SU1372517A1 - Apparatus for measuring emf variation rate of static converter - Google Patents

Abstract

The invention relates to electrical engineering, in particular, to measuring the parameters of the operating modes of static (thyristor) converters in automatic control systems of electric drives. The aim of the invention is to increase speed and simplify for a given accuracy. This goal is achieved by integrating the voltage of the converter in the first interval of discreteness with the actual polarity of the voltage, and in the next with the opposite polarity. The result of the integration during the two intervals of discreteness during the third interval of discreteness is remembered and given as the result of the measurement. 3 il. cl

Description

113

The invention relates to electrical engineering and can be used to measure the operating parameters of static converters in automatic control systems for electric drives, made according to the static converter-motor scheme.

The purpose of the invention is to increase the speed and simplify the device for a given measurement accuracy.

FIG. 1 is a block diagram of the device; in fig. 2 - scheme of the implementation of the recalculated cell; fig.Z - explanatory time diagrams.

The device for measuring the rate of change of the EMF of a static converter contains the main 1- and additional 2 and 3 measuring units, made identically in the form of control unit 4 and integrating unit 5. Each of control units 4 consists of a pulse generator 6 and a counting cell 7. Each The integrating unit consists of the first 8 and second 9 input keys, the inputs of which form the measuring input of the measuring blocks 1-3, connected to the voltage sensor of the static converter, and the outputs of the first key

8 directly, and the second key

9 through the inverter 10 is connected to the input of the integrator 11 with the reset key 12 of the integrating condenser to zero, the output of which is connected to the input of the output switch 13, the output of which is the output of the measuring blocks 1-3. The outputs of blocks 1-3 are interconnected and are the output of the device. The input cell 7 of each unit 1-3 is the control input of this measuring unit, which is connected to the output of the pulse-phase control system (SIFU) of the converter.

The first output of the cell 7 of the block 1 is connected to the control input of the key 8, the second to the control input of the key 9 and the third to the control input of the key 13 and to the input of the driver 6. The first output of the cell 7 of the block 2 is connected to the control input the key 9, the second to the control input of the key 13 and to the input of the imaging unit 6 and the third to the control input of the key 8. The first output of the cell 7 of the unit 3 is connected to the control input of the key 13 and to the input of the imaging unit 6, the second to the control key input 8 and the third - to the control input key 9. The output of the imaging unit 6 of each block 1-3 is connected to the control input of the key 12 of the corresponding measuring unit.

As a counting cell 7 with the number of possible states equal to the number of measuring blocks, a ring scaling circuit can be used or a shift register in which the output is connected to the input and a unit is written, or it can consist of a pulse counter, the binary code of which is the decoder is converted to the voltage at the outputs of the decoder corresponding to the counter codes (Fig. 2).

The device works as follows.

The input of each measuring unit is supplied with the voltage of the converter and a sequence of pulses formed from CIF pulses with an interval equal to the discrete interval of the converter. At the output of each block 1-3 during the interval of discreteness, the measured value of the difference of the integrals of the voltage of the converter in the two preceding intervals acts.

As an example, consider the operation of block 1, which is illustrated by the timing diagram in FIG. 3

The diagram in the upper part shows the EMF. A 6-phase converter when its mean value changes from zero to some finite value. In this case, the lag angle of the converter valves is evenly reduced in each interval of discreteness according to the law.

90 ° - 90 ° - p. . where is the increment of the lag angle; n- is the number of the interval of discreteness, starting with the one in which the lag angle of the ignition has become less than 90 °; - increment of the lag angle in the same interval of discreteness. When the next pulse arrives from the SIFU, cell 7 goes from the previous state to the next one, and the signal of the logical unit goes from one output to the next. When moving conversion

313

the cells 7 of the unit 1 in the third position to the first with the help of the driver 6 and the key 12, its integrator is set to zero. In blocks 2 and 3, the installation of integrators 11 to zero occurs, respectively, when the cells transition from the second to the third and from the first to the second position.

After the transition of the cell 7 .block 1 to the first position, the contactless key 8 is switched on, and the keys 9 and 13 are disabled. The process of integrating the converter voltage is in progress. The voltage at the integrator output is indicated by the dotted line. The impulse received from the SIFU at the input of the cell 7 and indicating the end of the first interval of discreteness in the converter operation sets the unit to the second output of the cell 7, this opens the key 9 and the key 8 closes. Through the switch 8, the voltage of the converter is supplied to the integrator 11 through the inverter 10 with the opposite polarity. The third pulse from the SIFU turns off the key 9 and turns on the key 13. The inputs of the integrator 11 are turned off, it is transferred to the memory mode, and its output voltage is fed through the key 13 to the output of the ycT device.

The fourth impulse from the SIFU transfers the cell 7 to the first position, while the driver 6 at the time of the transition of cell 7 from the third position to the first - for a short time opens the key 12 for setting the integrator 11 to the zero state. Further, the sequence of operations implemented by block 1 is repeated.

Blocks 2 and 3 operate similarly to the first, however, the sequence of operations implemented by each one as follows starts one discrete interval later than the previous one.

Such an order of operation of the blocks ensures that the signals of the rate of change of the EMF of the converter in each interval of discreteness are indicated. At the same time, the minimum number of blocks is three, and the maximum is unlimited. According to the number of blocks used, the number of positions of the cells 7 is selected. Thus, for four blocks, a 4-position cell should be chosen, for five - a 5-position cell, etc. A device consisting of four blocks may be necessary in the event that

Q 2 25, Q

Xq

45

cn

35

five

174

Yes, it will take time within one discrete interval to set integrators 11 to zero. A device of five blocks will be required in the case when to set the integrator 11 to zero, a time in the range from one to two discrete intervals is required.

Despite the fact that integrators 11 integrate the voltage of the converter, the result of integration over two discrete intervals is the increment of the emf of the converter, not the voltage. This is due to the fact that the current in the converter circuit varies very little during the integration time (the time constant of the circuit into which the static converter is connected, usually a order of magnitude longer than the discrete interval of the converter).

A signal proportional to the rate of change of the EMF of the converter after the beginning of its measurement is obtained after two intervals of the converter's discreteness, however, the change of the speed itself is recorded after one interval of discreteness.

Thus, by issuing the results of measuring the rate of change of the EMF of the converter in each discrete interval, the speed is increased, and integration in analog form simplifies the device.

Claims (1)

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