SU788328A2 - Device for control of two-phase induction motor - Google Patents

Description

The invention relates to automation and computing, in particular, to pulse devices of automation with pulse-width modulated signal, and can be widely used in control systems of two-phase asynchronous motors, in those cases when it is necessary to have linear regulation in the whole range non-torque characteristics of the engine,. According to the main author. St. 649117, a device flj for controlling a two-phase asynchronous motor is known, which contains a control unit, an N-bit counter, (N-1) -dbit counter, two AND schemes, two static flip-flops, a switch, a power amplifier and a counting flip-flop with a dynamic output . One of the outputs of the control unit is connected through the AND circuit with the counting input of the N-bit and (N + 1) -bit counters, the second output is connected to the switch,. the third output is connected to the control inputs of the N-bit counter with the control inputs of the N-bits and with the installation input of (N + 1) a row, (N + 1) -disk counter and with the first input of the static trigger The information inputs of the N-bit counter are supplied with a direct code of a number, and the information inputs of the (N + l) -pa3 counter of the counter are fed with the reverse code of a number. The second input of one of the static triggers is connected to the output of the (N + 1) -disable counter, the second input of the other static trigger is connected to the dynamic output of the counting trigger, the counting input of which is connected to the output of the discharge counter, and the setup input to the third control unit output. The first output of one of the static triggers is connected to the switch and the enable input: I circuits. The first output of the other static trigger is connected to the enable input of another AND circuit, and the second, the output is connected to the switch. The device generates control signals on the windings of an induction motor from the middle of the half-cycle, while the starting torque of the engine is 3 p11KA Mn AeUo6Uo4lK coefficients proportional to K. Kdz; voltage on the motor winding; UQ (. - voltage on the motor control winding; Ln - relative time; T - power supply voltage period K-A - duration of control pulses; A - input code of a number. Consequently, the starting moment is proportional to the input signal A only for small 1 when it can be assumed that 51пН (.0, i.e. the main disadvantage of the known device is not a sufficiently large linear control range. The purpose of the invention is to obtain linear control over the entire control range. This goal is achieved by In addition, two control channels are added to the phase asynchronous motor, each of which contains a serially connected digital controlled attenuator and a pulse generator, the generator outputs being connected to the first and second inputs of the control unit respectively, and the direct code is fed to the inputs of one of the digital controlled resistances numbers, to the inputs of another - the inverse code of the number. In Fig. 1 is a block diagram of the proposed device f in Fig. 2 timing charts of signals; in fig. 3 - torque characteristics of the engine. The device contains a control unit 1, inputs 2 and 3 of which are connected to the outputs of controlled oscillators 4 and 5 frequencies, and the inputs for each channel of controlled oscillators 4 and 5 of the frequency are connected to the outputs of digital controlled attenuators b and 7, to the inputs of one from which comes. the direct code of the number A, and to the inputs of the other, the reverse code of the number K. The output 8 of the control unit 1 is connected via AND 9 to the counting input of the M-bit counter 10, consisting of countable triggers 11 with dynamic output, output 12 of the block 1 is connected via an AND 13 circuit with a counting input (M + 1) of a discharge counter 14. The output 15 of the control unit is connected to the switch 1 The output 17 of the control unit 1 is connected to the control inputs of the N-bits and the setup input (N + 1) a discharge (N + 1) discharge counter 14. The output 17 of the control 1 is also connected to the inputs 18 and 19 of static t Igger 20 and 21. The second input of the static trigger 21 is connected to the output of the (N + I) -disk counter 14. The second input of the static trigger 20 is connected to the dynamic output of the counting trigger 22, the counting input of which is connected to the output of the M-bit counting 10 , a setting input - to the output 17 of the control unit 1. The output 23 of the static trigger 20 is connected to the switch 16 and allows the input of the AND 9 circuit. The output 24 of the static trigger 21 is connected to the interrupting input of the And 13 circuit, and the output 25 to the switch 16. The outputs 26 of the switch 16 are connected to the power amplifier 28. FIG. 2 shows signal timing diagrams explaining the operation of the device, where signal 29 at output 15 of control unit 1, signal 30 at output 3 and output 12 of control unit 1 are indicated, signal 31 at output 2 and output 8 of control unit 1, the signal 32 from the output 17 of the control unit 1, the signal 33 at the output 23 of the static trigger 20, the signal 34 at the output 25 of the static trigger 21, the signals 35 and 36 respectively from the outputs 26 and 27 of the switch 16. In FIG. 3 shows the characteristics. the relative moment of the crown motor, depending on the relative time, with 37-moment characteristic of the asynchronous motor to; the introduction of devices 4-7 / 38 is the inverse moment characteristic, 39 is the compensated moment characteristic. The operation of the device in one half cycle of the operating frequency of the engine is as follows. From the output 17 of the control unit 1, pulses with a frequency of 2f (where f is the working frequency of the induction motor) are fed to the control inputs of the N-bit counter 10, to the installation of the counting trigger 22 in 1, to the control inputs of the N-bits and to the installation in O (N + 1) -discharge of counter 14, as well as to inputs 18 and 19 of static flip-flops 20 and 21, set them in a position allowing the passage of pulses of frequency F and fj from outputs 8/12 of control unit 1 through AND 9 circuits, 13, to the counting inputs of an N-bit counter 10 and a (N + 1) -bit counter 14. Depending on the number code, it changes voltage at the output of the digital controlled attenuator b, 7, thereby changing the frequency of generator 5 actuated, 4. The pulse frequency controlled reYiepaTopa 4 is determined from the expression 2fK (). The frequency of the pulses of the controlled oscillator 5 is determined from the expression f 2fK2 (), (3) where f is the operating frequency of the asynchronous motor; - the number of bits of the control code;

K is a coefficient characterizing the change in the value of the torque of an asynchronous motor from the direct control code of the number A:

K is a coefficient characterizing the change in the magnitude of the torque of an asynchronous motor from the reverse control code of the number A.

The pulse from the dynamic output of the counting trigger 22 is fed to the second input of the static trigger 20 and sets to state 1, while prohibiting the passage of pulses through the AND 9 circuit to the rest of the semi-period. The pulses from the output of the (N + 1) -disable counter 14 arrive at the second input of the static trigger 21 and set it to state 1, prohibiting the passage of pulses through the AND 13 circuit to the counting input of the (N + 1) -disable counter 14. Pulses from outputs 23, 25 of static triggers (signals 33 and 34 in Fig. 2), the duration of which is proportional to the input number A and the change, the torque values of the induction motor from the control number A, are fed to the input of the switch 16. In addition to these pulses to the inputs of the switch 16 a reference signal is output from output 15 of block 1 pack The signal and the signal of the input signal A. As a result, the switch 16 produces a wide-pulse control signal for the power amplifier 28, equal in duration to the sum of the pulses from the outputs 23, 25 of the static triggers (signals 33 and 34 in Fig. 2), the phase of which is determined by the sign of the input number A. These voltages (signals 35 and 36 in Fig. 2). shifted relative to the reference signal 15 from the output of control unit 1 (signal 29) by a quarter period. The control code of the number A is fed simultaneously to the information inputs of the (N + 1) -disable counter 14, to the information inputs of the N-bit counter 10 and to the inputs of digital controlled attenuators b and, moreover, to the inputs of one of them direct the code of the number A, to the inputs of the other is the inverse code of the number A., The resistances of each of the digital controlled attenuators are chosen so that the frequencies of the controlled oscillators 4 and 5 change in proportion to the change in the moment characteristic, compensating for its nonlinearity (curve 38 on FIG 3 ) according to formulas (2) and (3), curve 38 is a torque compensating characteristic of the engine, as well as a characteristic of a digital controlled attenuator. The resultant torque characteristic of an induction motor (curve 39 in FIG. 3) is linear in all

0 control range.

Thus, the width of the pulses of signals 35 and 36 is proportional to the magnitude of the input signal and depends on the change in the magnitude of the torque of the asynchronous motor.

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In the second half-period, the operation of the analogy device: on.

Since the first harmonic of the signal produced by amplifier 28 when the input signal changes, has a constant phase shift with respect to the reference signal, and the nonlinearity of the moment characteristic is compensated by the characteristic of the digital controlled attenuator, all this gives

5 it is possible to obtain linear adjustment over the entire input signal range.

Thus, the introduction of two control channels, each of which contains a digital y control e J j attenuator and a controlled pulse generator, makes it possible to extend the range of linear control and, accordingly, the linearity of control. .

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Claims (1)

1. USSR author's certificate 649117, 20.12.77. I I i I i I I M I M I I I M I I I t thirty I I I I t I M I I I I I I I I I I I t 31