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.

观点2的结果并不完全正确，因为PTC电热元件不是绝缘材料。

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

观点1是不正确的，除非能证明PTC材料是材料组Ⅲa并将其视为绝缘材料。

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)

不能在整个表面应用注1，因为处于污染等级3 – 端子之间的距离通常取决于加热元件的安装方式。

注2不相关，因为它仅指“用于玻璃、陶瓷和其他无机绝缘材料”。PTC电热元件不是绝缘材料。

爬电距离永远不会小于其相应的电气间隙——这是不可能的。（参见下面 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 爬电距离与电气间隙的关系

爬电距离不会小于相应的电气间隙，所以最短的爬电距离有可能是等于要求的电气间隙。但是，除此尺寸限值外，在空气中的最小电气间隙和最小可接受的爬电距离之间没有物理关系。

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，爬电距离限值要求小于电气间隙的情况仅适用于以下情况：

在污染等级1和2，当爬电距离可以承受相应电气间隙所需的电压时（表F.2），此时爬电距离可以承受相关电气间隙所要求的电压（表F.2）。供测试用，见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 功能性绝缘爬电距离的尺寸

功能绝缘的爬电距离可按表 F.5 的规定确定尺寸对应于所考虑的爬电距离两端的稳态工作电压。

注：表 F.5 的值可用于功能绝缘，但不同的爬电距离值可能是合适的。

当使用稳态工作电压进行尺寸标注时，允许对中间电压值进行插值法计算。插值时，应使用线性插值，值应四舍五入到与从表中选取的值相同的位数。

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

上面的 NOTE 文本很重要，所以我们可以忽略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.

功能绝缘的间隙在 29.1.4 中给出，在这种情况下，表16的值适用，即1.5mm。这与第 29 章中注1和5.3.2.5第2段完全一致。但是，根据29.1.4，对于 PTC电热元件（穿过表面），这可以减少到1mm。这些值与污染等级无关。

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，考虑到上述情况，污染等级3的PTC电热器元件表面的爬电距离不能小于1mm，除非器具在爬电距离短路时符合第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. 

但对于这种情况,电压为220V，如果在125V的材料组1污染等级3和250V的 220 V 值之间进行插值，将得到2.332mm {= 1.8 + 95×[(2.5–1.8)/125] }小于2.39mm的测量值。所以在我们看来，即使忽略上述内容，结构也是OK的。

Confirmed.

确认。