SU1203682A1 - Adjustable-frequency induction drive for motor testing bed - Google Patents

Description

to the output of the angle determiner between the current and flux linkage vectors, the output of the adder is connected to the second input of the logic generator of a given current, the output of the setpoint amplitude of the flux linkage is connected to another input of the reference element, and the meter output

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The invention relates to electrical engineering, namely, variable frequency asynchronous electric drives and can be used in installations where an asynchronous machine is used as a load device, for example, in engine test stands.

The aim of the invention is to improve the accuracy of regulation,

FIG. 1. shows a functional diagram of a frequency-controlled asynchronous electric drive for a test bench of engines; FIG. 2 is a functional diagram of a frequency correction unit; FIG. 3 is a diagram of a logic signal comparison element; FIG. 4 and 5 are the circuits of the drivers of the logical Signal of the actual and specified currents, respectively.

The frequency-controlled asynchronous electric drive for the engine test bench contains an asynchronous motor 1 (Fig. 1) with a short-circuited rotor, the stator windings of which, through the sensor 2 phase currents and the sensor 3 phase voltages, are connected to the outputs of the controlled variable The inverter 5, the choke 6 and the autonomous inverter 7 TOKaj are a rectifier control unit 8 and an inverter control unit 9 equipped with a flux coupling signal generator 10 connected by inputs to you the sensor moves 2 phase currents and to the outputs of the sensor 3 of the phase voltage, frequency correction node 11, connected by the first input 12 to the output of the rapper 10 signal03682

Amshtud flux linkage sg) is unified with the first input of the correction node 1n frequency; the input of the operational amplifier forms a quarter input of the frequency correction node, in, r; is connected to the frequency control point code, and the third input of the frequency correction node is connected to the output of the torque setting point „

a flow link, and the second input 13 to the input of the sensor 2 phase currents. The inverter control unit 9 is provided, in addition, with a pulse shaper 14 connected by an input to a frequency correction unit 1 1 and an output to a control input of an autonomous current inverter 7. The input of the control unit 8 by the actuator is combined with the third input 15 of the frequency correction unit 11 and connected to the output of the input torque generator 16, made in the form of a potentiometer. The output of the entered frequency adjuster 17 is connected to the fourth input 18 of the frequency correction node 11,

The shaft of an asynchronous motor 1 with a short-circuited rotor is mechanically connected to the shaft of another test bench motor 19, the windings of which are connected to terminals 21 via a contact group 20 for connecting the supply network.

The power inputs of the controlled rectifier 5 through the contact group 22 are connected to the terminals 21 for connecting the mains supply,

 11 corrections and frequencies are provided with the determinant 23 (FIG. 2) of the angle vectors: current and flux linkage, shaper 24 logic signal of a given current, shaper 25 logical signal of the actual current, element 26 comparison of logic signals and operational amplifier 27, The feedback circuit of which includes a parallel-connected resistor 28 and a control key 29, and a resistor 30 is connected at the input. The control input of the control key 29 is connected to the output of the logic signal comparison element 26. The first input 12 of the frequency correction unit 11 is formed by the first input of a logical current signal generator 24 of a predetermined current, the second input of which is connected to the output of the angle determiner 23 between the current and flux link vectors, the input of which forms the third input 15 of the frequency correction unit 11. The code of the logical current generator 24 of a given current is connected to the first input of the logic signal comparison element 26 connected by the second input to the output of the actual current logical signal generator 25, whose input and output of the operational amplifier 27 form the second input 13 and the output of the frequency correction unit 11, respectively. Node 11 frequency correction is provided with an additional setting device 31. amplitudes of flux linkage, performed in a potentiometer bidet and connected in series by measuring instrument 32 flux link amplitudes, comparison element 33, flux linkage regulator 34 and adder 35, the other input of which is connected to the output of the angle determiner 23 between the current and flux coupler vectors, the output of adder 35 is connected to the second the input of the driver 24 of the logical signal of a given current., the output of the setpoint amplitude 31 unit is connected to another input of the reference element 33, and the input of the meter 32 of the amplitude of the linkage connected to the first node 11 12 vhddom frequency correction, the input of the operational amplifier 27 through the resistor 30 forms the fourth input 18, a frequency correction unit 11. I

Comparison element 26 of logic signals contains a six-input circuit OR 36 (FIG. 3) and six three-input circuits AND 37-42 connected to its inputs, the inputs of which form the corresponding inputs of logic comparison element 26.

The actual current logic driver 25 contains three comparators 43-45 (FIG. 4), each of which is provided with a null organ 46 and an inverting amplifier 47.

Shaper 24 logical signal of a given current contains in each

before phase comparators 48 and 49 (Fig. 5) and the trigger 50.

The frequency-controlled asynchronous electric drive for the test engine stand 5 works as follows.

An asynchronous motor 1 (Fig. 1) with a short-circuited rotor is powered by an alternating current from a 0 L 4 frequency converter. The amplitude of this current is determined by the setpoint of the torque setting device 16, acting on the input of the rectifier control unit 8. The characteristic input-output unit of the 5–8 control of the rectifier is selected based on the dependence of the current amplitude on the moment at constant flow and taking into account the closed automatic current control system.

20. The frequency of the alternating current is determined by the average value of the signal at the input of the pulse shaper 14, which is the output signal of the operational amplifier 27 (FIG. 2)

25 and is determined by the magnitude of the signal,. from the output of the setpoint generator 17 and the relative duration of the closed state of the control key 29. The signal value at the output of the frequency adjuster 17 is taken such that when the control key 29 is open, the output frequency of the autonomous inverter 7 is equal to the network frequency

35 given the maximum possible upward deviation. In the steady state operation of the electric drive, the actual frequency at the output of the autonomous current inverter 7 will be equal to

40 of the current grid frequency, reduced by the absolute values of the slip frequency of the asynchronous motors 1 and 19. The slip values depend on the moment and individual characteristics of these motors, but in all cases the actual frequency of the autonomous inverter 7 current will be less than the value set by the frequency adjuster 17 . The reduction in the input signal of the driver of the pulse generator 14 as compared with the value determined by the frequency adjuster 17 is ensured by the fact that every 60 output frequency of the autonomous inverter current 7 is key 29

closes for a while. This time is determined by the pulse at the output of the comparison element 26 logi5

signal, it is equal to the time shift in advance of the logical signal of the actual current compared with the logical signal of a given current. These logic signals are fed to the inputs of the element 26 comparing the logic signals from the outputs of the logic drivers of the specified and actual currents 24 and 25. The logical signal of the current I will always be ahead of the logic signal of the specified current 1a, since the required frequency is lower than the frequency set by 17.

When the duration of the signals Ij and 1, equal to 180 e. degree., element 26 of the comparison of logical signals implements the following logical relation (FIG. 3)

M 1, DyDa + i +

- - VV where a, b, c are the phase indices of the asynchronous motor 1.

In the actual current logic driver 25 (Fig. 4), a pair-wise comparison of the currents of the currents is made using three comparators 43-45.

In the driver 24 of the logic signal of a given current (FIG. 5) at the inputs of the comparators 48 and 49, the output signal U, - adder 35 is compared with the corresponding signals + cfg, + q) j, +,. At the same time, the duration of the logic signals, which is required for the operation of the logic signal comparison element 26, is 180 ee, degrees.

 The asynchronous motor 1 with a short-circuited rotor operates in the generator mode, which corresponds to the zone of corners

Oh whereS

2 the angle between the current and flow vectors, and the expansion of the output signals of the comparators 48 and 49 to 180 el. hail, can be done, for example, with the help of the RS flip-flop 50, to the inputs R and S of which comparators 48 and 49 are fed with antiphase reference sinusoids

The correspondence between the output signal setpoint 14 moment and

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40

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the value of the angle 9 is measured by the element 23, which determines the angle between the current and flow vectors. However, 11 are possible in the system (errors5 associated with many circumstances, for example, parametric parametric assignment of the current amplitude and angle 9 as a function of the magnitude of the specified moment e by the presence of a fixed value of the phase error between the logical current assignment signals and the actual current, etc.

As a result, the actual value of the flow of the machine does not remain non-H3MeHHFjiM5 and the actual value of the moment corresponds to the value to be set. To improve the accuracy of the formation of the moment, the phase of the logical specified current is corrected by changing the logic signal at the input of the driver 24 to the specified current of the control signal ;; 5 from the output of the adder 35. This correction is carried out using a flux linkage regulator 34 (e.g., proportional to integral), at the input of which, using a comparison element 33, the amplitude link signal of the flux linkage is compared with the actual amplitude. In the steady state mode of operation, the signal at the input of the flow coupling regulator 34 is equal to ZERO; and the flow in the asynchronous motor 1 is unchanged; But

Thus, the introduction into the frequency-controlled asynchronous electric drive for the engine test bench sets the torque and frequency setting unit (instead of the speed controller and the frequency control and frequency blocks BpaoieHHft in the known device), a also inserts the setting frequency of the setting unit; the meter, the flow amplitude regulator and the adder provides automatic control of the frequency and phase of the current of the asynchronous two-phase with short-circuited ro :: Orom, thereby increasing the accuracy of maintaining a given electromagnetic mode, and hence the formation accuracy of the moment in s) Note with a known device.

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Claims (1)

A FREQUENCY-REGULATED ASYNCHRONOUS ELECTRIC DRIVE FOR THE TEST STAND OF MOTORS, comprising an asynchronous motor with a squirrel-cage rotor, the stator windings of which are connected to the outputs of a frequency converter and a voltage converter, equipped with an in-line control unit and an in-line control unit with an in-line control unit and a controlled by-wire control unit an inverter equipped with a shaper of the flux linkage signal, connected by inputs to the outputs of the phase current sensors and voltages, a frequency correction unit, connected by the first and second inputs, respectively, to the outputs of the flux linkage signal conditioner and the phase current sensor, and a pulse shaper, connected by an input to the output of the frequency correction unit, and by an output - to the control input of an autonomous current inverter, the input of the rectifier control unit is combined with the third input node of the frequency correction, equipped with a determinant of the angle between the vectors of current and flux linkage, formers of logical signals of a given and actual currents, an element comparing logic signals with an operational amplifier, the feedback circuit of which includes a parallel-connected resistor and a controlled key connected by a control input to the output of the logic signal comparison element, the first input of the frequency correction unit is formed by the first input of the logic current generator of a given current, the second input of which is connected to the output determinant of the angle between the current vectors and the flux linkage, the input of which forms the third input of the frequency correction unit, the output of the logical signal former a predetermined current is connected to the first input of the logical signal comparison element connected to the second input with the output of the actual current logic signal former, the input of which and the output of the operational amplifier form respectively the second input and output of the frequency correction unit, characterized in that, in order to increase accuracy, a torque generator and a frequency controller are introduced, and the frequency correction unit is equipped with a sensor for the amplitude of the flux linkage and a series-connected meter for the amplitude of the flux link, element m of comparison, by the flux linkage regulator and the adder, the other input of which is connected to the output of the angle determiner between the current and flux vectors, the adder output is connected to the second input of the logic current signal conditioner, the output of the flux linker is connected to the other input of the comparison element, and the meter output . the amplitude of the flux linkage is connected to the first input of the frequency correction unit, while the input of the opamp amplifier forms the fourth input of the frequency correction unit connected to the output of the frequency setter, and the third input of the frequency correction unit is connected to the output of the moment sensor. ί