ELECTROSTATIC SHIELDS
There are two distinct types of transients present on the power grid; Common Mode and Transverse. Transverse noise are transients present, but not referenced to ground. Typical examples are switching power supplies, universal motors, etc. This noise is usually extinguished at its source with line filters. Common mode noise are transients present on the power grid but referenced to ground. Typical examples are lighting strikes, switching, electromagnetic pulses, etc. To decrease common mode noise, transformers can be modified by incorporating an electrostatic shield between the primary and secondary windings. The capacitance between the primary and the shield channels most of the common mode noise to ground.
THERMAL PROTECTION
There are two types of thermal protection available for transformers; Non–reset and Auto–reset. The Non–reset is used primarily for protection from internal transformer faults, tripping at a preset temperature. The Auto–reset provides intermittent protection from internal transformer faults and external overloads. This device will open at a preset high temperature and close at a preset lower temperature. These devices are mounted internal to the transformer and wired in series with the winding.
MOUNTING PRECAUTONS
The inadvertent design of a shorted turn by providing a conductive loop (turn) through the center of a toroidal transformer must be avoided. This typically occurs when designing special mounting hardware for the transformer. A shorted turn results in high circulating currents, excessive heat, and poor performance.