Hello, Can anyone tell me what the criteria are for saying that a certain material is an insulator? IEC950, clause 2.2.2 tells to test according to clause 5.3.2. This clause says that there is insulation breakdown if "the current which flows as a result of the application of the test voltage rapidly increases in an uncontrolled manner". Are there no maximum resistance values for determining what is an insulator and what not?
My particular problem is a signal transformer where a certain distance (Basic Insulation) is needed between the transformer windings and a groundplane on the board. The transformer is made of ferrite and almost totally encloses the windings. The ferrite is connected by metal brackets on that groundplane (emc and stability reasons) and the transformer windings are very close (less than the required Basic Insulation) to that ferrite encapsulation. conclusion: - If the ferrite is classified as insulator, The Basic Insulation is achieved with respect to the groundplane. - If the ferrite is classified as a conductor, B. I. is not achieved with respect to the groundplane. Remark: Depending on the type of ferrite, it seems that the resistivity can vary from 1 ohm.meter till 10exp5 ohm.meter., which are very high values. I really appreciate Your reaction, Kind regards, Carpentier Kris Product Safety Engineer Alcatel Telecom Fr. Wellesplein B-2018 Antwerp - Belgium tel.: 32 3 240 7986 fax.: 32 3 240 9933 email: [email protected] ref: kcarpentier/[email protected]
