PCBA board between the shell and safety requirements

A safe distance from including the electrical clearance (distance), creepage distance (creepage distance) and insulation penetration distance

Clearance: two adjacent conductor or a conductor and adjacent the shortest distance along the air measurement on the surface of the motor housing.

Creepage distance: two adjacent conductor or a conductor and adjacent electricity on the surface of the casing along the shortest distance measuring insulation surface.

1, the decision of the clearance:

According to measuring the working voltage and insulation level, can be decided from a lateral line clearance size requirements, see table 3 and table 4 of secondary side line clearance size requirements are shown in table 5

But usually: a side ac parts: fuse before L – N acuity 2.5 mm, L.N PE (earth) or 2.5 mm, fuse 臵 later do not require, but as far as possible to keep a certain distance to avoid the damage of short-circuit power.

Primary side ac to dc part acuity 2.0 mm

Primary side dc to earth acuity 2.5 mm (primary side float grounding to the earth) primary side parts on the secondary side acuity 4.0 mm, crossover between the secondary side of some secondary side of components of electric acuity 0.5 mm gap clearance can be secondary side to earth acuity 1.0 mm

Note: before decide whether to conform to the requirements, the internal parts should be in 10 n force, shell with 30 n force, in order to reduce the distance, make the confirmation for the worst case, the space distance is still within the rules.

2, the decision of creepage distance:

According to the working voltage, and insulation level, table 6 May decide the creepage distance

But usually:

Part (1), a lateral communication: fuse before L – N acuity 2.5 mm, L.N earth acuity 2.5 mm, the fuse after do not require, but try to keep a certain distance to avoid the damage of short circuit power supply.

(2), a side ac to dc part acuity 2.0 mm

(3), a side dc ground-to-ground acuity 4.0 mm as a primary side of the earth

(4), a side of secondary side acuity 6.4 mm, such as optical coupling, Y capacitance components parts foot spacing of 6.4 mm or less to slot.

(5), acuity 0.5 mm between the secondary side part

(6), secondary side of the earth or more than 2.0 mm

(7), transformer between two levels of more than 8.0 mm or more

3, the penetration distance of insulation:

According to the working voltage and insulation applications meet the following requirements:

– working voltage is less than 50 v peak (71 v ac or dc value), no thickness requirements;

– additional insulation should be 0.4 mm minimum thickness;

– when the reinforced insulation not bear under normal temperature may lead to deformation of the insulating material or performance of any mechanical stress, the smallest of reinforced insulation thickness should be 0.4 mm.

If the insulation is provided with protection shell, and the operating personnel when maintenance will not be knock against or scratches, and belong to any kind of situation, the above requirement does not apply to regardless of their thickness of the thin layer of insulating material;

– for additional insulation, use at least two layers of material