The following principles have been adopted in the development of this part of GB 4943.
These principles do not cover performance or functional characteristics of equipment.
0.1 General Principles of Safety
It is essential that designers understand the underlying principles of safety requirements in order that they can engineer safe equipment.
These principles are not an alternative to the detailed requirements of this part, but are intended to provide designers with an appreciation of the basis of these requirements. Where the equipment involves technologies and materials or methods of construction not specifically covered, the design of the equipment should provide a level of safety not less than those described in these principles of safety.
Designers shall take into account not only normal operating conditions of the equipment but also likely fault conditions, consequential faults, foreseeable misuse and external influences such as temperature, altitude, pollution, moisture, overvoltages on the MAINS SUPPLY and overvoltages on a TELECOMMUNICATION NETWORK or a CABLE DISTRIBUTION SYSTEM. Dimensioning of insulation spacings should take account of possible reductions by manufacturing tolerances, or where deformation could occur due to handling, shock and vibration likely to be encountered during manufacture, transport and normal use.
The following priorities should be observed in determining what design measures to adopt:
- where possible, specify design criteria that will eliminate, reduce or guard against hazards;
- where the above is not practicable because the functioning of the equipment would be impaired, specify the use of protective means independent of the equipment, such as personal protective equipment (which is not specified in this part);
- where neither of the above measures is practicable, or in addition to those measures, specify the provision of markings and instructions regarding the residual risks.
There are two types of persons whose safety needs to be considered, USERS (or OPERATORS) and SERVICE PERSONS.
USER is the term applied to all persons other than SERVICE PERSONS. Requirements for protection should assume that USERS are not trained to identify hazards, but will not intentionally create a hazardous situation. Consequently, the requirements will provide protection for cleaners and casual visitors as well as the assigned USERS. In general, USERS should not have access to hazardous parts, and to this end, such parts should only be in SERVICE ACCESS AREAS or in equipment located in RESTRICTED ACCESS LOCATIONS.
When USERS are admitted to RESTRICTED ACCESS LOCATIONS they shall be suitably instructed.
SERVICE PERSONS are expected to use their training and skill to avoid possible injury to themselves and others due to obvious hazards that exist in SERVICE ACCESS AREAS of the equipment or on equipment located in RESTRICTED ACCESS LOCATIONS. However, SERVICE PERSONS should be protected against unexpected hazards. This can be done by, for example, locating parts that need to be accessible for servicing away from electrical and mechanical hazards, providing shields to avoid accidental contact with hazardous parts, and providing labels or instructions to warn personnel about any residual risk.
Information about potential hazards can be marked on the equipment or provided with the equipment, depending on the likelihood and severity of injury, or made available for SERVICE PERSONS. In general, USERS shall not be exposed to hazards likely to cause injury, and information provided for USERS should primarily aim at avoiding misuse and situations likely to create hazards, such as connection to the wrong power source and replacement of fuses by incorrect types.
MOVABLE EQUIPMENT is considered to present a slightly increased risk of shock, due to possible extra strain on the supply cord leading to rupture of the earthing conductor. With HAND-HELD EQUIPMENT, this risk is increased; wear on the cord is more likely, and further hazards could arise if the units were dropped. TRANSPORTABLE EQUIPMENT introduces a further factor because it can be used and carried in any orientation; if a small metallic object enters an opening in the ENCLOSURE it can move around inside the equipment, possibly creating a hazard.
0.2 Hazards
Application of a safety standard is intended to reduce the risk of injury or damage due to the following:
- electric shock;
- energy related hazards;
- fire;
- heat related hazards;
- mechanical hazards;
- radiation;
- chemical hazards.
0.2.1 Electric shock
Electric shock is due to current passing through the human body. The resulting physiological effects depend on the value and duration of the current and the path it takes through the body. The value of the current depends on the applied voltage, the impedance of the source and the impedance of the body. The body impedance depends in turn on the area of contact, moisture in the area of contact and the applied voltage and frequency. Currents of approximately 0.5mA can cause a reaction in persons in good health and may cause injury indirectly due to involuntary reaction. Higher currents can have more direct effects, such as burn or muscle tetanization leading to inability to let go or to ventricular fibrillation.
Steady state voltages up to 42.4V peak, or 60V d.c., are not generally regarded as hazardous under dry conditions for an area of contact equivalent to a human hand. Bare parts that have to be touched or handled should be at earth potential or properly insulated.
Some equipment will be connected to telephone and other external networks. Some TELECOMMUNICATION NETWORKS operate with signals such as voice and ringing superimposed on a steady d.c. supply voltage; the total may exceed the values given above for steady-state voltages. It is common practice for the SERVICE PERSONS of telephone companies to handle parts of such circuits bare-handed. This has not caused serious injury, because of the use of cadenced ringing and because there are limited areas of contact with bare conductors normally handled by SERVICE PERSONS. However, the area of contact of a part accessible to the USER, and the likelihood of the part being touched, should be further limited (for example, by the shape and location of the part).
It is normal to provide two levels of protection for USERS to prevent electric shock. Therefore, the operation of equipment under normal conditions and after a single fault, including any consequential faults, should not create a shock hazard. However, provision of additional protective measures, such as protective earthing or SUPPLEMENTARY INSULATION, is not considered a substitute for, or a relief from, properly designed BASIC INSULATION.
Harm may result from: Examples of measures to reduce risks:
Contact with bare parts normally at HAZARDOUS VOLTAGES. Prevent USER access to parts at HAZARDOUS VOLTAGES by fixed or locked covers, SAFETY INTERLOCKS, etc. Discharge accessible capacitors that are at HAZARDOUS VOLTAGES.
Breakdown of insulation between parts normally at HAZARDOUS VOLTAGES and accessible conductive parts. Provide BASIC INSULATION and connect the accessible conductive parts and circuits to earth so that exposure to the voltage which can develop is limited because overcurrent protection will disconnect the parts having low impedance faults within a specified time; or provide a metal screen connected to protective earth between the parts, or provide DOUBLE INSULATION or REINFORCED INSULATION between the parts, so that breakdown to the accessible part is not likely to occur.
Contact with circuits connected to TELECOMMUNICATION NETWORKS that exceed 42.4 V peak or 60V d.c. Limit the accessibility and area of contact of such circuits, and separate them from unearthed parts to which access is not limited.
Breakdown of USER-accessible insulation. Insulation that is accessible to the USER should have adequate mechanical and electrical strength to reduce the likelihood of contact with HAZARDOUS VOLTAGES.
TOUCH CURRENT (leakage current) flowing from parts at HAZARDOUS VOLTAGES to accessible parts, or failure of a protective earthing connection. TOUCH CURRENT may include current due to EMC filter components connected between PRIMARY CIRCUITS and accessible parts. Limit TOUCH CURRENT to a specified value, or provide a high integrity protective earthing connection.
0.2.2 Energy related hazards
Injury or fire may result from a short-circuit between adjacent poles of high current supplies or high capacitance circuits, causing:
- burns;
- arcing;
- ejection of molten metal.
Even circuits whose voltages are safe to touch may be hazardous in this respect.
Examples of measures to reduce risks include:
- separation;
- shielding;
- provision of SAFETY INTERLOCKS.
0.2.3 Fire
Risk of fire may result from excessive temperatures either under normal operating conditions or due to overload, component failure, insulation breakdown or loose connections. Fires originating within the equipment should not spread beyond the immediate vicinity of the source of the fire, nor cause damage to the surroundings of the equipment.
Examples of measures to reduce risks include:
- providing overcurrent protection;
- using constructional materials having appropriate flammability properties for their purpose;
- selection of parts, components and consumable materials to avoid high temperature which might cause ignition;
- limiting the quantity of combustible materials used;
- shielding or separating combustible materials from likely ignition sources;
- using ENCLOSURES or barriers to limit the spread of fire within the equipment;
- using suitable materials for ENCLOSURES so as to reduce the likelihood of fire spreading from the equipment.
0.2.4 Heat related hazards
Injury may result from high temperatures under normal operating conditions, causing:
- burns due to contact with hot accessible parts;
- degradation of insulation and of safety-critical components;
- ignition of flammable liquids.
Examples of measures to reduce risks include:
- taking steps to avoid high temperature of accessible parts;
- avoiding temperatures above the ignition point of liquids;
- provision of markings to warn USERS where access to hot parts is unavoidable.
0.2.5 Mechanical hazards
Injury may result from:
- sharp edges and corners;
- moving parts that have the potential to cause injury;
- equipment instability;
- flying particles from imploding cathode ray tubes and exploding high pressure lamps.
Examples of measures to reduce risks include:
- rounding of sharp edges and corners;
- guarding;
- provision of SAFETY INTERLOCKS;
- providing sufficient stability to free-standing equipment;
- selecting cathode ray tubes and high pressure lamps that are resistant to implosion and explosion respectively;
- provision of markings to warn USERS where access is unavoidable.
0.2.6 Radiation
Injury to USERS and to SERVICE PERSONS may result from some forms of radiation emitted by equipment. Examples are sonic (acoustic), radio frequency, infra-red, ultraviolet and ionizing radiation, and high intensity visible and coherent light (lasers).
Examples of measures to reduce risks include:
- limiting the energy level of potential radiation sources;
- screening radiation sources;
- provision of SAFETY INTERLOCKS;
- provision of markings to warn USERS where exposure to the radiation hazard is unavoidable.
0.2.7 Chemical hazards
Injury may result from contact with some chemicals or from inhalation of their vapours and fumes.
Examples of measures to reduce risks include:
- avoiding the use of constructional and consumable materials likely to cause injury by contact or inhalation during intended and normal conditions of use;
- avoiding conditions likely to cause leakage or vaporization;
- provision of markings to warn USERS about the hazards.
0.3 Materials and Components
Materials and components used in the construction of equipment should be so selected and arranged that they can be expected to perform in a reliable manner for the anticipated life of the equipment without creating a hazard, and would not contribute significantly to the development of a serious fire hazard. Components should be selected so that they remain within their manufacturers' ratings under normal operating conditions, and do not create a hazard under fault conditions.
Information Technology Equipment—Safety—
Part 1: General Requirements
1 General
1.1 Scope
1.1.1 Equipment covered by this part
This part of GB 4943 is applicable to mains-powered or battery-powered information technology equipment, including electrical business equipment and associated equipment, with a RATED VOLTAGE not exceeding 600 V.
This part is also applicable to such information technology equipment:
- designed for use as telecommunication terminal equipment and TELECOMMUNICATION NETWORK infrastructure equipment, regardless of the source of power;
- designed and intended to be connected directly to, or used as infrastructure equipment in, a CABLE DISTRIBUTION SYSTEM, regardless of the source of power;
- designed to use the AC MAINS SUPPLY as a communication transmission medium (see Clause 6, Note 4 and 7.1, Note 4).
This part is also applicable to components and subassemblies intended for incorporation in information technology equipment. It is not expected that such components and subassemblies comply with every aspect of the part, provided that the complete information technology equipment, incorporating such components and subassemblies, does comply.
NOTE 1 Examples of aspects with which uninstalled components and subassemblies may not comply include the marking of the power rating and access to hazardous parts.
NOTE 2 This part may be applied to the electronic parts of equipment even if that equipment does not wholly fall within its Scope, such as large-scale air conditioning systems, fire detection systems and fire extinguishing systems. Different requirements may be necessary for some applications.
This part specifies requirements intended to reduce risks of fire, electric shock or injury for the OPERATOR and layman who may come into contact with the equipment and, where specifically stated, for a SERVICE PERSON.
This part is intended to reduce such risks with respect to installed equipment, whether it consists of a system of interconnected units or independent units, subject to installing, operating and maintaining the equipment in the manner prescribed by the manufacturer.
Examples of equipment that is in the scope of this standard are:
Generic product type Specific example of generic type
data and text processing machines and associated equipment data preparation equipment, data processing equipment, data storage equipment, personal computers, plotters, printers, scanners, text processing equipment, visual display units
data network equipment bridges, data circuit terminating equipment, data terminal equipment, routers
electrical and electronic retail equipment cash registers, point of sale terminals including associated electronic scales
NOTE 3 The requirements of GB 8898 may also be used to meet safety requirements for multimedia equipment. See IEC Guide 112, Guide on the safety of multimedia equipment.
This list is not intended to be comprehensive, and equipment that is not listed is not necessarily excluded from the Scope.
Equipment complying with the relevant requirements in this standard is considered suitable for use with process control equipment, automatic test equipment and similar systems requiring information processing facilities. However, this standard does not include requirements for performance or functional characteristics of equipment.
1.1.2 Additional requirements
Requirements additional to those specified in this standard may be necessary for:
- equipment intended for operation in special environments (for example, extremes of temperature; excessive dust, moisture or vibration; flammable gases; and corrosive or explosive atmospheres);
- electromedical applications with physical connections to the patient;
- equipment intended to be used in vehicles, on board ships or aircraft, at altitudes greater than 5 000 m;
- equipment intended for use where ingress of water is possible; for guidance on such requirements and on relevant testing, see Annex T.
NOTE Attention is drawn to the fact that authorities of some countries impose additional requirements.
1.1.3 Exclusions
This standard does not apply to:
- power supply systems which are not an integral part of the equipment, such as motor- generator sets, battery backup systems and transformers;
- building installation wiring;
- devices requiring no electric power.
1.2 Terms and Definitions
For the purpose of this Part the following definitions apply. Where the terms "voltage" and "current" are used, they imply the r.m.s. values, unless otherwise specified.
supply voltage (for a three-phase AC MAINS SUPPLY, the line-to-line voltage) as declared by the manufacturer
Foreword I Introduction VIII 0 Principles of Safety VIII 0.1 General Principles of Safety VIII 0.2 Hazards IX 0.3 Materials and Components XIV 1 General 1.1 Scope 1.2 Terms and Definitions 1.3 General Requirements 1.4 General Conditions for Tests 1.5 Components 1.6 Power Interface 1.7 Markings and Instructions 2 Protection from Hazards 2.1 Protection from Electric Shock and Energy Hazards 2.2 SELV Circuits 2.3 TNV Circuits 2.4 Limited Current Circuits 2.5 Limited Power Sources 2.6 Provisions for Earthing and Bonding 2.7 Overcurrent and Earth Fault Protection in Primary Circuits 2.8 Safety Interlocks 2.9 Electrical Insulation 2.10 Clearances, Creepage Distances and Distances through Insulation 3 Wiring, Connections and Supply 3.1 General 3.2 Connection to a Mains Supply 3.3 Wiring Terminals for Connection of External Conductors 3.4 Disconnection from the Mains Supply 3.5 Interconnection of Equipment 4 Physical Requirements 4.1 Stability 4.2 Mechanical Strength 4.3 Design and Construction 4.4 Protection against Hazardous Moving Parts 4.5 Thermal Requirements 4.6 Openings in Enclosures 4.7 Resistance to Fire 5 Electrical Requirements and Simulated Abnormal Conditions 5.1 Touch Current and Protective Conductor Current 5.2 Electric Strength 5.3 Abnormal Operating and Fault Conditions 6 Connection to Telecommunication Networks 6.1 Protection of Telecommunication Network Service Persons, and Users of Other Equipment Connected to the Network, from Hazards in the Equipment 6.2 Protection of Equipment Users from Overvoltages on Telecommunication Networks 6.3 Protection of the Telecommunication Wiring System from Overheating 7 Connection to Cable Distribution Systems 7.1 General 7.2 Protection of Cable Distribution System Service Persons, and Users of Other Equipment Connected to the System, from Hazardous Voltages in the Equipment 7.3 Protection of Equipment Users from Overvoltages on the Cable Distribution System 7.4 Insulation between Primary Circuits and Cable Distribution Systems Annex A (Normative) Tests for Resistance to Heat and Fire Annex B (Normative) Motor Tests Under Abnormal Conditions Annex C (Normative) Transformers Annex D (Normative) Measuring Instruments for Touch Current Tests Annex E (Normative) Temperature Rise of A Winding Annex F (Normative) Measurement of Clearances and Creepage Distances Annex G (Normative) Alternative Method for Determining Minimum Clearances Annex H (Normative) Ionizing Radiation Annex J (Normative) Table of Electrochemical Potentials Annex K (Normative) Thermal Controls Annex L (Normative) Normal Load Conditions for Some Types of Electrical Business Equipment Annex M (Normative) Criteria for Telephone Ringing Signals Annex N (Normative) Impulse Test Generators Annex P (Normative) Normative References Annex Q (Normative) Voltage Dependent Resistors (VDRs) Annex R (Informative) Examples of Requirements for Quality Control Programmes Annex S (Informative) Procedure for Impulse Testing Annex T (Informative) Guidance on Protection Against Ingress Of Water Annex U (Normative) Insulated Winding Wires for Use Without Interleaved Insulation Annex V (Normative) AC Power Distribution Systems Annex W (Informative) Summation of Touch Currents Annex X (Informative) Maximum Heating Effect in Transformer Tests Annex Y (Normative) Ultraviolet Light Conditioning Test Annex Z (Informative) Overvoltage Categories Annex AA (Normative) Mandrel Test Annex BB (Informative) Difference from GB 4943- Annex CC (Informative) Comparison of Normative References/ Bibliography between IEC 60950-1:2005 and This Part Annex DD (Normative) Instruction on New Safety Warning Sign in the Standard Annex EE (Informative) Cross-reference of the Safety-Related Description Examples Written in Chinese, Tibetan, Mongolian, Zhuang and Uyghur languages . Bibliography Figure 2A Test Finger Figure 2B Test Pin Figure 2C Test Probe Figure 2D Accessibility of Internal Conductive Parts Figure 2E Voltages in SELV Circuits under Single Fault Conditions Figure 2F Maximum Voltages Permitted after a Single Fault Figure 2G Test Generator Figure 2H Examples of Application of Insulation Figure 2J Thermal Ageing Time Figure 2K Abrasion Resistance Test for Coating Layers Figure 4A Impact Test Using a Steel Ball Figure 4B Examples of Cross-sections of Designs of Openings Preventing Vertical Access Figure 4C Examples of Louvre Design Figure 4D Enclosure Openings Figure 4E Typical Bottom of a Fire Enclosure for Partially Enclosed Component or Assembly Figure 4F Baffle Plate Construction Figure 5A Test Circuit for Touch Current of Single-phase Equipment on a Star TN or TT Power Supply System Figure 5B Test Circuit for Touch Current of Three-phase Equipment on a Star TN or TT Power Supply System Figure 6A Test for Separation between a Telecommunication Network and Earth Figure 6B Application Points of Test Voltage Figure B.1 Determination of Arithmetic Average Temperature Figure C.1 Determination of Arithmetic Average Temperature Figure D.1 Measuring Instrument Figure D.2 Alternative Measuring Instrument Figure F.1 Narrow Groove Figure F.2 Wide Groove Figure F.3 V-shaped Groove Figure F.4 Rib Figure F.5 Uncemented Joint with Narrow Groove Figure F.6 Uncemented Joint with Wide Groove Figure F.7 Uncemented Joint with Narrow and Wide Grooves Figure F.8 Narrow Recess Figure F.9 Wide Recess Figure F.10 Coating around Terminals Figure F.11 Coating over Printed Wiring Figure F.12 Measurements through Openings in Enclosures Figure F.13 Intervening, Unconnected Conductive Part Figure F.14 Solid Insulating Material Figure F.15 Thin Sheet Insulating Material Figure F.16 Cemented Joints in Multi-Layer Printed Board Figure F.17 Component Filled with Insulating Compound Figure F.18 Partitioned Bobbin Figure M.1 Definition of Ringing Period and Cadence Cycle Figure M.2 ITS1 Limit Curve for Cadenced Ringing Signal Figure M.3 Peak and Peak-To-Peak Currents Figure M.4 Ringing Voltage Trip Criteria Figure N.1 ITU-T Impulse Test Generator Circuit Figure N.2 GB 8898 Impulse Test Generator Circuit Figure S.1 Waveform on Insulation Without Surge Suppressors and No Breakdown Figure S.2 Waveforms on Insulation During Breakdown Without Surge Suppressors Figure S.3 Waveforms on Insulation With Surge Suppressors in Operation Figure S.4 Waveform on Short-Circuited Surge Suppressor and Insulation Figure V.1 Examples of TN-S Power Distribution Systems Figure V.2 Example of TN-C-S Power Distribution System Figure V.3 Example of TN-C Power Distribution System Figure V.4 Example of Single-Phase, Three-Wire TN-C Power Distribution System Figure V.5 Example of Three Line and Neutral TT Power Distribution System Figure V.6 Example of Three Line TT Power Distribution System Figure V.7 Example of Three Line (and Neutral) IT Power Distribution System Figure V.8 Example of Three Line IT Power Distribution System Figure W.1 Touch Current from A Floating Circuit Figure W.2 Touch Current from An Earthed Circuit Figure W.3 Summation of Touch Currents in a PABX Figure AA.1 Mandrel Figure AA.2 Initial Position of Mandrel Figure AA.3 Final Position of Mandrel Figure AA.4 Position of Metal Foil on Insulating Material Table 1A Voltage Ranges of SELV and TNV Circuits Table 1B Equivalence of Flammability Classes Table 1C Capacitor Ratings According to GB/T Table 1D Informative Examples of Application of Capacitors Table 2A Distance through Insulation of Internal Wiring Table 2B Limits for Power Sources without an Overcurrent Protective Device Table 2C Limits for Power Sources with an Overcurrent Protective Device Table 2D Minimum Size of Protective Bonding Conductors Table 2E Test Duration, a.c. Mains Supplies Table 2F Examples of Protective Devices in Single-Phase Equipment or Subassemblies Table 2G Examples of Protective Devices in Three-Phase Equipment Table 2H Examples of Application of Insulation Table 2J AC Mains Transient Voltages Table 2K Minimum Clearances for Insulation in Primary Circuits and between Primary and Secondary Circuits (Applicable to Those to be Operated below 2 000 m above the Sea Level) Table 2L Additional Clearances in Primary Circuits (Applicable to Those to be Operated below 2 000 m above the Sea Level) Table 2M Minimum Clearances in Secondary Circuits (Applicable to Those to be Operated below 2 000 m above Sea Level) Table 2N Minimum Creepage Distances Table 2P Tests for Insulation in Non-separable Layers Table 2Q Minimum Separation Distances for Coated Printed Boards Table 2R Insulation in Printed Boards Table 3A Sizes of Cables and Conduits for Equipment Having a Rated Current not Exceeding 16 A Table 3B Sizes of Conductors Table 3C Physical Tests on Power Supply Cords Table 3D Range of Conductor Sizes to be Accepted by Terminals Table 3E Sizes of Terminals for Mains Supply Conductors and Protective Earthing Conductors a Table 4A Minimum Property Retention Limits after UV Exposure Table 4B Temperature Limits, Materials and Components Table 4C Touch Temperature Limits Table 4D Size and Spacing of Openings in Metal Bottoms of Fire Enclosures Table 4E Summary of Material Flammability Requirements Table 5A Maximum Current Table 5B Test Voltages for Electric Strength Tests Based on Peak Working Voltages Table 5C Test Voltages for Electric Strength Tests Based on Required Withstand Voltages Table 5D Temperature Limits for Overload Conditions Table B.1 Temperature Limits for Motor Windings (Except for Running Overload Test) Table B.2 Permitted Temperature Limits for Running Overload Tests Table C.1 Temperature Limits for Transformer Windings Table F.1 Value of X Table G.1 AC Mains Transient Voltages Table G.2 Minimum Clearances up to 2 000 m Above Sea Level Table J.1 Electrochemical Potentials (V) Table N.1 Component values for Figures N.1 and N Table R.1 Rules for Sampling and Inspection—Coated Printed Boards Table R.2 Rules for Sampling and Inspection—Reduced Clearances Table T.1 Extract from GB Table U.1 Mandrel Diameter Table U.2 Oven Temperature Table X.1 Test Steps Table Z.1 Overvoltage Categories
Introduction
0 Principles of Safety
The following principles have been adopted in the development of this part of GB 4943.
These principles do not cover performance or functional characteristics of equipment.
0.1 General Principles of Safety
It is essential that designers understand the underlying principles of safety requirements in order that they can engineer safe equipment.
These principles are not an alternative to the detailed requirements of this part, but are intended to provide designers with an appreciation of the basis of these requirements. Where the equipment involves technologies and materials or methods of construction not specifically covered, the design of the equipment should provide a level of safety not less than those described in these principles of safety.
Designers shall take into account not only normal operating conditions of the equipment but also likely fault conditions, consequential faults, foreseeable misuse and external influences such as temperature, altitude, pollution, moisture, overvoltages on the MAINS SUPPLY and overvoltages on a TELECOMMUNICATION NETWORK or a CABLE DISTRIBUTION SYSTEM. Dimensioning of insulation spacings should take account of possible reductions by manufacturing tolerances, or where deformation could occur due to handling, shock and vibration likely to be encountered during manufacture, transport and normal use.
The following priorities should be observed in determining what design measures to adopt:
- where possible, specify design criteria that will eliminate, reduce or guard against hazards;
- where the above is not practicable because the functioning of the equipment would be impaired, specify the use of protective means independent of the equipment, such as personal protective equipment (which is not specified in this part);
- where neither of the above measures is practicable, or in addition to those measures, specify the provision of markings and instructions regarding the residual risks.
There are two types of persons whose safety needs to be considered, USERS (or OPERATORS) and SERVICE PERSONS.
USER is the term applied to all persons other than SERVICE PERSONS. Requirements for protection should assume that USERS are not trained to identify hazards, but will not intentionally create a hazardous situation. Consequently, the requirements will provide protection for cleaners and casual visitors as well as the assigned USERS. In general, USERS should not have access to hazardous parts, and to this end, such parts should only be in SERVICE ACCESS AREAS or in equipment located in RESTRICTED ACCESS LOCATIONS.
When USERS are admitted to RESTRICTED ACCESS LOCATIONS they shall be suitably instructed.
SERVICE PERSONS are expected to use their training and skill to avoid possible injury to themselves and others due to obvious hazards that exist in SERVICE ACCESS AREAS of the equipment or on equipment located in RESTRICTED ACCESS LOCATIONS. However, SERVICE PERSONS should be protected against unexpected hazards. This can be done by, for example, locating parts that need to be accessible for servicing away from electrical and mechanical hazards, providing shields to avoid accidental contact with hazardous parts, and providing labels or instructions to warn personnel about any residual risk.
Information about potential hazards can be marked on the equipment or provided with the equipment, depending on the likelihood and severity of injury, or made available for SERVICE PERSONS. In general, USERS shall not be exposed to hazards likely to cause injury, and information provided for USERS should primarily aim at avoiding misuse and situations likely to create hazards, such as connection to the wrong power source and replacement of fuses by incorrect types.
MOVABLE EQUIPMENT is considered to present a slightly increased risk of shock, due to possible extra strain on the supply cord leading to rupture of the earthing conductor. With HAND-HELD EQUIPMENT, this risk is increased; wear on the cord is more likely, and further hazards could arise if the units were dropped. TRANSPORTABLE EQUIPMENT introduces a further factor because it can be used and carried in any orientation; if a small metallic object enters an opening in the ENCLOSURE it can move around inside the equipment, possibly creating a hazard.
0.2 Hazards
Application of a safety standard is intended to reduce the risk of injury or damage due to the following:
- electric shock;
- energy related hazards;
- fire;
- heat related hazards;
- mechanical hazards;
- radiation;
- chemical hazards.
0.2.1 Electric shock
Electric shock is due to current passing through the human body. The resulting physiological effects depend on the value and duration of the current and the path it takes through the body. The value of the current depends on the applied voltage, the impedance of the source and the impedance of the body. The body impedance depends in turn on the area of contact, moisture in the area of contact and the applied voltage and frequency. Currents of approximately 0.5mA can cause a reaction in persons in good health and may cause injury indirectly due to involuntary reaction. Higher currents can have more direct effects, such as burn or muscle tetanization leading to inability to let go or to ventricular fibrillation.
Steady state voltages up to 42.4V peak, or 60V d.c., are not generally regarded as hazardous under dry conditions for an area of contact equivalent to a human hand. Bare parts that have to be touched or handled should be at earth potential or properly insulated.
Some equipment will be connected to telephone and other external networks. Some TELECOMMUNICATION NETWORKS operate with signals such as voice and ringing superimposed on a steady d.c. supply voltage; the total may exceed the values given above for steady-state voltages. It is common practice for the SERVICE PERSONS of telephone companies to handle parts of such circuits bare-handed. This has not caused serious injury, because of the use of cadenced ringing and because there are limited areas of contact with bare conductors normally handled by SERVICE PERSONS. However, the area of contact of a part accessible to the USER, and the likelihood of the part being touched, should be further limited (for example, by the shape and location of the part).
It is normal to provide two levels of protection for USERS to prevent electric shock. Therefore, the operation of equipment under normal conditions and after a single fault, including any consequential faults, should not create a shock hazard. However, provision of additional protective measures, such as protective earthing or SUPPLEMENTARY INSULATION, is not considered a substitute for, or a relief from, properly designed BASIC INSULATION.
Harm may result from: Examples of measures to reduce risks:
Contact with bare parts normally at HAZARDOUS VOLTAGES. Prevent USER access to parts at HAZARDOUS VOLTAGES by fixed or locked covers, SAFETY INTERLOCKS, etc. Discharge accessible capacitors that are at HAZARDOUS VOLTAGES.
Breakdown of insulation between parts normally at HAZARDOUS VOLTAGES and accessible conductive parts. Provide BASIC INSULATION and connect the accessible conductive parts and circuits to earth so that exposure to the voltage which can develop is limited because overcurrent protection will disconnect the parts having low impedance faults within a specified time; or provide a metal screen connected to protective earth between the parts, or provide DOUBLE INSULATION or REINFORCED INSULATION between the parts, so that breakdown to the accessible part is not likely to occur.
Contact with circuits connected to TELECOMMUNICATION NETWORKS that exceed 42.4 V peak or 60V d.c. Limit the accessibility and area of contact of such circuits, and separate them from unearthed parts to which access is not limited.
Breakdown of USER-accessible insulation. Insulation that is accessible to the USER should have adequate mechanical and electrical strength to reduce the likelihood of contact with HAZARDOUS VOLTAGES.
TOUCH CURRENT (leakage current) flowing from parts at HAZARDOUS VOLTAGES to accessible parts, or failure of a protective earthing connection. TOUCH CURRENT may include current due to EMC filter components connected between PRIMARY CIRCUITS and accessible parts. Limit TOUCH CURRENT to a specified value, or provide a high integrity protective earthing connection.
0.2.2 Energy related hazards
Injury or fire may result from a short-circuit between adjacent poles of high current supplies or high capacitance circuits, causing:
- burns;
- arcing;
- ejection of molten metal.
Even circuits whose voltages are safe to touch may be hazardous in this respect.
Examples of measures to reduce risks include:
- separation;
- shielding;
- provision of SAFETY INTERLOCKS.
0.2.3 Fire
Risk of fire may result from excessive temperatures either under normal operating conditions or due to overload, component failure, insulation breakdown or loose connections. Fires originating within the equipment should not spread beyond the immediate vicinity of the source of the fire, nor cause damage to the surroundings of the equipment.
Examples of measures to reduce risks include:
- providing overcurrent protection;
- using constructional materials having appropriate flammability properties for their purpose;
- selection of parts, components and consumable materials to avoid high temperature which might cause ignition;
- limiting the quantity of combustible materials used;
- shielding or separating combustible materials from likely ignition sources;
- using ENCLOSURES or barriers to limit the spread of fire within the equipment;
- using suitable materials for ENCLOSURES so as to reduce the likelihood of fire spreading from the equipment.
0.2.4 Heat related hazards
Injury may result from high temperatures under normal operating conditions, causing:
- burns due to contact with hot accessible parts;
- degradation of insulation and of safety-critical components;
- ignition of flammable liquids.
Examples of measures to reduce risks include:
- taking steps to avoid high temperature of accessible parts;
- avoiding temperatures above the ignition point of liquids;
- provision of markings to warn USERS where access to hot parts is unavoidable.
0.2.5 Mechanical hazards
Injury may result from:
- sharp edges and corners;
- moving parts that have the potential to cause injury;
- equipment instability;
- flying particles from imploding cathode ray tubes and exploding high pressure lamps.
Examples of measures to reduce risks include:
- rounding of sharp edges and corners;
- guarding;
- provision of SAFETY INTERLOCKS;
- providing sufficient stability to free-standing equipment;
- selecting cathode ray tubes and high pressure lamps that are resistant to implosion and explosion respectively;
- provision of markings to warn USERS where access is unavoidable.
0.2.6 Radiation
Injury to USERS and to SERVICE PERSONS may result from some forms of radiation emitted by equipment. Examples are sonic (acoustic), radio frequency, infra-red, ultraviolet and ionizing radiation, and high intensity visible and coherent light (lasers).
Examples of measures to reduce risks include:
- limiting the energy level of potential radiation sources;
- screening radiation sources;
- provision of SAFETY INTERLOCKS;
- provision of markings to warn USERS where exposure to the radiation hazard is unavoidable.
0.2.7 Chemical hazards
Injury may result from contact with some chemicals or from inhalation of their vapours and fumes.
Examples of measures to reduce risks include:
- avoiding the use of constructional and consumable materials likely to cause injury by contact or inhalation during intended and normal conditions of use;
- avoiding conditions likely to cause leakage or vaporization;
- provision of markings to warn USERS about the hazards.
0.3 Materials and Components
Materials and components used in the construction of equipment should be so selected and arranged that they can be expected to perform in a reliable manner for the anticipated life of the equipment without creating a hazard, and would not contribute significantly to the development of a serious fire hazard. Components should be selected so that they remain within their manufacturers' ratings under normal operating conditions, and do not create a hazard under fault conditions.
Information Technology Equipment—Safety—
Part 1: General Requirements
1 General
1.1 Scope
1.1.1 Equipment covered by this part
This part of GB 4943 is applicable to mains-powered or battery-powered information technology equipment, including electrical business equipment and associated equipment, with a RATED VOLTAGE not exceeding 600 V.
This part is also applicable to such information technology equipment:
- designed for use as telecommunication terminal equipment and TELECOMMUNICATION NETWORK infrastructure equipment, regardless of the source of power;
- designed and intended to be connected directly to, or used as infrastructure equipment in, a CABLE DISTRIBUTION SYSTEM, regardless of the source of power;
- designed to use the AC MAINS SUPPLY as a communication transmission medium (see Clause 6, Note 4 and 7.1, Note 4).
This part is also applicable to components and subassemblies intended for incorporation in information technology equipment. It is not expected that such components and subassemblies comply with every aspect of the part, provided that the complete information technology equipment, incorporating such components and subassemblies, does comply.
NOTE 1 Examples of aspects with which uninstalled components and subassemblies may not comply include the marking of the power rating and access to hazardous parts.
NOTE 2 This part may be applied to the electronic parts of equipment even if that equipment does not wholly fall within its Scope, such as large-scale air conditioning systems, fire detection systems and fire extinguishing systems. Different requirements may be necessary for some applications.
This part specifies requirements intended to reduce risks of fire, electric shock or injury for the OPERATOR and layman who may come into contact with the equipment and, where specifically stated, for a SERVICE PERSON.
This part is intended to reduce such risks with respect to installed equipment, whether it consists of a system of interconnected units or independent units, subject to installing, operating and maintaining the equipment in the manner prescribed by the manufacturer.
Examples of equipment that is in the scope of this standard are:
Generic product type Specific example of generic type
banking equipment monetary processing machines including automated teller (cash dispensing) machines (ATM)
data and text processing machines and associated equipment data preparation equipment, data processing equipment, data storage equipment, personal computers, plotters, printers, scanners, text processing equipment, visual display units
data network equipment bridges, data circuit terminating equipment, data terminal equipment, routers
electrical and electronic retail equipment cash registers, point of sale terminals including associated electronic scales
electrical and electronic office machines calculators, copying machines, dictation equipment, document shredding machines, duplicators, erasers, micrographic office equipment, motor-operated files, paper trimmers (punchers, cutting machines, separators), paper jogging machines, pencil sharpeners, staplers, typewriters
other information technology equipment photoprinting equipment, public information terminals, multimedia equipment
postage equipment mail processing machines, postage machines
telecommunication network infrastructure equipment billing equipment, multiplexers, network powering equipment, network terminating equipment, radio base stations, repeaters, transmission equipment, telecommunication switching equipment
telecommunication terminal equipment facsimile equipment, key telephone systems, modems, PABXs, pagers, telephone answering machines, telephone sets (wired and wireless)
NOTE 3 The requirements of GB 8898 may also be used to meet safety requirements for multimedia equipment. See IEC Guide 112, Guide on the safety of multimedia equipment.
This list is not intended to be comprehensive, and equipment that is not listed is not necessarily excluded from the Scope.
Equipment complying with the relevant requirements in this standard is considered suitable for use with process control equipment, automatic test equipment and similar systems requiring information processing facilities. However, this standard does not include requirements for performance or functional characteristics of equipment.
1.1.2 Additional requirements
Requirements additional to those specified in this standard may be necessary for:
- equipment intended for operation in special environments (for example, extremes of temperature; excessive dust, moisture or vibration; flammable gases; and corrosive or explosive atmospheres);
- electromedical applications with physical connections to the patient;
- equipment intended to be used in vehicles, on board ships or aircraft, at altitudes greater than 5 000 m;
- equipment intended for use where ingress of water is possible; for guidance on such requirements and on relevant testing, see Annex T.
NOTE Attention is drawn to the fact that authorities of some countries impose additional requirements.
1.1.3 Exclusions
This standard does not apply to:
- power supply systems which are not an integral part of the equipment, such as motor- generator sets, battery backup systems and transformers;
- building installation wiring;
- devices requiring no electric power.
1.2 Terms and Definitions
For the purpose of this Part the following definitions apply. Where the terms "voltage" and "current" are used, they imply the r.m.s. values, unless otherwise specified.
Definitions in alphabetical order of nouns
AREA, OPERATOR ACCESS 1.2.7.1
AREA, SERVICE ACCESS 1.2.7.2
BODY 1.2.7.5
CABLE, INTERCONNECTING 1.2.11.6
CABLE DISTRIBUTION SYSTEM 1.2.13.14
CHEESECLOTH 1.2.13.15
CIRCUIT, ELV 1.2.8.7
CIRCUIT, LIMITED CURRENT 1.2.8.9
CIRCUIT, PRIMARY 1.2.8.4
CIRCUIT, SECONDARY 1.2.8.5
CIRCUIT, SELV 1.2.8.8
CIRCUIT, TNV 1.2.8.11
CIRCUIT, TNV-1 1.2.8.12
CIRCUIT, TNV-2 1.2.8.13
CIRCUIT, TNV-3 1.2.8.14
CLEARANCE 1.2.10.1
CONDUCTOR, PROTECTIVE BONDING 1.2.13.11
CONDUCTOR, PROTECTIVE EARTHING 1.2.13.10
CORD, DETACHABLE POWER SUPPLY 1.2.5.5
CORD, NON-DETACHABLE POWER SUPPLY 1.2.5.6
CURRENT, PROTECTIVE CONDUCTOR 1.2.13.13
CREEPAGE DISTANCE 1.2.10.2
CURRENT, RATED 1.2.1.3
CURRENT, TOUCH 1.2.13.12
CUT-OUT, THERMAL 1.2.11.3
CUT-OUT, THERMAL, AUTOMATIC RESET 1.2.11.4
CUT-OUT, THERMAL, MANUAL RESET 1.2.11.5
EARTHING, FUNCTIONAL 1.2.13.9
ENCLOSURE 1.2.6.1
ENCLOSURE, ELECTRICAL 1.2.6.4
ENCLOSURE, FIRE 1.2.6.2
ENCLOSURE, MECHANICAL 1.2.6.3
ENERGY LEVEL, HAZARDOUS 1.2.8.10
EQUIPMENT, CLASS I 1.2.4.1
EQUIPMENT, CLASS II 1.2.4.2
EQUIPMENT, CLASS III 1.2.4.3
EQUIPMENT, DIRECT PLUG-IN 1.2.3.6
EQUIPMENT FOR BUILDING-IN 1.2.3.5
EQUIPMENT, HAND-HELD 1.2.3.2
EQUIPMENT, MOVABLE 1.2.3.1
EQUIPMENT, PERMANENTLY CONNECTED 1.2.5.4
EQUIPMENT, PLUGGABLE 1.2.5.3
EQUIPMENT, PLUGGABLE, TYPE A 1.2.5.1
EQUIPMENT, PLUGGABLE, TYPE B 1.2.5.2
EQUIPMENT, STATIONARY 1.2.3.4
EQUIPMENT, TRANSPORTABLE 1.2.3.3
FREQUENCY, RATED 1.2.1.4
INSULATION, BASIC 1.2.9.2
INSULATION, DOUBLE 1.2.9.4
INSULATION, FUNCTIONAL 1.2.9.1
INSULATION, REINFORCED 1.2.9.5
INSULATION, SOLID 1.2.10.4
INSULATION, SUPPLEMENTARY 1.2.9.3
INTERLOCK, SAFETY 1.2.7.6
LIMIT, EXPLOSION 1.2.12.15
LIMITER, TEMPERATURE 1.2.11.2
LOAD, NORMAL 1.2.2.1
LOCATION, RESTRICTED ACCESS 1.2.7.3
MATERIALS, FLAMMABILITY CLASSIFICATION 1.2.12.1
MATERIAL, 5VA CLASS 1.2.12.5
MATERIAL, 5VB CLASS 1.2.12.6
MATERIAL, HB40 CLASS 1.2.12.10
MATERIAL, HB75 CLASS 1.2.12.11
MATERIAL, HBF CLASS FOAMED 1.2.12.9
MATERIAL, HF-1 CLASS FOAMED 1.2.12.7
MATERIAL, HF-2 CLASS FOAMED 1.2.12.8
MATERIAL, V-0 CLASS 1.2.12.2
MATERIAL, V-1 CLASS 1.2.12.3
MATERIAL, V-2 CLASS 1.2.12.4
MATERIAL, VTM-0 CLASS 1.2.12.12
MATERIAL, VTM-1 CLASS 1.2.12.13
MATERIAL, VTM-2 CLASS 1.2.12.14
NETWORK, TELECOMMUNICATION 1.2.13.8
OPERATOR 1.2.13.7
PART, DECORATIVE 1.2.6.5
PERSON, SERVICE 1.2.13.5
RANGE, RATED FREQUENCY 1.2.1.5
RANGE, RATED VOLTAGE 1.2.1.2
RATING, PROTECTIVE CURRENT 1.2.13.17
SUPPLY, AC MAINS 1.2.8.1
SUPPLY, DC MAINS 1.2.8.2
SUPPLY, MAINS 1.2.8.3
SURFACE, BOUNDING 1.2.10.3
TEST, ROUTINE 1.2.13.3
TEST, SAMPLING 1.2.13.2
TEST, TYPE 1.2.13.1
THERMOSTAT 1.2.11.1
TIME, RATED OPERATING 1.2.2.2
TIME, RATED RESTING 1.2.2.3
TISSUE, WRAPPING 1.2.13.16
TOOL 1.2.7.4
USER 1.2.13.6
VOLTAGE, DC. 1.2.13.4
VOLTAGE, HAZARDOUS 1.2.8.6
VOLTAGE, MAINS TRANSIENT 1.2.9.10
VOLTAGE, PEAK WORKING 1.2.9.8
VOLTAGE, RATED 1.2.1.1
VOLTAGE, REQUIRED WITHSTAND 1.2.9.9
VOLTAGE, RMS WORKING 1.2.9.7
VOLTAGE, TELECOMMUNICATION NETWORK TRANSIENT 1.2.9.11
VOLTAGE, WORKING 1.2.9.6
1.2.1 Equipment electrical ratings
1.2.1.1
RATED VOLTAGE
supply voltage (for a three-phase AC MAINS SUPPLY, the line-to-line voltage) as declared by the manufacturer
Contents of GB 4943.1-2011
Foreword I
Introduction VIII
0 Principles of Safety VIII
0.1 General Principles of Safety VIII
0.2 Hazards IX
0.3 Materials and Components XIV
1 General
1.1 Scope
1.2 Terms and Definitions
1.3 General Requirements
1.4 General Conditions for Tests
1.5 Components
1.6 Power Interface
1.7 Markings and Instructions
2 Protection from Hazards
2.1 Protection from Electric Shock and Energy Hazards
2.2 SELV Circuits
2.3 TNV Circuits
2.4 Limited Current Circuits
2.5 Limited Power Sources
2.6 Provisions for Earthing and Bonding
2.7 Overcurrent and Earth Fault Protection in Primary Circuits
2.8 Safety Interlocks
2.9 Electrical Insulation
2.10 Clearances, Creepage Distances and Distances through Insulation
3 Wiring, Connections and Supply
3.1 General
3.2 Connection to a Mains Supply
3.3 Wiring Terminals for Connection of External Conductors
3.4 Disconnection from the Mains Supply
3.5 Interconnection of Equipment
4 Physical Requirements
4.1 Stability
4.2 Mechanical Strength
4.3 Design and Construction
4.4 Protection against Hazardous Moving Parts
4.5 Thermal Requirements
4.6 Openings in Enclosures
4.7 Resistance to Fire
5 Electrical Requirements and Simulated Abnormal Conditions
5.1 Touch Current and Protective Conductor Current
5.2 Electric Strength
5.3 Abnormal Operating and Fault Conditions
6 Connection to Telecommunication Networks
6.1 Protection of Telecommunication Network Service Persons, and Users of Other Equipment Connected to the Network, from Hazards in the Equipment
6.2 Protection of Equipment Users from Overvoltages on Telecommunication Networks
6.3 Protection of the Telecommunication Wiring System from Overheating
7 Connection to Cable Distribution Systems
7.1 General
7.2 Protection of Cable Distribution System Service Persons, and Users of Other Equipment Connected to the System, from Hazardous Voltages in the Equipment
7.3 Protection of Equipment Users from Overvoltages on the Cable Distribution System
7.4 Insulation between Primary Circuits and Cable Distribution Systems
Annex A (Normative) Tests for Resistance to Heat and Fire
Annex B (Normative) Motor Tests Under Abnormal Conditions
Annex C (Normative) Transformers
Annex D (Normative) Measuring Instruments for Touch Current Tests
Annex E (Normative) Temperature Rise of A Winding
Annex F (Normative) Measurement of Clearances and Creepage Distances
Annex G (Normative) Alternative Method for Determining Minimum Clearances
Annex H (Normative) Ionizing Radiation
Annex J (Normative) Table of Electrochemical Potentials
Annex K (Normative) Thermal Controls
Annex L (Normative) Normal Load Conditions for Some Types of Electrical Business Equipment
Annex M (Normative) Criteria for Telephone Ringing Signals
Annex N (Normative) Impulse Test Generators
Annex P (Normative) Normative References
Annex Q (Normative) Voltage Dependent Resistors (VDRs)
Annex R (Informative) Examples of Requirements for Quality Control Programmes
Annex S (Informative) Procedure for Impulse Testing
Annex T (Informative) Guidance on Protection Against Ingress Of Water
Annex U (Normative) Insulated Winding Wires for Use Without Interleaved Insulation
Annex V (Normative) AC Power Distribution Systems
Annex W (Informative) Summation of Touch Currents
Annex X (Informative) Maximum Heating Effect in Transformer Tests
Annex Y (Normative) Ultraviolet Light Conditioning Test
Annex Z (Informative) Overvoltage Categories
Annex AA (Normative) Mandrel Test
Annex BB (Informative) Difference from GB 4943-
Annex CC (Informative) Comparison of Normative References/ Bibliography between IEC 60950-1:2005 and This Part
Annex DD (Normative) Instruction on New Safety Warning Sign in the Standard
Annex EE (Informative) Cross-reference of the Safety-Related Description Examples Written in Chinese, Tibetan, Mongolian, Zhuang and Uyghur languages .
Bibliography
Figure 2A Test Finger
Figure 2B Test Pin
Figure 2C Test Probe
Figure 2D Accessibility of Internal Conductive Parts
Figure 2E Voltages in SELV Circuits under Single Fault Conditions
Figure 2F Maximum Voltages Permitted after a Single Fault
Figure 2G Test Generator
Figure 2H Examples of Application of Insulation
Figure 2J Thermal Ageing Time
Figure 2K Abrasion Resistance Test for Coating Layers
Figure 4A Impact Test Using a Steel Ball
Figure 4B Examples of Cross-sections of Designs of Openings Preventing Vertical Access
Figure 4C Examples of Louvre Design
Figure 4D Enclosure Openings
Figure 4E Typical Bottom of a Fire Enclosure for Partially Enclosed Component or Assembly
Figure 4F Baffle Plate Construction
Figure 5A Test Circuit for Touch Current of Single-phase Equipment on a Star TN or TT Power Supply System
Figure 5B Test Circuit for Touch Current of Three-phase Equipment on a Star TN or TT Power Supply System
Figure 6A Test for Separation between a Telecommunication Network and Earth
Figure 6B Application Points of Test Voltage
Figure B.1 Determination of Arithmetic Average Temperature
Figure C.1 Determination of Arithmetic Average Temperature
Figure D.1 Measuring Instrument
Figure D.2 Alternative Measuring Instrument
Figure F.1 Narrow Groove
Figure F.2 Wide Groove
Figure F.3 V-shaped Groove
Figure F.4 Rib
Figure F.5 Uncemented Joint with Narrow Groove
Figure F.6 Uncemented Joint with Wide Groove
Figure F.7 Uncemented Joint with Narrow and Wide Grooves
Figure F.8 Narrow Recess
Figure F.9 Wide Recess
Figure F.10 Coating around Terminals
Figure F.11 Coating over Printed Wiring
Figure F.12 Measurements through Openings in Enclosures
Figure F.13 Intervening, Unconnected Conductive Part
Figure F.14 Solid Insulating Material
Figure F.15 Thin Sheet Insulating Material
Figure F.16 Cemented Joints in Multi-Layer Printed Board
Figure F.17 Component Filled with Insulating Compound
Figure F.18 Partitioned Bobbin
Figure M.1 Definition of Ringing Period and Cadence Cycle
Figure M.2 ITS1 Limit Curve for Cadenced Ringing Signal
Figure M.3 Peak and Peak-To-Peak Currents
Figure M.4 Ringing Voltage Trip Criteria
Figure N.1 ITU-T Impulse Test Generator Circuit
Figure N.2 GB 8898 Impulse Test Generator Circuit
Figure S.1 Waveform on Insulation Without Surge Suppressors and No Breakdown
Figure S.2 Waveforms on Insulation During Breakdown Without Surge Suppressors
Figure S.3 Waveforms on Insulation With Surge Suppressors in Operation
Figure S.4 Waveform on Short-Circuited Surge Suppressor and Insulation
Figure V.1 Examples of TN-S Power Distribution Systems
Figure V.2 Example of TN-C-S Power Distribution System
Figure V.3 Example of TN-C Power Distribution System
Figure V.4 Example of Single-Phase, Three-Wire TN-C Power Distribution System
Figure V.5 Example of Three Line and Neutral TT Power Distribution System
Figure V.6 Example of Three Line TT Power Distribution System
Figure V.7 Example of Three Line (and Neutral) IT Power Distribution System
Figure V.8 Example of Three Line IT Power Distribution System
Figure W.1 Touch Current from A Floating Circuit
Figure W.2 Touch Current from An Earthed Circuit
Figure W.3 Summation of Touch Currents in a PABX
Figure AA.1 Mandrel
Figure AA.2 Initial Position of Mandrel
Figure AA.3 Final Position of Mandrel
Figure AA.4 Position of Metal Foil on Insulating Material
Table 1A Voltage Ranges of SELV and TNV Circuits
Table 1B Equivalence of Flammability Classes
Table 1C Capacitor Ratings According to GB/T
Table 1D Informative Examples of Application of Capacitors
Table 2A Distance through Insulation of Internal Wiring
Table 2B Limits for Power Sources without an Overcurrent Protective Device
Table 2C Limits for Power Sources with an Overcurrent Protective Device
Table 2D Minimum Size of Protective Bonding Conductors
Table 2E Test Duration, a.c. Mains Supplies
Table 2F Examples of Protective Devices in Single-Phase Equipment or Subassemblies
Table 2G Examples of Protective Devices in Three-Phase Equipment
Table 2H Examples of Application of Insulation
Table 2J AC Mains Transient Voltages
Table 2K Minimum Clearances for Insulation in Primary Circuits and between Primary and Secondary Circuits (Applicable to Those to be Operated below 2 000 m above the Sea Level)
Table 2L Additional Clearances in Primary Circuits (Applicable to Those to be Operated below 2 000 m above the Sea Level)
Table 2M Minimum Clearances in Secondary Circuits (Applicable to Those to be Operated below 2 000 m above Sea Level)
Table 2N Minimum Creepage Distances
Table 2P Tests for Insulation in Non-separable Layers
Table 2Q Minimum Separation Distances for Coated Printed Boards
Table 2R Insulation in Printed Boards
Table 3A Sizes of Cables and Conduits for Equipment Having a Rated Current not Exceeding 16 A
Table 3B Sizes of Conductors
Table 3C Physical Tests on Power Supply Cords
Table 3D Range of Conductor Sizes to be Accepted by Terminals
Table 3E Sizes of Terminals for Mains Supply Conductors and Protective Earthing Conductors a
Table 4A Minimum Property Retention Limits after UV Exposure
Table 4B Temperature Limits, Materials and Components
Table 4C Touch Temperature Limits
Table 4D Size and Spacing of Openings in Metal Bottoms of Fire Enclosures
Table 4E Summary of Material Flammability Requirements
Table 5A Maximum Current
Table 5B Test Voltages for Electric Strength Tests Based on Peak Working Voltages
Table 5C Test Voltages for Electric Strength Tests Based on Required Withstand Voltages
Table 5D Temperature Limits for Overload Conditions
Table B.1 Temperature Limits for Motor Windings (Except for Running Overload Test)
Table B.2 Permitted Temperature Limits for Running Overload Tests
Table C.1 Temperature Limits for Transformer Windings
Table F.1 Value of X
Table G.1 AC Mains Transient Voltages
Table G.2 Minimum Clearances up to 2 000 m Above Sea Level
Table J.1 Electrochemical Potentials (V)
Table N.1 Component values for Figures N.1 and N
Table R.1 Rules for Sampling and Inspection—Coated Printed Boards
Table R.2 Rules for Sampling and Inspection—Reduced Clearances
Table T.1 Extract from GB
Table U.1 Mandrel Diameter
Table U.2 Oven Temperature
Table X.1 Test Steps
Table Z.1 Overvoltage Categories
