The Shields form allows you to optionally include or exclude shield windings on the transformer. You can also change the shield parameters for a previously created design if required.
The purpose of shield windings is to reduce capacitive coupling from primary windings to secondary windings. A shield winding is a floating winding, separating the primary and the secondary windings. One end of this shield winding is held at ground potential. If properly designed, shield windings can substantially reduce this capacitive coupling and improve EMI performance.
Shield parameters are available for viewing only. The following controls are available in the Shields form:
Use Shield Windings - Select to activate shield windings in the transformer.
Flux Band - Select to add a flux band around the outside of the transformer. Flux band can be also called a bellyband, copper strap, flux strap or hum strap.
The flux band acts as a shorted turn for stray flux outside the magnetic circuit formed by transformer windings and the core. Stray magnetic field around the transformer can interfere with adjacent circuitry and contribute to EMI. The flux band can also be connected to a stable DC node to help reduce electrostatically coupled interference. Care should be taken to maintain the required creepage between primary and secondary windings of the transformer.