CN101908752A - Overload protector - Google Patents

Abstract

The invention provides an overload protector, which includes a casing, a thyristor, a diode, a control resistor, an electromagnet, a button, and a voltage dividing resistor. The diode is connected in series with the control resistor and then paralleled with the voltage dividing resistor, and then the button is connected in series. The diode anode terminal of the aforementioned circuit is connected to the live wire end of the power grid, the circuit button is connected to the neutral wire end of the power grid, in addition, the anode end of the thyristor is connected to the live wire end of the power grid, the control terminal is connected between the diode and the control resistor, and the cathode terminal is connected in series with the electromagnet It is then connected to the neutral terminal of the power grid, the electromagnet is coupled to the button, and the button is disconnected when the current in the electromagnet reaches the overload zero threshold. The overload protector can not only accurately realize circuit breaking protection when the current in the main circuit reaches the overload critical current, but also can conveniently restore the original state after circuit breaking.

Description

overload protector

Technical field

The invention relates to the field of electric power, in particular to a highly accurate current overload protector.

Background technique

Current household circuits are generally equipped with overload protectors, which are generally fuses and fuses, which are installed in knife switches. Once the fuse is broken, it cannot be restored, and it needs to be replaced to connect the circuit, which makes the follow-up work very troublesome, especially at night, after a power failure, the internal structure of the switch blade cannot be seen clearly, and it is difficult to connect the fuse safely. In addition, consider To the heat dissipation of the fuse and other issues, in fact, the specific value of the overload fusing current is very inaccurate.

In addition, in some industrial equipment with high requirements, the overload protectors used mainly include thermal relays, electromagnet type tripping circuit breakers, and various deformations of the two. The former also disconnects the main circuit by deforming the metal sheet through the thermal effect. Considering the heat dissipation instability of the metal sheet, the accuracy of the overload current of the open circuit protection is not high. The latter directly attracts the armature through the electromagnet to disconnect the main circuit. The circuit realizes overload protection. However, when the current reaches the zero threshold value, the armature will be in the state of not moving. At this time, the switch is prone to arc phenomenon. Moreover, the above two overload protectors involve many mechanical motion pairs, so it is difficult to achieve greater accuracy in terms of mechanical structure. Secondly, the above overload protectors are difficult to install in the junction box of ordinary household users. middle.

Contents of the invention

In view of the above problems, the purpose of the present invention is to provide an overload protector, which can not only accurately realize the circuit breaker protection when the current in the main circuit reaches the overload critical current, but also can be conveniently restored to its original state after the circuit breakage. , the overload protector can also be installed in the junction box of ordinary users.

The technical solution adopted by the present invention to solve the technical problem is: the overload protector includes a shell, a thyristor, a diode, a control resistor, an electromagnet, a button, and a voltage dividing resistor, and the diode is connected in series with the control resistor and then connected to the The voltage dividing resistors are connected in parallel, and then the button is connected in series. The diode anode terminal of the aforementioned circuit is connected to the live wire end of the power grid, and the button end of the circuit is connected to the neutral wire end of the power grid. In addition, the anode end of the thyristor is connected to the live wire end of the power grid, and the control terminal is connected to the Between the above-mentioned diode and the control resistor, the cathode terminal is connected in series with the electromagnet and then connected to the zero line terminal of the power grid. open.

As a preference, in the above-mentioned overload protector, the housing wraps all parts except the button, the button is embedded in the housing, and the housing is provided with a metal lug with a screw hole, which can pass through the The metal lug is directly installed on the fuse installation of the ordinary switch blade.

The beneficial effects of the present invention are: in the overload protector, when the current in the main circuit reaches the overload critical value, in the positive half cycle of the AC voltage, the current flows through the control resistor and the voltage dividing resistor at the same time, and a voltage is generated at both ends of them drop, that is, the critical potential difference, so that the thyristor is turned on. At this time, the electromagnet is energized, and once energized, it can generate a huge magnetism, and quickly disconnect the button. Compared with ordinary electromagnet relay switches, When the magnetism of the electromagnet gradually increases, the action of the overload protector is more precise and rapid. When recovering, you only need to press the button again. Accurately achieve circuit break protection, and can be easily restored to the original state after circuit break, in addition, the overload protector can also be installed in the junction box of ordinary users.

Description of drawings

Figure 1 is a circuit diagram of the overload protector.

Fig. 2 is a coordination diagram of the button and the electromagnet in the overload protector.

In Figure 1: 1, live wire terminal; 2, neutral wire terminal; 3, thyristor; 4, diode; 5, control resistor; 7, electromagnet; 8, button; 9, voltage dividing resistor.

In Fig. 2: 71, iron core; 72, liner; 81, contact; 82, armature; 83, neck; 84; button cap.

Detailed ways

Below in conjunction with Fig. 1, Fig. 2 and embodiment the present invention is further described:

In the specific embodiment shown in Fig. 1 and Fig. 2, the overload protector includes a housing (shown in a dotted line box in Fig. 1), a thyristor 3, a diode 4, a control resistor 5, an electromagnet 7, a button 8, and a voltage dividing resistor 9 , the diode 4 is connected in series with the control resistor 5 and then connected in parallel with the voltage dividing resistor 9, and then connected in series with the button 8, the anode terminal of the diode 4 of the aforementioned circuit is connected to the live wire terminal 1 of the power grid, and the terminal of the circuit button 8 is connected to the power grid The neutral terminal 2, in addition, the anode terminal of the thyristor 3 is connected to the live terminal 1 of the grid, the control terminal is connected between the diode 4 and the control resistor 5, and the cathode terminal is connected to the neutral terminal 2 of the grid after the electromagnet 7 is connected in series. The electromagnet 7 is coupled with the button 8, and it is ensured that the button 8 is disconnected when the current in the electromagnet 7 reaches a zero overload value.

In the above-mentioned overload protector, the resistance values of the control resistor 5 and the voltage dividing resistor 9 are equal, and in order to ensure the utilization rate of electric energy, a smaller resistance value is preferred, generally below 2Ω.

Above-mentioned overload protector, the induced conduction voltage value of described thyristor 3 control terminals gets the product of the value of 2/3rds of critical overload current and described control resistance 5, and its basis of calculation is as follows: set critical overload current as I, because in In one cycle of the AC voltage, in the first half cycle, current flows through the control resistor 5 and the voltage dividing resistor 9, and in the second half cycle, only the current flows through the voltage dividing resistor 9, so the critical overload current I is The average effective value in one AC cycle in the main circuit, if the average effective value of the current in the half AC cycle in the control resistor 5 is i, then the relationship between i and I can be drawn as: (i+i+i+0) /2=I, i=2I/3.

In the above overload protector, the shell wraps all parts except the button 8, the button 8 is embedded in the shell, and the shell is provided with a metal lug with a screw hole, which can be passed through the metal The lug is directly installed on the fuse installation of the common switch blade.

In the above overload protector, the electromagnet 7 includes: a coil (not shown in the figure), an iron core 71, and an inner container 72, and the button 8 includes: a contact 81, an armature 82, a neck 83, and a button cap 84. The iron core 71 is in the shape of a cylinder, the coil is wound on the outside, and the inner container 72 is arranged inside. The contacts 81 of the button 8 are four metal protrusions, two of which are respectively connected to the main The live wire end and the neutral wire end of the circuit, the other two are at the two ends of the armature 82, and to ensure that the armature 82 can switch on and off the main circuit during the movement process, the armature 82 is arranged on the neck 83 One end, the neck 83 is an insulating material, and the other end passes through the electromagnet 7 and is solidified with the button cap 84. The neck 83 and the inner tank 72 are roughly matched by the protrusions and depressions on the surface, and the friction The resistance is greater than the gravity of the button 8, and the sum of the frictional resistance and the gravity of the button 8 is smaller than the suction force when the electromagnet 7 is energized.

In the above overload protector, when the button cap 84 is pressed, the contacts 81 are in contact, the main circuit is connected, and when the armature 82 where the contact 81 is located is attracted by the electromagnet 7, the armature 82 moves to The electromagnet 7 separates the contacts 81, and the main circuit is disconnected.

For the above-mentioned overload protector, if the critical overload current designed by it is assumed to be 9A, and the resistances of the control resistor 5 and the voltage dividing resistor 9 are both 1Ω, then when the current in the main circuit is less than 9A, the voltage across the control resistor 5 is less than 6V, the thyristor 3 is disconnected, and the electromagnet 7 is not energized and has no magnetism. When the current in the main circuit reaches 9A, the voltage across the control resistor 5 reaches 6V, which induces the thyristor 3 to be turned on, and the electromagnet 7 is also energized, and the current is close to 9A, a huge suction force is generated instantly, and the button 8 is disconnected.

In the above overload protector, when the current in the main circuit reaches the overload critical value, in the positive half cycle of the AC voltage, the current flows through the control resistor 5 and the voltage dividing resistor 9 at the same time, and generates a voltage drop across them, that is The critical potential difference makes the thyristor 3 conduct, and the electromagnet 7 is energized at this time, and once energized, it can generate a great magnetism, and quickly disconnect the button 8. Compared with the ordinary electromagnet relay switch, the electromagnetic When the ferromagnetism gradually increases, the action of the overload protector is more precise and rapid. When recovering, you only need to press the button 8 again. Accurately achieve circuit break protection, and can be easily restored to the original state after circuit break, in addition, the overload protector can also be installed in the junction box of ordinary users.

Claims (5)

1. An overload protector, comprising a shell, an electromagnet (7), and a button (8), is characterized in that: the overload protector also includes a thyristor (3), a diode (4), a control resistor (5), a voltage divider Resistor (9), the diode (4) is connected in parallel with the voltage dividing resistor (9) after being connected in series with the control resistor (5), and then the button (8) is connected in series, the diode 4 anode terminals of the aforementioned circuit Connected to the live wire end (1) of the power grid, the circuit button (8) is connected to the neutral wire end (2) of the power grid, in addition, the anode terminal of the thyristor (3) is connected to the live wire end (1) of the power grid, and the control terminal is connected to the diode ( 4) Between the control resistor (5), the cathode end is connected in series with the electromagnet (7) and then connected to the grid neutral terminal (2), the electromagnet (7) is coupled with the button (8), and the electromagnetic When the current in the iron (7) reaches the overload zero threshold, the button (8) is disconnected. 2. The overload protector according to claim 1, characterized in that: the resistance values of the control resistor (5) and the voltage dividing resistor (9) are equal, and both are below 2Ω. 3. The overload protector according to claim 1, characterized in that: the induced conduction voltage value of the control terminal of the thyristor (3) is the product of two-thirds of the critical overload current and the control resistor (5) . 4. The overload protector according to claim 1, characterized in that: the outer shell wraps all parts except the button (8), the button (8) is embedded in the outer shell, and the outer shell Features metal lugs with screw holes. 5. The overload protector according to claim 1, characterized in that: the electromagnet (7) includes: a coil, an iron core (71), and an inner container (72), and the button (8) includes: Contact (81), armature (82), neck (83), button cap (84), the iron core (71) is in the shape of a cylinder, the coil is wound on the outside, and the inner tank is provided inside (72), the contacts (81) of the button (8) are four metal protrusions, two of which are respectively connected to the live wire end and the neutral wire end of the main circuit, and the other two are at the two ends of the armature (82) , and ensure that the armature (82) can connect and disconnect the main circuit during the movement process, the armature (82) is arranged at one end of the neck (83), the neck (83) is made of insulating material, and the other end After passing through the electromagnet (7), it is solidified with the button cap (84), and the neck (83) and the liner (72) are roughly matched by the protrusions and depressions on the surface, and its frictional resistance is greater than that of the button ( 8) gravity, and the sum of the friction resistance and the gravity of the button (8) is less than the suction force when the electromagnet (7) is energized.

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