My first thought is that, where you have potting you do not have creepage, hence CTI is not involved. However, on a related topic, I've had problems with vacuum-impregnated transformers.
It seems that, in drawing a partial vacuum there's often a little air left. Then, even with pressure impregnating, the epoxy doesn't penetrate fully: it has higher viscosity than air, and tape will sometimes pull up, "burping" out the air, then reseal under positive pressure. The result is that pockets of partial vacuum are left in inner windings, and the transformer breaks down at voltages BELOW it's unpotted level! Whenever possible, I recommend the use of split or multi-part bobbins which assure spacings without relying on manufacturing skill. Good, safe transformers are deceptively hard to design, build and verify, especially when coupling requirements prevent the use of such bobbins. __________________ Heber Farnsworth Physio-Control, Seattle, USA > -----Original Message----- > From: [email protected] [SMTP:[email protected]] > Sent: Thursday, April 02, 1998 11:49 PM > To: [email protected] > Subject: Transformer potting + CTI spacer tape > > > Anybody with any experience how potting is influencing the parameter > and > characteristics of CTI rated spacer tape? > > A spacer tape with CTI rating >600 is used, and the transformer will > finally be potted. > > My anxiety is that the potting liquid is penetrating the spacer tape, > hence > degrading the quality of the spacer tape's glue and CTI capabilities. > > What do you think? > > R. Keller >
