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PCBA Board And The Shell Between The Requirements
Jan 29, 2018

  PCBA board safety clearances include clearance (space distance), creepage distance (creepage distance) and insulation penetration distance

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

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

1, the decision of clearance:

According to the measurement of the operating voltage and insulation level, you can determine the distance from the primary side of the gap size requirements, see Table 3 and Table 4 secondary side of the gap size requirements in Table 5

But usually: Primary side AC part: L-N≥2.5mm before fuse, L.NPE (earth) ≥2.5mm, not required after fuse installation, but keep a certain distance as far as possible to avoid short circuit and damage the power supply.

Primary side of the AC part of the DC ≥ 2.0mm

Primary side of the ground ≥ 2.5mm DC (primary floating ground on the ground) primary part of the secondary side of the Ministry of ≥ 4.0mm, across the secondary side between the secondary part of the gap between the electrical gap ≥ 0.5mm to the secondary side of the earth can be ≥ 1.0mm

Note: Before deciding whether the requirements are met, the internal parts should be applied with 10N force and the shell with 30N force to reduce the distance. In the worst case, the space distance still meets the requirement.

2, the decision of creepage distance:

According to the working voltage and insulation level, look-up table 6 can determine the creepage distance

But usually:

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

(2), on the primary side of the DC part of ≥ 2.0mm

(3), the primary side of DC ≥ 4.0mm on the ground as a side to the ground

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

(5), between the secondary side of ≥ 0.5mm can be

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

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

3, Insulation penetration distance:

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

- The working voltage does not exceed 50V (71V AC peak or DC value), no thickness requirements;

- Additional insulation minimum thickness should be 0.4mm;

- The minimum thickness of reinforced insulation shall be 0.4 mm when the reinforced insulation is not subject to any mechanical stress that may cause deformation or deterioration of the insulation under normal temperatures.

The above requirements do not apply to thin insulating materials regardless of their thickness if the insulation provided is used in a protective device enclosure and is not subject to bump or abrasion when maintained by the operator and falls under any of the following conditions ;

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

- Additional insulation consisting of three layers of material, of which the combination of any two layers of material is capable of passing the additional dielectric strength test; or:

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

- Reinforced insulation consisting of three layers of insulating material, of which the combination of any two layers of material passes the dielectric strength test of reinforced insulation.