SU760280A1 - Device for overload protection of electric equipment - Google Patents

Description

The invention relates to automation and can be used in control systems of various objects, in particular in shipboard * control systems and protection of electrohydraulic mechanisms against overload.

A device for the protection of heat and power equipment is known, which contains a sensor of a monitored parameter, a logic and separation unit, a logic element, And, an actuating element and a power source (ί) ·

The device protects the object from false triggering only in the event of damage to the logic unit, which does not allow it to be used to protect the actuators in unsteady transient operating modes of the hydraulic system.

The elimination of this drawback is associated with the installation of time delay blocks, for example, in a device for protecting an automation system containing a sensor, a comparator, a power amplifier, AC and DC voltage sources, a power supply control unit, a supply voltage switch, ele2

delayed cops and the “Prohibition” and the executive body [2].

This device is closest to the invention to the technical essence and the achieved result.

However, in this device, the time delay is constant and does not depend on the size of the output signal of the alarm sensor, which reduces the efficiency of the device, as it leads to unnecessary loss of working fluid in the hydraulic system where the sensor is installed.

The aim of the invention is to increase the response speed of the device.

This goal is achieved by the fact that a device containing an alarm sensor, the output of which through the first input of the comparison unit is connected to the triggering input of the time delay, the output of which through the logic unit is connected to the executive body, a source of operating voltage connected to the second input of the comparator, equipped with a maximum voltage isolation unit, two inputs of which are connected respectively to the alarm sensor and to the source

15

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reference voltage, and the output - to the control input of the time delay unit.

FIG. 1 is a schematic diagram of the device; in fig. 2 - a graph of the time delay (ί) of the excess ΔΕΙ sensor output signal (U) over the value of the reference voltage Nia ⁵ (and _again) at which the comparison unit is triggered.

The output signal of the alarm sensor 1 through the first input of the 2-comparison unit is connected to the trigger input 3 of the block ₁₀ time delay consisting of input 5, regulating 6 and output 7,

8 transistors, a capacitor 9 of the timed EC circuit and resistors 10-13. The control input 14 of the time delay unit 4 connected to the output selection unit 15 to the maximum voltage ^13, including a matching transistor 16 with resistor 17 in the emitter circuit and the diodes 18, 19, the cathodes of which are connected with the matching base of the transistor 16. The anode of diode 18 soedi- _m is not connected with the output of the alarm sensor 1 "” and the first input of the comparator 2, the anode of the diode 19 is connected to the voltage source 20 and the second input of the comparator 2, the output of the time delay 4 through the logic block 21 is connected to the 25th actuator m 22.

The device works as follows.

If the output signal of the sensor 1 alarm is less than the setpoint voltage, comparison unit ^{30 is} turned off and there is no signal at trigger input 3 of time delay 4.

Wherein the input transistor 5 is closed, the transistor 7 is opened, the capacitor 9 is charged almost to the supply voltage with po- _3ί polarity indicated in Fig. 1. The supply voltage through the resistor 13 keeps the transistor 8 open. Since the sensor voltage is less than the reference voltage, the diode 19 is open, and the active state of the matching transistor 16 and, ⁴⁰ therefore, the voltage across the resistor 17 will be determined by the value of the reference voltage. The voltage across the resistor 17 keeps the control transistor 6 of the time delay unit 4 active. The choice of the resistor 11 sets the collector current of the transistor 6. The capacitor 9 and the transient resistance of the collector-emitter junction of the transistor 6 together with the resistor 11 form a time-determining ECtch ^. Since in this EC circuit, the value of the equivalent discharge resistance depends on the magnitude of the output voltage of block 15, which in turn depends on the ratio between the values of Q? and Pe,., then the time delay will be a variable value dependent on the magnitude of the sensor output.

When the sensor output voltage 1

becomes larger than the set value

unit 2 compares, diode 19 closes, diode 18 opens, and the voltage across resistor 17 will be determined by the output signal of sensor 1. When this happens, transistor 5 opens and capacitor 9 begins to discharge in a circuit: emitter-collector of open transistor 5 -emitter junction of transistor 6 — resistor 11. At the time of discharge of capacitor 9, transistor 7 turns out to be shifted in the negative direction and closes. At the output of the resistor 12, a voltage appears that is almost equal to _n , which the transistor 8 maintains in the open state. At the output of the resistor 13, the voltage disappears at the moment of opening of the transistor 5. After the end of the discharge of the capacitor 9, the transistor 7 opens, at the output of the resistor 12 the voltage drops to almost zero, and the transistor 8 closes. The output signal from block 4 of the time delay through the logic unit 21 includes an actuator 22.

With the selected resistors 10, 11, 17 and the value of the reference voltage in the working range of possible values of the output signal of the sensor, the time delay will depend only on ΔΕΙ = E) ^ - I ^, and the larger value of the output signal of the sensor corresponds to meyyny time delay. The law of variation of the time delay on the value of the AP can be chosen, for example, linear, as shown in FIG. 2

A constant and maximum time delay value in region A is achieved due to the selection of such values of resistors 10, 11, 17 and the reference voltage at which the diode 18 is closed and the voltage on the resistor 17 is minimum, and the equivalent discharge resistance of the timing EC circuit is maximum, which corresponds to the maximum exposure of time. The steepness of the characteristics in the area B is set by the resistor 11. In this case, the transistor 6 becomes in the mode of large collector currents, which reduces the discharge resistance for the capacitor 9, and, consequently, reduces the time delay.

In region C, the value of equivalent discharge resistance is determined mainly by the value of resistor 11, which corresponds to the minimum time delay.

The positive effect is that compared with the known device in the proposed device, the time delay for $ 0 depends on the value of the output signal of the sensor, which allows to increase the response speed of the device in emergency mode of the system and the efficiency of the device.

The test results of the prototype of the device showed that in emergency mode of operation (the appearance of leaks in the event of a leakage of the hydraulic system) you

the signal, which is used to turn off the emergency section of the hydraulic system, is formed over time, an order of magnitude less than before (from 5 s the time delay decreased to 0.5 s).

Claims (1)

Claim A device for overload protection of a power installation, comprising an alarm sensor, the output of which is connected to the trigger input of the time delay through the first input of the comparison unit, the output of which is connected to the actuator via a logic block body, the source of the reference voltage, connected to the second input of the comparator, different in that, in order to increase the speed of the device, it is equipped with a maximum voltage extraction unit, two inputs of which are connected respectively to the alarm sensor and the reference voltage source, and the output to the control input of the time delay unit.