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Safety requirements between PCBA board and housing
Source: | Author: | Add time: 2019-03-14 | | Share to:
Safety distance includes electrical clearance (spatial distance), creepage distance (creep distance) and insulation penetration distance

Safety distance includes electrical clearance (spatial distance), creepage distance (creep distance) and insulation penetration distance

Clearance: The shortest distance measured by air between two adjacent conductors or one conductor and the surface of an adjacent motor case.

Creepage distance: the shortest distance between two adjacent conductors or one conductor and the surface of an adjacent motor case measured along an insulated surface.

1. Decision of electrical clearance:

According to the measured working voltage and insulation level, the distance clearance requirements of the primary line can be determined. See Table 3 and Table 4. The clearance clearance requirements of the secondary line are shown in Table 5.

But usually: Primary AC part: L—N≥2.5mm in front of fuse, L.N PE (earth) ≥2.5mm, there is no requirement after fuse is installed, but keep a certain distance as far as possible to avoid short circuit damage to power supply.

Primary side AC to DC part ≥2.0mm

Primary side DC ground to ground ≥ 2.5mm (primary side floating ground to ground) Primary side to secondary side ≥ 4.0mm, the gap clearance of the secondary side of the component across the primary and secondary sides ≥ 0.5mm can be secondary side to ground ≥ 1.0mm

Note: Before deciding whether to meet the requirements, the internal parts should be applied with a force of 10N and the shell with a force of 30N to reduce the distance, so that in the worst case, the space distance still meets the requirements.

2, the decision of the 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 fuse, L.N earth ≥2.5mm, there is no requirement after fuse, but try to keep a certain distance to avoid short circuit damage to power

(2) Primary AC to DC section ≥2.0mm

(3) DC primary ground to ground ≥ 4.0mm, such as primary ground to earth

(4). Primary side to secondary side ≥ 6.4mm, such as photocoupler, Y capacitor, and other component parts with a pitch of ≤ 6.4mm should be slotted.

(5) ≥0.5mm between the secondary parts

(6), secondary side to ground ≥ 2.0mm

(7) ≥8.0mm between two levels of transformer

3. Insulation penetration distance:

The following requirements should be met according to the working voltage and insulation application:

——For working voltage not exceeding 50V (71V AC peak or DC value), no thickness requirement;

-The minimum thickness of additional insulation shall be 0.4 mm;

——When the reinforced insulation does not withstand any mechanical stress that may cause the insulation material to deform or reduce its performance at normal temperature, the minimum thickness of the reinforced insulation shall be 0.4mm.

The above requirements do not apply to thin-layer insulation materials regardless of their thickness if the insulation provided is used inside the equipment's protective enclosure and is not subject to bumps or abrasions during maintenance by the operator, and is one of the following: ;

-For additional insulation, use at least two layers of material, each of which can pass the electrical strength test of the additional insulation; or

—— supplementary insulation consisting of three layers of materials, in which any combination of two layers of materials can pass the dielectric 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 of reinforced insulation; or:

——Reinforced insulation composed of three layers of insulating materials, where any combination of two layers of materials can pass the electrical strength test of reinforced insulation.