Article 71.  The allowable locking time of increased safety motors with cage-type rotors shall not be less than 5 seconds, except where it is apparent that the temperature of windings of motors will not exceed by a protective device the temperature corresponding to the allowable locking time.

2. The motors under the provision of the preceding para. shall attach a label indicating an allowable locking time and an allowable locking current, in addition to the items given in para.1(excluding item 3), Article 4.

Article 72.  Transformers (excluding measuring transformers in which low voltage circuits are grounded) used for transformation between a high voltage and a low voltage shall have an isolating screen between the high and low voltage winding.

2. The provision of the preceding para. applies mutatis mutandis to the transformers used for transformation between a low voltage exceeding 300 volts and a low voltage up to 300 volts.

Article 73.  Circuit-breakers and switches and controllers which are used in d.c.circuits shall not be of protection 'oil-immersion' type.

Article 74.  Disconnecting switches shall be so constructed that all of the blades are made and broken by a single operating action and that the on-off condition of the switches is discernible from the outside.

2. The disconnecting switches under the preceding para. shall be interlocked with the relevant power switches so that load current cannot be broken, or their operating parts shall be shrouded.

Article 75.  Flameproof and pressurized fuses shall be those which do not have a possibility of increasing the internal pressure, resulting from the melting of fuses, such as cartridge fuses filled with arc-distinguishing medium, etc.

2. Oil-immersed fuses shall not be used for purposes other than the protection of high voltage circuits of measuring or controlling transformers.

3. The fuses under the preceding para. shall have a rated current and voltage not exceeding 6 amperes and 6,900 volts, respectively, and shall be of enclosed type.

Article 76.  Liquid resistors shall be of protection 'increased safety' type, and comply with the following requirements:

(1) They shall be fitted with a liquid-level indicator.

(2) Parts which may be corroded by the liquid shall use anti-corrosive insulating materials.

(3) Oil-exhaust devices shall be so constructed that no oil leaks occur.

(4) Screws used for oil-exhaust devices shall be shrouded and provided with fittings against loosening.

Article 77.  Increased safety semiconductor-rectifiers shall not produce any sparks or arcs when the elements have caused faults, and the temperature-rise of the parts to which gases and vapours may have access shall not exceed the values given in Article 13.

Article 78.  Batteries shall comply with the following requirements:

(1) Holes for gas exhaust shall be so constructed that the electrolyte will not spatter.

(2) The covering of cells shall be robustly constructed and the cell shall be contained in a case.

(3) The height of a case shall not be less than half the depth of a battery container, and a case shall be firmly fixed in a battery container.

(4) Creepage distances between cells placed side by side in a case shall not be less than 35 mm, and when the discharge voltage exceeds 24 volts, the distances shall be increased by 1 mm for every 2 volts exceeded.

(5) Batteries shall be housed in a separate case or provided with isolating walls within a case, for a unit of voltage not exceeding 50 volts. In the latter case, the height of walls shall not be less than half the depth of battery container.

Article 79.  Type of leading conductors from a terminal box to the body of flameproof measuring equipment which is used with the voltage and current not exceeding 250 volts a.c. or 110 volts d.c. and not exceeding 1 ampere, respectively, may be flameproof resin-sealing type.

Article 80.  Measuring equipment coming under the following cases may be of protection 'increased safety' type:

(1) Where the voltage or current circuits conform to one of the following items;
  a. They do not have any moving current-passing parts.
  b. Temperature-rise of any parts of measuring equipment, due to short circuits or faulted contacts, does not exceed the values given in Article 13 even if they have moving current-passing parts.

(2) Where power consumptions of glow-tubes, amplifying tubes and similar high vacuum tubes in measuring equipment do not exceed 100 volts-amperes.

(3) In a circuit, when turnover switches, resistance transmitters or rotary or sliding variable-resistors are made or broken, their sliding contacts are floated, or the resistance conductors are broken, and where circuit voltages, breaking currents and circuit inductances do not exceed 6 volts, 20 milliamperes and 0.1 henries, respectively, and capacitancesare not included, excluding the case involving gases and vapours of explosion class 3.

(4) Where the voltage of circuits having pure resistance only are 6 volts and the breaking current does not exceed 100 milliamperes, excluding the case involving gases and vapours of explosion class 3).

(5) Where the temperature-rise of power transformers in measuring equipment does not exceed the values given in Article 13.

Article 81. Increased safety measuring equipment shall comply with the following requirements:

(1) When current passing parts with a sectional area not exceeding 2.5 mm2 are connected, they shall be soldered.

(2) Where live parts of internal elements and circuits, which maximum working voltages are not higher than 220 volts, are insulated with insulation varnish, etc., the creepage distances and clearances shall not be less than 1.5 mm and 1 mm, respectively.

Article 82.  Lighting luminaires and pilot lamps, etc. shall be provided with a protective cover and guards, excluding those which are installed at locations where no damages to them are expected or those which are constructed not to suffer serious damages and provided with a protective cover.

2. The protective covers under the preceding para. shall comply with the following requirements:

(1) The materials of the covers shall be of good quality glass, except where synthetic plastics which are resistant to the maximum temperature expected during service and which are physically and chemically stable, are used for flashlights with cells, or for increased safety fluorescent or pilot lamps.

(2) A sufficient degree of safety shall be ensured in respect of the thickness, strength, gap between the lamp and the cover and so forth.

(3) The fixing parts shall not be threaded.

3. The guards under the provision of the preceding para.1 shall have a sufficient degree of safety in respect of the strength, size of grids, gaps between the lamp and the cover and so forth.

Article 83.  The temperature-rise of parts of lighting luminaires and plot lamps, etc. shall not exceed the limits of temperature-rise specified for the parts.

Article 84.  Unfixed luminaires shall comply with the following requirements:

(1) Parts leading unfixed cables to movable luminaires shall withstand a load of 150 N.

(2) Hand-carried flashlights with cells shall be those operated at a voltage not higher than 12 volts and with a capacity of not more than 40 volts-amperes.

(3) Cap lamps and inspection flashlights with cells shall be those operated at a voltage not higher than 6 volts and with a capacity not more than 7.5 volts-amperes.

Article 85.  Wall outlets and plugs shall comply with the following requirements:

(1) The wall outlets and plugs shall be so constructed that pulling-out and putting-in of the plugs are possible only when the switches concerned are interrupted.

(2) The grounding blade shall be so constructed that it is at least equivalent electrically and mechanically to the main blades, and that when the plugs are put in, the grounding blade is contacted earlier than or at the same time as the main blades.

(3) Unfixed conductors shall be the chloroprene cab-tire cables in which a conductor is used exclusively for grounding.

(4) Parts leading unfixed conductors to the plugs shall withstand a load of 150 N.