Coaxial Transformer Bobbin
Original Publication Date: 1983-Nov-01
Included in the Prior Art Database: 2005-Feb-07
This design meets creepage requirements while eliminating the need for a shield between primary and secondary windings in miniature safety transformers. Safety standards specify a creepage distance between primary and secondary windings in safety transformers. In addition, certain countries require a grounded metal shield if the equipment can be attached to the public telephone network. One method of meeting these requirements is to wind the primary and secondary such that a void is left at both ends of the winding to satisfy creepage requirements. This effectively reduces the width of the winding window, and special winding procedures and precautions must be employed to keep the windings in place during and after assembly. Leakage inductance is also increased due to the increased height-to- width ratio of the winding.