IEC 60669-1cl 19.2这段话怎么理解？

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IEC60335试验指甲

19.2 Switches intended for fluorescent lamp loads shall withstand, without excessive wear or other harmful effect, the electrical and thermal stresses occurring when controlling fluorescent lamp circuits with power factor correction, with load inserted between the test circuit terminals as indicated in figure 14, with the following test conditions.
8 y. C; \6 r6 x) iThe prospective short-circuit current of the supply shall be between 3 kA and 4 kA at cos ϕ = 0,9 ± 0,05 (lagging).
; I+ t) ~4 }- N% X% f' {F is a copper-wire fuse of 0,1 mm nominal diameter having a length not less than 50 mm.
9 d, t4 i; h# c. {4 VR1 is a resistor limiting the current to about 100 A.
The twin-core cable shall have a suitable length to give a resistance R3 equal to 0,25 Ω in the test circuit to the load. It shall have a cross-sectional area of 1,5 mm2 when switches with rated current up to and including 10 A are being tested and 2,5 mm2 when switches with rated current over 10 A up to and including 20 A are being tested.
; H( t9 {9 F  u; o8 w3 t& O问题：
4 p4 k4 I- C5 Z1 k- ^5 c8 a. M1， 3 kA and 4 kA at cos ϕ = 0,9 ± 0,05 (lagging)的预期短路电路如何才能知道？需要做实验来测量吗？
" Y6 T5 W# H1 q* l7 z4 h7 u2，负载A和负载B前面的电路是负载设备本身即有的，还是负载买回来后需要外接，这其中包括接地短路电阻R1, 起保险丝作用的细铜丝，以及阻值R3为0.25 Ω的双芯电缆。
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谢谢！
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