Safety requirements between PCBA board and enclosure

Safety distances include clearance (space distance), creepage distance (span distance) and insulation penetration distance

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

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

1, the decision of the clearance:

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

But usually: the primary side AC part: L-N ≥ 2.5mm before the fuse, L.N PE (earth) ≥ 2.5mm, the fuse can be installed after the fuse is not required, but as far as possible to avoid a 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, bridging gap between the secondary side of the component between the secondary side ≥ 0.5mm can be used on the secondary side to the ground ≥1.0mm

Note: Before deciding whether the requirements are met, the internal parts should be applied to 10N force first, and the outer shell should be applied with 30N force to reduce the distance, so that the space distance is still in compliance with the regulations.

2. The decision of creepage distance:

According to the working voltage and insulation level, check the table 6 to determine the creepage distance

But usually:

(1), primary side AC part: L-N ≥ 2.5mm before the fuse, L.N earth ≥ 2.5mm, the fuse can not be required after, but try to keep a certain distance to avoid short circuit damage to the power supply.

(2), primary side AC to DC part ≥ 2.0mm

(3), the primary side of the DC ground to the ground ≥ 4.0mm, such as once to the ground to the earth

(4), the primary side to the secondary side ≥ 6.4mm, such as optocoupler, Y capacitor and other components of the foot spacing ≤ 6.4mm to be slotted.

(5), ≥0.5mm between the secondary side parts

(6), the second side of the ground to the earth ≥ 2.0mm or more

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

3. Insulation penetration distance:

The following provisions shall be complied with according to the operating voltage and insulation applications:

——The operating voltage does not exceed 50V (71V AC peak or DC value), no thickness requirement;

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

- When the reinforced insulation is not subjected to any mechanical stress at normal temperature which may cause deformation or performance degradation of the insulating material, the minimum thickness of the reinforced insulation shall be 0.4 mm.

If the insulation provided is used in the protective casing of the equipment and is not subject to bumps or abrasions during maintenance by the operator and is in any of the following cases, the above requirements do not apply to thin-layer insulation materials regardless of their thickness. ;

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

- additional insulation consisting of three layers of material, any combination of which can pass the test of the electrical strength of the additional insulation; or:

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

- reinforced insulation consisting of three layers of insulating material, any combination of which can pass the reinforced electrical strength test.