塑料黄卡解释

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14.1.1 Materials that do not comply with the minimum hot-wire ignition levels shown in Table 8.1 or may be evaluated by an abnormal overload test or the glow-wire end-product test. The abnormal overload test passes abnormal currents through current-carrying members as described in 14.2. Over-current values and times are shown in Table 51.1 as a function of the circuit over-correct device rating. The glow-wire end-product test subjects the end-product to an electrically heated wire. Glow-wire test temperatures are shown in Table 75.1 and are determined by end-product use.

Exception No. 1: The abnormal overload test or the glow-wire end-product test need not be conducted if the electrically live parts are spaced 0.8 mm (1/32 inch) or more from the material. Exception No. 2: The abnormal overload test or the glow-wire end-product test need not be conducted for non-hazardous energy circuits.

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HWI Range Assigned

Mean Ignition Time (In Sec) PLC

120 and longer 0

60 through 119 1

30 through 59 2

15 through 29 3

7 through 14 4

Less than 7 5

High Current Arc Resistance to Ignition (HAI)

b

13.1 A polymeric material shall resist ignition to the levels shown in Table 8.1 when tested in accordance with the High Current Arc Resistance to Ignition Test described in the Standard for Polymeric Materials – Short Term Property Evaluations, UL 746A.

Exception: The high current arc resistance-to-ignition test need not be conducted for

non-hazardous energy circuits.

HAI Range

Mean Number of Arcs to

Cause Ignition

120 and longer

60 through 119

30 through 59

15 through 29

Less than 15

Relative Thermal Index¡RTI:¬G

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E Elec¡G Electrical¡A°

E IMP¡G Impact¡A y

E Str¡G Stress¡A O

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37.1 The relative thermal index of a material is to be based upon an evaluation of long-term thermal-aging data obtained under a program described in the Standard for Polymeric Materials – Long Term Property Evaluations, UL 746B.

37.2 Essentially, the Standard for Polymeric Materials – Long Term Property Evaluations, UL

746B, procedure allows the thermal-aging characteristics of a material to be determined bymeasuring the changes in its properties to a predetermined level by aging at each of several elevated temperatures, plotting the logarithm of time at each temperature against the reciprocal of absolute temperature using the best-fit straight line by the least squares method of regression analysis. The time-temperature relationship may be expressed as:

Ln(t) = A + B/T

in which:

A is Constant (frequency factor)

B is Activation (Energy Constant)

T is Absolute temperature, °K (°C + 273.16) and

In is Natural logarithm

37.3 A comparison of the thermal aging characteristics of the candidate material against those of a concurrently tested control material having proven field service, provides a means for estimating a relative thermal index level where the candidate material is expected to have an acceptable field service history.

For each material, a number of relative thermal indices can be established, each index being related to a specific property, color, and thickness of the material.

37.4 A polymeric material having a use operating temperature higher than the applicable relative thermal index, shall be considered acceptable if it complies with the requirements for Functional Use Temperature Indices (Section 35) or Relative Thermal Capability (Section 38).

37.4 revised November 5, 2002

NOVEMBER 5, 2002 UL 746C 48

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Comparative Tracking Index (CTI)

3.21 IEC Glow Wire Ignitability Temperature (GWIT) – in accordance with IEC 60695-2-1/3, is expressed as the temperature in degrees C which is 25°C hotter than the maximum temperature of the tip of the glow-wire which does not cause ignition of the material.

Added 3.21 effective June 1, 2004

3.22 IEC Glow Wire Flammability Temperature (GWFT) – in accordance with IEC 60695-2-1/2, is expressed as the highest temperature (in degrees C) at which flaming or glowing of the material extinguishes within 30 seconds after removal of the glow-wire and without ignition of the specified indicator by burning drips or particles.