Safety distances include clearance (space distance), creepage distance (span distance) and insulation penetration distance
The decision of the clearance:
According to the measured working voltage and insulation level, the distance can be determined.
Clearance dimension requirements for primary side lines
Clearance dimension requirements for secondary side lines
usually:
Primary side AC part: L-N ≥ 2.5mm before the fuse, L.NPE (earth) ≥ 2.5mm, the fuse device can not be required afterwards, but keep a certain distance as far as possible 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)
The primary side part is ≥4.0mm on the secondary side part, and the component is connected between the secondary side
The gap of the secondary side can be ≥0.5mm
The secondary side can be ≥1.0mm on the earth
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.
Determine the clearance step
Determine the peak value and effective value of the working voltage;
Determining the supply voltage and power supply facility category of the equipment;
Determining the magnitude of the transient overvoltage entering the device based on the overvoltage category;
Determine the pollution level of the equipment (general equipment is pollution level 2);
Determine the type of insulation across the gap (functional insulation, basic insulation, additional insulation, reinforced insulation).
Determine clearance requirements
According to the measured working voltage and insulation level, look up the table (4943:2H and 2J and 2K, 60065-2001: Table 8 and Table 9 and Table 10). Retrieve the required clearance to determine the distance; as a clearance replacement Method, 4943 is replaced with Appendix G, and 60065-2001 is replaced with Appendix J.
GB 8898-2001: The main factor considered in the electrical clearance is the working voltage, as shown in Figure 9. (For components that are electrically connected to the grid power supply with a voltage effective value in the range of 220-250V, these values ​​are equal to those corresponding to the peak voltage of 354V: basic insulation 3.0mm, reinforced insulation 6.0mm)
Determine creepage distance and clearance notice
Movable components should be placed in the most unfavourable position;
The creepage distance value cannot be less than the clearance value;
Subject to mechanical stress testing; [2]
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