Safety distance includes electrical clearance (spatial distance), creepage distance (creepage distance) and insulation penetration distance
Electric clearance: the shortest distance measured along the air between two adjacent conductors or a conductor and the surface of the adjacent motor casing.
Creepage distance: The shortest distance between two adjacent conductors or one conductor and the surface of the adjacent motor casing measured along the insulating surface.
1. The decision of electrical clearance:
But usually: primary AC part: L—N≥2.5mm before the fuse, L.N PE (earth)≥2.5mm, no requirement after the fuse is installed, but as far as possible to keep a certain distance to avoid short-circuit damage to the power supply.
Primary side AC to DC part ≥2.0mm
Primary side DC ground to earth ≥2.5mm (primary side floating ground to earth) Primary side part to secondary side part ≥4.0mm, the gap gap of the secondary side part of the component connected between the primary and secondary sides ≥ 0.5mm is enough for the secondary side ground to the earth ≥1.0mm
Note: Before deciding whether to meet the requirements, the internal parts should be applied with a force of 10N, and the outer shell should be applied with a force of 30N to reduce the distance, so that the space distance still meets the requirements in the worst case.
2. Determination of creepage distance:
According to the working voltage and insulation level, check table 6 can determine its creepage distance
But usually:
(1) Primary AC part: L—N≥2.5mm before the fuse, L.N earth≥2.5mm, after the fuse, no requirement is required, but try to keep a certain distance to avoid short-circuit damage to the power supply.
(2) The AC to DC part of the primary side≥2.0mm
(3), primary side direct current ground to ground≥4.0mm, such as primary side ground to ground
(4), the primary side to the secondary side ≥6.4mm, such as optocouplers, Y capacitors and other component parts with foot spacing ≤6.4mm should be slotted.
(5) ≥0.5mm between the secondary side parts is enough
(6), the secondary side ground to the ground ≥ 2.0mm or more
(7) Between the two stages of the transformer ≥8.0mm
PCBA processing
3. Insulation penetration distance:
According to the working voltage and insulation application, the following regulations should be met:
——The working voltage does not exceed 50V (71V AC peak value or DC value), and there is no thickness requirement;
——The minimum thickness of additional insulation should be 0.4mm;
——When the reinforced insulation does not withstand any mechanical stress that may cause deformation or performance degradation of the insulating material under normal temperature, the minimum thickness of the reinforced insulation should be 0.4mm.
If the insulation provided is used in the protective enclosure of the equipment and will not be bumped or scratched during maintenance by the operator, and falls under any of the following conditions, the above requirements do not apply to thin-layer insulation materials regardless of their thickness ；
-For supplementary insulation, at least two layers of materials are used, each of which can pass the electrical strength test for supplementary insulation; or:
——Additional insulation composed of three layers of materials, of which any combination of two layers of materials can pass the electrical strength test of the additional insulation; or:
——For reinforced insulation, use at least two layers of materials, each of which can pass the electrical strength test for reinforced insulation; or:
——Reinforced insulation composed of three layers of insulating materials, of which any combination of two layers of materials can pass the electrical strength test of the reinforced insulation.