DSH 727 Creepage and clearance

小米

广东安规检测
有限公司提供：

小型摆管淋雨试验机

IPX5X6X7喷水试验机

1000L恒温恒湿箱

各种试验指现货

可程式恒温恒湿试验箱

水平垂直燃烧机

自动卷线器试验机

耐划痕试验机

各种灯头量规现货

灼热丝试验机现货

GB1002插头量规

IPX1-X7淋雨现货

IEC61347/UL935镇流器热试验箱

灯具防风罩

IK冲击试验机

UL498插头插座量规

VDE0620插头插座量规

稳定性试验台

家电温升测试角

针焰试验机现货

热电偶焊机现货

家电125mm试验指

E12灯头量规

无绳壶无绳电熨斗插拔寿命试验机

IEC60335试验指甲

DSH 727 ; F  s1 p+ b' Z+ D/ x. r) H* I

Creepage and clearance

29.1.3 , [6 I$ ^# h) y  I

60335-1(ed.4);am1;am2

Question:
Clause 29.1.3, reads: "29.1.3 Clearances of reinforced insulation shall be not less than those specified for basic insulation in table 16, but using the next higher step for rated impulse voltage as a reference."
+ Q- ^; o" i3 r  v( l7 [! b& vThe standard is not very precise about how to apply this clause in the situation for appliances having higher working voltages than rated voltage, for which the clearance are determined by interpolation, as described in clause in clause 29.1.5.
Examples:
1) Appliances with working voltage = rated voltage = 120V, overvoltage category II. For basic insulation, the rated Impulse voltage for 120V appliance = 1500 V. For reinforced insulation, the rated impulse voltage to take into account is 2500V (category above 1500V).
* B- \, _: n) g0 `0 Q2) Appliance with working voltage 300V AC, rated voltage 120V AC, overvoltage category II. For basic insulation, Impulse voltage determined following 29.1.5 =1754 V.
For reinforced insulation, what is the correct impulse voltage ?:
a) 2500 V ?
b) 4000 V ?
- W  i0 N' u% B6 _1 S: \* kc) Value given by application of IEC60664-1:2007, clause 5.1.6: 160% * 1754 = 2800V ?
1 L" m5 T" U- a3 u& s& W3 {! Ud) Others ?
Extract of clause 5.1.6 of IEC60664-1:2007:
4 |2 z1 x5 g, k  u2 |) i% |“With respect to impulse voltages, clearances of reinforced insulation shall be dimensioned as specified in Table F.2 corresponding to the rated impulse voltage but one step higher in the preferred series of values in 4.2.3 than that specified for basic insulation. If the impulse withstand voltage required for basic insulation according to 4.3.3.4.2(parts or circuits within equipment specifically protected against transient over voltages) , is other than a value taken from the preferred series, reinforced insulation shall be dimensioned to withstand 160% of the impulse withstand voltage required for basic insulation.
4 z* R3 t/ m5 dDecision:
; ^3 c0 d& j1 }2 ]; B- i( Z(1) If the clearances applied for basic insulation are selected from table F.7 of IEC 60664-1, the clearances of reinforced insulation shall be dimensioned as specified in Table F.7 to withstand 160 % of the withstand voltage required for basic insulation.
" T* t# T) m+ p(2) If the clearances applied for basic insulation are selected from clause 4 of IEC 60664-4, the clearances of reinforced insulation shall be twice the value required for basic insulation.
2 R$ i/ z# \6 d3 g% L
8 H, k2 n0 ~$ J1 O; G

; C$ L/ Z' j* H9 ]7 M