Current overload and short circuit hazard demonstration instrument

Abstract

The present invention provides a current overload and short circuit hazard demonstration instrument, which belongs to a demonstration instrument. The current overload and short circuit hazard demonstration instrument provided by the present invention includes a short circuit demonstration unit and an overload demonstration unit, a regulator and a selector, which can demonstrate the process of causing harm when the circuit is short-circuited and the circuit is overloaded. The selector is used to select a unit from the short circuit demonstration unit and the overload demonstration unit to connect the power supply and enter the working state, and the regulator is used to adjust the voltage or current input to the short circuit demonstration unit or the overload demonstration unit. In this way, the intensity of the circuit overload or circuit short circuit voltage and the degree and duration of wire burning are controlled, which is conducive to visitors to carefully observe and understand the process of harm caused by circuit short circuit and understand the importance of safe use of electricity.

Description

Technical Field

[0001] The invention relates to a demonstration instrument, in particular to a current overload and short circuit hazard demonstration instrument. Background Art

[0002] In the process of learning and promoting electricity safety, existing circuit short circuit or overload demonstration devices usually use fuse action demonstrators for demonstration. During the demonstration, the wire will burn immediately when the switch is closed, which is not conducive to visitors' careful observation and understanding of the process of harm caused by circuit short circuit, and fails to leave a deep impression on visitors. Summary of the invention

[0003] In view of the problems existing in the above-mentioned prior art, the present invention provides a current overload and short circuit hazard demonstrator, which can control the intensity of circuit overload or circuit short circuit voltage and the degree and duration of wire burning, so as to help visitors carefully observe and understand the process of hazards caused by circuit short circuit.

[0004] In a first aspect, an embodiment of the present invention provides a current overload and short circuit hazard demonstrator for demonstrating a circuit short circuit process and a circuit overload process, wherein the demonstrator comprises a short circuit demonstration unit, an overload demonstration unit, a regulator and a selector; the selector and the regulator are used to be connected to a power supply;

[0005] The selector is connected to the short-circuit demonstration unit and the overload demonstration unit, and is used to select the short-circuit demonstration unit or the overload demonstration unit to be powered on;

[0006] The regulator is connected to the short-circuit demonstration unit and the overload demonstration unit, and is used to adjust the voltage or current input to the short-circuit demonstration unit, or to adjust the voltage or current input to the overload demonstration unit.

[0007] In combination with the first aspect, an embodiment of the present invention provides a first possible implementation of the first aspect, wherein the demonstrator further includes a mutual inductor, and the mutual inductor is connected between the regulator and the short-circuit demonstration unit and the overload demonstration unit.

[0008] In combination with the first aspect, an embodiment of the present invention provides a second possible implementation method of the first aspect, wherein the short-circuit demonstration unit includes a positive terminal and a negative terminal; when the short-circuit demonstration unit is connected to the power supply, if the positive terminal is in contact with the negative terminal, the circuit is short-circuited.

[0009] In combination with the second possible implementation manner of the first aspect, the embodiment of the present invention provides a third possible implementation manner of the first aspect, wherein the positive terminal is a graphite electrode.

[0010] In combination with the second possible implementation of the first aspect, an embodiment of the present invention provides a fourth possible implementation of the first aspect, wherein the negative terminal includes one or more pure copper electrodes, the pure copper electrodes are connected to a wiring clamp arranged on the base, a guide rail is arranged under the base, and the base is movably connected to the guide rail.

[0011] In combination with the fourth possible implementation of the first aspect, an embodiment of the present invention provides a fifth possible implementation of the first aspect, wherein the guide rail includes a lead screw, a slider is slidably connected to the lead screw, and the base is fixedly connected to the slider.

[0012] In combination with the fifth possible implementation of the first aspect, an embodiment of the present invention provides a sixth possible implementation of the first aspect, wherein a stepper motor is provided at the end of the lead screw, and the stepper motor drives the lead screw to rotate so that the slider slides on the lead screw.

[0013] In combination with the fourth possible implementation of the first aspect, an embodiment of the present invention provides a seventh possible implementation of the first aspect, wherein a slide groove is provided on the guide rail, a pulley is connected below the base, and the pulley is movably connected in the slide groove.

[0014] In combination with the first aspect, the embodiment of the present invention provides an eighth possible implementation of the first aspect, wherein the overload demonstration unit includes an overload demonstration wire.

[0015] In combination with the first aspect, an embodiment of the present invention provides a ninth possible implementation manner of the first aspect, wherein the selector includes a toggle switch, a first selection branch and a second selection branch connected to the toggle switch;

[0016] The first selection branch includes a normally closed contact of a second relay, a first branch switch and a first contactor connected in series, and a first normally open contact of a first relay connected in parallel with the first branch switch;

[0017] The second normally open contact of the first relay is connected to the overload demonstration unit;

[0018] The second selection branch includes a normally closed contact of a first relay, a second branch switch and a second contactor connected in series, and a first normally open contact of a second relay connected in parallel with the second branch switch;

[0019] The second normally open contact of the second relay is connected to the short circuit demonstration unit.

[0020] The embodiments of the present invention bring the following beneficial effects:

[0021] The current overload and short circuit hazard demonstration instrument provided by the embodiment of the present invention includes a short circuit demonstration unit and an overload demonstration unit, a regulator and a selector, which can demonstrate the process of causing harm when a circuit is short-circuited or overloaded. The selector is used to select a unit from the short circuit demonstration unit and the overload demonstration unit to connect the power supply and enter the working state, and the regulator is used to adjust the voltage or current input to the short circuit demonstration unit or the overload demonstration unit. In this way, the intensity of the circuit overload or circuit short circuit voltage and the degree and duration of wire burning are controlled, which is conducive to visitors to carefully observe and understand the process of causing harm by circuit short circuit and understand the importance of safe use of electricity.

[0022] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention are realized and obtained by the structures particularly pointed out in the description, claims and drawings.

[0023] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 A structural block diagram of a current overload and short circuit hazard demonstration device provided by an embodiment of the present invention;

[0026] Figure 2 A structural block diagram of a current overload and short circuit hazard demonstration device provided by another embodiment of the present invention;

[0027] Figure 3 A circuit schematic diagram of a current overload and short circuit hazard demonstrator provided by an embodiment of the present invention;

[0028] Figure 4 A schematic diagram of the structure of a current overload and short circuit hazard demonstration device provided by an embodiment of the present invention;

[0029] Figure 5 A circuit schematic diagram of a current overload and short circuit hazard demonstrator provided by another embodiment of the present invention.

[0030] Icons: 1-power switch; 2-selector; 3-regulator; 4-mutual inductor; 5-short circuit demonstration unit; 6-overload demonstration unit; 7-display; 8-indicator light; 51-positive terminal; 52-negative terminal; 53-negative terminal; 54-terminal clamp; 55-base; 56-slider; 57-lead screw; 58-stepping motor; 61-overload demonstration wire; 62-overload terminal; 63-jumping post. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. The components of the embodiments of the present invention generally described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0032] In view of the problem that in the existing demonstrator, the wire will burn immediately when the switch is closed during demonstration, an embodiment of the present invention provides a current overload and short circuit hazard demonstrator.

[0033] Figure 1 FIG. 1 shows a structural block diagram of a current overload and short circuit hazard demonstration device provided by an embodiment of the present invention. Figure 1 As shown, the current overload and short circuit hazard demonstration instrument provided in this embodiment includes a short circuit demonstration unit 5, an overload demonstration unit 6, a regulator 3 and a selector 2. The selector 2 and the regulator 3 are used to connect to a power supply.

[0034] The power supply may be a mains power supply or an AC power supply converted by a voltage converter, and the selector 2 and the regulator 3 may be connected to the power supply through a power switch 1, or may be connected to a socket through a plug, and the socket provides the mains power supply.

[0035] The selector 2 is connected to the short circuit demonstration unit 5 and the overload demonstration unit 6, and is used to select the short circuit demonstration unit or the overload demonstration unit to be powered on. The selector 2 can be a selection switch or a toggle switch. For example, the toggle switch can be set to three positions: short circuit, stop, and overload. When the toggle switch is in the short circuit position, the short circuit demonstration unit 5 is powered on and is in a working state; when the toggle switch is in the overload position, the overload demonstration unit 6 is powered on and is in a working state.

[0036] The regulator 3 is connected to the short-circuit demonstration unit 5 and the overload demonstration unit 6 , and is used to adjust the voltage or current of the input short-circuit demonstration unit 5 , or to adjust the voltage or current of the input overload demonstration unit 6 .

[0037] The regulator 3 can be a variable resistor, a thyristor or a controlled rectifier. When the short-circuit demonstration unit 5 is in operation, the regulator, the short-circuit demonstration unit and the power supply form a power supply loop, and the regulator is used to adjust the voltage across the short-circuit demonstration unit. When the overload demonstration unit 6 is in operation, the regulator, the overload demonstration unit and the power supply form a power supply loop, and the regulator is used to adjust the current in the power supply loop.

[0038] The short circuit demonstration unit 5 includes a positive terminal and a negative terminal. When the short circuit demonstration unit 5 is powered on, if the positive terminal contacts the negative terminal, the circuit is short-circuited.

[0039] The overload demonstration unit 6 includes an overload demonstration wire. The overload demonstration wire can be a common thin wire, including an internal metal wire and an insulating skin wrapped around the outside of the metal wire. When an overload phenomenon occurs in the current, the overload demonstration wire will heat up, the insulating skin will melt or even burn.

[0040] The current overload and short circuit hazard demonstration instrument provided in this embodiment is provided with a regulator, which can adjust the voltage or current of the input short circuit demonstration unit or overload demonstration unit, thereby controlling the intensity of the circuit overload or circuit short circuit voltage and the degree and duration of wire burning, which is conducive to visitors to carefully observe and understand the process of the hazard caused by the circuit short circuit and understand the importance of safe use of electricity.

[0041] In a more preferred embodiment, Figures 2 to 4 As shown, the current overload and short circuit hazard demonstration instrument includes a power switch 1, a short circuit demonstration unit 5, an overload demonstration unit 6, a regulator 3, a selector 2 and a mutual inductor 4. The power switch 1 (as shown Figure 3 K1) shown in the figure is used to connect to the power supply, and the selector 2 and the regulator 3 are connected to the power switch 1.

[0042] The selector 2 is connected to the short circuit demonstration unit 5 and the overload demonstration unit 6, and is used to select the short circuit demonstration unit 5 or the overload demonstration unit 6 to turn on the power supply. The selector 2 includes a toggle switch K2, a first selection branch connected to the toggle switch K2, and a second selection branch. The first selection branch includes a normally closed contact J22 of the second relay connected in series, a first branch switch K3 and a first contactor KM1, and a first normally open contact J11 of the first relay connected in parallel with the first branch switch K3. The second selection branch includes a normally closed contact J12 of the first relay connected in series, a second branch switch K4 and a second contactor KM2, and a first normally open contact J21 of the second relay connected in parallel with the second branch switch K4.

[0043] The second normally open contact J14 and the third normally open contact J15 of the first relay are connected in series with the overload demonstration unit 6. The fourth normally open contact J13 of the first relay is connected with the regulator 3.

[0044] The second normally open contact J24 and the third normally open contact J25 of the second relay are connected in series with the short circuit demonstration unit 5. The fourth normally open contact J23 of the second relay is connected with the regulator 3.

[0045] The regulator 3 may adopt a thyristor controller, and the regulator 3 is connected to the short-circuit demonstration unit 5 and the overload demonstration unit 6 through the mutual inductor 4, and is used to adjust the voltage or current of the input short-circuit demonstration unit 5, or adjust the voltage or current of the input overload demonstration unit 6.

[0046] like Figure 3 As shown, the short circuit demonstration unit 5 and the overload demonstration unit 6 are arranged on one side of the insulating plate, and the regulator, the mutual inductor and the selector can be arranged in the demonstrator housing, for example, arranged on the other side of the insulating plate. The regulator is provided with an adjustment knob. The insulating plate can be arranged on the upper half of the front wall of the demonstrator housing for easy observation. The adjustment knob of the regulator and the toggle switch of the selector can be arranged on the demonstrator housing, or on a control handle connected to the demonstrator.

[0047] The short-circuit demonstration unit 5 includes a positive terminal 51 and a negative terminal 52. When the short-circuit demonstration unit 5 is powered on, if the positive terminal contacts the negative terminal, the circuit is short-circuited.

[0048] The positive terminal 51 may be a graphite electrode or an electrode made of other high melting point materials. The positive terminal is fixedly mounted on an insulating plate and connected to the output end of a mutual inductor disposed in the demonstrator housing through a thick wire.

[0049] The negative terminal 52 includes one or more pure copper electrodes, which are connected to a wiring clamp 54 provided on a base 55, and the wiring clamp 54 is connected to the output end of the transformer through a wire and a negative terminal 53. A guide rail is provided below the base 55, and the base is movably connected to the guide rail.

[0050] exist Figure 4 In the illustrated embodiment, the guide rail includes a lead screw 57 , a slider 56 is slidably connected to the lead screw 57 , and a base 55 is fixedly connected to the slider 56 .

[0051] A stepper motor 58 is provided at the end of the lead screw 57, and the stepper motor 58 drives the lead screw 57 to rotate, so that the slider slides on the lead screw, thereby driving the negative terminal to move back and forth along the length direction of the lead screw. During the movement of the negative terminal, the pure copper electrode will contact or separate from the positive terminal.

[0052] It is understandable that a rotating handle may also be provided at the end of the lead screw 57 to replace the stepping motor. The lead screw may be rotated by rotating the rotating handle to allow the slider to slide on the lead screw.

[0053] In another optional embodiment, a slide groove can be provided on the guide rail, a pulley is connected below the base, and the pulley is movably connected in the slide groove. The movement of the pulley in the slide groove drives the negative terminal to move back and forth along the length direction of the guide rail.

[0054] The overload demonstration unit 6 includes an overload demonstration wire 61. The overload demonstration wire can be a common thin wire, including an internal metal wire and an insulating skin wrapped around the outside of the metal wire. When an overload phenomenon occurs in the current, the overload demonstration wire will heat up, the insulating skin will melt or even burn. Both ends of the overload demonstration wire 61 are connected to the output end of the transformer through the overload terminal 62. The input end of the transformer is connected to the regulator.

[0055] The insulating board is also provided with a plurality of staggered wiring posts for supporting the overload demonstration wire 61, so as to facilitate the use of a longer overload demonstration wire 61. The longer the overload demonstration wire 61 is, the closer it is to the actual circuit situation, and the more conducive it is for people to observe the harm of circuit overload to the conductive wire.

[0056] The demonstrator further includes an indicator light 8 mounted on the insulating plate. For example, two indicator lights 8 can be provided, one of which is a yellow indicator light connected between the power switch and the input end of the regulator. As long as the demonstrator is in working state, whether the short-circuit demonstration unit is powered on or the overload demonstration unit is powered on, the yellow indicator light will be illuminated. That is, the yellow indicator light is used to indicate that the demonstrator is in working state. The other is a red indicator light connected between the output end of the regulator and the power switch. Its brightness changes according to the magnitude of the voltage or current in the circuit, and is used to indicate the degree of circuit overload or the magnitude of the circuit short-circuit voltage.

[0057] In order to exhaust the smoke generated during the demonstration as soon as possible and prevent the audience from being affected by the smoke, the demonstrator can also be equipped with a smoke alarm above the overload demonstration unit and the short circuit demonstration unit. The smoke alarm includes a smoke sensor and an alarm unit. The alarm unit can use a buzzer or a flashing light. The smoke alarm is also connected to the exhaust fan switch through a time relay. When the smoke concentration exceeds the set value, the smoke alarm will sound an alarm. At the same time, the smoke alarm starts the exhaust fan switch through the time relay to exhaust the smoke through the flue.

[0058] The demonstrator housing is also provided with a display for measuring the voltage and current values ​​measured by the voltmeter and ammeter connected to the circuit. A voltmeter and an ammeter are connected to the input end of the transformer to detect the voltage and current output by the regulator. Another voltmeter and another ammeter are connected to the output end of the transformer to detect the voltage and current of the input short-circuit demonstration unit and the overload demonstration unit.

[0059] Considering that the demonstrator may be used outdoors, it is inconvenient to connect to the mains power supply. To this end, the demonstrator provided in the embodiment of the present invention also includes a power module, which includes a battery and an inverter circuit, such as Figure 5 As shown. The battery can be a storage battery, and the inverter circuit is a voltage conversion circuit composed of a MOS switch tube and an energy storage inductor, which is used to convert the direct current provided by the battery into alternating current and has the function of increasing the voltage. The inverter circuit can convert low voltage (12 or 24 volts or 48 volts) direct current into 220 volts alternating current.

[0060] During the demonstration, turn on the power switch, move the toggle switch to the first selection branch, and turn on the first branch switch K3. Since J22 is a normally closed contact, at this time, the first contactor KM1 is energized. Under the electromagnetic action, all the normally open contacts of the first relay are closed, that is, the normally open contact J11, the normally open contact J13, the normally open contact J14, and the normally open contact J15 are closed. The normally closed contact J12 of the first relay is opened. At this time, the regulator and the overload demonstration unit 6 are powered on, and the current flowing through the overload demonstration wire can be adjusted by the regulator.

[0061] When the current is low, the red indicator light is low or has no brightness, and the circuit is not overloaded. As the current continues to increase, the power consumption and temperature of the overload demonstration wire increase, and the overload demonstration wire begins to heat up. At this time, if the current continues to increase, the temperature of the overload demonstration wire continues to rise, and the insulation skin on its outside becomes soft, melts, smokes, and even burns. Since the current in the circuit is adjustable, the duration of this demonstration process can be controlled, and the current in the circuit can be reduced at any time when the overload demonstration wire is not burning or smoking, so that the audience can feel the process of the current in the circuit decreasing and the overload demonstration wire slowly recovering.

[0062] Through the demonstration of the circuit overload hazard process, the process of fire hazard caused by circuit overload when the socket is connected to a high-power electrical appliance in daily life is simulated, so that people can understand the principle of fire and pay more attention to electricity safety.

[0063] Move the toggle switch to the second selection branch, the first contactor KM1 is powered off, the normally closed contact J12 of the first relay is closed, and the second branch switch K4 is turned on. At this time, the second contactor KM2 is energized. Under the electromagnetic action, all the normally open contacts of the second relay are closed, that is, the normally open contact J21, the normally open contact J23, the normally open contact J24, and the normally open contact J25 are closed. The normally closed contact J22 of the second relay is opened. At this time, the regulator and the short-circuit demonstration unit 5 are powered on, and the voltage at both ends of the short-circuit demonstration unit 5 can be adjusted by the regulator.

[0064] At this time, move the negative terminal so that the pure copper electrode intermittently contacts the graphite electrode. When the two electrodes contact, the circuit is short-circuited and sparks fly.

[0065] When the voltage is low, the red indicator light is low or has no brightness. At this time, there are fewer sparks and the pure copper electrode does not change much. As the voltage continues to increase, at the moment when the pure copper electrode contacts the graphite electrode, it can be observed that the current in the circuit instantly reaches a large value. Under high temperature, the end of the pure copper electrode gradually melts and deforms to form a copper nail. Similarly, in this demonstration process, the voltage of the circuit is controllable, allowing people to observe the hazards of short circuits in the circuit when the voltage is high, and improve people's awareness of electricity safety.

[0066] The current overload and short circuit hazard demonstration instrument and the circuit fault hazard demonstration device provided in the embodiment of the present invention have the same technical features, so they can also solve the same technical problems and achieve the same technical effects.

[0067] In addition, in the description of the embodiments of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0068] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0069] Finally, it should be noted that the above-described embodiments are only specific implementations of the present invention, which are used to illustrate the technical solutions of the present invention, rather than to limit them. The protection scope of the present invention is not limited thereto. Although the present invention is described in detail with reference to the above-described embodiments, ordinary technicians in the field should understand that any technician familiar with the technical field can still modify the technical solutions recorded in the above-described embodiments within the technical scope disclosed by the present invention, or can easily think of changes, or make equivalent replacements for some of the technical features therein; and these modifications, changes or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A current overload and short circuit hazard demonstration instrument, used to demonstrate the circuit short circuit process and circuit overload process, characterized in that: The demonstrator comprises a short circuit demonstration unit, an overload demonstration unit, a regulator and a selector; the selector and the regulator are used to connect to a power supply; the short circuit demonstration unit and the overload demonstration unit are arranged on one side of an insulating plate, and the regulator and the selector are arranged on the other side of the insulating plate; wherein the power supply is a mains power supply or an alternating current power supply converted by a voltage converter; the power supply is used to provide 220 volts of alternating current; The selector is connected to the short-circuit demonstration unit and the overload demonstration unit, and is used to select the short-circuit demonstration unit or the overload demonstration unit to be powered on; The regulator is connected to the short-circuit demonstration unit and the overload demonstration unit, and is used to adjust the voltage or current input to the short-circuit demonstration unit, or to adjust the voltage or current input to the overload demonstration unit; wherein the regulator is a thyristor; the regulator is provided with an adjustment knob and a thyristor controller; when the short-circuit demonstration unit is in a working state, the regulator is used to adjust the voltage across the short-circuit demonstration unit; when the overload demonstration unit is in a working state, the regulator is used to adjust the current in the power supply loop formed by the regulator, the overload demonstration unit and the power supply; The demonstrator further comprises a mutual inductor, which is connected between the regulator and the short-circuit demonstration unit and the overload demonstration unit; The short-circuit demonstration unit includes a positive terminal and a negative terminal; when the short-circuit demonstration unit is connected to power, if the positive terminal contacts the negative terminal, the circuit is short-circuited; the negative terminal includes one or more pure copper electrodes; the positive terminal is a graphite electrode, the positive terminal is fixedly mounted on an insulating plate, and is connected to the output end of a mutual inductor arranged in the housing of the demonstrator through a thick wire.

2. The demonstrator according to claim 1, characterized in that: The negative terminal includes one or more pure copper electrodes, which are connected to a wiring clip arranged on the base. A guide rail is arranged under the base, and the base is movably connected to the guide rail.

3. The demonstrator according to claim 2, characterized in that: The guide rail comprises a lead screw, a slider is slidably connected to the lead screw, and the base is fixedly connected to the slider.

4. The demonstrator according to claim 3, characterized in that: A stepping motor is arranged at the end of the lead screw, and the stepping motor drives the lead screw to rotate so that the sliding block slides on the lead screw.

5. The demonstrator according to claim 2, characterized in that: A slide groove is arranged on the guide rail, a pulley is connected below the base, and the pulley is movably connected in the slide groove.

6. The demonstrator according to claim 1, characterized in that: The overload demonstration unit includes an overload demonstration wire.

7. The demonstrator according to claim 1, characterized in that: The selector comprises a toggle switch, a first selection branch and a second selection branch connected to the toggle switch; The first selection branch includes a normally closed contact of a second relay, a first branch switch and a first contactor connected in series, and a first normally open contact of a first relay connected in parallel with the first branch switch; The second normally open contact of the first relay is connected to the overload demonstration unit; The second selection branch includes a normally closed contact of a first relay, a second branch switch and a second contactor connected in series, and a first normally open contact of a second relay connected in parallel with the second branch switch; The second normally open contact of the second relay is connected to the short circuit demonstration unit.

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