Detail of GB 4793.1-2007

Introduction of GB 4793.1-2007

1 Scope and object 1.1 Scope 1.1.1 Equipment included in scope This part of GB 4793 specifies general safety requirements for electrical equipment intended for professional, industrial process, and educational use, any of which may incorporate computing devices, as defined in a) to d) below, when used under the environmental conditions of 1.4. a) Electrical test and measurement equipment This is equipment which by electrical means tests, measures, indicates or records one or more electrical or non-electrical quantities, also non-measuring equipment such as signal generators, measurement standards, power supplies, transducers, transmitters, etc. Note: All indicating and recording electrical measuring instruments (except those excluded in 1.1.2) fall within the scope of GB 4793 unless they are panel meters designed only for building-in to other equipment. Built-in panel meters are considered to be components and only need to meet the relevant requirements of GB 4793, or other standards, as part of the equipment into which they are built. b) Electrical control equipment This is equipment which controls one or more output quantities to specific values, with each value determined by manual setting, by local or remote programming, or by one or more input variables. c) Electrical laboratory equipment This is equipment which measures, indicates, monitors or analyses substances, or is used to prepare materials, and includes in vitro diagnostic (IVD) equipment. This equipment may also be used in areas other than laboratories, for example self-test IVD equipment may be used in the home. d) Accessories intended for use with the above (for example, sample handling equipment). 1.1.2 Equipment excluded from scope This standard does not apply to equipment within the scope of a) GB 8898 (Safety requirements for audio, video and similar electronic apparatus); b) GB 4706 (Safety of household and similar electrical appliances); c) GB 4943 (Safety of information technology equipment, except as specified in 1.1.3); d) GB 9706 (Medical electrical equipment); e) GB/T 15283 (Class 0.5, 1 and 2 alternating current watthour meters); f) GB 19212 (Power transformers, power supply units and similar); g) IEC 60204 (Controls for electrical machines); h) IEC 60364 (Electrical installations of buildings); i) IEC 60439-1 (Low-voltage switchgear and controlgear assemblies). 1.1.3 Computing equipment This standard applies only to computers, processors, etc. which form part of equipment within the scope of this standard or are designed for use exclusively with the equipment. Note: Computing devices and similar equipment within the scope of GB 4943 and conforming to its requirements are considered to be suitable for use with equipment within the scope of this standard. However, some of the requirements of GB 4943 for resistance to moisture and liquids are less stringent than those in this standard. If hazards from moisture or liquids could affect equipment that conforms to GB 4943 and is used with equipment which conforms to this standard, the instructions for use should specify any additional precautions required. 1.2 Object 1.2.1 Aspects included in scope The purpose of the requirements of this part is to ensure that the design and methods of construction used provide adequate protection for the operator and the surrounding area against a) electric shock or burn (see clause 6); b) mechanical hazards (see clauses 7 and 8); c) excessive temperature (see clauses 9 and 10); d) spread of fire from the equipment (see clause 9); e) effects of fluids and fluid pressure (see clause 11); f) effects of radiation, including lasers sources, and sonic and ultrasonic pressure (see clause 12); g) liberated gases, explosion and implosion (see clause 13). Note: Attention is drawn to the existence of additional requirements which may be specified by national authorities responsible for the health and safety of labour forces.

Contents of GB 4793.1-2007

Foreword i Introduction iii 1 Scope and object 1.1 Scope 1.1.1 Equipment included in scope 1.1.2 Equipment excluded from scope 1.1.3 Computing equipment 1.2 Object 1.2.1 Aspects included in scope 1.2.2 Aspects excluded from scope 1.3 Verification 1.4 Environmental conditions 1.4.1 Normal environmental conditions 1.4.2 Extended environmental conditions 2 Normative references 3 Terms and definitions 3.1 Equipment and states of equipment 3.2 Parts and accessories 3.3 Electrical quantities 3.4 Tests 3.5 Safety terms 3.6 Insulation 4 Tests 4.1 General 4.2 Sequence of tests 4.3 Reference test conditions 4.3.1 Environmental conditions 4.3.2 State of equipment 4.4 Testing in single fault condition 4.4.1 General 4.4.2 Application of fault conditions 4.4.3 Duration of tests 4.4.4 Conformity after application of fault conditions 5 Marking and documentation 5.1 Marking 5.1.1 General 5.1.2 Identification 5.1.3 Mains supply 5.1.4 Fuses 5.1.5 Terminals, connections and operating devices 5.1.6 Switches and circuit-breakers 5.1.7 Equipment protected by double insulation or reinforced insulation 5.1.8 Field-wiring terminal boxes 5.2 Warning markings 5.3 Durability of markings 5.4 Documentation 5.4.1 General 5.4.2 Equipment ratings 5.4.3 Equipment installation 5.4.4 Equipment operation 5.4.5 Equipment maintenance 6 Protection against electric shock 6.1 General 6.1.1 Requirements 6.1.2 Exceptions 6.2 Determination of accessible parts 6.2.1 Examination 6.2.2 Openings above parts that are hazardous live 6.2.3 Openings for pre-set controls 6.3 Permissible limits for accessible parts 6.3.1 Values in normal condition 6.3.2 Values in single fault condition 6.4 Protection in normal condition 6.5 Protection in single fault condition 6.5.1 Protective bonding 6.5.2 Double insulation and reinforced insulation 6.5.3 protective impedance 6.5.4 Automatic disconnection of the supply 6.6 Connections to external circuits 6.6.1 General 6.6.2 Terminals for external circuits 6.6.3 Circuits with terminals which are hazardous live 6.6.4 Accessible terminals for stranded conductors 6.7 Clearances and creepage distances 6.7.1 General requirements 6.7.2 Mains circuits 6.7.3 Circuits other than mains circuits 6.7.4 Measuring circuits 6.8 Procedure for dielectric strength tests 6.8.1 Reference test earth 6.8.2 Humidity preconditioning 6.8.3 Conduct of tests 6.8.4 Voltage tests 6.9 Constructional requirements for protection against electric shock 6.9.1 General 6.9.2 Enclosures of equipment with double insulation or reinforced insulation 6.9.3 Over-range indication 6.10 Connection to mains supply source and connections between parts of equipment 6.10.1 Mains supply cords 6.10.2 Fitting of non-detachable mains supply cords 6.10.3 Plugs and connectors 6.11 Disconnection from supply source 6.11.1 General 6.11.2 Requirements according to type of equipment 6.11.3 Disconnecting devices 7 Protection against mechanical hazards 7.1 General 7.2 Moving parts 7.3 Stability 7.4 Provisions for lifting and carrying 7.5 Wall mounting 7.6 Expelled parts 8 Mechanical resistance to shock and impact 8.1 Enclosure rigidity test 8.1.1 Static test 8.1.2 Dynamic test 8.2 Drop test 8.2.1 Equipment other than hand-held equipment and direct plug-in equipment 8.2.2 Hand-held equipment and direct plug-in equipment 9 Protection against the spread of fire 9.1 Eliminating or reducing the sources of ignition within the equipment 9.2 Containment of fire within the equipment, should it occur 9.2.1 Constructional requirements 9.3 Limited-energy circuit 9.4 Requirements for equipment containing or using flammable liquids 9.5 Overcurrent protection 9.5.1 Permanently connected equipment 9.5.2 Other equipment 10 Equipment temperature limits and resistance to heat 10.1 Surface temperature limits for protection against burns 10.2 Temperatures of windings 10.3 Other temperature measurements 10.4 Conduct of temperature tests 10.4.1 Temperature measurement of heating equipment 10.4.2 Equipment intended for installation in a cabinet or a wall 10.5 Resistance to heat 10.5.1 Integrity of clearances and creepage distances 10.5.2 Non-metallic enclosure 10.5.3 Insulating material 11 Protection against hazards from fluids 11.1 General 11.2 Cleaning 11.3 Spillage 11.4 Overflow 11.5 Battery electrolyte 11.6 Specially protected equipment 11.7 Fluid pressure and leakage 11.7.1 Maximum pressure 11.7.2 Leakage and rupture at high pressure 11.7.3 Leakage from low-pressure parts 11.7.4 Overpressure safety device 12 Protection against radiation, including laser sources, and against sonic and ultrasonic pressure 12.1 General 12.2 Equipment producing ionizing radiation 12.2.1 Ionizing radiation 12.2.2 Accelerated electrons 12.3 Ultraviolet (UV) radiation 12.4 Microwave radiation 12.5 Sonic and ultrasonic pressure 12.5.1 Sound level 12.5.2 Ultrasonic pressure 12.6 Laser sources 13 Protection against liberated gases, explosion and implosion 13.1 Poisonous and injurious gases 13.2 Explosion and implosion 13.2.1 Components 13.2.2 Batteries and battery charging 13.2.3 Implosion of cathode ray tubes 13.2.4 Equipment rated for high pressures 14 Components 14.1 General 14.2 Motors 14.2.1 Motor temperatures 14.2.2 Series excitation motors 14.3 Overtemperature protection devices 14.4 Fuse holders 14.5 Mains voltage selecting devices 14.6 High integrity components 14.7 Mains transformers tested outside equipment 14.8 Printed circuit boards 14.9 Circuits or components used as transient overvoltage limiting devices 15 Protection by interlocks 15.1 General 15.2 Prevention of reactivating 15.3 Reliability 16 Test and measurement equipment 16.1 Current measuring circuits 16.2 Multifunction meters and similar equipment Annex A (Normative) Measuring circuits for accessible current (see 6.3) Annex B (Normative) Standard test finger (see 6.2) Annex C (Normative) Measurement of clearances and creepage distances Annex D (Normative) Parts between which insulation requirements are specified (see 6.4 and 6.5.2) Annex E (Normative) Reduction of pollution degrees Annex F (Normative) Routine tests Annex G (Informative) Leakage and rupture from fluids under pressure Bibliography Figure 1 Maximum duration of short-term temporary accessible voltages in single fault condition [see 6.3.2 a)]………………………………………………………………….. Figure 2 Charged capacitance level in normal condition and single fault condition [see 6.3.1 c) and 6.3.2 c)] 37_Toc26945_Toc Figure 3 Detachable mains supply cords and connections Figure 4 Impact test using sphere Figure 5 Flow chart to explain the requirements for protection against the spread of fire Figure 6 Baffle Figure 7 Area of the bottom of an enclosure to be constructed as specified in 9.2.1 b) 1) Figure 8 Ball-pressure test apparatus Figure 9 Ratio between hydraulic test pressure and rated maximum working pressure Figure 10 Flow chart for conformity options 14.1 a), b), c) and d) Figure A.1 Measuring circuit for a.c. with frequencies up to 1MHz and for d.c. Figure A.2 Measuring circuits for a.c. with sinusoidal frequencies up to 100Hz and for d.c. Figure A.3 Current measuring circuit for electrical burns Figure A.4 Current measuring circuit for wet contact Figure B.1 Rigid test finger (test probe 11 of GB/T 16842) Figure B.2 Jointed test finger (test probe B of GB/T 16842) Figure C.1 Examples of methods of measuring clearance and creepage distance Figures D.1 a) to D.1 d) Protection between hazardous live circuits and circuits not exceeding the values of 6.3.2 in normal condition and having external terminals of accessible parts Figures D.1 e) to D.1 h) Protection between hazardous live circuits and other circuits which do not exceed the values of 6.3.2 in normal condition and which have external terminals Figure D.2 a) and D.2 b) Protection from a hazardous live internal circuit for an accessible part which is not bonded to other accessible) parts Figure D.2 c) and D.2 d) Protection from a hazardous live primary circuit for accessible terminals of a secondary circuit which does not exceed the values of 6.3.2 in normal condition Figure D.3 Protection of external accessible terminals of two hazardous live circuits Figure G.1 Conformity verification process (see G.2) Table 1 Symbols Table 2 Tightening torque for screw assemblies Table 3 Multiplication factors for clearance for altitudes up to 5 000m Table 4 Clearances and creepage distances for mains circuits Table 5 Clearances for circuits derived from mains circuits Table 6 Clearance values for the calculation of 6.7. Table 7 Creepage distances Table 8 Clearances for measurement categories II, III and IV Table 9 Test voltages for basic insulation Table 10 Correction factors for test voltage according to test site altitude Table 11 Physical tests on power supply cords Table 12 Acceptable perforation of the bottom of an enclosure Table 13 Limits of maximum available current Table 14 Overcurrent protective device Table 15 Surface temperature limits in normal condition Table 16 Insulation material of windings Table 17 Impulse withstand voltages Table 18 Output impedance for impulse generators Table C.1 Pollution degree table Table E.1 Reduction of the pollution degree of internal environment through the use of additional protection Table G.1 Test pressures for equipment with pressures above 14MPa