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29.2.4

Answer:

回答：

The outcome of opinion 2 is correct but not completely for the reason given since PTC heating elements are not insulation material.

觀點(diǎn)2的結(jié)果并不完全正確，因?yàn)镻TC電熱元件不是絕緣材料。

Opinion 1 is not correct unless you can prove that PTC material is Material group Ⅲa and consider it as insulation material.

觀點(diǎn)1是不正確的，除非能證明PTC材料是材料組Ⅲa并將其視為絕緣材料。

Reason:

原因：

You cannot apply Note 1 across the surface since you are in pollution degree 3 – The distance between terminations will generally depend on how the heating element is mounted.
Note 2 is not relevant since it only refers to “For glass, ceramics and other inorganic insulating materials”. PTC heating elements are not insulating material.
A creepage distance can never be less than its associated clearance – that is impossible. (See 5.3.2.5 of IEC 60664-1 ED3 below)

不能在整個(gè)表面應(yīng)用注1，因?yàn)樘幱谖廴镜燃? – 端子之間的距離通常取決于加熱元件的安裝方式。

注2不相關(guān)，因?yàn)樗鼉H指“用于玻璃、陶瓷和其他無機(jī)絕緣材料”。PTC電熱元件不是絕緣材料。

爬電距離永遠(yuǎn)不會(huì)小于其相應(yīng)的電氣間隙——這是不可能的。（參見下面 IEC 60664-1 ED3 的 5.3.2.5）

5.3.2.5 Relationship of creepage distance to clearance

A creepage distance cannot be less than the associated clearance so that the shortest creepage distance possible is equal to the required clearance. However, there is no physical relationship, other than this dimensional limitation, between the minimum clearance in air and the minimum acceptable creepage distance.

5.3.2.5 爬電距離與電氣間隙的關(guān)系

爬電距離不會(huì)小于相應(yīng)的電氣間隙，所以最短的爬電距離有可能是等于要求的電氣間隙。但是，除此尺寸限值外，在空氣中的最小電氣間隙和最小可接受的爬電距離之間沒有物理關(guān)系。

Creepage distance less than the clearance required in case A of Table F.2 may only be used under conditions of pollution degree 1 and 2 when the creepage distance can withstand the voltage required for the associated clearance (Table F.2).For testing, see 6.2.

在表F.2中的案例A中，爬電距離限值要求小于電氣間隙的情況僅適用于以下情況：

在污染等級1和2，當(dāng)爬電距離可以承受相應(yīng)電氣間隙所需的電壓時(shí)（表F.2），此時(shí)爬電距離可以承受相關(guān)電氣間隙所要求的電壓（表F.2）。供測試用，見6.2。

5.3.4 Dimensioning of creepage distances of functional insulation

Creepage distance of functional insulation may be Dimensioned as specified in Table F.5 corresponding to the steady-state working voltage across the creepage distance considered.

NOTE The values of Table F.5 can be used for functional insulation however different values of creepage distance can be appropriate.

When the steady-state working voltage is used for dimensioning, it is allowed to interpolate values for intermediate voltages. When interpolating, linear in interpolation shall be used and values shall be rounded to the same number of digits as the values picked up from the tables.

5.3.4 功能性絕緣爬電距離的尺寸

功能絕緣的爬電距離可按表 F.5 的規(guī)定確定尺寸對應(yīng)于所考慮的爬電距離兩端的穩(wěn)態(tài)工作電壓。

注：表 F.5 的值可用于功能絕緣，但不同的爬電距離值可能是合適的。

當(dāng)使用穩(wěn)態(tài)工作電壓進(jìn)行尺寸標(biāo)注時(shí)，允許對中間電壓值進(jìn)行插值法計(jì)算。插值時(shí)，應(yīng)使用線性插值，值應(yīng)四舍五入到與從表中選取的值相同的位數(shù)。

Above NOTE text is important, so we can ignore IEC 60664-1.

上面的 NOTE 文本很重要，所以我們可以忽略IEC 60664-1。

The clearance for functional insulation is given in 29.1.4 and in this case the Table 16 value applies i.e. 1,5 mm. This is completely consistent with NOTE 1 in Clause 29 and the 2nd paragraph of 5.3.2.5. However, this can be reduced to 1 mm for PTC heating elements (going across the surface) according to 29.1.4. These values are irrespective of pollution degree.

功能絕緣的間隙在 29.1.4 中給出，在這種情況下，表16的值適用，即1.5mm。這與第 29 章中注1和5.3.2.5第2段完全一致。但是，根據(jù)29.1.4，對于 PTC電熱元件（穿過表面），這可以減少到1mm。這些值與污染等級無關(guān)。

So taking account of the above, the creepage distance across the surface of the PTC heater element in pollution degree 3 cannot be less than 1 mm unless the appliance complies with Clause 19 when the creepage distance is short-circuited.

因此，考慮到上述情況，污染等級3的PTC電熱器元件表面的爬電距離不能小于1mm，除非器具在爬電距離短路時(shí)符合第19章要求。

But for this case the voltage is 220 V and if you interpolate between the Material Group 1 Pollution degree 3 values at 125 V and 250 V for 220 V you get 2.332 mm {= 1.8 + 95 × [(2.5 – 1.8)/125]} which is less than the measured value of 2.39 mm. So in our opinion, the construction is OK even if you ignore the above. 

但對于這種情況,電壓為220V，如果在125V的材料組1污染等級3和250V的 220 V 值之間進(jìn)行插值，將得到2.332mm {= 1.8 + 95×[(2.5–1.8)/125] }小于2.39mm的測量值。所以在我們看來，即使忽略上述內(nèi)容，結(jié)構(gòu)也是OK的。

Confirmed.

確認(rèn)。