本帖最后由 火水晶 于 2020-5-21 16:54 编辑 $ O; }. z* u2 k+ _8 Z; r+ c: h
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最近在读UL 840,对Clearance与Creepage的理解不知对错，请大家指正。UL840 1. Clearance
9 Y7 K6 H* W2 a& ^' Z) Pa) The first concept detailed in Section 7, Clearance A (Equivalency), of this standard is an alternative approach to measuring spacings currently defined in various product standards. This approach uses a dielectric voltage-withstand test impulse to evaluate equivalence of designed spacings to the predefined dimension. An actual reduction in spacings can be permitted through a refinement in manufacturing techniques while maintaining equivalent breakdown levels.' B8 ~# k, F- g
- {* J9 G0 W7 Z; E4 n5 D6.2节的a) :第7章电气间隙A是用耐压测试脉冲评估设计电气间隙与预定尺寸的等效性。 b) The second concept detailed in Section 8, Clearance B (Controlled Overvoltage), of this standard, a step in the insulation coordination process, is the selection of clearances based on the level of overvoltage protection and pollution degree.8 Y8 [: t' U E3 ]. K7 G
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6.2节的b) :第8章电气间隙B是根据过电压保护水平和污染等级选择电气间隙。
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7 Clearance A（Equivalency） 7.2 A clearance, less than the specified minimum through air spacing, in the product standard, may be suitable if acceptable results are obtained when tested in accordance with Section 14, Dielectric Voltage-Withstand Tests, using a voltage with a value in accordance with Table 7.1. For specified minimum clearances between the values in Table 7.1, interpolation may be used to determine the test voltage. 按照14章表格的要求进行试验，可以使用表7.1的最小电气间隙值。 8 Clearance B(Controlled Overvoltage)8.4.2 Surge protective devices may be employed in order to improve the transient impulse over-voltage control within an assembly and decrease required clearance distances. This reduction in required clearance distance is based on the voltage protection rating (VPR) of the surge protective device and the resulting clearance distance as shown in Table 8.1. The surge protective device shall comply with 8.4.1 and items a) and b) below:3 j7 ?9 e% l0 s+ x e, y
用浪涌保护装置，减少电气间隙。电气间隙的减少是基于浪涌保护装置的电压保护额定值（VPR）和表8.1中所示的电气间隙。浪涌保护装置应符合8.4.1和以下a）和b）项的要求：
6 L/ U' ?: n4 |. la) The Measured Limiting Voltage (MLV) of the surge protective device shall not exceed the impulse voltage withstand value provided in Table 8.1 for the measured clearance, and . ^ m9 x ~4 K
b) Be provided with one of the following:! F0 e$ ]2 W* b4 c- v; A% O
1. A Nominal Current Discharge Rating (In) or Operating Duty Cycle based on a kV/kA combination test waveform equal to the values given in Table 8.2. The impulse voltage withstand value chosen shall be at least that equal to the impulse voltage withstand value in Table 8.1 based on the system input voltage and Over-Voltage Category of the equipment under test, 3 {- b4 o7 P$ n7 z3 ^0 h( X( j
2. A Nominal Current Discharge Rating (In) or Operating Duty Cycle based on a kV/kA combination test waveform equal to the impulse voltage value given in Table 8.2 and current value equal to rated impulse voltage divided by the circuit impedance on the input side of the surge protective device plus 2 ohms. The impulse voltage withstand value chosen shall be at least equal to the impulse voltage withstand value in Table 8.1 based the system input voltage and Over-Voltage Category of the equipment under test, or.
( `% O6 a" E: R; w3 e$ G 3. The entire assembly complies with the Operating Duty Cycle testing as outlined in the Standard for Surge Protective Devices, UL 1449, using a combination waveform as defined in item 1 above.3 Z. ]9 z2 }3 g; W' a0 j% [8 u
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8.4.1 Devices or systems used for overvoltage control shall comply with the following items a through d:# `$ E3 n9 f) N `
a) The requirements in the Standard for Surge Protective Devices, UL 1449.6 u3 a( Z2 W7 n! ?0 }3 S6 j
b) Type 1, Type 2, and Type 3 surge protective devices shall have a maximum continuous operating voltage not less than the operational voltage rating of the power system configuration to which the surge protective devices is connected." |3 E/ D: f+ N* d: G$ i
c) Type 4 and 5 surge protective devices shall have a maximum continuous operating voltage at least equivalent to the line-to-line voltage of the input system of the assembly.5 z8 b+ e8 n" `
Exception: Type 4 surge protective devices that have been subjected to limited current, intermediate current and short circuit current tests need only be rated for the maximum continuous operating voltage of the power system.
. N+ Y% `# X% R6 I# Zd) Be evaluated for use for one of the following:0 |8 O- E) U' G8 r* K
1. Type 1 applications when used on the line side of service equipment,& e. N& b+ F$ E& _/ m( n
2. Type 1 or Type 2 applications when used on the load side of service equipment feeder circuit applications or branch circuit applications,: c" T- o* \7 B+ s
3. Type 3 applications when used in branch circuit or control circuit applications or,
2 b6 ]* l6 `$ N: x 4. Type 5 discrete component surge suppressors or Type 4 component assemblies when used in branch circuit or control circuit applications and rated with a nominal discharge current (In) where the In value is as specified in Table 8.2 based on the system operating voltage and the Over-Voltage category,
; a9 o7 G1 X0 U0 r# Y 5. Type 4 component surge suppressors when used in branch circuit or control circuit applications and provided with “other” rating where the Operating Duty Cycle is based on a kV/kA combination waveform test equal to the values given in Table 8.2 based on the system input voltage and Over-Voltage Category of the equipment.4 n9 c' q' F" n0 K
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其中浪涌保护装置要符合8.4.1和以下a）和b）项中最重要的要求是符合UL 1449《浪涌保护装置标准》与通过表8.2的测试. 综上所述，电气间隙的确定可以通过： ①通过表14.1的测试后，通过测试耐压来确定电气间隙是否合适； ②选用一个符合UL1449并能通过表8.2测试的浪涌保护器后，再根据表8.1来确定电气间隙需求。
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发表于 2020-5-21 16:55
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