Safety distance includes electrical clearance (space distance), creepage distance (distance along the surface) and insulation penetration distance
1, electrical clearance: two adjacent conductors or a conductor and the surface of the adjacent motor casing along the shortest distance measured along the air. 2, creepage distance: two neighboring conductors or a conductor and the surface of the adjacent motor casing along the insulation surface measurement of the shortest distance.
The decision of the electrical clearance:
According to the measurement of the operating voltage and insulation level, you can decide the distance
The secondary side of the line of the electrical clearance dimensional requirements of the primary side of the line of the electrical clearance dimensional requirements, see Table 3 and Table 4, but usually: the primary side of the AC portion of the: before the fuse L - N ≥ 2.5mm, L.N PE (earth) ≥ 2.5mm, after the fuse device can not
requirements, but as far as possible to maintain a certain distance in order to avoid short-circuit damage to the power supply. Primary AC to DC part ≥ 2.0mm
Primary DC ground to earth ≥ 2.5mm (primary floating ground to earth)
Primary part of the secondary swashbuckling frame? .0mm, across the primary and secondary side of the components between
Secondary side of the part of the gap gap ≥ 0.5mm
Secondary side of the earth to earth ≥ 1.0mm Note: To determine whether to comply with the requirements of the internal parts should be applied to the internal parts of the 10N force, the shell applied to the 30N force, in order to reduce the distance between them, so as to confirm that the worst
case, the distance between the space still The distance between the space and the housing should be reduced so that in the worst case scenario, the space distance is still in compliance.
Creepage distance decision:
According to the working voltage and insulation level, check Table 6 to determine the creepage distance
But usually: (1), the primary side of the AC part: L - N ≥ 2.5mm before the fuse, L.N ≥ 2.5mm to the earth, the fuse can not be done after the requirements,
but try to maintain a certain distance to avoid short-circuit damage to the power supply. distance to avoid short-circuit damage to the power supply.
(2), the primary side of the AC to DC part ≥ 2.0mm (3), the primary side of the DC ground to ground ≥ 4.0mm, such as the primary side of the ground to the earth (4), the primary side of the secondary side of the ≥ 6.4mm, such as optocouplers, Y capacitors and other meta parts of the foot spacing ≤ 6.4mm to be slotted.
(5), the secondary side of the part between ≥ 0.5mm can be
(6), the secondary side of the ground to the earth ≥ 2.0mm or more
(7), between the two levels of the transformer ≥ 8.0mm or more
3, the insulation penetration distance:
Should be based on the operating voltage and the insulation application of the occasion in accordance with the following provisions:
-For working voltage not exceeding 50V (71V AC peak or DC value), there is no thickness requirement;
-The minimum thickness of additional insulation shall be 0.4mm;
-For working voltage not exceeding 50V (71V AC peak or DC value), there is no thickness requirement -When the reinforced insulation is not subjected to any mechanical stress that may cause deformation or degradation of the insulation at normal temperatures, the minimum thickness of the reinforced insulation shall be 0.4 mm.
The above requirements do not apply to thin layers of insulation regardless of thickness if the insulation provided is used within the protective enclosure of the equipment and is not subject to knocks or abrasions during maintenance by the operator and if either of the following applies material is capable of passing the electrical strength resistance test for additional insulation; or:
-- For additional insulation consisting of three layers of material, where any combination of two layers of material is capable of passing the electrical strength resistance test for additional insulation; or:
-- For reinforced insulation, at least two layers of material are used, each of which is capable of passing the electrical strength test for reinforced insulation; or:
--Reinforced insulation consisting of three layers of insulating material, where any combination of two layers of material is capable of passing the electrical strength test for reinforced insulation.
4, there are wiring process notes:
Such as capacitors and other flat paste components, must be flat paste, do not need to spot glue
Such as the two conductors in the application of 10N force can be made to shorten the distance, less than the distance requirements of the safety regulations, you can spot glue to fix the part to ensure that its electrical clearance.
Some of the shell equipment laying PVC film, should pay attention to ensure that the safety distance (pay attention to the processing technology)
Parts of the dispensing of glue fixed to pay attention to the PCB board can not be made to have a glue wire and other foreign objects.
When processing parts, should not cause insulation damage.
5, on the requirements of flame-proof materials: heat shrinkable tubing V-1 or VTM -2 or more; PVC tubing V-1 or VTM -2 or more
Teflon tubing V-1 or VTM -2 or more; plastic materials such as silicone or other materials. V-1 or VTM -2 or more; plastic materials such as silicone sheet, insulating tape V-1 or VTM -2 or more PCB board 94V-1 or more
6, about the insulation level (1), working insulation: the insulation required for the normal operation of the equipment
(2), the basic insulation: the insulation to provide basic protection against electric shock (3), additional insulation: in addition to the basic insulation is applied to the independent insulation, to protect the basic insulation once the failure of electric shock can still be prevented
(4), double insulation: by the basic insulation plus the additional insulation constitutes the insulation
in the double insulation
the various types of insulation is applicable as follows.
A, operational insulationoprational insulation (5), reinforced insulation: a single insulation structure, under the conditions specified in this standard, the level of protection against electric shock provided by the equivalent
a, between the two different voltages of the parts of the
b, between the ELV circuit (or SELV circuit) and the grounded conductive parts. between ELV circuits (or SELV circuits) and grounded conductive parts.
B, basic insulation basic insulation a, between parts with dangerous voltage and grounded conductive parts;
b, between SELV circuits with dangerous voltage and dependent on grounding; c, between the primary side of the power supply conductor and the grounding shield or the core of the main power transformer;
d, as a part of the double insulation. part of the double insulation.
C, supplementary insulation a, in general, between the parts of the conductor that can be touched and the parts that may carry dangerous voltages after the damage of the basic insulation, such as:
Ⅰ, between the handle, knob, handle or the like, and its exterior and the ungrounded core.
Ⅱ, between the metal casing of a Class II device and the outer jacket of the power cord that passes through this casing.
Ⅲ, between the ELV circuit and the ungrounded metal housing.
b, as part of double insulation
D, double insulation
Double insulation Reinforced insulation
Generally, between the primary side of the circuit and
a, accessible ungrounded conductive parts, or
c. Between TNV circuits b, floating connections, TNV circuits b. circuits with floating SELV or
Double insulation = basic insulation + supplementary insulation
Note: ELV circuits: extra low voltage circuits
Secondary circuits in which the peak value of alternating current (AC) does not exceed 42.4V or the value of direct current (DC) does not exceed 60V, between or among conductors, under normal operating conditions. .
SELV circuit: Safety Extra Low Voltage circuit.
A secondary circuit properly designed and protected so that under normal conditions or under a single fault condition, the voltage between any two accessible parts,
as well as between any accessible part and the protective earth terminal of the equipment (for Class I equipment only), will not exceed the safe value.
TNV: Telecommunication Network Voltage Circuitry
Circuits that carry communication signals under normal operating conditions.