RU1791800C - Device for temperature control - Google Patents

Abstract

The invention relates to automatic control systems and can be used, for example, in film processing complexes for stabilizing the temperature of chemical photographic solutions, washing water and drying air. The purpose of the invention: increasing the accuracy of regulation while simplifying the circuit and expanding the scope of the device for a three-phase load. The inventive device includes a temperature sensor 1, a thyristor control element 2, a three-phase heater 3, drivers 4, 5 and 6 of the clock pulses, an integrating amplifier 7, made in the form of an operational amplifier 8 with a capacitor 9 and resistors 10 and 14, D-flip-flops 11, 12, 13. 1 C.p. f-ls, 1 ill.

Description

The invention relates to automatic control systems and can be used, for example, in film processing complexes for stabilizing the temperature of chemical photographic solutions, washing water and drying air.

Known automatic temperature control systems containing a temperature sensor, an electronic controller, thyristors and heater 1. In these systems, the electronic controller contains a phase shifting device, as a result of which the phase of switching on of the thyristor changes, which leads to regulation of the current value in the heater and its temperature condition. However, with phase control, the thyristors emit significant radio interference into the network, which leads to a malfunction in shared digital computing equipment.

.. Closest to the technical essence is a control device, which is an automatic temperature control system | 2.

This device contains a temperature sensor. a thyristor control element connected to the heater and a clock driver, as well as a control logic circuit. This ensures that the set temperature is maintained by periodically turning on the thyristor control element at the beginning of the supply voltage period without causing radio interference.

However, this technical solution is not without some drawbacks, such as the positional regulation law, which does not allow to obtain high regulation accuracy, as well as the limited power of the single-phase heater, because the inclusion of a powerful single-phase heater leads to phase imbalance in a three-phase network of limited power.

The purpose of the invention is to increase the accuracy of regulation while simplifying the circuit and expanding the scope of the device for a three-phase load.

The goal is achieved in that in a device for controlling the temperature; containing a temperature sensor, a thyristor control element connected to the heater, and a clock driver, D-triggers and an integrating amplifier are introduced, with an output connected to the D-input of the D-trigger, the C-input of which is connected to the output of the clock driver, and the direct output with input

the house of the thyristor control element and with the first information input of the integrating amplifier, the second information input of which is connected to the output of the temperature sensor.

The most rational application of the invention is to operate the device on a three-phase load, while the device contains in each subsequent phase 10 a D-trigger and a clock driver connected to its C-input, as well as a thyristor control element connected to the inverse output of the D-trigger, the inverse D-trigger output first

The 15th phase is connected to the D-input of the D-trigger of the second phase, the direct output of which is connected to the D-input of the D-trigger of the third phase.

New features in the proposed technical solution are manifested in the fact that the integrating amplifier together with the D flip-flop, covered by feedback, are converted into a proportional link, the operation of which, in addition, is synchronized with the network by network clock pulses,

25 arriving at the C-input of the D-trigger. The resulting single-phase controller is simpler than the prototype, because contains fewer elements, but provides an increase in the accuracy of regulation, because proportional

30 law of regulation in the system provides greater accuracy than positional.

Integrated D-flip-flops are manufactured with several flip-flops in one housing, which was used to obtain an additional positive effect - the expansion of functionality due to the rational control of a three-phase control element under a three-phase load, and this

40 is carried out with almost no increase in the size of the regulator. A chain of sequentially triggered triggers transmits a signal with a shift of 1203 el. hail. Moreover, this scheme has potential

45 to manually control the heating or, conversely, turn off the heating (in case of emergency) by supplying additional signals to the S- or R-inputs of all D-triggers .RO; .;

50 The invention is illustrated in the drawing, which shows a functional diagram of a temperature control device.

The device comprises a temperature sensor 1, a thyristor control element 2 connected to a three-phase heater 3, which is the object of regulation, formers 4, 5 and 6 of clock pulses, an integrating amplifier 7, made in the form of an operational

b

an amplifier 8 with a capacitor 9 in the negative feedback circuit and resistors 10 and 14 connected to its input, D-triggers 11,12 and 13.

The thyristor control element 2 contains power optic symmetric thyristors 15, 16 and 17. A terminal 18 for manually turning on the heating and a terminal 19 for turning off the heating.

The sensor 1 is connected to the second information input of the integrating amplifier 7, the output of which is connected to the D-input of the D-trigger 11, the output of which is connected to the first control input of the thyristor control element 2 and simultaneously to the first information input of the integrating amplifier. The outputs of the forms and: rotators 4, 5, 6 of the clock pulses are connected to the C-inputs of the D-flip-flops 11, .12., 13, respectively, the inverse output of the first D-flip-flop 11 is connected to the D-input of the second D-flip-flop .12, the output of which is connected with the D-input of the third D-flip-flop 13, and the inverse outputs of the D-flip-flops 12 and 13 are connected to the second and third control inputs of the thyristor control element 2.

The temperature control device operates as follows.

Shapers 4, 5, and 6 generate clock pulses from the voltage of the three-phase supply network at the moment the voltage passes through zero, and the clock pulses 5 are shifted by. 120 electric city in relation to the pulses of the shaper 4, and the shaper 6 - 120 el. in relation to the pulses of the shaper 5.

The output voltage of the temperature sensor 1 having a negative polarity is inverted by the integrating amplifier 7, gradually increasing to the level of operation of the D-trigger 11 at the D input. However, the triggering of the D-flip-flop 11 does not occur at this moment, but when a nearby clock pulse appears at its C-input, which overturns the D-flip-flop, at the output of which a high-level signal appears, as a result of which the optocoupler thyristor 15 opens and the heater 3 supplies the voltage of the first phase of the supply network.

At the same time, at the inverted output of the D-flip-flop 11, the high-level signal has changed to zero, and the second D-flip-flop 12 will be overturned through 120 degrees. shaper pulses 5, at the inverse output of the D-flip-flop 12, a high level signal is generated, as a result of which the optocoupler thyristor 16 is opened and the voltage of the second phase is applied to the heater 3, and at the non-inert output of the D-flip-flop 12, the high-level signal will change to zero As a result, with D-flip-flop 13, the same thing will happen as with D-flip-flop 12, only with a delay of another 120 electric degrees, and the optocoupler thyristor 17 will open, which will lead to the appearance of the third phase of the voltage on the heater 3.

At the same time, at the first operation of the D-flip-flop 11, its output voltage

a high level is applied to resistor 14.

If until this moment the capacitor 9 is charged only through the resistance 10,

from that moment in time, it began to be simultaneously discharged through the resistor 14. The voltage at the output of the integrating amplifier will begin to decrease, and then: -o will decrease to zero,

in which the nearest clock pulse of the driver 4 translates the D-trigger 11 to the state of zero output levels. As a result, the optocoupler thyristor 15 closes and the heater 3 stops

receive energy from the first phase of the mains voltage, and the capacitor 9 again starts to charge. At the same time, a high level signal is detected at the inverse output of the D-flip-flop 11, which after 120 el. will lead to the switching of the D-flip-flop 12 and the shutdown of the optocoupler thyristor 16 and the second phase (at the moment of arrival of the nearest clock from the former 5). Similarly, the switching of the D-flip-flop 13 will occur and the optocoupler thyristor 17 and the third phase voltage will turn off.

As the capacitor 9 charges and discharges, the D-triggers will turn on and off.

The ratio of the times of on and off states of the D-triggers, and, accordingly, of the thyristor control element 2 determines the average energy released in the heater 3 and, of course, its heating temperature.

Let us see what regulation law the proposed system operates in.

The capacitor 9 is charged and discharged during operation to the same voltage levels. Consequently, the magnitude of the electric charge received and delivered by the capacitor is the same and is determined by the product of the current by the time it flows:

isx Ti. (i0 - iux) T.

where TI is the charge time of the capacitor; Ta - capacitor discharge time:

(D

IPX input current of the integrating amplifier through resistor Pvc resistance 10

JJnx. RBX

10 - input current of the integrating amplifier through the resistance RO of resistor 14.

From equality (1) we obtain the ratio of the times of charge and discharge, the expressed ratio of currents:

IBX

in

IBX

-1

The duty cycle K of the periodic sequence of output pulses of the D-trigger 11 can be expressed through these currents:

T2

T2

T + T (TL + 1) T2-

1

T2

 +

In this expression, we replace the ratio of times by the ratio of currents from the equations

(2):

TO

1

 IB

-1 + 1

In the resulting final equation (4), the duty cycle is directly proportional to the input current of the integrating amplifier.

Thus, when negative feedback is fed through the resistor 14 of the series-connected integrating amplifier and the D-trigger, the duty cycle of the output pulses of the D-trigger is directly proportional to the input signal.

Therefore, the system operates according to the proportional control law, while providing more accurate temperature stabilization and better quality of transition processes than can be achieved by the prototype, and at the same time its functionality is wider due to the fact that the proposed technical solution allows apply more powerful

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fifteen

iO

B

thirty

35

n "to

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three-phase heaters as an object to regulate ovechi and prevent phase imbalance. :

Additional operational convenience is provided by the presence of R- and S-inputs of control for D-flip-flops, which are combined and output to terminals 18 and 19. In the operating states of the system, a voltage of zero potential is applied to these terminals. As necessary, manual control by, the roar, a high potential voltage is applied to terminal 18. And in emergency situations, when the heating must be turned off, a high level voltage is applied to the terminal

nineteen-

The proposed technical solution while maintaining the positive properties of the prototype — the absence of radiation of radio interference — allows to simplify the control circuit, at the same time, to increase the accuracy of regulation of the system under single-phase load and also expand the scope of application, taking into account turn on and turn on the three-phase load.

Claims (2)

1. A temperature control device comprising a temperature sensor, a thermistor control element connected to a heater, and a clock generator, for example, in order to increase the accuracy of regulation, D- triggers, an integrating amplifier, with an output connected to the D-input of a D-flip-flop, the C-input of which is connected to the output of the clock generator, and the direct output is the input of the thyristor control element and the first information input of the integrating amplifier, the second inform which is connected to the output of the temperature sensor. 2. The device according to claim 1, with the proviso that, in order to expand the scope of the device to a three-phase load, it contains in each subsequent phase. D-flip-flop and a clock driver connected to its C-input, as well as a thyristor control element connected to the inverse output of the D-flip-flop, the inverse output of the D-flip-flop of the first phase connected to the D-input of the D-flip-flop of the second phase, direct output which is connected to the D-input of the D-trigger of the third phase.