SU1334347A1 - Frequency-regulated electric drive - Google Patents

Abstract

The invention relates to electrical engineering. The aim of the invention is to simplify and reduce maintenance costs. This goal is achieved by the fact that in a variable frequency drive, the third input 16 of frequency control unit 11 is connected to the output of speed setting unit 7. The output of the block 11 is connected to the second input of the comparison element 8. The indicated connection of block 11 made it possible to use the output signal of block 11 as a feedback signal by frequency, which made it possible to exclude their tachogenerator circuits. 3 il. with ig i O) ©

Description

The invention relates to electrical engineering and can be used in automatic control systems for variable-frequency electric drives in various industries, based on an asynchronous short-circuited motor and thyristor frequency converter with an autonomous current inverter.

The purpose of the invention is to simplify the e-drive and reduce operating costs;

Fig. 1 shows the functional-js chom 21 in the input circuit and with the resistor 22 and the control switch 23 in the feedback circuit, the formers 24 and 25 logic signals of a given

20

on the scheme. frequency-controlled electric drive; 2 shows a current control unit; on fig.Z - node frequency correction,

Frequency adjustable) Your electric drive contains an asynchronous short-circuited engine 1 - (FIG,), connected to a frequency converter 2 based on a standalone current inverter with two | control inputs 3 and 4, respectively, for current and frequency, sensors 5 and 6 of phase currents and voltages, respectively, are connected in series by a frequency setting unit 7, a comparison element 8, a regulator of rotational speed 9 and a control unit 10 for current, output connected to control input 3 for a current of the frequency converter 2, triple-in. A frequency control terminal unit 11 with a shaper of 12 signals for flow monitoring and a frequency correction unit 13 connected by a first input to the output of shaper 12 for streaming signals At the same time the first input of shaper 12 signals

40

1st actual

1 current, element

26 logical comparison, the corresponding outputs of which are connected to the control inputs of the controlled keys 21 and 23 "

The inputs of the formers 24 and 25 of the logic signals of the given and actual currents and the combined terminals of the resistors 19 and 20 form the first, second and third inputs of the frequency correction unit 13, respectively.

Each of the formers 24 and 25 logical signals of a given and actual currents contains three comparators based on operational amplifiers with resistor summers at the input and an inverting element at the output. The element 26 of logical comparison 2 can be built on the basis of twelve three-input circuits I and two six-input circuits IG1I "

Variable frequency drive works as follows.

The second inputs of the flux linkage signal generator 12 and the frequency correction unit 13 and the third input of the frequency correction unit 13 form the first, second and third inputs 14-16 of the frequency control unit 11, the output of which is formed by the output of the frequency correction unit 13, respectively connected to control input 4 for frequency converter 2 frequency. The first and second inputs 14 and 15 of the frequency control unit 11 are connected respectively to the codes of the sensors 6 and .5 phase voltages and currents,

In the variable frequency drive, the third input 16 and the output of the frequency control unit 11 are connected

respectively to you} ;; one unit of the rotational speed reference 7 and to another input of the comparison element 8.

The current control unit 10, which is a functional converter, can be implemented on the oine of operational amplifier 17 (FIG. 2) covered by non-linear feedback: and using resistors and diodes S

Frequency correction node 13 contains an operational amplifier 18 (FIG. 3) with resistors 19 and 20 controlled by a switch.

about

five

0

five

1st actual

1 current, element

26 logical comparison, the corresponding outputs of which are connected to the control inputs of the controlled keys 21 and 23 "

The inputs of the formers 24 and 25 of the logic signals of the given and actual currents and the combined terminals of the resistors 19 and 20 form the first, second and third inputs of the frequency correction unit 13, respectively.

Each of the formers 24 and 25 logical signals of a given and actual currents contains three comparators based on operational amplifiers with resistor summers at the input and an inverting element at the output. The element 26 of logical comparison 2 can be built on the basis of twelve three-input circuits I and two six-input circuits IG1I "

Variable frequency drive works as follows.

The output signal of the frequency reference unit 7 is compared in the comparison element 8 with the output signal of the frequency control unit 11. The signal error from the output of the comparison element 8 is fed to the input of the rotational frequency controller 9, at the output of which a moment signal is generated

:

engine 1 j in function: i; and whose in

In the current treatment unit 10, a signal for setting the current amplitude of the frequency converter 2 is generated using a functional converter.

The output signal of the frequency setting unit 7 of Ephastia is also fed to the input of the frequency control unit 11, where it is converted into an output frequency signal of the converter 2.

The conversion of the speed setting signal to the output frequency signal in frequency control block 11 is determined by the phase error between the set and actual positions of the stator current vector of the motor 1 relative to the rotor flux vector. If the real position of the current vector lags the set one, frequency correction unit 13 generates signals that increase the output signal of frequency control unit 11 relative to that set at input 16. The current frequency at the output of frequency converter 2 increases. The stator current vector overtakes the flux vector.

If the real position of the current vector is ahead of the set one, frequency correction unit 13 generates signals that reduce the output signal of frequency control unit 11 relative to the input one. The frequency of the stator current decreases. The flux linking vector overtakes the stator current vector.

Thus, the phase error signal split by the frequency correction unit 13 between the real and predetermined positions of the current vector changes the actual frequency of the output of the frequency converter 2 compared to the frequency setting set at the output of the speed setting unit 7, continuously adjusting the frequency of the converter 2 to the actual frequency rotation of the engine 1. Due to this, the engine is stable without overturning at any (within the allowable) fluctuations of the load torque on its shaft. At the same time, the comparison element 8 detects the error of the actual frequency of the converter 2 relative to the one set by block 7, which changes the output signals of the rotational frequency controller 9, the current control unit 10, and hence the stator current value of the motor 1 and its electromagnetic moment until the actual current frequency Converter 2 will not be equal to the specified one.

The position (phase angle) of the stator current vector is set using the comparators of the driver of 24 logical signals of a given current, at the input of which the signals of couplings of different phases are summed, formed in a driver of the stream of 12

connections from the output signals of sensors of 5 phase currents and sensors of 6 phase voltages.

The real position of the stator current vector is measured by comparators of the shape of the logic of the actual current logic signals 25, the input of which summarizes the output signals of the sensors 5 phase currents.

Logic signals 1 from the output of the mapper 24 are compared with the logical signals of the - - output of the imaging unit 25 in the logic comparison element 26, at the output of which the phase onibka signal is extracted. If a

logical signals

lagging behind

phase from the corresponding logical signals loj. (the phase angle between the stator current and flux linkage vectors is less than the specified), a signal is produced at the output B of the logical comparison element 26. It closes the e key of the node 21 of the frequency correction node 13, increasing the signal at the output of the operational amplifier 18 relative to the input signal.

If logic signals are 1, signals 1 are out of phase (the phase angle is not the current vector vectors and the flow is not greater than the specified one), a smaller signal is produced at the output of the M signal of the logical comparison 26, which closes the key 23 of the frequency correction unit 13, as a result of which the output signal of the operational amplifier 18 becomes less than the input (goes to zero). When the phase of the logical signals of actual and second-hand currents coincides (the phase angle between the current and flux linkage vectors is equal to the specified one), the signals at the outputs of the logic comparison element 26 are not generated, the keys 21 and 23 are open, the output signal of the frequency correction angle 13 is equal to the input

Thus, injecting-se into the frequency-regulating electric drive of additional connections between the output of the frequency setting unit 7 and the input 16 of the frequency control unit 11 as well as between the output of the frequency control unit 11 and the second input of the reference element 8 makes it possible to use As a feedback signal on the frequency, the output signal of the frequency control unit 11, thereby simplifying the design of the electric drive by eliminating the tachogenerator and the simpler execution of the frequency control unit and reducing operating costs. At the same time, high adjustment and dynamic characteristics are preserved in the electric drive due to accurate reproduction of the specified phase angle between the stator current and flux linkage vectors.

Claims (1)

The invention is an adjustable frequency drive containing an asynchronous short-circuited motor connected to a frequency converter based on a standalone current inverter with two control inputs for current and frequency TOTHj phase current and voltage sensors connected in series to a speed reference unit, comparison element , a speed controller and a current control unit, an output connected to a control input for a current frequency converter, and a three-input control unit the frequency with the frequency broker of the flux couplings and the frequency correction node connected by the first input to the output of the flux coupler signal generator, while the first input of the flux linkage signal generator, the second inputs of the coaxial coupling signal generator and the frequency correction node and the third input of the frequency correction node together form the first, the second and third inputs of the frequency control block whose output, formed the output of the frequency correction node is connected to the control input for the frequency of the frequency converter, and the first and second inputs of the frequency control unit are connected respectively to the outputs of the phase voltage and current sensors, characterized in that, in order to simplify and reduce operating costs, the third input and output of the frequency control unit are connected respectively to the output of the speed setting unit and to another input of the reference element. X ten fib.Z