Hi to you all,
We would appreciate your views please.
We drive a FET based H-bridge from rectified 230VAC mains; thus
320Vpk across the bridge. We have assumed the insulation between the
rectified power return and chassis (Class 1 product) is basic, thus
requiring 4mm creepage (IEC950). The proposed FETs need to be attached to a
heat sink and we would like to use the chassis for this purpose.
Our problem is that the FETs have around 2mm creepage between their
exposed heatsink surface and the fixing screw, insufficient to meet the
basic insulation creepage distance.
Is our interpretation regarding basic insulation correct/reasonable?
If we use an insulative thermal pad between the FET and chassis,
does the compression of the pad exclude the air path thus offering
sufficient protection? I am aware of such pads offering 4.5kV breakdown.
Thank you
Vic Gibling
Compliance Engineer
e2v technologies Ltd
Waterhouse Lane
Chelmsford
ESSEX CM1 2QU
Telephone: +44 (0) 01245 493493
Direct Line: +44 (0) 01245 453352
Facsimile: +44 (0) 01245 453410
E-mail: vic.gibl...@e2vtechnologies.com
Internet: www.e2vtechnologies.com
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