GB/T 14822-1993 Guidelines for the design of safety protection structures for hand-held power tools
Some standard content:
National Standard of the People's Republic of China
Directives for safety protecting construction design of hend-held electric tool1Subject content and scope of application
This standard specifies the general principles that should be followed in the design of safety protection structures of hand-held electric tools. GB/T 14822—93
This standard applies to hand-held electric tools (hereinafter referred to as tools) used under general environmental conditions. For hand-held electric tools used under special environmental conditions and special occasions, if special structures or special requirements are required, they should also meet the requirements of the corresponding standards. This standard only explains and provides design tips for GB3883.1 Safety of hand-held power tools Part 1: General requirements (available for certification).
2 Referenced standards
GB3883.1 Safety of hand-held power tools Part 1: General requirements (available for certification)GB3883.2 Safety of hand-held power tools Part 2: Special requirements for screwdrivers and wrenches (available for certification)GB3883.3 Safety of hand-held power tools Part 3: Special requirements for electric grinders, polishers and disc sanders (available for certification)
GB3883.4 Hand
Part 4: Special requirements for sanders (available for certification)Safety of hand-held power tools
GB3883.5 Safety of hand-held power tools Part 5: Special requirements for circular saws and circular knives (available for certification)Safety of hand-held power tools
GR 3883.6
Part 6: Special requirements for electric drills (for certification) GB 3883. 7
GB 3883. 8
Safety of hand-held electric tools
Safety of hand-held electric tools
GB 3883. 9↓
Safety of hand-held electric tools
Part 7: Special requirements for electric hammers (for certification) Part 8: Special requirements for electric scissors (for certification) Part 9: Special requirements for electric tapping machines (for certification) Part 10: Special requirements for electric tapping machines (for certification) GB3883.10 Safety of hand-held electric tools GB 3883. 11
Safety of hand-held electric tools
For certification purposes)
Part 11: Special requirements for electric reciprocating saws (jig saws, knife saws) (for certification purposes) Part 12: Special requirements for concrete vibrators (insertion vibrators) Safety of hand-held electric tools
GB 3883.12
(for certification purposes)
GB4706.1 General safety requirements for household and similar electrical appliances GB3100 International system of units and its application
GB1002 Types, basic parameters and dimensions of single-phase plugs and sockets GB1003 Types, basic parameters and dimensions of three-phase plugs and sockets GB2099 Technical conditions for single-phase and three-phase plugs and sockets GB 9088 Method for compiling electric tool models
GB2900.28 Electrical terminology Electric tools Rubber insulated cables with rated voltages of 450/750V and below Part 2 General purpose rubber sheathed flexible wires GB 5013. 2 Table
Approved by the State Administration of Technical Supervision on December 30, 1993, and implemented on October 1, 1994
GB973 Cross recessed flat round head screws
GB/T.14822-93
GB11918 General requirements for industrial plugs, sockets and couplers GB11919 Dimensions of pins and sockets for industrial plugs, sockets and couplers, requirements for interchangeability GB192 Basic tooth form of common thread
GB193 Diameter and pitch series of common thread (diameter 1 to 600 mm) GB194
Diameter of common thread 0.250.9 mm Basic size GB195 Ordinary thread diameter 0.25~～0.9mm tolerance GB196 Ordinary thread basic size (diameter 1~600mm) GB197 Through thread tolerance and fit (diameter 1～355mm) GB5023.2 Rated voltage 450/750V and below PVC insulated cable (wire) Cable (wire) for fixed installation GB5023.3 Rated voltage 450/750V and below PVC insulated cable (wire) Flexible cable (wire) for connection Rubber insulation nitrile sheath lead wire
JB 1171
JB1812 Chlorosulfonated polyethylene rubber insulated lead wire JB1138 Butyl polyvinyl chloride composite insulated lead wire ZBK64009 Internal wiring connector for electric tools ZBK61 010 Power cord sheath for electric tools
3 Definition
3.1 Handheld electric tools
Electric tools that are operated by holding or hanging by hand. The following electric tools also fall within the scope of handheld electric tools: a. Tools that are operated by hand during normal operation, such as rock drills, electric picks, etc.; b. Flexible shaft transmission electric tools, regardless of whether the motor is portable or fixed; c. Handheld tools that can be installed on a bracket and used as fixed tools without any modification. Tools equipped with electric heating elements must comply with the relevant parts of GB4706.1 for electric heating elements in addition to complying with GB3883. 3.2 Class I electric tools
Tools not only rely on basic insulation for protection against electric shock, but also include an additional safety protection measure, which is to connect the accessible metal parts to the protective (grounding) conductor in the installed fixed circuit so that the accessible metal parts will not become live when the basic insulation fails.
Those accessible metal parts of Class I tools that will become live when the basic insulation fails shall be permanently and reliably connected to the grounding terminal in the tool or the grounding pin of the appliance socket. For tools equipped with non-detachable cables or cords, the grounding terminal in the tool must be connected to the core wire of the flexible cable or cord used as the protective (grounding) wire. If the accessible metal parts of Class I tools are not connected to the grounding terminal or grounding pin, and are not completely separated from the live parts by the metal parts connected to the grounding terminal or grounding pin, they shall be designed as the corresponding parts of Class I tools, as shown in Figure 1. For example, the design of Class I tools is as shown in Figure 2. The nameplate b is separated from the gearbox by a casing made of insulating material and is not grounded, and the nameplate and the winding end shall meet the requirements of reinforced insulation. If the nameplate is moved back to the end of the group and is completely isolated by the stator core, when the stator core is not grounded, the nameplate and the winding shall meet the requirements of double insulation. If the stator core is grounded, the nameplate and the winding only need to meet the basic insulation requirements. Class I tools can have double insulation or reinforced insulation parts, or parts that operate at safe extra-low voltage. Unless otherwise specified, the parts of Class I tools that operate at safe extra-low voltage are designed in accordance with the requirements of Class I tools, and are designed in accordance with the requirements of Class I tools with respect to the ground. GB/T 14822-93
Ungrounded accessible metal parts b Solid insulation material or air spacer; c—Live parts Id—Grounded accessible metal parts Note: The design between a and c should be in accordance with the requirements of reinforced insulation. (b)
&- Ungrounded accessible metal parts; b- Solid insulating material or air intermittently; d- Grounded accessible metal parts; e- Live parts: a and c should be designed according to the requirements of double insulation. Figure 1
a--Metal gearbox body; b- Metal nameplate; c- Stator core; d- Casing made of insulating material; e- Only painted assembly end Figure 2
3.31 Class I power tools
Tools not only rely on basic insulation to protect against electric shock, but also provide additional safety protection measures such as double insulation or reinforced insulation. There is no protective grounding or safety measures that rely on installation conditions. In Class I tools, except for parts operating at safety extra-low voltage, all accessible metal parts and live parts must be separated by double insulation or reinforced insulation.There shall be no parts isolated only by basic insulation. GB/T14822-93
The parts of Class I tools that operate at a safety extra-low voltage shall be designed as required for Class I tools internally and to ground, and as required for Class II tools with respect to other parts of the tool. Class I tools shall not be provided with grounding devices.
Class 1 power tools may be made into: insulating casing, metal casing, or casing with both metal and insulation. Insulating casing Class I power tools have a durable, strong, substantially continuous insulating casing. Except for some small metal parts such as nameplates, nails, screws, etc., other metal parts are contained in the insulating casing, and these small metal parts are separated from the live parts by insulation that is at least equivalent to reinforced insulation.
Metal casing Class 1 power tools have a strong, substantially continuous metal casing, and the entire casing has double insulation except for those that obviously cannot achieve double insulation and use reinforced insulation. 3.4 Class 1 power tools
The protection of tools against electric shock relies on a safety extra-low voltage. The power supply and the internal part of the tool will not generate any voltage higher than the safety extra-low voltage.
The safety extra-low voltage of Class I tools is supplied by the internal power supply of the tool or other independent power supply (such as batteries, internal combustion generator sets, etc.). When the power supply is from the power grid, it must be supplied by a safety isolation transformer or a converter with an equivalent degree of isolation and separate windings. Internal circuits operating at non-safety extra-low voltage are not allowed in Class 1 tools. 3.5 Basic insulation
Insulation on live parts that provides basic protection against electric shock. Basic insulation was once called working insulation, but its definition is narrower than that of "working insulation". In the scope covered by GB3883.1, basic insulation refers to the most basic and necessary insulation used to prevent electric shock. It does not necessarily include insulation that is completely functional (used only for circuit division) and is not related to electric shock protection, such as inter-sub-insulation. 3.6 Supplementary insulation: Independent insulation used outside basic insulation to prevent electric shock when basic insulation is damaged. Here, the concept of "independent" has two meanings: one is that the supplementary insulation is independent of the basic insulation in structure, and the two can be separated without damaging itself and its other components, that is, there is a discontinuous surface between the supplementary insulation and the basic insulation, so that the fault occurring in one insulation does not affect and spread to the other insulation, truly forming two independent protection measures; the second is that the supplementary insulation can be tested separately according to the requirements of the standard, and there are electrodes that can be drawn out in the structure of the tool itself to test this part of the insulation (including metal foil attached to the accessible surface of the insulating material according to the test requirements). 3.7 Double insulation: Insulation composed of basic insulation and supplementary insulation. Double insulation is the main insulation form of Class II tools, except for Except for specific parts and components where double insulation is difficult to implement due to structural, dimensional and technical rationality reasons, the live parts of Class I tools shall be isolated from accessible metal parts or accessible surfaces by double insulation. In terms of structure, basic insulation is placed on the live parts and directly in contact with the live parts, and supplementary insulation is close to the accessible metal parts or is accessible to the user.
According to the construction principle of basic insulation and supplementary insulation, inseparable insulation composed of two different materials in the same degraded environment and at the same location cannot constitute double insulation. For example, in Figure 38, two layers of insulation between the winding and the core cannot be considered to constitute double insulation. For example, in Figure 3h, one layer of insulation is set on the shaft, and one layer of insulation is set between the winding and the core. Double insulation is formed between the shaft and the winding. The basic insulation is between the winding and the core, and the supplementary insulation is between the core and the shaft. Each should meet the requirements specified in GB3883.1. 3.8 Reinforced insulation
A separate insulation structure equivalent to the degree of double insulation protection. Absolute House 2
GB/T 14822—93
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Reinforced insulation is placed between live parts and accessible metal parts in structure or its surface is accessible. Reinforced insulation can be composed of a single insulating material of the same material or a combination of several insulating materials of different materials. Insulation composed of several different materials can achieve the same level of electric shock protection as double insulation, but if the insulation between its components cannot be tested separately as basic insulation and supplementary insulation, even if it can be separated in mechanical structure, it is also regarded as reinforced insulation. Since reinforced insulation cannot provide two independent protection measures like double insulation, it can only be equivalent to double insulation in terms of protection level and cannot be completely equivalent to double insulation, so its application in Class 1 tools is limited. GB3883.1 stipulates that reinforced insulation can only be used when it is obviously impractical to provide separate basic insulation and supplementary insulation. The requirements for basic insulation, supplementary insulation and reinforced insulation do not mean that live parts must be completely enclosed and separated by solid insulation. Air gaps can also be used instead of solid insulation to achieve the purpose of insulation. The air gap used for insulation is called electrical clearance and must meet the relevant provisions of GB3883.1. www.bzxz.net
3.9 Live parts
Conductors or conductive parts at normal use voltage. Live parts also include neutral conductive parts connected to the above parts, such as neutral wires. Conductors in the grounding loop such as the grounding core wire, grounding terminal, and grounding internal wiring in the power cord only have current and potential difference with the ground when the insulation is damaged or the tool is in a fault state. These conductors are not considered live parts. For electric shock protection only, unless otherwise specified, any part operating at a safety extra-low voltage not exceeding 24V may not be considered as a live part.
3.10 Touchable parts or touchable surfaces When the tool is inspected with the standard test finger specified in GB3883.1, the parts or surfaces of the tool that can be touched by the finger. If the accessible parts are metal, other metal parts that are in conductive connection with these parts are also included. Parts covered by covers and housing parts of tools that can be removed without the aid of tools or cannot withstand mechanical strength tests, which can be touched by the fingers after these covers or housing parts are removed, are also considered as accessible parts. Parts that cannot be directly touched from the outside but are in conductive connection with accessible metal parts, such as the stator core, armature core, shaft, gear, bearing and other metal parts installed on these parts in Class I tools that are in contact with the metal housing, should be considered as accessible parts in terms of electric shock protection.
3.11 Power cord
Refers to the flexible cable or cord that is fixed or assembled with the tool as follows for connecting the power supply. GB/T 14822-93
X-type connection, the original flexible cable or cord can be easily replaced with a flexible cable or cord that does not require any special preparation without the help of special tools.
M-type connection: The original flexible cable or cord can be easily replaced with a special one (such as a sheath molded on the cord or a rolled terminal flexible relay or cord) without the help of special tools. Y-type connection: The flexible cable or cord can only be replaced with the help of special tools available to the manufacturer and its agents. Z-type connection: A part of the tool must be damaged or destroyed to replace the flexible cable or cord. The connection methods described in this article are distinguished by the preparations required by the user when replacing the power cord and the state of the power tool. If the power cord installed on an electric tool in its delivery state is specially prepared (for example, the wire connector has a wiring lug), and the user can replace it with a flexible cable or cord that has not been specially prepared without special tools, the connection method is X-type connection. The so-called special preparation does not include the arrangement of the wire ends before inserting them into the terminal and the twisting of the disassembled wires to strengthen the wire ends. Twist.
The specialized tools referred to in this article are those specially manufactured non-standard screwdrivers, wrenches and other assembly tools. 3.12 Rated value
-A value generally specified by the manufacturer for the tool under specified working conditions. The rated value is listed in the enterprise product standard and nameplate. The value listed on the nameplate is the rated value. 4 General requirements
4.1 Tools should be designed and manufactured to be safe and reliable in normal use, and will not cause danger to people and surrounding objects even if mishaps occur during normal use.
-In general, a tool is considered to have met the requirements if it can pass all the tests specified in GB3883.1. The various provisions of GB3883.1 are the minimum requirements for tools and must be met when designing tools. 5'Marking
5.1 The various markings of tools are important bases for users to understand the performance and use of tools. They must be correct and comply with GB 3883.1 Chapter 7.
5.2 GB3883.1 Article 7.1 stipulates that the items marked should generally be concentrated on the nameplate, and the nameplate should be placed in a conspicuous position on the tool. According to GB3100 Article 5.Article 8 stipulates that the units of each value on the nameplate should be represented by international symbols, and the unit name or Chinese symbols shall not be used.
Other symbols on the nameplate shall comply with Article 7.6 of GB3883.1. The name of the rated value (such as rated voltage, rated frequency, etc.) may or may not be marked (see Figure 4 and Figure 5 for examples). The model marking shall comply with the provisions of GB9088.
JIZ:××02-6A power
rated output 220V~ rated frequency 50HZ
rated current IA rated empty capsule revolution millimeter 10000T/min rated benefit time wmiNo
large station hole diameter 6mm
XX Electric Tool Factory
Note: The "rated\" in the rated value name can be omitted. J1Z-×X02-6A power station
220 Y - 50Hz 6m.
1A n. 1000 r/min
so min No
XX Electric Tool Factory
Note: If the fixed speed is marked, the symbol "," should be added before the speed. If there are more than one physical quantity of the same unit on the nameplate, such as the number of impacts, speed, etc., which need to be marked at the same time, it is recommended to use the nameplate in the form of Figure 4.
5.3 The number 0 can only be used as a symbol to indicate the disconnect position of the power switch in the tool, and shall not be used as other symbols. ..comGB/T14822—93
For the power switch that also serves as an adjustment or control device, if the "disconnected\ position is marked with a number, it must be marked with "0". Other positions should be marked with higher numbers, and the size of the number should correspond to the value it controls or adjusts. Devices that can be adjusted during operation should have adjustment direction marks for increasing or decreasing the adjusted parameter. Generally, "ten and * two" are used. Other symbols that will not cause misunderstanding can also be used, such as shown in Figure 6.调妞
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5.4 The nameplate or other signs required by Chapter 7 of GB3883.1 shall not be lost or fall off during the entire service life and shall remain clearly legible. For this reason, various signs of the tool can be cast or engraved on the tool, or the nameplate can be fixed to the tool by rivets, screws or other reliable methods. The requirements and test methods for fixing the nameplate by bonding are under study. At present, if the bonding method is to be used, the nameplate must not protrude from the surrounding tool surface (as shown in Figure 7), and it must be ensured that it will not warp or curl during the entire test period. After the test, the sign should still be easy to identify, and the nameplate cannot be easily moved. 工外亮
6 Electric shock protection
6.1 The electric shock protection of the tool shall comply with the provisions of Chapter 8 of GB3883.1. 6.2 The insulation properties of paint, enamel, ordinary paper, cotton fabric, oxide film of metal parts, glass powder or sealant should not be relied upon to provide the protection required to prevent accidental contact with live parts. Wood, cotton, silk, ordinary paper, asbestos and similar fibrous materials and hygroscopic materials that have not been impregnated or chemically treated to become non-fibrous should not be used for insulation. These materials either have too low mechanical strength or are easy to absorb moisture and their insulation properties cannot be guaranteed for a long time. Live parts protected only by the above materials are regarded as bare conductors. 6.3 When selecting wires for internal wiring, it should be noted that their insulation should be at least electrically equivalent to the insulation of conductors of flexible cables or cords, or be able to withstand an electrical strength test of 2000V. Otherwise, regardless of whether it meets the standards of the wire itself, it is considered a bare conductor and this part should be considered as a bare conductor during structural design.
6.4 Openings in the earthed metal casing of a Class I tool, if these openings lead to the interior of the tool, shall be so designed that when a standard feeler is inserted into these openings, the feeler shall not touch exposed live parts or live parts considered to be exposed within the scope of this standard. Openings in the unearthed metal casing of a Class I tool and a Class 1 tool leading to the interior of the tool shall be so designed that when a standard feeler is inserted into these openings, the feeler shall not touch metal parts separated from live parts by basic insulation only and the surface of basic insulation, and when a probe is inserted into these openings, it shall not touch exposed live parts or live parts considered to be exposed within the scope of this standard. Air inlets that are not near fans (exhaust ventilation structures) shall not be of such size or structure that a steel ball can pass through them into the interior of the tool.
The examples shown in Figure 8 are considered to meet the requirements. GB/T 14822-93
Note: The finger or probe can be partially inserted into the tool. Within the reachable range of the finger or probe (the area indicated by the double-dotted line), there should be no parts that are not allowed to be touched as specified in the standard.
Note: The finger-shaped part of the finger and the needle of the probe can fully enter the interior of the tool. Within the reachable range of the finger or probe (the area indicated by the double-dotted line), there should be no parts that are not allowed to be touched as specified in the standard (c)
7 Mechanical hazards
7.1 The protection of tools against mechanical hazards must comply with Chapter 18 of GB3883.1 and the corresponding special requirements of GB3883.2~3883.12.
7.2 More detailed and clear requirements for the protection of tools against mechanical hazards are under study. 8 Mechanical strength
8.1 The tool shall have sufficient mechanical strength to withstand the test specified in Chapter 19 of GB3883.1. To this end, it should be noted during design that the strength and structure of the external parts of the tool shall be compatible with the test requirements, and there shall be no too weak parts and avoid protrusions that are subject to concentrated forces; the internal parts shall be properly positioned and fixed to prevent displacement or falling off when impacted, causing the electrical space or creepage distance to be reduced to an inadequate level.
9 Structure
GB/T 14822-93
9.1 The setting position can only be changed with the help of a tool or can only be changed by hand but with more than one conscious action, such as the operating part of the adjustment device is placed in the housing or is enclosed by a cover that must be removed by hand, or the operating part is exposed but cannot be operated by hand, which is considered to have met the requirements of GB3883.1 Articles 20.1 and 20.2 that the setting position cannot be accidentally changed. 9.2 According to the requirements of Article 20.4 of GB3883.1, if the handle or button of a switch or similar component is used to indicate the control position of the component (such as the on or off position), the position where these components are installed on the tool should ensure that these components can be installed correctly without misalignment. For example, the symmetrical inverted plate switch shown in Figure 9a is not considered to meet the requirements if it is only marked with "on" and "off" on the shell of the tool without other special positioning measures. The switch with the same structure is shown in Figure 9b, which is considered to meet the requirements. 7Z7Z0UZ7ZZ
9.3· When designing tools, wood, cotton, silk, ordinary paper asbestos and similar fibrous materials or condensed materials that have not been impregnated or chemically treated to become non-fibrous shall not be used as electrical insulating materials. Transmission belts (such as the transmission belts on electric planers), whether or not there is metal in their components, shall not be used as insulating parts, and the insulation of the transmission belts cannot be relied on to provide the required electrical protection. Double insulation should be used between the live parts of Class 9.4 tools and accessible metal parts or accessible surfaces. Reinforced insulation may only be used when it is obviously impractical to provide separate basic insulation and supplementary insulation. Figure 10 and Table 1 show an example of the insulation structure of a Class 1 tool. Serial number
GB/T14822-93
Between the end of the armature winding and the accessible parts or accessible surfacesBetween the end of the stator winding and the accessible parts or accessible surfacesBetween the part in the slot of the stator winding and the accessible parts or accessible surfacesBetween the part in the slot of the armature winding and the accessible parts or accessible surfacesBetween the live parts of the brushes and the uninsulated live parts connected thereto and the accessible parts or accessible surfacesBetween the live parts of the commutator and the accessible parts or accessible surfacesBetween the live parts of switches and similar components and the accessible parts or accessible surfaces Between live parts and accessible surfaces of radio interference suppressors, between internal wiring conductors and accessible neutral or accessible surfaces, between plugs
Insulation type
Double insulation or
Double insulation or
Reinforced insulation
Double insulation
Reinforced insulation
Double insulation or
Reinforced insulation
Reinforced insulation
Double insulation
Reinforced insulation
9.5 The sheath of a flexible cable or cord refers to the outermost covering of a flexible cable or cord used for mechanical protection. Although the materials are all insulating materials such as rubber, vinyl chloride or other organic synthetic materials, their main function is to provide mechanical protection for the core wire, so they should not be used as additional insulation in general. They can only be used as additional insulation in places such as between the wire fixture and the terminal where they will not be subjected to inappropriate thermal and mechanical stress, but they must meet the corresponding requirements for additional insulation. GB/T14822-93
The sheath of natural or synthetic rubber acid used as additional insulation must be tested in pressurized oxygen according to Article 20.13 of GB3883.1 to confirm that it has sufficient aging resistance. 9.6 Article 20.11 of GB3883.1 stipulates: Any assembly gap with a width exceeding 0.3mm in the additional insulation should not overlap with any such gap in the basic insulation; any such gap in the reinforced insulation should not cause a straight path for live parts. This type of gap is mainly the assembly gap formed between the tool handle and the switch wrench. When designing, it should be noted that these gaps cannot directly face the switch wiring connector or connecting wire. 9.7 GB 3883.1 Article 20.12 stipulates: Class 1 tools should be designed and manufactured so that when any wire, screw, nut, washer, spring and similar parts are loose or fall off from the source position, it will not cause the accessible metal parts to be charged. Class I tools should be designed and manufactured so that when any such parts are loose or fall off from the original position, it will not cause the creepage distance and electrical clearance on the additional insulation or reinforced insulation to be reduced to less than 50% of the value specified in Article 27.1. In addition, except for those with an isolated casing, Class I tools should have an insulating barrier between the accessible metal parts and the motor part and other live parts. 9.7.1 The wire is considered to be likely to fall off from its connection in the following cases: a. There is no special device to fix the wire near the terminal or welding place; the connecting parts such as screws, nuts, connectors, elastic clips, etc. used to connect the wires do not have sufficient locking means; the wire joints are made of lugs, connectors or similar connecting parts, and the connecting parts do not clamp the wire insulation together. c. 9.7.2 The wire is considered to be unlikely to fall off from its connection in the following cases: a. The wire is fixed at the connection outside the connection by a special device (such as shown in Figures 11 and 12); there is a fixing plate. Note: For the fixing device, the screw has been prevented from loosening by a spring washer, and the hole for the wire to pass through near the connection is slightly larger than the outer diameter of the insulated wire.
b The wire is fixed on the terminal, and the loose part of the terminal connection (screws, nuts, etc.) remains in the original position (for example, as shown in Figure 13):
Short hard wire (generally refers to single-core hard wire) can remain in the original position when the terminal connection (screws, nuts, etc.) is loose: the wires are hooked together before welding (as shown in Figure 14). d.
Note: The terminal and the screw are pressed by other parts to fix them after they are connected. Figure 14
GB/T1482293
9.7.3 The screws, nuts and washers in the following cases are considered not to loosen or fall off:, in mechanical connection, elastic a. Screws and nuts locked with spring washers, elastic washers or stop washers; b. Screws and nuts locked with adhesives and not turned by the user. 9.7.4 For electrical connections, it is not sufficient to lock with spring washers alone. The so-called electrical connection refers to the connection made to connect the circuit, whether the connection is movable or fixed. 9.7.5 When considering the impact of the falling off or loosening of parts in the design, it is considered as a single fault state. It is not assumed that two independent parts will loosen or fall off at the same time, and the impact caused by the loosening or falling off of two or more parts at the same time can be ignored. 9.7.6 In order to meet the requirements of Article 20.12 of GB3883.1, the following measures can generally be taken: set up sufficient The gap and creepage distance are large enough to ensure that the creepage distance and air gap cannot be reduced to an unacceptable level even if these parts become loose or fall off. For example, as shown in Figure 15, the surface of the housing joint is not connected with a flat surface, but with a stopper to increase the creepage distance and air gap, so that there is no straight gap between the live part and the interface of the tool; the creepage distance and air gap between the live part and the tool's outer surface is 6mm, and the creepage distance and air gap between the live part and the tool's outer surface is mm. b. The parts that are considered to be loose or fall off are encapsulated with other fixed parts or resin or sealing glue (sealing wax) with a certain bonding force (for example, as shown in Figure 16). Sealing glue can only be used to seal screws or nuts that are not subject to torsion in normal use: C. Set obstacles in the direction where the parts may loosen and move to prevent them from falling off (for example, as shown in Figure 17). The nuts may loosen and move but cannot fall off. The obstacles used to limit the falling off of electrical connectors must be made of insulating materials or charged bodies with the same potential: Sealing mouth
Note: It can only be used in the parts that will not be disassembled after connection. Figure 17
Note: L is h, and the position between the bolt and the obstacle is relatively fixed under normal conditions.12. The following measures can be taken to meet the requirements of Article 12: Set up sufficiently large clearance and creepage distance to ensure that the creepage distance and air gap cannot be reduced to an unacceptable level in case of loosening or falling off of these parts. For example, as shown in Figure 15, the creepage distance and air gap are increased by using stopper instead of flat joint on the joint surface of the housing, so that there is no straight gap between the interface of the live part and the tool; the creepage distance and air gap between the live part of the tool and the outer surface of the tool are 6mm; the creepage distance and air gap between the live part of the tool and the outer surface of the tool are 6mm; the creepage distance and air gap between the live part of the tool and the outer surface of the tool are 6mm; b. Encapsulate the parts that are considered to be loose or falling off with other fixed parts or resin or sealing glue (sealing wax) with a certain adhesive force (for example, as shown in Figure 16). The sealant can only be used to seal screws or nuts that are not subject to torsion in normal use: C. Set obstacles in the direction where the parts may loosen and move to prevent them from falling off (for example, as shown in Figure 17). The nuts may loosen and move but cannot fall off. The obstacles used to limit the falling off of electrical connectors must be made of insulating materials or charged bodies with the same potential: Sealing mouth
Note: It can only be used in parts that will not be disassembled after connection. Figure 17
Note: L is h, and the position between the bolt and the obstacle is relatively fixed under normal conditions.12. The following measures can be taken to meet the requirements of Article 12: Set up sufficiently large clearance and creepage distance to ensure that the creepage distance and air gap cannot be reduced to an unacceptable level in case of loosening or falling off of these parts. For example, as shown in Figure 15, the creepage distance and air gap are increased by using stopper instead of flat joint on the joint surface of the housing, so that there is no straight gap between the interface of the live part and the tool; the creepage distance and air gap between the live part of the tool and the outer surface of the tool are 6mm; the creepage distance and air gap between the live part of the tool and the outer surface of the tool are 6mm; the creepage distance and air gap between the live part of the tool and the outer surface of the tool are 6mm; b. Encapsulate the parts that are considered to be loose or falling off with other fixed parts or resin or sealing glue (sealing wax) with a certain adhesive force (for example, as shown in Figure 16). The sealant can only be used to seal screws or nuts that are not subject to torsion in normal use: C. Set obstacles in the direction where the parts may loosen and move to prevent them from falling off (for example, as shown in Figure 17). The nuts may loosen and move but cannot fall off. The obstacles used to limit the falling off of electrical connectors must be made of insulating materials or charged bodies with the same potential: Sealing mouth
Note: It can only be used in parts that will not be disassembled after connection. Figure 17
Note: L is h, and the position between the bolt and the obstacle is relatively fixed under normal conditions.
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