RU2599822C1 - Coolant supply device control unit - Google Patents

Abstract

FIELD: control units; heating.

SUBSTANCE: coolant supply device control unit comprises power controller, which is connected with electric heater, intended for arrangement in Dewar vessel at the distance of 0-10 mm from the bottom. Control key element in power controller is bidirectional thyristor, which first anode is power control unit input terminal and is intended for connection to first output of AC voltage power supply, second anode of bidirectional thyristor is output terminal and connected to first heater output through the first group of detachable connector terminals, which second output is output, intended, through detachable connector second group of terminals, for connection to AC voltage power supply second output. Coolant supply device control unit is equipped with absence of nitrogen light indicator, presented by light-emitting diode, tracking unit and liquid nitrogen level sensor arranged in Dewar vessel at 10-30 mm above the heater. Level sensor first output is connected to tracking unit input. Tracking unit is equipped with absence of nitrogen light indicator output connection and two outputs, positive and negative, for connection to stabilized voltage power supply, the latter of which is connected through detachable connector to level sensor and heater outputs connection point. Light-emitting diode anode is connected with tracking unit light indicator, and cathode is with its negative terminal. Connection of outputs, intended for connection to AC voltage power supply second output and stabilized voltage power supply unit negative output is common for control unit power supply circuit.

EFFECT: technical result of disclosed control unit is smooth adjustment of electric heater power output in operating Dewar vessel with help of phase control, absence of liquid nitrogen in Dewar vessel alarm indication, automatic disconnection of heater at the end of liquid nitrogen in operating Dewar vessel.

1 cl, 3 dwg

Description

The proposed solution relates to the field of electrical engineering and can be used as a control unit for pumping devices, filling liquid nitrogen, as well as for freezing vacuum traps.

It is known "Device for supplying refrigerant to the freezer", USSR copyright certificate No. 964380, publ. 10/07/1982. Bull. Number 37. The device contains a container, which is a metal cup and placed in the lower part of the Dewar vessel. The bottom of the tank is equipped with a ball valve, and on top of it are inserted, flush with the cover, an air supply pipe, and, with a minimum clearance with the bottom, a refrigerant supply pipe. Both of these pipelines are leaky through the lid of the Dewar vessel, in which there is an opening for filling the refrigerant into the Dewar vessel and the release of its natural vapor. At the other end, a refrigerant supply line is led into the freezer. An electromagnetic air valve, controlled by the control unit, is installed on the air supply pipe. The electromagnetic air valve is connected in series with the receiver, dehumidifier and compressor.

When a command is received from the control unit, the electromagnetic valve stops the connection of the pipeline with the atmosphere and connects it to the receiver, thereby providing compressed compressed air from the compressor through the dehumidifier and receiver to the tank from which the refrigerant is extruded through the pipeline into the freezer.

The disadvantage of this device is that in order to create a pressure in the tank displacing liquid nitrogen, a lot of additional equipment is needed (receiver, dehumidifier and compressor), and the control unit switches the solenoid valve in key mode. When using Dewar vessels of small capacity, for example, ASD-15 with a narrow neck, it is problematic to place a container of sufficient volume in it. The control unit will fail with each initial start-up. The nitrogen in the tank will not be enough to freeze, for example, (warm) vacuum, purged nitrogen traps used in experimental scientific equipment, so the electromagnetic valve will not shut off and air will go through the nitrogen supply pipe into the cold chamber. The electromagnetic valve switching incorporated in the control unit eliminates the possibility of smooth adjustment of the supply of liquid nitrogen to the cold chamber. At the end of nitrogen in the Dewar vessel, the control unit does not provide commands to turn off the compressor and turn on the display-alarm.

It is known "Device for supplying refrigerant to the cold chamber", USSR copyright certificate No. 350216, publ. 09/04/1972. Bull. No. 26. The device is a tube-shaped feeder, in the lower part of which there is a low-power heater (20 W) outside, hermetically sealed by a casing. At the place where the tube exits the neck of the Dewar vessel, a sealing device is located. The end of the tube outside the vessel has a union nut for connection to the fitting of the working chamber.

When electric power is supplied to the heater, it is heated, liquid nitrogen evaporates, and the pressure created in the Dewar vessel displaces liquid nitrogen through the tube into the working chamber.

The control unit of this device containing a power regulator connected to a low-power heater (20 W), placed in a Dewar vessel, is the closest analogue to the claimed technical solution, therefore, it is selected as a prototype.

The disadvantages of the control unit of this device is:

low adjustable power;

there is no indication-signaling the end of liquid nitrogen in a working Dewar vessel;

it is not intended to turn off the heater at the end of liquid nitrogen in a working Dewar vessel (in a gaseous medium, the heater overheats and burns out).

The task of this technical solution is to create a control unit for a refrigerant supply device, providing:

the possibility of smooth adjustment of power released by an electric heater in a working Dewar vessel;

indication-alarm of the absence of liquid nitrogen in the Dewar vessel;

automatic shutdown of the heater at the end of liquid nitrogen in a working Dewar vessel.

The solution to the technical problem of the proposed control unit for a refrigerant supply device containing a power regulator connected to an electric heater designed to be placed in a Dewar vessel at a distance of 0-10 mm from the bottom is achieved by the fact that the power regulator is equipped with an input terminal intended for connection to the first terminal AC power source and an output terminal connected through a first group of pins of a detachable connector to a first terminal of a heater, the second terminal of which is I have an output intended for connecting to the second output of an AC voltage source through a second group of contacts of a detachable connector, the control unit of the refrigerant supply device is supplemented with a light indicator, a tracking unit and a liquid nitrogen level sensor designed to be placed in the Dewar vessel, 10-30 mm higher heater, while the first output of the level sensor, through the third group of contacts of the detachable connector, is connected to the input terminal of the tracking unit, the tracking unit is also equipped with leads for connecting indicator connected to the terminals of the light indicator, and two terminals designed to connect a stabilized voltage to the power supply - plus and minus, the last of which, through the second group of contacts of the detachable connector, is connected to the connection point of the second terminals of the level sensor and heater, the connection of the conclusions intended for connecting to the second output of the AC voltage power source and the negative output of the stabilized voltage power supply is for circuits The power supply to the control unit is common.

In FIG. 1 shows a functional diagram of the proposed control unit of the refrigerant supply device with key elements of a technical solution. Electrical connections are shown by lines, points of contact by dots, transmission of control signals by arrows, electrical leads designed to connect circles to power supply terminals.

In FIG. 2 shows an electrical diagram of the connections of nodes and parts of a control unit of a refrigerant supply device.

In FIG. 3 shows an electrical schematic diagram of the proposed control unit.

The control unit of the refrigerant supply device (Fig. 1) contains a power regulator 1 connected to an electric heater 2, designed to be placed in the Dewar vessel 3 at a distance of 0-10 mm from the bottom, characterized in that the power regulator 1 is equipped with an input terminal intended for connecting to the first output of the AC power source and the output output connected through the first group of contacts of the connector 4 to the first output of the heater 2, the second output of which is the output intended for connections to the second output of the AC power source through the second group of contacts of the detachable connector 4, the control unit of the refrigerant supply device is supplemented by a light indicator 5, a tracking unit 6 and a liquid nitrogen level sensor 7, designed to be placed in the Dewar vessel 3, 10-30 mm higher heater 2, while the first output of the level sensor 7, through the third group of contacts of the detachable connector 4 is connected to the input terminal of the tracking unit 6, the tracking unit 6 is also equipped with terminals for connecting an indicator, connected with the terminals of the indicator light 5, and two terminals designed to connect a stabilized voltage to the power source - positive and negative, the last of which, through the second group of contacts of the connector 4, is connected to the connection point of the second terminals of the level sensor 7 and heater 2, connection the conclusions intended for connection to the second output of the AC power source and the negative output of the stabilized voltage power source is for power supply circuit b general control lock.

As an example of the specific implementation of FIG. 2 shows an electrical diagram of the connections of elements and nodes of the proposed control unit of the refrigerant supply device.

The tracking unit 6 also contains a relay 8, a polar capacitor 9, a first controlled key element 10, an optocoupler relay 11 and a chain of series-connected resistor 12, the LEDs of the optocoupler relay 11 in compliance with the polarity, trimming resistor 13, the second output of which is the input terminal of the tracking unit 6, the connection point of the positive terminal of the polar capacitor 9, the first terminal of the relay coil 8 and the first terminal of the resistor 12 is the positive terminal of the power supply of the tracking unit 6, the control terminal of the first controlled key element 10 with is single with the output of the sliding contact of the tuning resistor 13, the first output of the closing contact group of the optocoupler relay 11 is connected to the connection point of the second terminal of the winding of the relay 8 and the negative output of the polar capacitor 9, and the second output of the closing contact group of the optocoupler relay 11 is connected to the first output of the first controlled key element 10, the second terminal of which is the negative terminal of the power of the tracking unit 6, the first terminal of the first (disconnecting) group of contacts 14 of the relay 8 is connected to the positive terminal of the power of the node of tracking 6, and the second is the first output of the indicator connection, and the second output of the indicator connection is the negative power output of the tracking unit 6, the indicator light 5, which uses LED 5, is connected to the terminals of the connection of the indicator of the tracking unit 6 with the correct polarity, power regulator 1 contains a control key element, which is used as a triac 15, as well as an opto-simistor 16, a rectifier bridge 17, a pulse generator consisting of a second controlled key element 18, in which uses a single-junction transistor in a phase-shifting circuit of a series-connected capacitor 19, a resistor 20, and a variable resistor 21, in which a sliding contact terminal is connected to a connection point of its first terminal and a second terminal of a phase-shifting circuit resistor 20, a first terminal of a phase-shifting circuit capacitor 19 is connected to a connection point the negative output of the rectifier bridge 17 and the cathode of the LED of the optosymistor 16, the first base of the single-junction transistor 18 is connected to the connection point of the pluses the first output of the rectifier bridge 17 and the second output of the variable phase-shifting resistor 21, the second base of the single-junction transistor 18 is connected to the anode of the LED of the opto-simistor 16, the control output of the triac 15 is connected to the output of the first anode of the opto-simistor 16, the first AC output of the rectifier bridge 17 is connected to the output of the first anode triac 15, which is the input terminal of the power regulator, and the second AC terminal of the rectifier bridge 17 is connected to the first terminal of the second (closing) group of contacts 22 p le 8, the second terminal group 22 closing relay contacts 8 connected to the point connecting the output of the second optosimistora anodes 16 and the triac 15, the last of which is the output terminal of the power controller 1.

Let us consider the operation of the control unit of the refrigerant supply device according to the functional diagram shown in FIG. one.

Assume that the Dewar vessel 3 is charged with liquid nitrogen, and the refrigerant supply control unit is connected to electrical power sources.

The potential difference at the terminals of the level 7 sensor in liquid nitrogen is sufficient for the tracking unit 6 to operate, and it is in the tracking mode, the indicator light 5 is off and a signal is sent from the tracking unit 6 to the power regulator 1, making it ready for operation work. When applying the maximum current (determined by the rated power of the heater 2) from the power controller 1 to the heater 2, the heater 2 is heated, the evaporation of nitrogen, which creates pressure on the surface of liquid nitrogen in the Dewar vessel 3, extrudes it into the cold chamber. Maximum power provides the minimum time to create maximum pressure (determined by the pressure of the safety valve of the device supplying refrigerant) and exit to the operating mode of the cold chamber. After reaching the operating mode, the power supplied to the heater 2 is regulated in the mode of maintaining the necessary parameters in the cold chamber. When the flow of liquid nitrogen in the Dewar vessel 3 comes the moment when the level sensor 7 is in a gaseous environment (above the level of liquid nitrogen). The level sensor 7 begins to be heated by the current passing through it, this causes a decrease in the potential difference at the terminals of the level sensor 7 and the transition of the tracking unit 6 to standby mode. When the tracking unit 6 enters standby mode, the indicator light 5, which is an indicator of the absence of nitrogen, lights up, and a signal to turn it off comes to power regulator 1. If it is necessary to continue working, it is necessary to switch to the reserve Dewar vessel connected to the cold chamber. To do this, from the socket of the connecting connector 4, the plug of the spent Dewar vessel is disconnected and the plug of the backup Dewar vessel is connected. The described duty cycle is repeated on the reserve Dewar vessel.

Now, let us consider the operation of the control unit of the refrigerant supply device according to the electric circuit shown in FIG. 3.

Suppose that a dewar vessel is charged with liquid nitrogen, and the control unit of the refrigerant supply device is connected to electrical power sources.

Through the chain of series-connected resistor 12, the LED of the optocoupler relay 11, the tuning resistor 13 and the level sensor 7, a current begins to flow, causing the LED of the optocoupler relay 11 to glow, leading to a decrease in resistance (to the minimum) on its closing group of contacts. The potential difference at the terminals of the level 7 sensor located in liquid nitrogen is sufficient to open the first controlled key element 10. The response threshold is adjusted by a trimming resistor 13. Through a chain of series-connected first controlled key elements 10, the contact group of the optocoupler relay 11 and the relay coil 8 a current begins to flow, causing the latter to trip. The contacts 14 of the first group are opened and the contacts 22 of the second group of relays 8 are closed. The closed contacts 22 of the relay 8 bring the power regulator 1, which is the phase power regulator, into operational state. During operation, by moving the sliding contact of the variable resistor 21 of the phase-shifting circuit of the phase power regulator 1, the heat power released by the heater 2 is regulated. The operation of the phase power regulator and the automation of the temperature maintenance process are known [1]. As the flow of liquid nitrogen in the Dewar vessel 3 comes the moment when the level sensor 7 is in a gaseous environment. The current passing through it begins to heat it, which in turn leads to a decrease in the potential difference at its terminals. A decrease in potential at the control terminal of the first controlled key element 10 leads to its disconnection and shutdown of relay 8. The contacts of the first group 14 of relay 8 are closed. LED 5 lights up, signaling that nitrogen in the Dewar 3 vessel has run out. The contacts of the second 22 group of relay 8 are opened, disconnecting the phase power regulator 1. If necessary, continue to work, it is necessary to switch to the backup Dewar vessel connected to the cold chamber. To do this, the plug of the spent Dewar vessel 3 is disconnected from the socket of the connecting socket 4 and the plug of the backup Dewar vessel 3 is connected. The described duty cycle is repeated on the backup Dewar vessel 3. At the end of work, the plug is disconnected from the socket of the connecting socket 4.

When the circuit of the level sensor 7 is broken, the optocoupler relay 11 breaks the switching circuit of the relay 8, which does not allow turning on the power regulator 1.

In FIG. 3 shows a circuit diagram of the proposed control unit, where the L5313URC LED was used as a 5 HL indicator light, and the KD520A diode is used as a liquid nitrogen level sensor 7. As the first controlled key element 10 VD2 used precision parallel voltage regulator TL431. As a regulating key element 15 VS2, phase power regulator 1, the triac BTA12-600 is used. This triac allows you to adjust the current of the heater 2 in the range 0-12 A.

To maximize the production of liquid nitrogen in the Dewar vessel 3, the heater 2 should be located as close as possible to the bottom of the Dewar vessel 3 (0-10 mm). The heater 2 can also be located at the bottom of the Dewar vessel 3. In order to avoid overheating of the heater 2 with increased power (≥20 W) and its burning out, the level sensor 7 is located 10-30 mm higher. Due to this arrangement, the inclusion of the heater 2 occurs only in liquid nitrogen.

Thus, in comparison with the prototype, the proposed control unit of the refrigerant supply device has enhanced functionality:

apply heaters with power ≥20 W;

stepless adjustment of power emitted by an electric heater;

indication-signaling the absence of liquid nitrogen in the Dewar vessel;

automatic shutdown of the heater at the end of liquid nitrogen in a working Dewar vessel.

List of references

1. Phase power controller. RF patent for the invention No. 2298217, publ. 04/27/2007, Bull. No. 12.

Claims (1)

The control unit of the refrigerant supply device containing a power regulator connected to an electric heater designed to be placed in the Dewar vessel at a distance of 0-10 mm from the bottom, characterized in that the power regulator is equipped with an input terminal designed to connect to the first output of the AC voltage source and an output terminal connected through a first group of pins of a detachable connector to a first terminal of a heater, the second terminal of which is a terminal for connection to the second output of the AC power source through the second group of contacts of the detachable connector, the control unit of the refrigerant supply device is supplemented by a light indicator, a tracking unit and a liquid nitrogen level sensor designed to be placed in the Dewar vessel, 10-30 mm above the heater, while the first output the level sensor, through the third group of contacts of the detachable connector, is connected to the input terminal of the tracking unit, the tracking unit is also equipped with terminals for connecting an indicator connected to the terminals of the a commercial indicator, and two terminals designed to connect a stabilized voltage to the power source - positive and negative, the last of which, through the second group of contacts of the detachable connector, is connected to the connection point of the second terminals of the level sensor and heater, the connection of the terminals intended for connection to the second the output of the AC power supply and the negative output of the stabilized voltage power supply is common to the power supply circuit of the control unit.

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