CN109596879B - External overcurrent alarm for industrial and mining electrical equipment - Google Patents
External overcurrent alarm for industrial and mining electrical equipment Download PDFInfo
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- CN109596879B CN109596879B CN201811327059.6A CN201811327059A CN109596879B CN 109596879 B CN109596879 B CN 109596879B CN 201811327059 A CN201811327059 A CN 201811327059A CN 109596879 B CN109596879 B CN 109596879B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/165—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values
- G01R19/16566—Circuits and arrangements for comparing voltage or current with one or several thresholds and for indicating the result not covered by subgroups G01R19/16504, G01R19/16528, G01R19/16533
- G01R19/16571—Circuits and arrangements for comparing voltage or current with one or several thresholds and for indicating the result not covered by subgroups G01R19/16504, G01R19/16528, G01R19/16533 comparing AC or DC current with one threshold, e.g. load current, over-current, surge current or fault current
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
- G01R15/14—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
- G01R15/18—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using inductive devices, e.g. transformers
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
- G01R15/14—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
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Abstract
The invention discloses an external overcurrent alarm of electric equipment based on a current transformer, which comprises two current transformer module circuits, a resistance sampling circuit, an LED luminous circuit, a photoresistor circuit, an RS trigger type bistable circuit, a main loop protection circuit, a multivibrator circuit, an audible and visual alarm circuit and a +9V alternating current-direct current power supply module circuit. And the two secondary loops of the current transformer module circuit are connected in series with VR1 to form a sampling circuit, and the sampling voltage is used as the control voltage of the whole alarm. When the control voltage drop is high enough to enable the D 1 and the D 2 to emit light, the light emitting diode controls the resistance value of the photoresistor CDS, the photoresistor is immediately triggered to output a high level when the resistance value is reduced to a certain degree, the high level enters the base electrode of the T1 through the resistor R2, the T1 is cut off, the relay J and the contactor C are disconnected, and the equipment is protected. T1 after cut-off causes pin 4 of IC 2 to go high, and IC 2 produces an oscillation that pushes the horn to sound an alarm.
Description
Technical Field
The invention relates to a technology of an external overcurrent alarm suitable for electric equipment in the fields of industry, agriculture, mine and the like, in particular to an external overcurrent alarm of electric equipment based on a current transformer. The design can be integrated into a power distribution cabinet circuit, and more skillfully can be independently designed into a module circuit, and the alarm module can be randomly applied to almost all electrical equipment systems on the premise of ensuring normal work of a load.
Background
Safety production is one of important indexes for evaluating coal mines, and the importance of electromechanical equipment in coal mine production is self-evident, so that the safety operation of the electromechanical equipment in the mine plays a significant role in coal mine safety production.
In order to prevent the short circuit of the main circuit equipment or the damage of the electric equipment such as a generator, a main rectifying cabinet or a motor due to the overlarge current of the main circuit caused by the occurrence of ring fire of the motor, the overcurrent of the main circuit should be protected or controlled, and the equipment loss is controlled in a sprouting state.
For example, the most typical example is a motor that is severely overloaded for some abnormal reasons, such as a short circuit of a coil or a mechanical jam, etc., in which case the current of the main circuit of the power supply exceeds the normal operating current, which would still be in the normal range for the generator or the power distribution cabinet, but if the motor is not over-protected, or even if the over-current protection device is in an unreliable protection mode, which is simply a bimetallic strip, the motor is easily damaged if it is operated for a long period of abnormal overload.
The most trouble-saving and most common method is that each phase of a main loop is respectively connected with a current transformer, the secondary of the current transformer is respectively connected with an overcurrent relay with a corresponding protection current rated value in series, once the current of the main loop exceeds the rated value, the overcurrent relay immediately breaks the main loop to protect power supply equipment and electric equipment in the loop, and the application structure is simple and mature and is widely used in the industry, but the overcurrent relay is expensive, has poor action accuracy, is still not very safe and is very humanized.
The external overcurrent alarm for the electrical equipment is designed, the secondary of the current transformer is used for measuring the current of a main loop, the induced current of the secondary is used as sampling current to control the overcurrent alarm, the alarm gives an audible and visual alarm, the load error is displayed or a short circuit phenomenon occurs, and meanwhile, the main loop can be disconnected to protect an electrical equipment system.
The alarm is external to the electrical equipment, so that the structure of the original electrical equipment is not damaged, and the rated current protection value of the main loop can be flexibly adjusted through a potentiometer, so that the alarm is very humanized. The design can be integrated into a power distribution cabinet circuit, and more skillfully can be independently designed into a module circuit, and the alarm module can be randomly applied to almost all electrical equipment systems on the premise of ensuring normal work of a load.
Disclosure of Invention
The invention aims to solve the technical problem of providing the safety protection device which has simple structure, low manufacturing cost, reliable use, and can accurately and quickly implement power-off protection and audible and visual alarm on the overcurrent electric equipment.
In order to achieve the above purpose, the invention provides an external overcurrent alarm for industrial and mining electrical equipment, which comprises two current transformer module circuits, a resistance sampling circuit, an LED luminous circuit, a photoresistor circuit, an RS trigger type bistable circuit, a main loop protection circuit, a multivibrator circuit, an audible and visual alarm circuit and a +9V alternating current-direct current power supply module circuit; the LED light-emitting circuit is formed by connecting an integrated circuit IC1 with a peripheral circuit, and sequentially connecting a +9V power supply, a reset switch SW1, a resistor R1 and a working place in series, wherein the LED light-emitting circuit is formed by connecting light-emitting diodes D1 and D2 in anti-parallel and connected with two sides of a potentiometer VR1 through a resistor R0 in a bridging manner; the connection point of the reset switch SW1 and the resistor R1 is connected with the 6 pin of the IC1 to provide a reset signal for the RS trigger type bistable circuit; the +9V power supply, the variable resistor VR2, the photoresistor CDS and the workplace are sequentially connected in series, and the connection point of the variable resistor VR2 and the photoresistor CDS is connected with the 2 pin of the IC1 to provide a setting signal for the RS trigger type bistable circuit; the A phase and C phase loops of the three-phase power supply loop are respectively used as the secondary of the two current transformer module circuits, the secondary of the two current transformers are connected in series in the forward direction, the resistor sampling circuit consisting of the potentiometer VR1 is connected in series in the two secondary loops after the series connection, and the obtained sampling voltage is used as the control voltage of the whole alarm; when the voltage drop across the potentiometer VR 1 is high enough to make the light emitting diodes D 1 and D 2 emit light, the light emitting diode controls the resistance value of the photoresistor CDS, and the resistance value is used as the bias resistance of the input control end of the RS trigger type bistable circuit, and when the resistance value of the photoresistor drops to a certain degree, the bistable trigger is immediately triggered to output a high level; the high level enters the base electrode of a transistor T1 of the main loop protection circuit through a current limiting resistor R2, the T1 is changed from on to off, the coil end of a relay J is powered off, the joint end of the relay J is open, the joint end of the relay J is connected with the coil end of a contactor C, and the joint end of the contactor C is disconnected, so that the power supply of the protected electrical equipment is interrupted, and the equipment is protected; after the transistor T1 is turned off, the high level of the collector electrode of the transistor T1 causes the 4 pin of the multivibrator circuit IC 2 to be changed into the high level, the IC 2 generates oscillation to push the loudspeaker to sound an alarm, and the light-emitting diode D 4 emits light; the direct current output of the +9V alternating current-direct current power supply module circuit provides the working voltage of the whole low-voltage control circuit.
The current transformer module circuit is formed by connecting CT1 and CT2 in series in the forward direction, namely, the synonym end of CT1 is connected with the homonym end of CT 2.
And the negative electrode of the electrolytic capacitor C 01、C02 is connected with the negative electrode of the resistor sampling circuit, the positive electrode of the electrolytic capacitor C 01、C02 is respectively connected with the two sides of the serially connected transformers in a bridging way, the larger starting current of the motor is filtered, and the remaining secondary working current of the transformer is used for obtaining the control voltage of the whole protector through the potentiometer VR 1.
The emitter of the transistor T1 is grounded, the collector is connected with one end of a J coil of the relay, the other end of the J coil is connected with +9V for supplying power, and the normally closed switch SB1, the J joint end of the relay and the C coil end of the contactor are sequentially connected in series and bridged on A, B phases of a three-phase alternating current power supply; the junction of the relay J is connected in parallel with the normally open switch SB 2.
Drawings
Fig. 1, fig. 2, fig. 3, and fig. 4 are electrical schematic diagrams of a design and implementation method of an external overcurrent alarm for an industrial and mining electrical device according to the present application, which are used to provide a further understanding of the present application and form a part of the present application. Fig. 2 is a schematic diagram of the current transformer in detail. Fig. 3 is a diagram of the internal circuit of the 555 timer. FIG. 4 is a waveform comparison chart of each reference point of the alarm circuit.
Detailed Description
The electric schematic diagram of the overcurrent alarm is shown in figure 1, and comprises a bias circuit, an RS trigger type bistable circuit, a main loop protection circuit, a multivibrator circuit, an audible and visual alarm circuit and a +9V alternating current-direct current power supply module, wherein the bias circuit is composed of a current transformer module circuit, a resistor sampling circuit, an LED luminous circuit and a photoresistor. The internal circuitry of the +9v power supply module will not be described in detail for reasons of brevity.
Current transformer circuit
The English name of the current transformer is Current Transformer, the abbreviation CT, fig. 2 is a detailed diagram of the symbol of the current transformer, and the transformer is a special transformer from the basic structure and working principle. The number of turns of the primary winding of the current transformer is very small (some types of current transformers do not have one-side winding yet, a primary circuit penetrating through an iron core of the current transformer is used as the primary winding, the number of turns is equal to 1), and the primary winding is quite thick; the secondary winding has more turns and finer conductors. When in operation, the primary winding is connected in series in the circuit, and the secondary winding is connected in series with the current coils of the instrument, the relay and the like to form a closed loop. Because of the small impedance of these current coils, the secondary circuit is close to a short circuit condition when the current transformer is in operation.
A sampling potentiometer VR 1 is connected in series in a secondary circuit of the current transformer as the control voltage of the whole alarm.
In fig. 1, the main circuit (live wire) of the electrical equipment is used as a secondary coil (1 turn) of a current transformer CT, commonly called a through current transformer, and two secondary coils of the CT 1、CT2 are connected in series (note the same name end) in the forward direction according to the drawing, and the obtained sampling current is not the sum of the two secondary currents of the two transformers, but is close to the average value of the separately connected currents. The cathode of the electrolytic capacitor C 01、C02 is connected, and the anode is respectively connected across two sides of the serially connected transformers to obtain a nonpolar capacitor with withstand voltage of 50V and capacity of 50uF, so that the problem that a large starting current of the motor flows through the sampling potentiometer VR 1 to generate false alarm and false operation can be prevented.
A current transformer with a transformation ratio of 200/5 may be selected if the main loop actual current is 150A. The secondary of the current transformer is connected in series with a sampling potentiometer VR 1, and in order to achieve the purpose of flexibly and accurately adjusting the maximum protection current, a precise multi-turn potentiometer is used for replacing a common potentiometer.
The value of the sampling potentiometer VR 1 is determined according to the maximum current value I MAX of the main circuit to be protected, and in order to ensure the safety of the electric circuit, the protection current value is always less than or equal to the output maximum current value of the generator or the power distribution cabinet, and I MAX can be arbitrarily defined on the premise of ensuring the normal operation of the electric equipment. When the electrical device main loop current exceeds a maximum value I MAX, then the secondary current through the current transformer CT is I MAX/40 (provided that a 200/5 ratio current transformer is selected).
Here, by sampling the current of potentiometer VR 1 to be critical, the value of VR 1 can be determined by the following method:
When a maximum protection current I MAX occurs, there should be a 1.8V voltage drop across VR 1, so:
The application of the light emitting diode and the photoresistor can realize the strong and weak current separation of the front stage and the rear stage, so that a small signal control circuit of the rear stage is safer, a computer control system is easy to connect, and the remote control is realized.
Photoresistor circuit
The photoresistor is a special resistor made of semiconductor materials such as a sulfuration spacer or a selenization spacer, and the working principle is based on the internal photoelectric effect. The stronger the illumination, the lower the resistance, the resistance is reduced rapidly along with the increase of the illumination intensity, and the bright resistance can be reduced to below 1KΩ.
The photoresistor is very sensitive to light, and is in a high-resistance state when no light exists, and the dark resistance can reach 1.5MΩ. The special properties of photoresistors are very widely used with the development of technology.
The secondary circuit of the current transformer is connected in series with a voltage sampling potentiometer VR 1, as shown in fig. 1, the voltage obtained on the potentiometer will be the control voltage of the whole alarm circuit, when the voltage drop across the potentiometer VR 1 is high enough to make Light Emitting Diodes (LEDs) D 1 and D 2 emit light, the light emitting diode controls the resistance value of the photoresistor CDS, this resistance value is used as the bias resistor at the control end of the bistable trigger, and when the resistance value of the photoresistor drops to a certain extent, the bistable trigger will be triggered immediately to output a high level, as shown in fig. 1.
Although one LED can make the circuit work normally, two LEDs should be used at the same time to ensure safety and stability.
Implementing R-S flip-flop bistable circuit using 555 timer
555. The timer has low cost and reliable performance, and comprises two voltage comparators, three equivalent series resistors, an RS trigger, a discharge tube T and a power output stage, wherein the two voltage comparators provide two reference voltages of 1/3U CC and 2/3U CC. Its internal voltage standard uses three 5K resistors, so the name 555 circuit is shown in fig. 3.
The 555 circuit can realize pulse generation and conversion circuits such as a multivibrator, a monostable trigger, a Schmitt trigger and the like only by connecting a plurality of resistors and capacitors, and is the most commonly used function of the 555 circuit.
One of the features of the present design is that the application 555 timer can implement the R-S flip-flop type bistable circuit in addition to the above functions, which are functions not mentioned in the general textbook.
Still referring to FIG. 3 versus FIG. 1, pin 6 of IC 1 can be considered the R terminal (reset terminal or 0 terminal), active high (> 2/3U CC); 2 feet areThe terminal (set terminal or set 1 terminal), active low (< 1/3U CC). This way of operation is different from the basic RS flip-flop described in textbooks. When positive pulse (> 2/3U CC) appears at the R-terminal, U O =0, 555 timer is in steady state; and/>When a negative pulse (1/3U CC) appears at the end, U O = 1, 555 timer is in another steady state.
555, There is a disadvantage in that when the power is turned on for the first time, the trigger may erroneously output a high level, resulting in the relay J being turned off erroneously, and the protected electrical equipment being powered off to stop working, and simultaneously the alarm gives an audible and visual false alarm. To solve this problem, a capacitor C 5 may be connected to ground at the reset pin R D (pin 4) of IC1, which will cause pin 4 to remain low for a period of time when power is turned on, which will reset the output (timer output 0), and timer initialization is complete.
When the operating current of the electrical device exceeds the maximum protection current, the light emitting diode D 1、D2 is turned on, and the light irradiation reduces the resistance of the photoresistor CDS, which causes the 2-pin (TL-side, R-S flip-flop type bistable circuit of the IC 1 Terminal) level < 1/3U CC, and the comparator N 2 outputs a low level; at this time, the threshold TH end (6 pins) of the timer is still at a low level, the level=2/3U CC of the control voltage CO end (5 pins), the comparator N 1 outputs a high level, the timer IC 1 sets 1 to output a high level, the relay J is released, the contactor C is opened, the power supply of the protected electrical equipment is interrupted, and the equipment is protected. Since pin 4 of alarm circuit IC 2 goes high, IC 2 oscillates to push the horn to sound an alarm, and led D 4 emits light.
After the electrical equipment is powered off, the LED D 1、D2 is turned off, the TL end (2 feet) level of the timer IC 1 is more than 1/3U CC, the comparator N 1、N2 outputs a high level, the timer IC 1 outputs a high level unchanged, the relay is continuously released, the power supply of the protected electrical equipment is still interrupted, and the equipment is continuously protected.
After the protected electrical equipment processes faults, the switch SW 1 is pressed down, the R end (6 pins of the IC 1) of the R-S trigger bistable circuit is reversed to be high level (> 2/3U CC）,IC1 output and restore to an initialized state (0 level), the relay J is sucked, the protected circuit is turned on again, the reset pin R D end of the alarm circuit IC2 is kept at low level, the reset function is completed, and the audible and visual alarm is stopped.
At the same time we obtain a functional table for implementing R-S flip flop type bistable circuit by 555 timer, as follows
555 Timer forming multivibrator
Timer IC 2, capacitor C 2, resistor R 3, and potentiometer VR 3 form a multivibrator, power to timer IC 2 is provided by power supply U CC, but the end (4 pins) of reset pin R D is controlled by the output level of timer IC 1, and timer IC 1 is initialized and outputs low level when the alarm circuit is powered on, resulting in timer IC 2 being reset at the same time (U IC2-4=0）,IC2 outputs low level and audible and visual alarm keeps silent state).
Since timer IC 2 operates in a multivibrator mode, whether IC 2 can oscillate depends entirely on the level of its reset pin R D terminal (4 pin), assuming for convenience of description that its reset pin R D terminal (4 pin) is always high, i.e., allowing IC 2 to oscillate, the oscillation process is described as follows:
At the moment of power-on of the alarm circuit, assuming that t=0 at this time, since the capacitor voltage cannot be suddenly changed, the initial voltage U C2 =0 of the capacitor C 2, the comparator N 1 of the high and low trigger terminal voltage V TH＝VTL＝０(<1/3UCC),IC2 of the timer IC 2 outputs a high level, the N 2 outputs a low level, the basic RS trigger is set to 1, and the timer IC 2 outputs U IC2-3 =1 (high level), at this time The internal discharge transistor of the timer is turned off, and the power supply U CC charges the capacitor C 2 via the resistor R 3 and the potentiometer VR 3, which is the first transient state, as shown in fig. 4.U C2 is gradually raised. When U C2 rises to 1/3U CC, the output of comparator N 2 is inverted from 0 to 1, and at this time, comparator N 1 still keeps the high output, and the RS flip-flop keeps the state unchanged. So during 0< t 1, timer IC 2 outputs U IC2-3 high.
At time t=t 1, U C2 rises to 2/3U CC, the output of comparator N 1 changes from 1 to 0, at which time the N 2 output is still 1, the rs flip-flop output is reset, inverted to 0, and timer IC 2 outputs U IC2-3 =0.
During the period of time t 1<t<t2,The discharge transistor T is turned on, the capacitor C 2 is discharged through the potentiometer VR 3 and the discharge tube T, and the U C2 drops exponentially, which is another transient state of the circuit, as shown in fig. 4; when U C2<2/3UCC, the comparator N 1 output changes from 0 to 1, the N 2 output is still 1, the q state is unchanged, and the timer IC 2 output U IC2-3 =0, is unchanged.
At time t=t 2, U C2 drops to 1/3U IC1-3, the output of comparator N 2 changes from 1 to 0, the output of comparator N 1 is still 1, the output of rs flip-flop is 1, timer IC 2 outputs U IC2-3 =1, discharge tube T is turned off, at this time, the power supply charges capacitor C 2 again, and the circuit returns to the first transient state, as shown in fig. 4. And repeating the above processes in a cyclic reciprocating manner, and generating rectangular waves at the output end.
The oscillation period t=t 1+T2, T1 is the charge time of the capacitor C 2, and T 2 is the discharge time of the capacitor C 2.
Charging time T 1=（R3+VR3）*C2㏑2≈0.7（R3+VR3）*C2
Discharge time T 2=VR3*C2*㏑2≈0.7VR3*C2
Oscillation period of rectangular wave T= T1+T2=㏑2(R3+2VR3)*C2≈0.7(R3+2VR3)*C2
Thus, the period and frequency of the rectangular wave can be changed by changing the values of R 3、VR3 and the capacitance C 2.
From the above analysis, when the capacitor C 2 is charged, the timer IC 2 outputs U IC2-3 =1, and when the capacitor C 2 is discharged, U IC2-3 =0, the capacitor C 2 is continuously charged and discharged, and the output end obtains a rectangular wave. The multivibrator has no external signal input, but can output rectangular waves, which is essentially to change the electric energy in the form of direct current into the electric energy in the form of rectangular waves.
The actual control process of the design is that the electric equipment is overcurrent, the timer IC 1 outputs high level, the reset pin R D end (4 pins) of the timer IC 2 is high level, the timer IC 2 multivibrator works, the oscillation signal pushes the loudspeaker to sound and alarm through the coupling capacitor C 4, and meanwhile the light-emitting diode D 4 emits light, so that the audible and visual alarm when the protected electric equipment is overcurrent is realized.
Make and notice
1) The type selection of the current transformer is very critical, the current transformers of different types often have larger difference in structure (comprising copper bar lap joint form, appearance, iron core and the like and dynamic heat stability tolerance capability), and when the transformation ratio of the current transformer is selected, the actual load rated current is obtained at first, and the current is preferably 65-85% of the measurement range of the current transformer. For example, a rated current of 70A, a transformer with a 100/5 transformation ratio should be selected.
2) The selection of the sampling potentiometer VR 1 is also critical, which is an important component for generating the trigger voltage of the whole protector or the alarm, and the adoption of the multi-turn precision potentiometer is the best choice, so that the secondary current value corresponding to the protection current value is always less than or equal to the output maximum current value of the generator or the power distribution cabinet in order to ensure the safety of an electric circuit, and the protection current value can be defined randomly on the premise of ensuring the normal operation of the electric equipment, which is one of the characteristics of the design and can be applied to almost all electric equipment protection fields.
3) The light emitting diode D 1 、D2 and the photoresistor CDS are also very critical to be assembled, and should be close to each other as much as possible, and one piece of the light emitting diode D 1 、D2 and the photoresistor CDS should be installed in a light-tight closed container, so that any other ambient light except the light of the light emitting diode D 1 、D2 should be prevented from being irradiated onto the photoresistor to be mistakenly controlled, so that accidental protection and alarm occur, and normal work is affected.
4) The choice of the bias potentiometer VR 2 is also critical, and none of the bias potentiometers has a certain resistance value, so that different resistance values can be tried out to be suitable for different coupling degrees between the photoresistor CDS and the light-emitting diode D 1、D2, and the specific operation is that when the light-emitting diode D 1、D2 is turned on, the alarm should immediately alarm and power supply of the electrical equipment is disconnected.
The design is ingenious in that the potentiometer is used for acquiring the sampling voltage of the secondary current of the current transformer, so that the purpose of randomly presetting the protection current of the main loop can be realized; the light-emitting diode and the photoresistor are used for realizing strong and weak electric isolation; the RS flip-flop bistable circuit is implemented with a 555 timer circuit, which is a feature of this design. The design can be integrated into a power distribution cabinet circuit, and more skillfully can be independently designed into a module circuit, and the alarm module can be randomly applied to almost all electrical equipment systems on the premise of ensuring normal work of a load.
According to the design we have tried out a batch of protection module in the last year, used it on some electromechanical devices of the first colliery of the pudding of Fenxi bureau, through the trial of recent year, found that probably false alarm sometimes, use is showing slightly trouble, but greatly reduced the spoilage of equipment, improved production efficiency, at the today that coal is scenery, corresponding improvement economic benefits.
One of the drawbacks of this design is that the protection circuit cannot automatically switch on the power supply of the protected electrical equipment after the failure has been handled, and remains in an alarm state all the time, and the protection and alarm can be released unless the switch SW 1 is pressed after the failure has been handled.
Claims (4)
1. An external overcurrent alarm for industrial and mining electrical equipment comprises two current transformer module circuits, a resistance sampling circuit, an LED luminous circuit, a photoresistor circuit, an RS trigger type bistable circuit, a main loop protection circuit, a multivibrator circuit, an audible and visual alarm circuit and a +9V alternating current-direct current power supply module circuit; the LED light-emitting circuit is formed by connecting an integrated circuit IC1 with a peripheral circuit, and sequentially connecting a +9V power supply, a reset switch SW1, a resistor R1 and a working place in series, wherein the LED light-emitting circuit is formed by connecting light-emitting diodes D1 and D2 in anti-parallel and connected with two sides of a potentiometer VR1 through a resistor R0 in a bridging manner; the connection point of the reset switch SW1 and the resistor R1 is connected with the 6 pin of the IC1 to provide a reset signal for the RS trigger type bistable circuit; the +9V power supply, the variable resistor VR2, the photoresistor CDS and the workplace are sequentially connected in series, and the connection point of the variable resistor VR2 and the photoresistor CDS is connected with the 2 pin of the IC1 to provide a setting signal for the RS trigger type bistable circuit; the A phase and C phase loops of the three-phase power supply loop are respectively used as the secondary of the two current transformer module circuits, the secondary of the two current transformers are connected in series in the forward direction, the resistor sampling circuit consisting of the potentiometer VR1 is connected in series in the secondary loops after the two current transformers are connected in series, and the obtained sampling voltage is used as the control voltage of the whole alarm; when the voltage drop across the potentiometer VR 1 is high enough to make the light emitting diodes D 1 and D 2 emit light, the light emitting diode controls the resistance value of the photoresistor CDS, and the resistance value is used as the bias resistance of the input control end of the RS trigger type bistable circuit, and when the resistance value of the photoresistor drops to a certain degree, the bistable trigger is immediately triggered to output a high level; the high level enters the base electrode of a transistor T1 of the main loop protection circuit through a current limiting resistor R2, the T1 is changed from on to off, the coil end of a relay J is powered off, the joint end of the relay J is open, the joint end of the relay J is connected with the coil end of a contactor C, and the joint end of the contactor C is disconnected, so that the power supply of the protected electrical equipment is interrupted, and the equipment is protected; after the transistor T1 is turned off, the high level of the collector electrode of the transistor T1 causes the 4 pin of the multivibrator circuit IC 2 to be changed into the high level, the IC 2 generates oscillation to push the loudspeaker to sound an alarm, and the light-emitting diode D 4 emits light; the direct current output of the +9V alternating current-direct current power supply module circuit provides the working voltage of the whole low-voltage control circuit.
2. The external overcurrent alarm of the industrial and mining electrical equipment according to claim 1, wherein: the current transformer module circuit is formed by connecting CT1 and CT2 in series in the forward direction, namely, the synonym end of CT1 is connected with the homonym end of CT 2.
3. The external overcurrent alarm of the industrial and mining electrical equipment according to claim 1, wherein: and the negative electrode of the electrolytic capacitor C 01、C02 is connected with the negative electrode of the resistor sampling circuit, the positive electrode of the electrolytic capacitor C 01、C02 is respectively connected with the two sides of the serially connected transformers in a bridging way, the larger starting current of the motor is filtered, and the remaining secondary working current of the transformer is used for obtaining the control voltage of the whole protector through the potentiometer VR 1.
4. The external overcurrent alarm of the industrial and mining electrical equipment according to claim 1, wherein: the emitter of the transistor T1 is grounded, the collector is connected with one end of a J coil of the relay, the other end of the J coil is connected with +9V for supplying power, and the normally closed switch SB1, the J joint end of the relay and the C coil end of the contactor are sequentially connected in series and bridged on A, B phases of a three-phase alternating current power supply; the junction of the relay J is connected in parallel with the normally open switch SB 2.
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| CN201811327059.6A CN109596879B (en) | 2018-11-08 | 2018-11-08 | External overcurrent alarm for industrial and mining electrical equipment |
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| CN201811327059.6A CN109596879B (en) | 2018-11-08 | 2018-11-08 | External overcurrent alarm for industrial and mining electrical equipment |
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| CN113835384B (en) * | 2021-09-30 | 2023-11-28 | 深圳市长龙铁路电子工程有限公司 | Monitoring system |
| CN113853043A (en) * | 2021-10-29 | 2021-12-28 | 冯世祥 | LED miner's lamp alarm control circuit |
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