the electric drive at speeds which do not involve the need for adjustment magnetic flux of the asynchronous motor, that is to say when the constant power operation is not necessary.

 In this particular embodiment of the electric terminal, according to the invention, the torque control on the asynchronous motor shaft 5 is effected by a signal from the active current setpoint member of the stator 1 for a magnetic flux of constant motor 5. the summing circuit 33 receives a sinusoidal signal U4 from the formatter 17.

 For simplicity, consider the operation of the electric drive by posing that the signal U1 and the rotational speed of the rotor of the motor 5 are constant. In this case, at steady state, the signals acting in the AC circuits have a sinusoidal character and lend themselves to an analytical description.

 The signal U1 comes on the input of the multiplier 35 which receives, on its other input, a voltage AsinUlt of the sinusoidal signal former 17 where: 990 is the reference frequency; A, the amplitude; t, the time. The multiplier 35 supplies a signal U3 = AU1 sin u) ot to one of the inputs of the summing circuit 33. the other input of the summing circuit 33 receives from the formatter 17 a signal U4 = AU2cos u) 0t, U2 being a characteristic constant total effective flux of the rotor.

qui vient sur les entrées 38, 39 et 40 du bloc de redressement sensible à la phase 3.The summing circuit 33 produces a signal defined by the expression:

which comes on the inputs 38, 39 and 40 of the straightening block sensitive to phase 3.

 Te block 3 receives, on its inputs 13, 14 and 15, the signals in the form of voltage pulses Ukm, the index m representing the sequence number of the phase of the reference signal former 10.

As in this case block 3 contains tro-is rectifiers sensitive to phase 41, 42 and 43, m = 3. Voltage pulses Uk7, Uk2, Uk3 constitute a three-phase system of voltage pulses at a frequency Wk = (W) o # W + W1), ovine: W is a rotation frequency of the motor rotor
asynchronous 5;
is the frequency of the rotor currents of the motor
asynchronous 5.

où K1 est le facteur de proportionnalité.the frequency Wk of the signals Ukm supplied by the formatter 10 is the sum of the frequencies of three signals coming from the rotation frequency multiplier 18, from the reference frequency generator 12 and from the frequency forming device of the rotor currents 8. block 3 has over its outputs a system of voltages Ux, U, U:

where K1 is the proportionality factor.

, leur fréquence étant égale à (+ fi
la fréquence W 1 des courants rotoriques est produite par le formateur 8 en conformité de l'expression: U1 . 1 ,
W1 = U2 T où: 4)' U2 T
T est la constante de temps du circuit rotorique.These voltages serve as setpoint signals to the adjustable current source 4 supplying the stator windings of the motor 5 with sinusoidal currents whose amplitude is proportional to the quantity

, their frequency being equal to (+ fi
the frequency W 1 of the rotor currents is produced by the trainer 8 in accordance with the expression: U1. 1,
W1 = U2 T where: 4) 'U2 T
T is the time constant of the rotor circuit.

 Since the proposed electrical terminal implements a method of controlling the asynchronous motor by frequency and current (see the Soviet author's certificate N 193604), the motor torque on the shaft is a linear function of the signal U1 for U2 = const which imposes on the engine 5 a regime where the total effective flux of the rotor is invariable.

 In order for the frequency o) 0 to be an integral part of the frequencies of the signals arriving at the inputs of the phase 3 rectifying block, the reference frequency generator 12 has its outputs connected to the input of the sinusoidal signal former 17, at the input 20 of the rotation frequency multiplier 18 and at the input 11 of the reference signal trainer 10.

In the electrical drive according to the invention, the routing circuit of the signals U1 and U2 determining the amplitude of the stator current and therefore the torque on the motor shaft 5 is also borrowed by the frequency signals 3 O of the trainer 17 to which
o is referenced the coordinate converter 2.

 Since the amplitudes of the signals of the formatter 17 are independent of the rotor rotation frequency and constants, the amplitude of the signal at the output of the coordinate converter 2 is due to the signals U1 and UT2 whatever the frequency of rotation 0 of the rotor.

 In this way, it is possible to ensure a high accuracy in forming the stator currents and the torque on the motor shaft 5, which makes it possible to use this electrical drive in the high precision control systems of metal machine tools. .

The purpose of setting the signal U2 is to enable a control motion of the machine tool processing members when the rotation frequencies are widely variable so as to obtain a constant power on the shaft at frequencies above the value. nomina]
It should be noted moreover that if the electric drive is subjected to conditions where the temperature of the motor asyn → ónevaries to the point of producing the change of the time constant n of the rotor circuit, the formation of the frequency u) 1 of the rotor currents in the trainer, must take place taking into account the action of the temperature.

 In order to maintain at a high level the torque control accuracy provided by the engine 5 at static and dynamic speeds and under the conditions where the total effective flux and the rotor temperature are variable, the electric drive uses a control device. the reactive current setpoint of the stator 22, a temperature increment sensor 23 and a formatter 8, provided with a pulse modulator 24. In this case, the coordinate converter 2 contains two multipliers 34 and 35. .

 the signals U1 and U2 coming from the reference devices 1 and 22 come to the inputs of the multipliers 34 and 35 which receive on their other inputs the signals Asint and Acos 0 and the sinusoidal signal former 17.

your multipliers 34 and 35 deliver the signals: U3 - AU1 sin U4ot,
U4 = AU2 cos ot, whose sum is made by the summing circuit 33.

the rectifying block sensitive to phase 3 receives on its amplitude inputs a voltage U5. the signals U1 and
U2 also come to the inputs 7 and 27 of the frequency converter of the -rotoric currents 8. Ive signal U2 also arrives at the input 28 for adjusting the characteristic slope of the temperature sensor 23 which provides a signal (- U2ckQ), where:
α is the factor of proportionality; Q, the positive temperature increment.

 This signal arrives on the input 29 of the trainer 8.

The summing circuit 25 (FIG. 2) delivers a signal
U6 = U2 (1-cLQ) at the amplitude input of the multiplier 46 which is the product of the signal by the sign of the function and whose second input receives the voltage pulses U7 of alternating polarity (FIG. 3c).

multiplier 46 (FIG. 2) produces a pulse voltage U8 (FIG. 3d) whose amplitude is equal to
U6. These pulses arrive on a filter SC, and the voltage Uc (FIG. 3b) on the capacitor C comes on the input of the comparator 44 (FIG. 2) which compares with the signal U1 sent on the input 7 of the formatter 8. the comparator 44 has a hysteretic response, the cycle constitutes 2U (Figure 3b) which allows a difference of + U between the voltage Uc and the voltage U1.

 when the voltage Uc reaches a level equal to (U1 + U) the signal at the output of the comparator 44 switches (FIG. 2) and causes the clock flip-flop 45 to go into the state where it delivers a negative voltage U7 at the input multiplier 46 which produces a negative voltage of amplitude U6.

 As soon as the voltage Uc reaches a level equal to (U1-U) the signal at the output of the comparator 44 is reversed to impose a latch-clock 45 a state in which it delivers a positive voltage U7 at the input of the multiplier 46 which generates on its output a positive voltage U6 (Figure 3d).

In this way, thanks to the closed circuit comprising the members 44, 45, 46 and the filter RC, the clock-latch 45 has on its output rectangular voltage pulses whose duration is subject to the amplitude of the signals U1 and
U2. These signals and the ratio of the duration t1 of the pulse to the period T1 (FIG. 3c) of the signal U7 modulated in duration are interrelated by a relation: U1 = U1 = T1 - 0.5
U6 U2 (1- α Q) T1 The period T1 is determined by the width of the thystisitic cycle as a function of the operating threshold voltage U of the comparator 44 and the filter time constant.
RC, the quantity t1 being fixed automatically by maintaining the average voltage U6 equal to the voltage U1.

 For U1 = O, U2 O the duration t1 = 0.5T1 and the output voltage U7 corresponds to the frequency i of the rotor currents which is zero.

For D1 f 0, U2 / O the duration t1 differs from the quantity 0.5T1 of a quantity # which is due to the value and the sign of
U1 ratio (1- α Q) and characterizes the frequency of the rotor currents.

the clock latch 45 makes it possible to form the period T1 and the duration t1 of the pulse as multiples of the period of the signals arriving on the input 30 from the reference frequency generator 12 as well as to impose a certain amount of time. phase relationship between the time-modulated signal and other signals coming from the formatter 10. In this way, in the pulse modulator 24 the duration (t1 -0.5) translates the ratio U1 which determines to his
U2 turn the required frequency W1 of the rotor currents.

As soon as the temperature of the motor 5 exceeds the average of a quantity Q, the temperature sensor 23 delivers a signal (-U2c (O), the quantity ('-O, S) having for expression U1
U2 (1- α Q), the frequency I of the rotor currents is made to take a larger value than for Q = O.

This is just what is needed for a practical drive when the engine temperature rises because the temperature increase produces that of the ohmic resistance of the rotor whose effect is the reduction of the time constant.
T of the rotor which imposes the increase of the frequency registers W1 of the rotor currents with respect to the initial frequency W1 for Q = O.

Let's now look at the functioning of the Wk = frequency formation pathway (Wo # W # W1) of Uk signals
Uk2, Uk applied to reference inputs 13, 14 and 15 of block 3.

 The output signal from the sensor 6, transformed by the angle incrementator 31 into a rotation frequency code of the rotor, comes to the inputs of the adjustable frequency divider 32, which receives on its scale input the The adjustable frequency divider 32 produces voltage pulses with a repetition frequency F1 which arrive at the input 21 of the formatter 10.

 The reference signal formatter 10 represents a series connection of a logic block, a binary frequency divider and a decoder (nonexistent in FIGS. 1 and 2). the frequency of the output signal of the binary frequency divider is equal to the number of pulses applied to its input, divided by its module. So the frequency component # W of the frequency Wk We is it the quotient of the frequency F1, the component (Wo (fiJ1) resulting from the variation of the average quantity of pulses applied to the input of the binary frequency divider for the duration of the period T1 of the modulated signal in duration U7.

For this purpose the logic block performs the function (F2J3 + F3) 3) 1 where: p is the modulated signal in duration; F2 is a sequence of pulses in excess of those of the sequence of pulses Fo frequency produced by the generator 12; F3 is a sequence of pulses elaborated from the sequence Fo truncated by as many pulses as there are in excess in the sequence F2. Also, if t1 = 2, the average frequency at the input of the binary frequency divider is equal to Eo and that at its output frequency to
If t1> T1, it is the following F2 which is preponderant
2 and the output frequency of the binary frequency divider is equal to (Wo + W1).

 The effect is that the binary frequency divider of the block 10 has on its output pulses with a frequency>) kw Wv # W1 # W)), transformed with the aid of the decoder into a three-phase system of pulses Uk1, Uk2 and Uk3.

 The fact that the information on the frequency W1 of the rotor currents is in the form of modulated pulses in duration and that on the rotor frequency (h) of rotation in the form of a series of pulses of constant duration, the phases of said pulses. being in a rigorous relationship to one another thanks to the synchronization by the pulses provided by the generator 12, makes it possible to fix with great precision the frequency of the rotor currents of the motor 5 whose torque must be adjusted so as to ensure on the tree a power is variable is constant and this under conditions where the temperature is highly variable.

 This makes it possible either to maintain or increase the control precision of the torque supplied by the motor 5 and to extend the possibilities of applying electrical powering in high-precision metalworking machine tools thanks to an exact regulation of the intensity of stator currents.

 The electrical power supply according to the invention enjoys soft mechanical characteristics. The motor torque is a function of the signal U1. Electric drive with soft characteristics applies to immediately adjust the acceleration of the load.

 In the case where the electric drive according to the invention is used to adjust the rotation frequency (angular position) of a load the information on the actual frequency (angular position) of the load comes from a frequency multiplier rotation of the rotor 18 and the active current setpoint member of the stator 1 is a frequency regulator.

 The application of the electric drive according to the invention, capable of controlling with high precision the engine torque at static and dynamic operating speeds, makes it possible to produce fast and high-precision systems for the regulation of speed and speed. the position of the processing members of various machine tools which will result in a high quality of parts processing the growth of equipment performance.

Claims (3)

claims  1. Asynchronous motor electric drive comprising, in series, a member (1) with active stator output of the squirrel-cage asynchronous motor stator, a coordinate converter (2), a phase-sensitive rectification unit (3) and an adjustable current source (4) with respect to the stator windings of the motor (5), another output of the stator active current reference element (1) being connected to a control input (7) of a trainer ( 8) of the frequency of the rotor currents having its output connected to the input (9) of a reference signal former (10) having its other input (11) connected to a reference frequency generator (12) and its outputs connected to the reference inputs (13, 14 and 15) of the phase-sensitive rectification unit (3) connected in turn to a rotor angular position sensor (6) and a connected sine-wave signal processor (17) at the output of said frequency generator of r 9, characterized in that it further comprises a multiplier (18) of rotation frequency of the rotor which has its inputs (19 and 20) connected to the outputs of the sensor (6) of angular position of the rotor and the generator of reference frequencies (12) and its output connected to the input (21) of the reference signal formatter (10), the outputs of the sinusoidal signal formatter (17) being connected to the reference inputs of the coordinate converter (2) .  Electrical drive according to claim 1, characterized in that the rotor frequency multiplier (18) comprises, in series, a rotor angle of rotation increment (31) and a adjustable frequency divider (32) whose input is connected to the output of the reference frequency generator (12).  3. Electrical drive according to claims 1 and 2, characterized in that when using a member (22) of the reactive current of the stator and a sensor (23) of the asynchronous motor temperature in electrical connection with the frequency converter (8) of the rotor currents, this formatter (8) comprises a pulse duration modulator (24) and an summing circuit (25) whose output is connected to the reference input (26). of said pulse modulator (24), the control input thereof forming the antenna input (7) of the frequency converter of the rotor currents (8) being connected to the output of the device (l) active stator setpoint of the stator, the input of the summing circuit (25) constituting the second control input (27) of the rotor current frequency formator (8) being connected to the output of the organ (22) setpoint of the reactive current of the stator also connected to input (28) for adjusting the characteristic slope of the asynchronous motor temperature sensor (23) whose output is coupled to the second input of the summing circuit (25) representing the trainer's thermal correction input (29) (8) frequency of the rotor currents, 11 input of the pulse modulator in duration (24) being connected to the output of the reference frequency generator (12).