The page "PCB Process Design Specification" has shown, standardize the PCB process design of the product, specify the relevant parameters of the PCB process design, make the PCB design meet the technical specifications such as manufacturability, testability, safety, EMC, EMI, and build product process, technology, quality and cost advantages，this page talk about the distance and related safety requirements about PCB design.
1. Electric clearance: the shortest distance measured along with the air between two adjacent conductors or a conductor and the surface of the adjacent motor casing.
2. Creepage distance: the shortest distance between two adjacent conductors or one conductor and the surface of the adjacent motor casing measured along the insulating surface.
According to the measured working voltage and insulation level, the distance can be determined.
But usually: primary side AC part: L—N≥2.5 mm before the fuse, L. N PE (earth)≥2.5 mm, after the fuse device, it is not required, but a certain distance should be kept as far as possible to avoid short-circuit damaged power supply.
Note: Before deciding whether to meet the requirements, the internal parts should be applied with a force of 10N, and the outer shell should be applied with a force of 30N to reduce the distance so that the space distance still meets the requirements in the worst case.
According to the working voltage and insulation level, check table 6 to determine the creepage distance
(7), Between the two stages of the transformer ≥8.0mm or more
According to the working voltage and insulation application, the following regulations should be met:
——The working voltage does not exceed 50V (71V AC peak or DC value), and there is 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 deformation or performance degradation of the insulating material under normal temperature, the minimum thickness of the reinforced insulation shall be 0.4 mm. If the insulation provided is used in the protective enclosure of the equipment and will not be bumped or scratched during maintenance by the operator, and falls under any of the following conditions, the above requirements do not apply to thin-layer insulation materials regardless of their thickness ；
-For supplementary insulation, use at least two layers of materials, each of which can pass the electrical strength test for supplementary insulation; or:
——Additional insulation composed of three layers of materials, of which any combination of two layers of materials can pass the electrical 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 for reinforced insulation; or:
——Reinforced insulation composed of three layers of insulating materials, of which any combination of two layers of materials can pass the electrical strength test of the reinforced insulation.
(5) Reinforced insulation: a single insulation structure, under the conditions specified in this standard, the protection level it provides against electric shock is equivalent to double insulation
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The applicable situations of various insulation are as follows:
a. Generally speaking, there may be a dangerous voltage between the accessible conductor parts and the damage of the basic insulation
Between the parts, such as:
b. As part of double insulation
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Generally speaking, between the primary circuit and
Double insulation = basic insulation + supplementary insulation
ELV circuit: extra low voltage circuit. Under normal working conditions, the AC peak value between the conductors or between any conductor does not exceed 42.4V or the DC value does not exceed 60V in the secondary circuit.
SELV circuit: safety extra-low voltage circuit. The secondary circuit is properly designed and protected so that under normal conditions or single fault conditions, between any two accessible parts, as well as any accessible parts and the protective earth terminal of the equipment (only for The voltage between Class I equipment) shall not exceed the safe value.
T NV: Communication network voltage circuit. Under normal operating conditions, a circuit carries communication signals.
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